I HC QUC GIA THNH PH H CH MINH TRNG I HC KHOA HC T NHIN

NGUYN HU TN

NGHIN CU QUI TRNH XC NH NG THI CC KIM LOI NNG TRONG T TRNG TRT BNG THIT B ICP-OES

LUN VN THC S KHOA HC - HA HC

THNH PH H CH MINH 2011

I HC QUC GIA THNH PH H CH MINH TRNG I HC KHOA HC T NHIN

NGUYN HU TN

NGHIN CU QUI TRNH XC NH NG THI CC KIM LOI NNG TRONG T TRNG TRT BNG THIT B ICP-OES

CHUYN NGNH: HA PHN TCH M S: 60 44 29

LUN VN THC S KHOA HC - HA HC

GIO VIN HNG DN KHOA HC TS. TRNG TH T OANH

THNH PH H CH MINH 2011

LI CM NTi xin chn thnh gi li cm n su sc n: - TS. Trng Th T Oanh, ngi tn tnh hng dn, nh hng gip ti hon thnh ti. - Hi ng chm lun vn c nhng nhn xt, gp qu bu v cc thiu st trong ti. - Thy c B mn Ha phn tch tn tnh truyn dy kin thc trong sut qu trnh hc tp ca ti. - Ban gim c Trung tm K thut 3 v tp th phng th nghim Mi trng to iu kin thun li cho ti ti thc hin ti. - Anh Nguyn Cng Chnh ng vin, ng h, nhit tnh gip ti hon thnh lun vn.

MC LCDANH MC CH VIT TT .............................................................................................. i DANH MC BNG .............................................................................................................ii DANH MC HNH .............................................................................................................. iv CHNG 1: M U ......................................................................................................... 1 1.1 1.2 t vn ..................................................................................................................... 1 Tnh hnh nghin cu kim loi nng Vit Nam ......................................................... 2

CHNG 2: TNG QUAN ................................................................................................. 6 2.1 c tnh ca mt s kim loi ........................................................................................... 6 2.2 S tch ly kim loi trong mi trng t: ...................................................................... 8 2.2.1 Hot ng nng nghip ......................................................................................... 8 2.2.2 Hot ng cng nghip ....................................................................................... 10 2.3 Phng php ICP-OES .................................................................................................. 13 2.3.1 Gii thiu phng php ICP-OES .............................................................................. 13 2.3.2 Nguyn tc o vi ICP-OES .............................................................................. 13 2.3.3 S lc cu to nguyn t v s xut hin ph pht x ..................................... 14 2.3.4 Ngun phng in plasma ICP v s kch thch ph trong plasma ICP ............. 15 2.3.5 Cc b phn chnh ca thit b ICP-OES ............................................................ 17 2.3.6 Cn nhiu trong php o vi ICP-OES............................................................... 20 CHNG 3: HOCH NH TH NGHIM ..................................................................... 26 3.1 Thit b-ha cht ............................................................................................................ 26 3.1.1 Thit b ................................................................................................................ 26 3.1.2 Ha cht .............................................................................................................. 26 3.2 Thc nghim ................................................................................................................. 26 3.2.1 Ti u thit b ..................................................................................................... 26 3.2.2 Kho st cn nhiu .............................................................................................. 27 3.2.3 X l mu .......................................................................................................... 29 3.2.4 nh tr phng php th................................................................................... 33 CHNG 4: KT QU - THO LUN ........................................................................... 36 4.1 Ti u ha thit b ...................................................................................................... 36 4.1.1 Cng sut RF ...................................................................................................... 36 4.1.2 Lu lng kh nebulizer ..................................................................................... 37 4.2 Kho st cn nhiu ........................................................................................................ 39

4.2.1 Cn nhiu quang ph .......................................................................................... 39 4.2.2 Cn nhiu vt l................................................................................................... 41 4.2.3 Loi tr cn nhiu ............................................................................................... 42 4.3 Kho st acid chit cc nguyn t trong mu t ......................................................... 44 4.4 4.5 Kho st chng trnh nhit cho microwave .............................................................. 47 nh tr phng php th ........................................................................................... 49 4.5.1 Khong tuyn tnh ............................................................................................... 49 4.5.2 Gii hn pht hin, gii hn nh lng ............................................................. 49 4.5.3 Hiu sut thu hi, chch, lp li v ti lp............................................ 49 4.5.4 khng m bo o ......................................................................................... 52 4.6 p dng qui trnh phn tch mu tht ......................................................................... 53 Mc ch ..................................................................................................................... 56 Phng thc kim sot ............................................................................................... 56 5.2.1 Kim sot thit b, dng c, cht chun .............................................................. 56 5.2.2 Kim sot qu trnh vn hnh thit b ................................................................. 56 5.2.3 p dng biu kim sot cht lng ............................................................... 60 CHNG 6: TM TT QUI TRNH ................................................................................ 65 6.1 Nguyn tc ca qui trnh ................................................................................................ 65 6.2 Thit b - Ha cht Cc dung dch chun .................................................................... 65 6.2.1 Thit b - Ha cht ...................................................................................................... 65 6.2.2 Cc dung dch chun ................................................................................................... 65 6.3 Chun b mu ................................................................................................................. 66 6.3.1 Chun b s b mu th .............................................................................................. 66 6.3.2 Phn hy mu bng microwave .................................................................................. 66 6.4 Phn tch trn thit b ..................................................................................................... 67 6.5 Tnh kt qu ................................................................................................................... 68 6.6 Cc lu v an ton....................................................................................................... 68 CHNG 7: KT LUN - KIN NGH ........................................................................... 70 A. B. Kt lun ...................................................................................................................... 70 Kin ngh .................................................................................................................... 71 CHNG 5: KIM SOT CHT LNG TH NGHIM ............................................ 56 5.1 5.2

TI LIU THAM KHO ................................................................................................... 58 PH LC

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DANH MC CH VIT TTCRM : Certified reference material - Mu chun c chng nhn. GF-AAS : Graphite furnace atomic absorption spectrometry - Ph hp thu nguyn t l graphite. F-AAS : Flame atomic absorption spectrometry - Ph hp thu nguyn t la. ICP-OES : Inductively coupled plasma optical emission spectrometry - Quang ph pht x ghp cp cao tn cm ng. IS LOD LOQ MDL MSF Rec r R : Internal standard - Ni chun. : Limit of detection - Gii hn pht hin. : Limit of quantitation - Gii hn nh lng. : Method detection limit - Gii hn pht hin ca phng php. : Multi component spectral fitting. : Recovery - Hiu sut thu hi. : Repeatability - lp li. : Reproducibility - ti lp. ngn

ii

DANH MC BNGBng 1.1: Hm lng mt s kim loi nng trong mt s loi t ti Vit Nam (tng t mt).................................................................................. 3 Bng 1.2: Hm lng mt s kim loi nng trong t ti khu vc Cng ty Pin Vn in......................................................................................... 3 Bng 2.1: Hm lng mt s kim loi trong phn bn.. 9 Bng 2.2: Hm lng mt s kim loi nng trong t gn ng giao thng ...... 12 Bng 2.3: Mt s v d so snh gia phn hy mu bng phng php c in v phng php vi sng..25 Bng 3.1: Cc gi tr kho st cng sut RF v nebulizer. 27 Bng 3.2: Thng s ca cc nguyn t cho kho st cn nhiu quang ph... 28 Bng 3.3: Cc matrix m phng nn t.................................................................. 29 Bng 3.4: Chng trnh nhit cho microwave......................................................... 32 Bng 3.5: Hm lng cc nguyn t thm vo mu kho st.................................. 34 Bng 4.1: Cc thng s vn hnh ICP-OES 5300DV.............................................. 38 Bng 4.2: Bng tm tt cn nhiu quang ph.......................................................... 39 Bng 4.3: Cc bc sng ca cc nguyn t s dng cho qui trnh phn tch.........40 Bng 4.4: Kho st cn nhiu vt l. 41 Bng 4.5.(a): Kho st loi tr cn nhiu vt l vi ni chun Sc 360.073.. 42 (b): Kho st loi tr cn nhiu vt l vi ni chun Y 371.029.....42 Bng 4.6: Cn nhiu i vi Cd 214.440................................................................. 43 Bng 4.7: Hm lng kim loi v hiu sut thu hi khi phn hy mu t bng cc acid khc nhau.......................................................................... 45 Bng 4.8: Hm lng cc kim loi trong mu t thu c vi cc chng trnh nhit khc nhau............................................................................... 47 Bng 4.9: Khong tuyn tnh....49 Bng 4.10: Gii hn pht hin, gii hn nh lng ca cc kim loi trong nn mu t 49

iii

Bng 4.11: Kt qu xc nh cc kim loi trong mu thm chun ti 3 mc hm lng khc nhau..... 50 Bng 4.12: Hiu sut thu hi, chch, lp li v ti lp ca kim loi trong mu thm chun ti 3 mc hm lng khc nhau.. 50 Bng 4.13: Kt qu xc nh cc kim loi trong mu thm chun ti mc nng 2 vi ICP-OES v AAS...........................51 Bng 4.14: khng m bo o ca cc nguyn t trn nn t ......................... 52 Bng 4.15: Kt qu xc nh kim loi trong mt s mu t................................... 54 Bng 5.1: Cc dung dch, cch s dng v cc yu cu cho vn hnh ICP-OES.... 56 Bng 5.2: Trnh t phn tch mu trn ICP-OES..................................................... 58 Bng 5.3: nh gi kt qu cc dung dch kim sot v hnh ng khc phc.......59 Bng 5.4: Hiu sut thu hi ca cc mu QC...........................................................62

iv

DANH MC HNHHnh 2.1: Cc qu trnh hp thu v pht x trong nguyn t v ion15 Hnh 2.2: Qu trnh hnh thnh ngn plasma..........................................................16 Hnh 2.3: Phn chia cc vng v nhit trong ngn plasma Argon.....................16 Hnh 2.4: Cc qu trnh din ra khi mu c a vo plasma............................17 Hnh 2.5: Cu to torch dng trong ICP-OES........................................................18 Hnh 2.6: Ch ly tn hiu ca ICP-OES..........................................................20 Hnh 3.1: Chun b s b mu t 30 Hnh 4.1.(a): nh hng cng sut RF n tn hiu cc nguyn t (As, Ni, Pb)... 36 (b): nh hng cng sut RF n tn hiu cc nguyn t (Cd, Cu, Zn)... 36 Hnh 4.2.(a): nh hng ca nebulizer n tn hiu cc nguyn t (As, Ni, Pb)... 37 (b): nh hng ca nebulizer n tn hiu cc nguyn t (Cd, Cu, Zn).. 38 Hnh 4.3: So snh hm lng cc kim loi trong mu t thu c i vi cc loi acid khc nhau............................................................................. 46 Hnh 4.4: Hiu sut chit cc kim loi khi nn mu t i vi cc acid khc nhau.................................................................................................. 46 Hnh 4.5: So snh hm lng cc kim loi thu c vi cc chng trnh nhit khc nhau......................................................................................... 48 Hnh 4.6: Cc dung dch chun dng cho phn tch mu....................................... 53 Hnh 5.1: Biu kim sot cht lng...60 Hnh 5.2.(a): Biu kim sot cht lng ca As 62 (b): Biu kim sot cht lng ca Cd 63 (c): Biu kim sot cht lng ca Cu 63 (d): Biu kim sot cht lng ca Ni 63 (e): Biu kim sot cht lng ca Pb. 64 (f): Biu kim sot cht lng ca Zn. 64

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CHNG 1: M U1.1 t vn : Ngy nay, nhim mi trng l mt vn nng bng c c th gii quan tm. Dn s ngy cng tng, qu trnh cng nghip ha, hin i ha, th ha din ra nhanh chng v mnh m cng vi thin tai, l lt lm cho cht lng mi trng din bin theo chiu hng xu. Hin nay, bn cnh nhim ngun nc, khng khth cht lng t cng ang din bin theo tnh trng ng lo ngi. t l mt thnh phn ca mi trng cng vi khng kh, nc v vnh ai sinh vt nn t tip nhn nhng cht nhim t cc thnh phn khc mi lc, mi ni. Mi trng ca Vit Nam ang chu tc ng mnh t cc hot ng pht trin ca cng nghip, nng nghip. Nc ta hin ang trong cng cuc cng nghip ha, hin i ha. Cc khu cng nghip c xy dng rt nhiu, cc lng ngh ti nng thn cng c khi phc v m rng. Tuy nhin, vic qun l cc ngun thi t cc khu cng nghip, lng ngh cn nhiu bt hp l, nhiu kh khn bn cnh thc bo v mi trng ca ngi sn xut, ngi dn cn thp nn dn n nhim mi trng sng, tc ng xu n ngun nc, khng kh, t ai. Song song vi hot ng cng nghip th hot ng nng nghip cng gy nhim t thng qua vic lm dng phn bn, thuc bo v thc vt. nhim t nh hng n nng nghip, cht lng nng sn v t gin tip nh hng n sc khe con ngi, ng vt sng thng qua lng thc, thc phm...Bn cnh , t nc ta gia nhp WTO - ha nhp gia th trng thng mi ton cu, chng ta c nhiu c hi pht huy li th nng nghip ca mnh nhng cng y kh khn, th thch. nng sn c xut ra th trng th gii th bt buc cht lng sn phm phi vt qua nhng ro cn k thut m th trng nhp khu yu cu. Hin nay, mt s mt hng nng sn nc ta v ang p dng qui trnh sn xut theo chun VietGAP - c kim sot cht ch cc yu t tc ng n cht lng nng sn nh nh kim loi nng trong t trng, ngun nc ti; ha cht bo v thc vt tn d trong t, trn nng sn...nhm to ra c sn phm t yu cu xut khu, a nng sn Vit Nam ha nhp vo th trng th gii, gp phn

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thc y t nc pht trin ni ring v nng cao uy tn ca Vit Nam trn th trng th gii ni chung. T thc t ny, gp thm cng c gip nh gi cht lng mi trng t trng trt, ti sau y c chn thc hin trong lun vn ny: NGHIN CU QUI TRNH XC NH NG THI CC KIM LOI NNG TRONG T TRNG TRT BNG THIT B ICP-OES. Mc tiu chnh ca ti l kho st ng thi cc nguyn t As, Cd, Cu, Ni, Pb, Zn trong mu t. Ngoi Ni, cc nguyn t cn li c kim sot v nh gi theo quyt nh 99/2008/Q-BNN[3] ca B Nng nghip v Pht trin nng thn cho t trng theo VietGAP v c th m rng i vi t s dng mt s mc ch khc theo mc qui nh ca TCVN 7209:2002.[15] 1.2 Tnh hnh nghin cu kim loi nng Vit Nam: Trn th gii, cc nh khoa hc quan tm n c tnh ca cc kim loi t lu. Cc phng php thng c p dng phn tch kim loi trong mi trng t l cc ph, quang ph (F-AAS, GF-AAS, ICP-OES), khi ph (ICP-MS). Hin nay, s dng ICP-OES, ICP-MS xc nh hm lng kim loi rt ph bin. C rt nhiu tc gi s dng thit b ny cho nghin cu ca mnh v c nhng cng b nht nh nh M.Bettinelli[23], M.Hoenig[31], A.Mazzucotelli[37], A.Miyazaki[38], H.Tao[49], G.A.Zachariadis[57]... u im ln nht ca ICP-OES, ICP-MS l c th o ng thi nhiu nguyn t, v vy thi gian phn tch mu s c rt ngn ng k, t c hi, thn thin hn vi mi trng... Ti Vit Nam, nghin cu v kim loi cng c s quan tm ca cc nh khoa hc. Tuy nhin, phng tin k thut phc v cho mc ch ny cn km pht trin so vi th gii. Cc cng trnh nghin cu ch yu s dng phng php cc ph v quang ph hp thu ngn la xc nh cc kim loi. C th k n kt qu mt s cng trnh nghin cu tiu biu ca cc tc gi trong nc c cng b trn mt s tp ch khoa hc trong nc v nc ngoi nh di y. Nm 1998, tc gi Trn Cng Tu v Trn Cng Khnh iu tra tng hm lng cc kim loi (Co, Cr, Fe, Mn, Ni, Pb, Zn) ti tng t mt ( su t 0-20 cm) ca mt s loi t nc ta cho kt qu nh trnh by trong bng 1.1.[16]

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Bng 1.1: Hm lng mt s kim loi nng trong mt s loi t ti Vit Nam (tng t mt).Loi t t Feralit pht trin trn bazan t ph sa vng ng bng sng Cu Long t ph sa vng ng bng sng Hng Nguyn t (mg/kg) Co Cr Fe Mn Ni Pb 59.5 257.6 125091 1192 227.1 9.0 6.1 30.8 17924 42280 239 227 18.6 34.9 13.6 43.2 Zn 81.0

29.1 36.2 37.1 86.7

Nm 1999, L Khoa v cng s thc hin kho st hm lng cc kim loi trong t gn khu vc Cng ty pin Vn in nh gi tc ng nhim do hot ng sn xutt ca cng ty, kt qu cho thy t khu vc ny b nhim Zn[11]. Hm lng Zn cao hn tiu chun cho php i vi t nng nghip theo TCVN 7209:2000[15] nh trong bng 1.2. Bng 1.2: Hm lng mt s kim loi nng trong t ti khu vc Cng ty Pin Vn in. su (cm) 0 - 20 20 - 40 Qui nh theo TCVN 7209:2000 Nguyn t (mg/kg) Cd Cu 0.98 31.4 0.91 2 25.5 50 Hg 0.12 0.096 Pb 32.6 25.2 70 Zn 268.2 256.0 200

Tip theo vo nm 2002, nghin cu ca tc gi Nguyn Ngc Hunh v L Huy B thc hin trn 126 mu t trng la thnh ph H Ch Minh cho thy rng c s tch ly cc kim loi Cr, Cu, Pb, Hg mt s mu tuy nhin vn di mc cho php. Mu t gn cc khu cng nghip pha Bc thnh ph H Ch Minh (qun Th c, qun 2, qun 9) c kh nng nhim Zn rt cao. Hm lng Zn ti tng t mt qun 2 dao ng trong khong 161-390 mg/kg, ti tng t mt qun 9 dao ng trong khong 356-679 mg/kg.[10] Nm 2006, nhm ca tc gi Phm Ngc Thy nghin cu hin trng kim loi Hg, As, Pb, Cd trong t, nc v mt s rau trng trn khu vc 14 x thuc huyn ng Anh-H Ni vi 39 mu t mt, 39 mu nc mt v 136 mu rau cc

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loi. Kt qu cho thy cha c biu hin nhim As trn cc i tng kho st. nhim Hg ch yu trong nc nng nghip, trong t v rau trng t trng hp b nhim nguyn t ny. Nhiu mu t, nc b nhim Pb v cc mu rau s dng t trng hay ngun nc ny u nhim Pb. Hm lng Cd trong cc mu t mc an ton, mt s mu nc v rau b nhim nguyn t ny.[18] Theo nghin cu nm 2007 ca cc tc gi Hong Th Thanh Thy, T Th Cm Loan, Nguyn Nh H Vy xc nh hm lng cc kim loi Cd, Cr, Cu, Pb, Zn trong trm tch sng ti Tp. H Ch Minh cho thy c s tch ly kim loi trong trm tch sng rch. c bit, ti nhiu v tr nh knh Tn Ha L Gm v Tu H-Bn Ngh, hm lng mt s kim loi vt qua gii hn cho php.[19] Nm 2008, tc gi Nguyn Th c Hnh cng tin hnh nghin cu v s nhim kim loi nng (Cd, Cr, Cu, Ni, Pb, Zn) trong lp bn y ti 10 v tr ly mu tri di trn ton b chiu di 32 km ca sng Th Vi. Kt qu cho thy bn y b nhim bi Ni, Cu, Cr. Cc kim loi khc nh Cd, Pb, Zn cng c hin din nhng vn nm trong gii hn an ton. Cc kim loi c hm lng cao ni u ngun (ni tip nhn nc thi t cc khu cng nghip) v gim dn v pha ca sng.[9] Nm 2009, tc gi Kien Chu Ngoc v cng s kho st cc kim loi (As, Cd, Cr, Cu, Mn, Ni, Pb, Zn) trong t trng xung quanh m khai thc thic v tungsten ti huyn i T, H Ni cho thy c s nhim Cu, Pb v c bit l As i vi t rng v t trng hoa mu.[34] Nh vy, vic nghin cu kim loi nng trong t, bn, trm tch ti Vit Nam c nhng kt qu nht nh. Cng c chnh xc nh hm lng kim loi trong nn mu ny l thit b quang ph hp thu nguyn t, thit b cc ph xc nh ln lt tng kim loi hin din trong dung dch mu th. Do vy, vic nh lng cc kim loi s mt rt nhiu thi gian, tiu tn nhiu nhn lc, ha cht... v c th phi s dng c quang ph v cc ph th mi c th xc nh c cc nguyn t cn thit trn mt mu th. Bn cnh , hai phng php ny cn chu rt nhiu nh hng t nn mu phc tp. Nhm khc phc nhng nhc im ny, qui trnh nghin cu s ng dng mt thit b mi i vi Vit Nam l ICP-OES kt hp vi k thut phn hy mu

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bng l vi sng nh lng cc kim loi trong mu t. ICP-OES s hu c nhiu u im vt tri nh xc nh c khong trn 70 nguyn t, tc phn tch nhanh, nhy cao, khong tuyn tnh rng, t cn nhiu v c bit l kh nng xc nh ng thi cc nguyn t ti cng mt thi im. Do , s dng ICPOES gip tit kim nhn lc, thi gian v tc phn tch mu nhanh, gim chi ph, t c hi...v quan trng l rt ngn khong cch v thit b cng ngh so vi cc nc trong khu vc v th gii. 1.3 Mc tiu khoa hc ca ti: ti thc hin c nhng mc ch nh sau: Nghin cu v xy dng mt qui trnh tin cy trong vic xc nh hm lng kim loi trong mu t bng thit b ICP-OES. p dng thit lp qui trnh th nghim v kim sot cht lng ca qui trnh th nghim p ng yu cu ca tiu chun ISO /IEC 17025:2005. Cung cp cng c gip nh gi v theo di cht lng t gip c quan chc nng a ra bin php x l thch hp i vi t nhim. Qui trnh c th m rng p dng trn nn mu cht thi rn, bn, trm tch. 1.4 Phng php nghin cu: ti vn dng tng hp cc phng php sau nghin cu: Tng hp cc bi bo co khoa hc, cng trnh nghin cu trong v ngoi nc nh hng cho qui trnh nghin cu. S dng l vi sng phn hy mu. Sau xc nh ng thi cc kim loi bng thit b ICP-OES. Hin nay, y l hai k thut hin i v c nhiu u im, c s dng rng ri cc nc pht trin. X l d liu thu c bng phng php x l thng k kt hp vi MS-Excel.-

Kim sot cht lng th nghim theo yu cu ca tiu chun ISO/IEC 17025:2005.

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CHNG 2: TNG QUAN2.1 c tnh ca mt s kim loi: Cc kim loi hin din trong mi trng do c sn trong t nhin v ch yu l do hot ng ca con ngi. Cc kim loi tch t trong t, c hp thu vo thc vt v sau theo chui thc n s xm nhp vo c th con ngi, ng vt. Kim loi tch t trong c th vi hm lng vt ngng an ton s dn n ng c, nh hng n sc khe, s sinh trng, pht trin ca c th. 2.1.1 As: c tnh cc hp cht v c ca As ph thuc vo trng thi oxi ha, thng thng cc hp cht As+3 c hn As+5. Cc cht c hp thu v phn b ch yu ti gan, thn, phi, l lch, ng mch ch v da.[40] Biu hin ca ng c cp tnh As thng qua ng d dy nh bun nn, i ma, tiu chy, ri lon nhp timNg c mn tnh As c cc triu chng nh c th suy nhc, yu t, rng tc, ri lon tinh thn[40]Ng c As v cc hp cht trong thi gian di gy ung th biu m da, ph qung, phi, cc xoang, gan [1],[17] i vi cy trng, As3+ c nh hng n s pht trin cy la non, lm cho l tht 1 v 2 ca cy la chm pht trin, c mu trng v xanh nht trong sut qu trnh tn ti,khng c kh nng tng hp dip lc t, khng c kh nng quang hp v sm b kh t.[2] 2.1.2 Cd: Cd hp thu vo c th ch yu thng qua phi (30-60%). Cd phn b khp c th nhng tp trung ch yu gan v thn (50-70% lng Cd trong c th).[41] Ty theo mc b nhim c Cd m con ngi c th b ung th phi, thng vch ngn mi, tn thng thn, nh hng ti ni tit, tim mch[16]Cd cng gy long xng, nt xng, kh khn trong vic c nh Ca trong c th. T l ung th tin lit tuyn v ung th phi cng kh ln nhng ngi thng xuyn tip xc vi Cd.[1] Vi thc vt, Cd tp trung nhiu trong m. Cd cha nhiu nht trong l i vi rau dip, carot, khoai ty, thuc l. Cd tp trung cao trong r cc cy yn mch, u nnh, c, bp, c chua lm cho r khng pht trin c[9]. Vi cy la, nng Cd

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trong nc khong 0.32-0.43 mg/L gy suy gim thn, l, r v la cht 100% sau 21 ngy gieo.[2] 2.1.3 Cu: Cu l nguyn t vi lng cn thit cho c th sng. Lng Cu hp thu an ton cho ngi ln l 1.5-3.0 mg/ngy, tr em l 0.7-2.5 mg/ngy.[42] i vi ngi, ng c Cu thng qua ng n ung c th gy au bng, tiu chy, h huyt p, hoi t gan, xut huyt d dy, co gitthm ch hn m v cht. Nhim c Cu thng qua da gy nga, vim da. [42] Vi thc vt, cy trng thiu Cu thng c t l quang hp bt thng. Tha Cu do dng thuc dit nm, thuc tr su, phn bn CuSO4 lm cho Cu tch t trong t cng xy ra nhng triu chng ng c c th dn n cy cht.[1] 2.1.4 Ni: i vi ngi, cc triu chng ng c Ni quan st c nh chong vng, nn ma, au bng, tiu chy... Ht th niken carbonyl dn n au u, au ngc, bun nnsau l tm ti, th gp, c th t vong [43]. Hp cht Ni c th gy ung th phi, xoang mi, ph qun[17] 2.1.5 Pb: i vi con ngi, Pb hp thu vo c th tch t chnh ti 3 ni: mu, m mm v xng. Xng l ni tch t Pb nhiu nht. Pb gy nh hng n h tiu ha, h tim mch, thn kinh trung ng v ngoi bin, h min dch, h sinh sn[44]. Pb cng km hm chuyn ha Canxi bng cch trc tip hoc gin tip km hm s chuyn ha Vitamin D.[17] i vi cy la, Pb lm suy gim cc b phn thn, l, r. Lng Pb trong nc t 0.31 mg/L la cht 50%, 0.44 mg/L la cht 100%. Vi cy rau mung, nng Pb trong nc khong 5 mg/L lm r rau mung en v thi, gy cht mt s cy sau khi trng c 1 tun.[2] 2.1.6 Zn: Zn l nguyn t chnh cn thit cho c th, lng yu cu hng ngy l 5mg Zn/tr em v 15 mg Zn/ph n. Zn phn b nhiu tuyn tin lit, thn, gan, tim v tuyn ty.[46]

8

i vi ngi, ng c cp tnh Zn qua ng n ung biu hin nh nn ma, tiu chy, co tht c bng, thm ch xut huyt d dy[45]. Zn cn c kh nng gy ung th t bin, ng c h thn kinh, h sinh sn, h min dch. Tuy nhin, thiu ht Zn trong c th cng gy cc triu chng nh lit dng, teo tinh hon, m mu, vim da, bnh v gan[1] Vi thc vt, d tha Zn gy bnh mt dip lc t. S tch t Zn trong cy n qu c lin h n mc d lng Zn trong c th ngi v gp phn pht trin vic Zn b tch t trong mi trng, c bit l mi trng t.[1] 2.2 S tch ly kim loi trong mi trng t: Vi sc p dn s ngy cng tng ko theo s pht trin nhanh chng ca cc khu th, khu cng nghip, tng cng c s h tng giao thng lm cho ti nguyn t b khai thc mnh m v suy thoi ngy cng nghim trng. nhim lm t ngho dinh dng, ph hy cu trc t v lm o ln mi trng sinh thi. Mi trng t c quan h mt thit vi mi trng nc v khng kh nn nhim t c lin kt cht ch, tc ng qua li ln nhau vi nhim ngun nc v khng kh. Mt s nguyn nhn chnh gy nhim mi trng t n t hot ng nng nghip, hot ng cng nghip v cc khu dn c th. 2.2.1 Hot ng nng nghip: S dng phn bn v thuc bo v thc vt mt cch ba bi trong sn xut nng nghip l hai nguyn nhn chnh gy nhim mi trng t. 2.2.1.1 Phn bn: Phn bn ha hc gip gia tng nng sut, tuy nhin vic s dng lp li vi liu cao gy ra s nhim t bi cc tp cht kim loi c trong phn bn (bng 2.1), cc kim loi ny c th tch ly tng mt ca t, c th di ng xung mch nc ngm, c cy trng hp thu v i vo chui thc n ca con ngi.

9

Bng 2.1: Hm lng mt s kim loi trong phn bn.[2]Kim loi As B Cd Co Cr Cu Ni Pb Zn Phn ln (mg/kg) 2-1200 1-115 0.1-170 1-12 66-245 1-300 7-38 7-225 50-1450 Phn m (mg/kg) 2.2-120 0.05-8.5 5.4-12 3.2-19 7-34 2 15-566

Nhiu nghin cu ca cc nh khoa hc ti Argentina, NewZealand, Anh v x Wales, Ty Ban Nha chng minh rng vic s dng phn bn ha hc gy tch t kim loi nh As, Cd, Cr, Cu, Hg, Ni, Pb, Zn trong t.[26],[30],[39],[50]. Bn cnh phn bn ha hc th phn chung cng gy tch ly kim loi Cu, Zn, Mn[56]... S dng phn bn ha hc nc ta ngy cng tng v s lng, chng loi. Trong , s dng nhiu nht l phn m, ln v kali. Vic s dng phn bn ty tin, khng ng k thut, bn phn khng cn i v ch trng v m v cht lng phn bn khng m bo gy sc p ln n mi trng t nng nghip. Trn 50% lng m, 50% lng kali v khong 80% lng phn ln d tha gy nhim t.[4] Mt khc, hin nay c lng ln phn bn nhp lu khng c kim sot, thm ch c phn bn gi ang tn ti trn th trng. Lng phn bn ny gy tc ng xu v nh hng khng nh n mi trng t. 2.2.1.2 Thuc bo v thc vt: Vic lm dng thuc bo v thc vt trong canh tc nng nghip gy nhim nhiu vng t trn phm vi c nc. Lng nng dc s dng nc ta ngy cng tng. T nm 2000 n nay, trung bnh mi nm tiu th trn 30.000 tn thuc bo v thc vt thnh phm.[4] Theo kt qu kho st Trung Quc cho thy s hin din ca Cd, Hg, As trong t nng nghip ch yu l do thuc tr su v phn bn[55]. Ti Ty Ban Nha, nghin cu ca tc gi Eugenia Gimeno-Garca v cng s cng cho thy

10

vic s dng thuc tr su v tr c lm tng nguy c tch t cc kim loi Cd, Fe, Mn, Zn, Pb, Ni trong t[30]. Nng dc tch lu trong t, c bit l cc thuc c cha cc nguyn t nh Pb, As, Cu, Hg... c c tnh ln, thi gian lu li trong t di. Cc cht ny c th c cy trng hp thu, tch t v xm nhp vo c th ngi, ng vt thng qua lng thc, thc phm, dn n nhng tc ng xu n sc khe. 2.2.2 Hot ng cng nghip: Hot ng ca khu cng nghip tc ng mnh n mi trng ch yu thng qua cht thi rn v nc thi. 2.2.2.1 Cht thi rn: S m rng cc khu cng nghip lm gia tng ng k lng cht thi rn, lng cht thi nguy hi cng tng cao. Vic thu gom, vn chuyn v x l cht thi rn cn nhiu vn tn ng dn n gy nhim mi trng. Vic qun l bn t h thng x l nc thi cng cha cht ch. iu ng lo ngi l bn thi t h thng x l nc thi tp trung ca cc khu cng nghip cha c xem l cht thi nguy hi mc d cha nhiu thnh phn c hi, trong c nhiu kim loi nh: Cd, Cr, Cu, Pb, Ni, Zn, Hg[11],[56]... Thm ch mt s ni ti thnh ph H Ch Minh, bn thi cn c lm phn bn cho cy xanh trong khu cng nghip (khu cng nghip L Minh Xun), c lm phn compost (khu cng nghip Vnh lc), bn cho cc c s lm phn vi sinh (khu cng nghip Tn To)[8]... Chnh vic cn tn ng nhiu bt cp trong qun l ngun cht thi rn m dn n nhim mi trng ni chung v mi trng t ni ring. Mt minh chng v tc hi nghim trng ca cht thi cng nghip trong thi gian gn y l s c v h cha bn ti Hungary. Bn l cht thi ca qu trnh tinh ch qung bauxite, c cha nhiu kim loi c hi, cht phng x v kim cao. Kim trong bn c th tiu dit mt phn thm thc vt, lm h hi din tch t canh tc. c bit, khi chy xung sng, bn s lm cht mi sinh vt nh tm, c... S c ny l mt bi hc cng nh l li cnh bo cho cc d n khai thc bauxit ca nc ta hin nay.

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2.2.2.1 Nc thi: Theo kt qu nghin cu ca tc gi Phm Ngc Thy v cng s th ngun nc ti tiu b nhim kim loi c lin quan cht ch n s hin din kim loi trong mi trng t v trong cy trng[18]. Theo bo co hin trng mi trng quc gia, mt s lu vc sng ca nc ta b nhim t ngun nc thi ca cc khu cng nghip, trong c nhim kim loi nng[5],[8]. Thnh phn nc thi t cc khu cng nghip ph thuc vo c trng ngnh ngh ca cc c s sn xut. Nhm ngnh gy nhim kim loi tp trung vo khai thc, ch bin khong sn, luyn kim, c kh ch to my, dt nhum... Nc sng ng Nai, on t nh my nc thin Tn n Long i-ng Nai bt u nhim cht hu c v cn l lng, ng ch l pht hin hm lng Pb vt tiu chun loi A ca TCVN 5942-1995 (tng ng QCVN 24:2009/BTNMT). Hm lng Hg ti cng Vedan, cng M Xun vt 1.5-4 ln, Zn vt 3-5 ln so vi nc thi loi B ca TCVN 5942-1995. Ti Tp. HCM, h thng sng Si Gn cng b nhim nghim trng, ch yu l nhim cht hu c, vi sinh v mt s ni c du hiu nhim kim loi. Nhiu knh rch thuc thnh ph tr thnh knh nc thi nh: knh Tn Ha-L Gm, knh Tu H, knh Ba B, Tham Lng, Nhiu Lc... i vi lu vc sng Cu, nhim ch yu do ngnh ch bin khong sn v ngnh kim kh. on sng Cu chy qua thnh ph Thi Nguyn c mc nhim nghim trng nht v chu nh hng bi vi ngnh ch lc l luyn kim, cn thp, ch to my vi hai khu cng nghip ln l Thi Nguyn v Sng Cng. c im nc thi ca cc ngnh cng nghip ny cha nhiu du m, kim loi. S dng ngun nc nhim phc v ti tiu cho nng nghip gp phn lm tng nguy c nhim kim loi trong t v nng sn. 2.2.4 Cc khu dn c, th: S pht trin mnh m ca cc khu th ko theo cc nguy c nhim t t cht thi rn v nc thi.

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S bng n dn s ko theo tng lng cht thi rn sinh hot. Thiu cc bi chn lp v h thng x l nc r rc t yu cu. Vic thu gom cht thi cn nhiu bt cp, t l thu gom cht thi cn mc thp. Cht thi thng tp trung ra ng, cc mng, rnh, hoc xung sng, sui[5]. y l ngun gy nhim ng k n ngun nc mt, nc ngm v t. Cc khu th thng tp trung ngay cnh sng, hu ht nc thi sinh hot u khng c x l m trc tip ra sng, h, knh, rch.. vi s lng ln gy tc ng trc tip n cht lng nc sng. c bit l nc thi y t cha nhiu ha cht c hi, cht hu c v cc vi khun gy bnh. Tuy vy, ngun nc thi ny vn khng c x l trit , c x thng ra mi trng gp phn gy gia tng nhim ngun nc[5]. Sau , ngun nc ny li c s dng cho nng lm nghip, gy nhim t trng, nng sn.[18] Bn cnh , hot ng giao thng vn ti cng gp phn quan trng vo nhim t. Hot ng giao thng vn ti cn sinh ra bi kim loi nh Pb, Cd, Ni, Zn... Cc kim loi ny c xu hng tch t cao ti tng t mt, khu vc gn ng v gim dn cc tng t xa hn theo kt qu kho st ca tc gi Ali FalahiArdakani (bng 2.2).[29] Bng 2.2: Hm lng mt s kim loi nng trong t gn ng giao thng.Kim loi Cd Khong cch t ng giao thng (m) 8 16 32 8 16 32 8 16 32 8 16 32 Tng t (cm) 0-5 5-10 Hm lng (mg/kg) 1.45 0.40 0.22 4.70 2.40 2.20 522.0 378.0 164.0 172.0 66.0 54.0 0.76 0.38 0.20 1.00 0.92 0.62 460.0 260.0 108.0 94.0 48.0 46.0 10-15 0.54 0.28 0.20 0.81 0.60 0.59 116.0 104.0 69.0 72.0 42.0 42.0

Ni

Pb

Zn

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2.3 Phng php ICP-OES: 2.3.1 Gii thiu phng php ICP-OES: Nm 1964, ln u tin Stanley Greenfield c bi bo co v vic xc nh mt s nguyn t bng k thut pht x vi ngun kch thch l plasma. Bo co ca ng chng t rng ngun kch thch plasma c nhiu u im hn ngn la, h quang in. Ngun plasma c n nh cao, hn ch to thnh cc hp cht bn nhit, c kh nng kch thch mt s nguyn t m ngn la thng thng c nhit thp khng kch thch c. Tuy nhin ti thi im ny, ngun plasma cn nhiu hn ch, ch tt hn ph hp thu nguyn t ngn la trong vic xc nh cc nguyn t to hp cht bn nhit. n nm 1973, sau mt thi gian ci tin thit b v k thut th ngun plasma khng nh c u th ca mnh so vi cc ngun kch ph pht x trc . K t y, ICP thu ht c s quan tm ca nhiu nh nghin cu, to nn s pht trin mnh m ca ngun kch thch quang ph ny.[24] ICP-OES s hu c nhiu u im so vi F-AAS, GF-AAS nh ngun kch thch n nh, nh lng c khong trn 70 nguyn t, xc nh ng thi cc nguyn t, tc phn tch nhanh, nhy cao, khong tuyn tnh rng, t cn nhiu v xc nh c cc mu c hm lng mui ha tan n 20%.[27],[35],[46] Ngy nay, ICP-OES c ng dng rt rng ri, l cng c xc nh hm lng cc nguyn t trong cc lnh vc nh nng nghip v thc phm, sinh hc v y t, a cht, mi trng v nc, kim loi, hu c, ha cht v m phm.[24] 2.3.2 Nguyn tc o vi ICP-OES:[12],[13] Nguyn t hay ion nhn nng lng kch thch t plasma chuyn t trng thi c bn ln trng thi kch thch. Tuy nhin, trng thi kch thch ch tn ti trong thi gian rt ngn (khong 10-12 -10-8s), sau nguyn t hay ion phng thch nng lng hp thu di dng bc x tr v trng thi bn nht-trng thi c bn. Bc sng pht ra l c trng cho tng nguyn t hoc ion v cng vch pht x t l vi nng ca nguyn t hay ion c trong dung dch theo phng trnh sau:

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(*) Trong : I : cng vch pht x. C: nng nguyn t hoc ion cho cng pht x I. a: c gi l hng s thc ngim. b: l hng s bn cht, ph thuc bn cht tng nguyn t. Da vo phng trnh (*) nh lng mt nguyn t trong dung dch khi so snh cng vch pht x gy ra bi nguyn t ny trong dung dch vi cng pht x ca mt dy dung dch chun bit trc nng . 2.3.3 S lc cu to nguyn t v s xut hin ph pht x: Nguyn t bao gm mt ht nhn v m my electron chuyn ng theo qu o xung quanh to thnh lp v nguyn t. Trong lp v nguyn t, in t phn b thnh tng lp ng vi s lng t chnh (n) ca nguyn t, trong tng lp li c nhiu phn lp ng vi s lng t ph (l). Cc phn lp ny u c mc nng lng nht nh v cc electron sp xp vo cc phn lp ny tun theo nguyn l vng bn, in t chim v lm y nhng phn lp c mc nng lng t thp n cao. Trong iu kin bnh thng, nguyn t tn ti trng thi c nng lng thp nht c mc nng lng Eo gi l trng thi c bn. Khi nguyn t nhn c nng lng t bn ngoi, cc electron lp v ngoi cng hp thu nng lng v chuyn ln trng thi kch thch c mc nng lng Em cao hn. Qu trnh ny gi l qu trnh hp thu. Tuy nhin, s tn ti ca nguyn t mc Em rt ngn (khong 10-12 -10-8s), sau nguyn t phng thch nng lng hp thu di dng bc x tr v trng thi bn nht, trng thi c bn. Qu trnh ny gi l qu trnh pht x. Nu nguyn t hp thu nng lng ln, electron ngoi cng tch khi nguyn t, lc ny nguyn t thiu electron tr thnh ion dng. Ion cng c mc nng lng c bn E0i v mc nng lng kch thch Emi v do cng c hin tng hp thu, pht x nh nguyn t (Hnh 2.1).

15

Hnh 2.1: Cc qu trnh hp thu v pht x trong nguyn t v ion. a,b: hp thu nguyn t; c: ion ha; d: kch thch ion ; e: pht x ion; f,g,h: pht x nguyn t. S chnh lch nng lng hin qua phng trnh: gia mc kch thch v mc c bn c th

Trong :

h: hng s Plank. : tn s ca bc x. c: vn tc nh sng. : chiu di sng.

Cc mc nng lng

tng ng vi cc bc sng hp thu hay pht x c

trng ca mi nguyn t. S dng tnh cht ny nh lng cc nguyn t theo phng php quang ph hp thu hay quang ph pht x. 2.3.4 Ngun phng in plasma ICP v s kch thch ph trong plasma ICP: 2.3.4.1 Ngun phng in plasma ICP: Plasma l trng thi th 4 ca vt cht sau rn, lng v kh. Plasma l trng thi kh b ion ha mt phn hoc ton b, trong nng khng gian in tch dng v m l bng nhau hoc xp x bng nhau.[12],[28] Ngun phng in ICP c duy tr nh s tng tc gia nng lng ghp cp cm ng v bu kh tr b ion ha. Kh Ar c s dng thng dng nht. Cc bc hnh thnh ngn la plasma Ar c minh ha hnh 2.2.

16

Hnh 2.2: Qu trnh hnh thnh ngn plasma. Trc tin, kh Ar (nng lng ion ha 15.7596 eV) chy quanh torch thch anh (Hnh 2.2.a). My pht cao tn c tn s 27.12 MHz hoc 40.68 MHz s to nn mt t trng trong torch thch anh thng qua cun ng bao quanh pha trn torch (Hnh 2.2.b). Tip n, mt dng electron c bn vo t trng ny (Hnh 2.2.c), electron c tng tc bi t trng va p vo Ar lm sinh ra Ar+ v electron (Hnh 2.2.d), phn ng dy chuyn xy ra v to thnh ngn plasma Ar (Hnh 2.2.e).[27] Ngn plasma Ar c hnh git nc, nhit khong 6000-1000 oK. Cc vng v phn b nhit trong plasma Ar c m t hnh 2.3.(a)&(b)[27]

Hnh 2.3: Phn chia cc vng v nhit trong ngn plasma Argon.

17

Vng cm ng (IR) c hnh vnh khuyn, mu trng do Ar pht x. Vng gia nhit s b (PHZ) c chc nng desolvate ha, ha hi, nguyn t ha mu. Vng bc x (IRZ) s kch hot v ion ha mu. Vng phn tch (NAZ) cng c nhim v kch hot v ion ha mu, tn hiu pht x s o ti vng ny. 2.3.4.2 S kch thch ph trong plasma ICP: Dung dch mu c a vo plasma di dng sng kh. Di tc dng nhit ca plasma cc ht sng ny s b loi b dung mi tr thnh ht rn, cc ht rn b ha hi thnh dng kh v sau chuyn thnh nguyn t t do, ion. Nguyn t v ion nhn nng lng t plasma chuyn ln trng thi kch thch, sau l phng thch bc x tr v trng thi c bn.(Hnh 2.4)

Hnh 2.4: Cc qu trnh din ra khi mu c a vo plasma.

2.3.5 Cc b phn chnh ca thit b ICP-OES:[24] H thng ICP-OES c th c chia thnh cc b phn quan trng nh sau: h thng chuyn mu vo plasma, my pht cao tn RF, torch, h quang hc v ghi o tn hiu (detector).

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2.3.5.1 H thng chuyn mu vo plasma: H thng ny bao gm cc thnh phn nh: bm, b phun sng (neulizer) v bung phun (spray chamber). Bm c s dng chuyn mu t bnh cha n b phun sng v chuyn dung dch thi t bun phun ra ngoi. Dng bm nhm n nh tc ht mu, gim thiu nh hng do nht, t trng, sc cng b mt. B phun sng c nhim v chuyn mu t dng lng sang dng sng chuyn vo plasma. C nhiu dng nebulizer khc nhau nh: concentric nebulizer, cross-flow nebulizer, ultrasonic nebulizer.... Mi dng c hiu qu to sng khc nhau v c s dng theo s chn la ca k thut vin vn hnh my da trn c im, yu cu ca mu th. Nebulizer cng tt th to c kch thc ht sng cng nh v mt cng cao. Bung phun c nhim v loi b nhng ht sng c kch thc ln hn 10 m, c t gia nebulizer v torch. C hai dng bung phun thng dng l double-pass v cyclonic. 2.3.5.2 Torch: Torch bao gm hai ng thch anh kt hp vi injector to thnh h gm ba ng trn ng tm chuyn kh Argon v mu dng sng vo plasma. (Hnh 2.5).

Hnh 2.5: Cu to torch dng trong ICP-OES.

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Mt trong nhng nhim v chnh ca dng kh plasma l lm ngui thnh torch thch anh. Dng kh auxiliary c tc dng gn ngn plasma chm vo injector v gip dn aerosol mu vo plasma d dng hn. Dng kh nebulizer c nhim v chuyn mu dng sng vo plasma. Injector c nhiu loi, ty vo dng mu m s dng loi thch hp. Injector ceramic c tnh cht chng n mn, injector narrow-bore s dng vi dung mi hu c hay injector wide-bore cho mu c hm lng cht rn ha tan cao. 2.3.5.3 Ngun pht sng cao tn RF: Ngun pht cao tn c nhim v cung cp nng lng hnh thnh v duy tr ngn plasma.Nng lng c chuyn t my pht cao tn vo plasma thng qua cun ng bao quanh torch. Tn s dng trong ICP-OES l 27.12 MHz v 40.68 MHz. Tuy nhin, hin nay tn s 40.68 MHz rt c a chung do hiu qu chuyn nng lng vo plasma cao, v vy lm tng nhit ca plasma v ci thin c tnh n nh ca plasma. iu ny dn n gim bc x nn, ng ngha vi vic tng nhy ca thit b. Ngoi ra, tn s 40.68 MHz s to c ngn plasma mng hn so vi tn s 27.12 MHz, do lm gim hin tng t hp thu, gim cn nhiu v m rng khong tuyn tnh ca thit b. C hai dng my pht RF l crystal-controlled v free-running. Dng freerunning c u im ch to n gin, nh gn, gi thnh thp v p ng tt hn i vi s thay i tr khng ca plasma gy ra bi cc dung dch mu khi a vo plasma so vi dng crystal-controlled. 2.3.5.4 H quang hc v ghi o tn hiu: Bc x t vng NAZ c hi t vo khe vo ca b tch sng thng qua mt s gng v thu knh. B tch sng c nhim v phn tch cc tia bc x thnh cc tia n sc, sau chuyn cc tia ny n detector. C 2 cch thu nhn tn hiu t vng NAZ ca plasma l dc trc (axial viewing, hnh 2.6.a) hoc xuyn tm (radial viewing, hnh 2.6.b). Cc thit b ICP-OES c in thng thu tn hiu theo cch xuyn tm, tuy nhin hin nay mt s thit b ICP-OES kt hp c hai cch thu tn hiu trn cng thit b, c gi l dual-view. Vic chuyn i cch thu tn hiu t

20

dc trc sang xuyn tm hay ngc li c thc hin rt d dng bi phn mm iu khin ca thit b.

Hnh 2.6: Ch ly tn hiu ca ICP-OES: a. dc trc (axial viewing). b. xuyn tm (radial viewing). i vi thit b ICP-OES c in, thit b tch sng l cch t echellete (dng bc nhiu x bng 1), lng knh, knh giao thoa. Detector ghi nhn tn hiu l ng nhn quang in PMT. Vi thit b ICP-OES hin i, cch t nhiu x echelle c s dng cho phn tch bc x a sc thnh tia n sc nhiu bc. Vic s dng nhiu bc nhiu x ca cch t echelle (bc nhiu x > 1) gip h quang hc c phn gii cao. Cc dng detector c s dng nh PDA (photodiode array), CID (charge injection devides), CCD (charge coupled devides), SCD (segmented array charge coupled devides) ghi nhn tn hiu. Cc detector ny c u im l c th ghi ng thi nhiu bc sng v dng ti thp khi lm lnh do lm gim tn hiu nn. 2.3.6 Cn nhiu trong php o vi ICP-OES: Cc yu t nh hng n kt qu trong php o ICP-OES c th chia thnh 3 nhm: cn nhiu quang ph, cn nhiu vt l v cn nhiu ha hc.

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2.3.6.1 Cn nhiu quang ph: bao gm pht x ph nn v chng lp ph: a) Pht x ph nn:[24],[54] S pht x ph nn ph thuc ch yu vo thnh phn nn mu. Thng thng, cc nguyn t c nng cao gy ra bc x nn lin tc lm ng nn ca ph ca nguyn t cn phn tch b tri so vi hnh dng ph thu c t dung dch tinh khit ca nguyn t ny. Hin tng ny cn gi l s tri nn, c 2 dng l tri nn dng phng v tri nn dng dc. y l dng cn nhiu quang ph thng gp v d x l nht khi phn tch bng ICP-OES. C th dng bc sng phn tch khc khng b nh hng ph nn hay dng phn mm iu khin thit b, thm hai im c gi l background point vo hai bn chn peak cht cn phn tch. Cng ph nn c t ng o ti hai im ny v v vy ph nn s c tr i. b) Chng lp ph:[24,[54] Hin tng ny xy ra khi hai peak ca cc cht phn tch b chng ln ln nhau do thit b khng phn gii c hay trong nn mu c mt nguyn t hin din vi nng cao s xut hin cc vch ph c rng ln lm che lp vch ph ca nguyn t cn o. C hai dng l che lp ton phn v che lp mt phn. khc phc cn nhiu ny, cch hiu qu nht l chn mt bc sng khc khng b nhiu. Trng hp khng c bc sng khc thay th, c th dng k thut MSF c tch hp cng phn mm iu khin thit b lc tch ph. Khi s dng MSF, i hi ngi vn hnh thit b phi hiu r bn cht nn mu, xc nh ng cc tc nhn gy nhiu. Chuyn cc dung dch blank, cht phn tch, cht gy nhiu vo plasma ghi nhn hnh dng ph ca cc dung dch ny, sau khai bo vi phn mm iu khin to m hnh MSF cho nn mu. M hnh MSF s nhn din c hnh dng ph ca blank, ph ca nguyn t cn phn tch v nguyn t gy nhiu t vng ph b chng lp do tnh ton c chnh xc nng cht phn tch. (Hnh 2.5)

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Hnh 2.5: Cc thnh phn ca ph o c trong m hnh MSF. K thut MSF da trn nn tng hi qui a bin. Nguyn t cn phn tch c xem l mt bin s Y ph thuc, cc nguyn t gy nhiu l cc bin Xi c lp. C th biu din nh sau: Y = k0 + k1X1 + k2X2 + .+ knXn Cc bin X do ngi phn tch khai bo vi phn mm iu khin, do i hi k thut vin phi hiu r bn cht nn mu. Cc h s k do phn mm t ng tnh ton. Phn mm s s dng phng trnh thit lp tnh ton chnh xc nng nguyn t cn phn tch trong nn mu c cha tc nhn gy nhiu. 2.3.6.2 Cn nhiu vt l: bao gm nht v sc cng b mt ca dung dch, hiu ng t hp thu v hiu ng lu: a) nht v sc cng b mt ca dung dch:[33],[54] Yu t ny nh hng n vn tc chuyn mu vo b phun sng v hiu qu ca qu trnh to sng. Tc dn mu t l nghch vi nht ca dung dch. S khc nhau v nng acid, loi acid, thnh phn nn mu gy ra s chnh lch v nht, sc cng b mt gia dung dch mu v dung dch chun. loi b nh hng ny, c th dng cc bin php nh: phng php thm chun, lm cho nn mu v nn chun ging nhau, pha long mu, dng bm nhu ng bm mu vi tc c nh hoc dng ni chun. i vi phng php dng ni chun, nguyn t dng lm ni chun phi tha mn c cc yu t nh: Khng hin din trong nn mu hoc hin din vi nng bit trc chnh xc. C cng iu kin to trng thi kch thch nh nguyn t phn tch.

23

Khng lm nhim bn mu. Khng gy nhiu quang ph cho cc nguyn t phn tch. Hin din vi nng khong 500 n 1000 ln LOD hoc t 1 mg/L n 10 mg/L. Nguyn tc s dng ni chun nh sau: Ni chun c thm vo tt c dung dch blank, dung dch chun, dung dch mu cng mt nng . Nu cng ni chun trong Blank c k hiu l IIS Blank, trong dung dch chun v mu k hiu l IIS, cng cht phn tch l Ia. Khi khng c ni chun, nng C ca cht phn tch v Ia c biu din nh sau:

Khi s dng ni chun, C l mt hm ton hc ca IIS Blank, IIS, Ia:

Do Ia, IIS cng chu nh hng ging nhau nn Ia/ IIS s lm trit tiu cc nh hng ny dn n nng C c xc nh chnh xc. b) Hiu ng t hp thu:[13],[24],[54] L hin tng cc nguyn t hay ion c kh nng hp thu tia pht x do chnh nguyn t, ion cng loi khc pht ra. Hin tng ny hay xut hin vng ui ca plasma do vng ny c nhit thp hay khi nng cht phn tch qu ln. Hiu ng ny lm mt i mt phn bc x ca cht phn tch. loi b hiu ng ny, thit b c b tr mt vi phun lung kh c gi l shear gas (c th l N2 hay khng kh nn, khng s dng Argon) ct b vng ui c nhit thp ca plasma (Hnh 2.6).

24

Hnh 2.6: S dng Shear Gas loi b ui ca Plasma c) Hiu ng lu:[54] Do cht phn tch tch t li trn h thng dn mu, b phun sng, torch lm nhim bn cc mu khc khi xc nh nguyn t ny. Hin tng ph thuc bn cht tng nguyn t, dng tn ti ca nguyn t trong nn mu. Ra h thng dn mu v a mu vo plasma sau mi ln ht dung dch, thng thng thi gian ra khong 60s l . Tuy nhin, vi mt s nguyn t c hiu ng lu mnh th cn tng thi gian ny ln. 2.3.6.3 Cn nhiu ha hc:[24],[33],[54] Cn nhiu ha hc c th do s to thnh cc hp cht phn t trong plasma, cc hp cht d bay hi, s ion ha. Tuy nhin, vi ICP th cc nh hng ny khng ng k, c th kim sot d dng bng cch la chn iu kin vn hnh (cng sut cun cm RF, cch ly tn hiu), bng phng php thm chun hay lm cho chun v mu c thnh phn nn ging nhau. 2.4 Phn hy mu bng k thut vi sng (microwave): Vi sng l cc sng cc ngn c bc sng t 1mm n 1m. Tn s ca vi sng thng c s dng trong cng nghip, y t v khoa hc l 915 MHz, 2.450 MHz (tng ng bc sng 12.2 cm), 5.800 MHz v 22.125 MHz. Tn s 2.450 MHz c s dng nhiu nht trong thit b chun b mu cho phn tch bng AAS, ICP, GC v HPLC. Cc phng php phn hy mu truyn thng (v c ha t, v c ha kh) t nng mu bng cch truyn nhit t bn ngoi vo bn trong mu da trn cc hin tng dn nhit, i lu v bc x. Nhit c truyn vo mu thng qua s

25

tip xc trc tip hoc gin tip. Ngc li, khi t nng mu bng vi sng , nhit c sinh ra ng u ti mi im trong mu ni bc x vi sng tip cn. Nng lng vi sng c pht ra t mt ngun pht sng in t. Bn cht ca vi sng l sng in t gm 2 yu t: yu t t trng v yu t in trng. Qu trnh chuyn ho nng lng in t thnh nng lng nhit bao gm 2 c ch: c ch chuyn dn ion v c ch quay cc phn t. Nhit sinh ra do s chuyn dn ion nh l kt qu ca s tng tr khng ca mi trng nhm chng li s dch chuyn ca cc ion trong trng in t. Cn c ch quay cc phn t l qu trnh quay phn t phn cc theo s i hng ca in trng. S t nng bng k thut vi sng da trn s hp th trc tip nng lng vi sng ca mu, do vy cc hin tng nh dn nhit, i lu nhit v bc x nhit ch ng vai tr th yu trong qu trnh cn bng nhit. Ngy nay, k thut vi sng tr nn rt hiu qu v ng tin cy, c p dng cho nhiu ngnh, c bit l ngnh ho hc. N gip cho cc qu trnh phn hu mu nhanh hn v hiu qu, k c i vi cc phn ng ho hc phc tp. C th p dng k thut ny cho rt nhiu cc ng dng khc nhau nh bng 2.3.

Bng 2.3: Mt s v d so snh gia phn hy mu bng phng php c in v phng php vi sng.

26

CHNG 3: HOCH NH TH NGHIMPhn thc nghim c thc hin ti Phng Mi trng, Trung tm K thut 3. a ch: S 7, ng s 1, KCN Bin Ha 1, Tnh ng Nai. 3.1 Thit b-ha cht: 3.1.1 Thit b: - My quang ph pht x ca hng Perkin Elmer, model ICP-OES Optima 5300DV. (Hnh minh ha c trnh by trong ph lc A1). - L microwave ca hng Milestone, model ETHOS E Touch Control, cng sut cc i 1000 W, rotor HPR1000/6M. (Hnh minh ha c trnh by trong ph lc A 2). - Cn phn tch Mettler Toledo, model AB204-S, khong s dng: 10 mg220g, chnh xc 0,01 mg. - T sy Memmert, model UFE 400, nhit ti a 3000C, phn gii 0.50C. - Bnh nh mc, pipet cc loi. 3.1.2 Ha cht: - Chun 1000 mg/L (Accu Trace) cc nguyn t: As, Cd, Cr, Cu, Pb, Zn, Ni, Ca, K, Mg, Na, Si, Sc, Y. - Chun 10000 mg/L (Accu Trace) cc nguyn t: Al, Fe. - Acid (Merck): HNO3 65%, HCl 37%, HF, H3BO3. 3.2 Thc nghim: Trong phn thc nghim, ln lt trnh by cch thc hin kho st cc yu t nh sau: - Ti u thit b gm 2 thng s l cng sut RF v lu lng kh nebulizer. - Cn nhiu vt l, quang ph v cch loi tr. - X l mu. - nh tr phng php th. 3.2.1 Ti u thit b: Ti u 2 thng s quan trng nht nh hng n tn hiu ca cc nguyn t phn tch l cng sut RF v lu lng kh nebulizer. Cng sut RF lin quan trc

27

tip n nng lng kch thch cc nguyn t, lu lng kh nebulizer lin quan n lng dung dch mu c a vo plasma. Ti u 2 thng s ny gp phn tng nhy, gim c cn nhiu. Cc thng s khc nh lu lng Ar s dng cho cc dng aux v plasma, tc bm mu p dng theo mc nh ca thit b. a dung dch nng 1.0 mg/L ca cc kim loi cn phn tch vo plasma, ln lt thay i thng s cn kho st nh trong theo bng 3.1 (cp nht mi cc thng s ti u, gi nguyn cc thng s khc), ghi nhn cng cc peak xut hin. Bng 3.1: Cc gi tr kho st cng sut RF v nebulizer.iu kin ban u Cng sut RF (W) 1300 Gi tr kho st 1100; 1200; 1300; 1400 0.2; 0.4; 0.5; 0.6; 0.7; 0.8; 1.0; 1.2 -

Ar cho nebulizer (L/pht)

0.7

Ar cho plasma (L/pht) Ar cho aux (L/pht) Nebulizer Tc bm mu (ml/pht)

15 0.4 Cross flow-gem tip 1.3

3.2.2 Kho st cn nhiu: Cn nhiu quang ph v cn nhiu vt l l 2 dng thng gp khi phn tch mu vi ICP-OES. 3.2.2.1 Cn nhiu quang ph: Ln lt phun cc dung dch chun n nguyn t c nng nh trong bng 3.2 vo plasma, ghi nhn peak ca cc nguyn t. Sau khi c c ph ca cht phn tch v cc nguyn t chnh ca nn t, dng phn mm Winlab32 kim

28

tra s cn nhiu quang ph. Nu cc peak chng chp ln nhau hoc b tri nn th c cn nhiu quang ph. Bng 3.2: Thng s ca cc nguyn t cho kho st cn nhiu quang ph.Nguyn t As Cd Cu Ni Pb Zn Al Fe Ca Mg K Na Si Bc sng (nm) 188.979; 228.812 214.440; 228.802 324.752; 327.393 231.604; 232.003 220.353; 283.306 202.548; 206.200 Nng (mg/L) 0.5 0.1 0.5 0.5 0.5 0.1 500 500 100 100 100 100 100 Cc nguyn t chnh c trong nn t (Al, Fe, Ca, Mg, K, Na, Si). (Chun c pha trong HNO3 2%) Ghi Ch Cc nguyn t ti kho st (As, Cd, Cu, Ni, Pb, Zn). (Chun c pha trong HNO3 2%)

Hai dng cn nhiu quang ph thng gp nht l tri nn v cc peak chng ln nhau. Cch x l i vi hai dng ny nh sau: - Nn b tri: o cng bc x nn hai bn chn peak, phn mm WinLab32 s tr i phn nn b dng cao. - Cc peak chng chp ln nhau: Dng k thut MSF c tch hp cng vi phn mm WinLab32 nhn dng peak ca nguyn t phn tch v nguyn t gy nhiu, sau phn mm WinLab32 s tnh ton li nng ca cc cht phn tch. 3.2.2.2 Cn nhiu vt l: Thm chun ca cc nguyn t cn phn tch cc nng 0.03 mg/L; 0.1 mg/L; 0.5 mg/L vo 3 matrix m phng nn t trong bng 3.3. Mi nng thc hin 10 mu c lp. Sau , xc nh nng cc kim loi thm vo, tnh ton hiu sut thu hi trung bnh nh gi nh hng ca nn mu.

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Bng 3.3: Cc matrix m phng nn t. Nguyn t (mg/L) Al Fe Ca K Mg Na Si Matrix 1 100 100 20 20 20 20 20 Matrix 2 500 500 50 50 50 50 50 Matrix 3 1000 1000 100 100 100 100 100

Hiu sut thu hi tnh theo cng thc:

Trong :

Rec: hiu sut thu hi (%). C1: nng thm vo (mg/L). C2: nng ca Blank (mg/L). C3: nng tm c (mg/L).

Cn nhiu vt l ch yu l do thnh phn nn mu v nn chun khng ging nhau dn n khc nhau v nht v sc cng b mt lm cho tc chuyn mu vo plasma khng ging nhau. Phng php thng dng v hiu qu l s dng ni chun loi tr nh hng ny. ti s kho st 2 ni chun l Scandium (Sc), Yttrium (Y). Ni chun s c thm vo cc matrix c biu din trong bng 3.3 vi nng 1 mg/L. Tnh hiu sut thu hi nh gi ni chun. 3.2.3 X l mu: X l mu l mt yu t quan trng quyt nh trc tip n kt qu phn tch. Mu t cn phi c x l s b ng nht mu trc khi c phn hy chuyn t dng rn sang dng lng phc v cho vic phn tch trn thit b.

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3.2.3.1 X l s b mu t:[13] Cc mu t trng trt c thc hin ly mu theo tiu chun TCVN 4046:1985 v TCVN 5297:1995. Tuy nhin, trong lun vn ny tc gi khng thc hin ly mu hin trng. Cc mu t dng cho kho st c ly mu bi cc c quan chc nng bn ngoi v chuyn mu n Quatest 3 th nghim. Mu t c chun b s b theo s hnh 3.1.

Hnh 3.1: Chun b s b mu t

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Mu t m hin trng c dn mng thnh mt lp khng dy qu 15 mm trn mt mt knh thy tinh hoc khay nha sch, kh, khng gy nhim bn mu. khay mu vo t sy di 40oC trong 24h. Thng xuyn lm v cc khi ht ln, o trn mu trong thi gian lm kh. Loi b cc vt ngoi lai nh : , si, thy tinh, nha, r cyc kch thc ln hn 2mm v nht bng tay. Lm v tt c mu n cp ht nh hn 2mm, trn tht u v dn thnh mt lp mng trn mt ci khay nha sch, kh, khng gy nhim bn mu. Chia mu thnh 4 phn bng nhau, gp 2 phn i din, loi b 2 phn kia. Lp li vic chia t kt hp vi nghin nh mu bng ci v chy s n khi thu c mu th vi khi lng v cp ht cn thit cho qui trnh phn tch. 3.2.3.2 Kho st acid phn hy mu: ti kho st 3 loi acid kt hp vi microwave chit cc kim loi trong mu t:

HNO3 65%. (Tham kho ASTM D 5258-02[21], US EPA 3051A[52]) HNO3 65% + HCl 37%.(T l 3:1 theo th tch, US EPA 3051A[52]) HNO3 65% + HCl 37%.(T l 1:3 theo th tch, ISO 11466:1995[32]) Cn khong 0.4g mu t vo ng cha mu ca microwave, thm 10 mL ha

cht, yn qua m. Sau dng chng trnh nhit B (phn 3.2.3.3) phn hy mu bng microwave. ngui dung dch, lc b cht khng tan, thm ni chun (nu c), nh mc thnh 50 mL v xc nh kim loi bng ICP-OES. Tnh ton hm lng kim loi trong mu i vi tng loi acid s dng. Thc hin mu Blank: thm y tc cht nh mu tht v x l nh mu tht. Ngoi ra, h tr cho s so snh gia cc kt qu thu c trong giai on ny, chng ti c s dng hn hp acid HNO3 + HCl + HF (t l 1:3:1 theo th tch) phn hy hon ton nn mu bng chng trnh nhit E (phn 3.2.3.3).

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Cng thc tnh hm lng kim loi trong mu:

Trong : X: hm lng kim loi trong mu (mg/kg). Cx: lng kim loi trong dung dch mu xc nh t ng chun(mg/L). Cb: nng ca Blank (mg/L). Vdm: th tch nh mc (mL). m: khi lng cn (g). 3.2.3.3 Kho st chng trnh nhit phn hy mu vi microwave: Cc chng trnh nhit s dng cho microwave c trnh by trong bng 3.4. Bng 3.4: Chng trnh nhit cho microwave. Chng trnh Bc Cng sut (W) Nhit (0C) Thi gian 1 250 25-180 (pht) 8 A 2 1000 180 10 3 0 15 1 250 25-180 8 B 2 1000 180 15 3 0 15 1 250 25-180 8 C 2 1000 180 20 3 0 15 1 250 25-180 8 D 2 1000 180 30 3 0 15 1 250 25-180 8 2 1000 180 15 E 3(*) 0 15 4 300 180 5 5 0 15 (*): sau bc 3, ngui dung dch ri thm 2 mL H3BO3 bo ha trc khi thc hin bc 4. Chng trnh nhit A, B, C, D dng kho st kh nng chit cc kim loi khi nn mu. Chng trnh nhit E dng phn hy hon ton nn mu nhm cung cp thng tin v tng hm lng cc kim loi c trong mu kho st, gip s so snh v nh gi r rng hn v kh nng chit cc kim loi t nn mu ca cc chng trnh nhit A, B, C, D.

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3.2.4 nh tr phng php th: [20],[28],[36] i vi cc phng th nghim p dng tiu chun ISO/IEC 17025:2005, cc phng php c p dng cho mt dng mu th u phi thc hin vic nh tr phng php th. nh tr phng php th l qu trnh khng nh bng kim tra v cung cp bng chng khch quan v cc yu cu cho vic s dng phng php th c th trn nn mu c th c thc hin. Cc yu t quan trng cn thc hin khi nh tr mt phng php th nh sau: - Khong tuyn tnh. - LOD, LOQ. - Hiu sut thu hi - chch. - chm. - khng m bo o. Sau y s trnh by cch thc hin kho st cc yu t ny. 3.2.4.1 Khong tuyn tnh: Chuyn dung dch chun ca cc nguyn t t nng thp n cao vo plasma, ghi nhn cng peak ca dung dch, sau xy dng mi tng quan gia nng v cng peak ghi nhn. 3.2.4.2 LOD, LOQ: Xc nh hm lng cc kim loi kho st trong 20 mu c lp c nng cc nguyn t nh matrix 2 (phn 3.2.2.2). Da vo kt qu trung bnh Mean (mg/kg) v lch chun SD ca cc kt qu ny tnh ton LOD, LOQ theo cng thc sau: LOD (mg/kg) = Mean + 3*SD. LOQ (mg/kg) = Mean + 10*SD. 3.2.4.3 Hiu sut thu hi: Thc hin thm dung dch chun ca cc nguyn t kho st vo mu bit trc hm lng vi cc mc nng miu t trong bng 3.5.

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Bng 3.5: Hm lng cc nguyn t thm vo mu kho st. Nguyn t As Cd Cr Cu Ni Pb Zn Hm lng (mg/kg) Mc 2 12.5 6.25 12.5 12.5 12.5 12.5 12.5

Mc 1 3.75 1.88 3.75 3.75 3.75 3.75 3.75

Mc 3 25.0 12.5 25.0 25.0 25.0 25.0 25.0

Thc hin phn hy mu theo chng trnh chit ti u ti phn 3.2.3.3. Sau xc nh hm lng cc kim loi v tnh ton hiu sut thu hi. Tnh ton hiu sut thu hi:

Trong : Rec: hiu sut thu hi (%) Xx: hm lng kim loi trong mu (mg/kg). Xb: hm lng kim loi trong mu Blank (mg/kg). Xsp: hm lng kim loi thm vo mu Blank (mg/kg). 3.2.4.4 ng ca phng php: ng th hin s sai lch gia gi tr trung bnh ca mt lot kt qu o so vi gi tr qui chiu chp nhn. Thng thng ng c biu din thng qua chch (bias). chch thu c t s chnh lch gia hiu sut thu hi trong phn kho st 3.2.4.3 v gi tr qui chiu chp nhn (gi tr qui chiu xem nh 100%). 3.2.4.5 chm ca phng php: chm ca mt phng php th hin mc phn tn gia cc kt qu th nghim c lp trn mt mu. chm thng c biu din qua hai thnh phn l lp li v ti lp.

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Thc hin thm chun nh phn 3.2.4.3 vi hai k thut vin khc nhau. Dng hm thng k anova x l kt qu thu c. 3.2.4.6 khng m bo o ca phng php: khng m bo o uc c tnh t chch (bias) v ti lp ni b phng th nghim (Rw) theo cng thc sau:

khng m bo o m rng U c tnh theo biu thc di y: U = k*uc , vi k=2, tin cy 95%

36

CHNG 4: KT QU - THO LUN4.1 Ti u ha thit b: Ti u 2 thng s lin quan trc tip n tn hiu ca cc nguyn t l: Cng sut RF. Lu lng kh nebulizer.

Ti u 2 thng s ny s gp phn lm tng nhy, gim cn nhiu. 4.1.1 Cng sut RF: Kt qu kho st cng sut RF nh hng n tn hiu cc nguyn t c trnh by trong hnh 4.1.(a) v 4.1.(b).(a)

(b)

Hnh 4.1.(a) nh hng cng sut RF n tn hiu cc nguyn t As, Ni, Pb. (b) nh hng cng sut RF n tn hiu cc nguyn t Cd, Cu, Zn.

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Nhn xt: Khi tng cng sut RF, tn hiu cc nguyn t u tng vi mc khc nhau ty thuc tng nguyn t, tng bc sng. Tng cng sut RF, tc tng nng lng ca plasma dn n c nhiu nguyn t hay ion c kch thch ln trng thi kch thch. Do , cng pht x s mnh hn nn cng o c cao hn. Cn c theo kt qu thu c, chn cng sut RF l 1400 W cho qui trnh phn tch. 4.1.2 Lu lng kh nebulizer: Kt qu kho st lu lng kh nebulizer c trnh by hnh 4.2.(a) v 4.2(b).

(a)

Hnh 4.2.(a): nh hng ca lu lng kh nebulizer n tn hiu cc nguyn t As, Ni, Pb.

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Hnh 4.2.(b): nh hng ca lu lng kh nebulizer n tn hiu cc nguyn t Cd, Cu, Zn. Nhn xt: - Ngoi tr Cu, cc nguyn t cn li u cho tn hiu cc i ti lu lng nebulizer 0.6 L/pht. Chn lu lng nebulizer l 0.6 L/pht. - Tm li, iu kin vn hnh thit b ICP-OES Optima 5300DV nh trnh by trong bng 4.1. Bng 4.1: Cc thng s vn hnh ICP-OES 5300DV Cng sut RF (W) Kh auxilay (L/pht) Kh plasma (L/pht) Kh nebulizer (L/pht) Dng nebulizer Dng spray chamber Tc bm mu (mL/pht) 1400 0.4 15 0.6 Cross flow-gem tip Double pass 1.3

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4.2 Kho st cn nhiu: 4.2.1 Cn nhiu quang ph: Thc hin kho st nh phn 3.2.2.1. S dng phn mm WinLab32 cho hin th ph cc nguyn t kho st cng mt ca s kim tra cn nhiu quang ph. Nu peak ca cc nguyn t b chng lp ln nhau hoc ng nn ca cc peak khng trng khp nhau th xem l c cn nhiu quang ph. Kt qu kho st c biu din trong bng 4.2. Bng 4.2: Bng tm tt cn nhiu quang ph.Cc nguyn t gy nhiu Al As 188.979 As 228.812 Cd 214.440 Cd 228.802 Cu 324.752 Cu 327.393 Ni 231.604 Ni 232.003 Pb 220.353 Pb 283.306 Zn 202.548 Zn 206.200 Tri nn Tri nn Tri nn Tri nn Fe Tri nn Tri nn Chng peak Tri nn Chng peak Tri nn Tri nn Tri nn Chng peak Chng peak Ca K Mg Na Si As Cd Chng peak Cu Ni Pb Zn -

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Mt s ph cn nhiu in hnh i vi cc nguyn t c trnh by ti ph lc B.

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Nhn xt: - Nguyn t gy nh hng nhiu nht l Al v Fe. Cc nguyn t nh Ca, K, Mg, Na, Si khng gy nh hng hoc nh hng khng ng k i vi cc nguyn t m ti nghin cu. - Cn nhiu quang ph thng dng nht l hin tng tri nn gy ra do cc nguyn t tn ti vi hm lng cao trong nn mu nh Al, Fe. y l dng cn nhiu thng gp khi phn tch vi ICP-OES v l loi d x l nht. - Hin tng chng peak cng xut hin nh: Cd 214.440, Cu 324.752, Zn 206.200 b nh hng bi Fe, Cd 228.802 v As 228.812 nh hng ln nhau. - Trong ti ny, u tin s dng cc bc sng chu t nh hng nht t nn mu. Do , cn c vo bng 4.2 xut s dng cc bc sng c trnh by trong bng 4.3 cho qui trnh phn tch. Bng 4.3: Cc bc sng ca cc nguyn t s dng cho qui trnh phn tch. Nguyn t As Cd Cu Ni Pb Zn Bc sng (nm) 188.979 214.440 327.393 231.604 220.353 202.548 Trng thi kch thch I (nguyn t) II (ion) I II II II Nng lng ion ha (eV) 9.7886 8.9938 7.7264 7.6398 7.4167 9.3942

- Da theo kt qu c trnh by trong bng 4.2 v cc vch ph c chn bng 4.3, qui trnh phn tch vn gp phi cn nhiu quang ph nn phi thc hin kho st phi loi tr. Dng tri nn hu nh c hiu chnh rt d dng, phn mm t ng o cng pht x ti hai pha peak ca nguyn t cn phn tch v sau ph nn s c tr i. Dng chng lp peak th i hi k thut phc tp hn, trong ti ny s dng k thut MSF c tch hp trong WinLab32 tch bit peak ca nguyn t Cd214.440 v nguyn t

41

gy nhiu Fe, t s tnh ton c nng chnh xc ca nguyn t Cd. Kt qu kho st s c trnh by trong phn 4.2.3. 4.2.2 Cn nhiu vt l: Cn nhiu thng gp nht l c s chnh lch v thnh phn gia nn ca dung dch chun v dung dch mu th khng ging nhau. Thc hin kho st nh phn 3.2.2.2, kt qu c trnh by trong bng 4.4. Bng 4.4: Kho st cn nhiu vt l.Nn mu Nng As Cu, Ni, Pb, Zn (mg/L) 0.03 0.1 0.5 0.03 0.1 0.5 0.03 0.1 0.5 Nng Cd (mg/L) 0.015 0.05 0.25 0.015 0.05 0.25 0.015 0.05 0.25 Rec (%) As 97.7 97.6 98.2 87.4 90.0 97.4 85.4 89.2 95.1 Cd 120.4 108.1 101.3 136.0 112.2 98.9 147.6 116.5 100.1 Cu 96.5 102.9 97.8 98.7 103.0 101.3 91.4 94.2 97.3 Ni 93.7 98.8 99.1 93.9 96.2 96.8 88.1 91.9 92.6 Pb 93.7 95.8 100.2 88.1 92.1 94.6 85.7 89.1 93.2 Zn 91.7 101.8 99.8 89.2 91.1 97.4 86.3 90.2 94.1

Matrix 1

Matrix 2

Matrix 3

Nhn xt: Vi matrix 1, nng cc nguyn t nn (Al, Fe, Ca, Na, K, Mg, Si) thp nn khng gy nh hng hay cha xut hin cn nhiu i vi cc nguyn t As, Pb, Ni, Zn. Vi matrix 2 v 3, nng cht nn tng ln, s chnh lch thnh phn gia dung dch chun v dung dch mu cng tng cao gy ra cn nhiu lm gim tn hiu cc nguyn t As, Pb, Ni, Zn. nh hng ny cng mnh khi nng nn tng cao v nng cht kho st thp. Vi Cd, cc matrix nn mu c nh hng ng k vi nng Cd thp, lm tng tn hiu Cd ti nng Cd 0.015 v 0.03 mg/L. nng Cd 0.25 mg/L, khng thy s tng tn hiu ca Cd na. Tn hiu ca Cu khng b nh hng khi tng nng cc nguyn t nn.

42

Vic tng hoc gim tn hiu cc nguyn t phn tch khi tng nng cc cht nn c th do cn nhiu vt l hay quang ph. Vn ny s c lm r trong phn loi tr cn nhiu. 4.2.3 Loi tr cn nhiu: 4.2.3.1 Cn nhiu vt l: Kt qu kho st loi tr cn nhiu vi hai ni chun Scandium (Sc, nng lng ion ha 6.5615 eV, bc sng 360.073 nm) v Yttrium (Y, nng lng ion ha 6.3173 eV, bc sng 371.029 nm) c biu din trong bng 4.5.(a) v 4.5(b). Bng 4.5.(a): Kho st loi tr cn nhiu vt l vi ni chun Sc 360.073.Nn mu Nng As Cu, Ni, Pb, Zn (mg/L) 0.03 0.1 0.5 0.03 0.1 0.5 0.03 0.1 0.5 Nng Cd (mg/L) 0.015 0.05 0.25 0.015 0.05 0.25 0.015 0.05 0.25 Rec (%) As 97.7 97.6 98.2 95.2 95.1 98.1 94.6 95.9 97.2 Cd 121.8 111.0 99.2 138.7 115.3 99.4 151.0 119.0 102.1 Cu 96.5 102.9 97.8 96.7 99.2 98.1 95.8 103.7 102.3 Ni 93.7 98.8 99.1 95.6 96.6 97.2 91.8 94.7 96.1 Pb 93.7 95.8 100.2 94.5 94.7 97.8 96.3 97.2 96.8 Zn 91.7 101.8 99.8 93.1 96.4 96.9 93.8 94.1 94.8

Matrix 1

Matrix 2

Matrix 3

Bng 4.5.(b): Kho st loi tr cn nhiu vt l vi ni chun Y 371.029.Nn mu Nng As Cu, Ni, Pb, Zn (mg/L) 0.03 0.1 0.5 0.03 0.1 0.5 0.03 0.1 0.5 Nng Cd (mg/L) 0.015 0.05 0.25 0.015 0.05 0.25 0.015 0.05 0.25 Rec (%) As 95.3 96.0 98.2 96.1 94.3 97.9 95.4 95.2 96.3 Cd 122.7 109.2 102.0 139.6 113.1 103.0 150.4 120.8 98.1 Cu 96.1 98.4 98.1 95.2 97.8 97.1 93.2 94.1 96.6 Ni 94.0 96.2 101.0 95.7 94.5 96.1 94.2 97.9 95.3 Pb 92.8 94.0 97.9 92.9 95.9 97.8 91.1 94.7 96.1 Zn 92.7 95.5 97.1 92.7 97.0 98.1 94.9 93.3 96.4

Matrix 1

Matrix 2

Matrix 3

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Nhn xt: Khi s dng ni chun Sc, Y tn hiu ca cc nguyn t As, Cu, Ni, Pb, Zn khng b nh hng ca cc matrix kho st. Hiu sut thu hi ca cc nguyn t ti cc nng kho st rt tt chng t ni chun loi b c nh hng do s khc bit v thnh phn nn gia cc dung dch kho st. C 2 ni chun u cho kt qu tt, do c th s dng Sc, Y lm ni chun cho qui trnh phn tch m ti nghin cu. Vic s dng ni chun cng lm tn hiu Cd c nng cao hn ti 2 nng Cd 0.015 v 0.05 mg/L. iu ny cho thy s dng ni chun khng loi b c ht nh hng ca matrix nn i vi Cd v ngoi nh hng vt l, Cd b chng peak bi Fe c trong matrix kho st v nh hng ny tng i mnh khi nng Cd thp. 4.2.3.2 Cn nhiu quang ph: Theo kt qu phn 4.2.1, cn nhiu chng peak ch xy ra vi Cd 214.440 nm. V vy, ch nghin cu loi tr cn nhiu vi nguyn t ny. Thc hin kho st nh 3.2.2.1 kt hp vi kt qu t 4.2.3.1 s c kt qu trnh by trong bng 4.6. Bng 4.6: Cn nhiu i vi Cd 214.440.Nn mu Nng Cd (mg/L) 0.015 0.05 0.25 0.015 0.05 0.25 0.015 0.05 0.25 Rec (%) Khng IS 120.4 108.1 101.3 136.0 112.2 98.9 147.6 116.5 100.1 IS Sc 121.8 111.0 99.2 138.7 115.3 99.4 151.0 119.0 102.1 IS Y 122.7 109.2 102.0 139.6 113.1 103.0 150.4 120.8 98.1 IS Y + MSF 94.7 96.8 97.1 101.0 95.0 97.1 103.0 96.5 96.9

Matrix 1

Matrix 2

Matrix 3

44

Nhn xt: Ni chun ch loi tr c cn nhiu vt l, khng loi tr c nh hng quang ph. Khi dng MSF kt hp vi ni chun Y gip gii quyt trit cn nhiu quang ph v cn nhiu vt l i vi Cd 214.440. Tm li, qui trnh phn tch cc nguyn t m ti kho st cn s dng n ni chun Y v k thut MSF loi b mt s cn nhiu gy ra bi cc nguyn t c s c trong nn mu t. 4.3 Kho st acid chit cc nguyn t trong mu t: Trc khi thc hin phn tch, cn phn hy mu chuyn cc nguyn t cn phn tch v dng tan trong dung dch thch hp. Cc cch phn hy thng dng nh kim chy, s dng cc acid hay hn hp cc acid v c kt hp vi cc ngun nhit nh: bp cch thy, bp cch ct, bp in... ha tan nguyn t cn phn tch. Cc k thut ny c mt s hn ch nh cn nhiu thi gian, nhn lc, s dng nhiu ha cht, d mt cht phn tch, nguy c nhim bn cao...[25],[47],[48] Hin nay, k thut phn hy mu bng microwave khc phc c nhng yu im va nu v c p dng rng ri trong phn tch nhiu loi mu nh thc phm, nc, rau qu, t, trm tch...K thut ny c u im l thi gian phn hy mu ngn, t tiu tn ha cht, hn ch nhim bn, d kim sot ... [25],[47],[48]. Tip tc xu hng pht trin ny, lun vn cng s dng k thut microwave chun b mu th nghim. ha tan hon ton cc kim loi c trong nn mu t th cn s dng n acid HF nhm ph v lin kt kim loi vi cu trc silicate. Tuy nhin, v HF rt c hi nn hn ch s dng trong qui trnh phn tch thng thng. Mt khc, phn kim loi lin kt cht ch vi silicate trong nn mu t khng c tnh linh ng v th sinh vt khng hp thu c, do phn kim loi ny hu nh khng gy nh hng n cht lng t. Theo quan im ny, cc nh khoa hc mi trng ch yu quan tm n phn kim loi c tnh linh ng, c th chit tch khi nn t bi cc acid v c khc HF. Phn kim loi cn li kt cht vo nn silicate ng vai tr th yu, khng quan trng.[25],[49]

45

Hin nay, c nhiu tiu chun quc t hng dn vic phn hy mu t. Tuy nhin, cc loi acid v thnh phn acid s dng cho phn hy mu trong cc tiu chun ny th khng thng nht vi nhau. Tiu chun ISO 11466:1995[32] dng hn hp nc cng thy chit kim loi t mu t c dng rt thng dng. Kt qu nghin cu cc tc gi M.Bettinelli[23], M.Cheng[26], J.Sastre[48] v cng s cho thy rng nc cng thy c kh nng chit tch c phn ln mt s kim loi nh As, Cd, Cu, Ni, Pb, Zn, Mn...vi hiu sut thu hi khong 89% -110% i vi nn mu t, trm tch. Bn cnh cng tn ti mt s tiu chun khc nh ASTM D5258-02[21], US-EPA 3050B[51], US-EPA 3051A[52], US-EPA 3052[53] s dng acid HNO3 hay hn hp HNO3 v HCl vi t l khc ISO 11466:1995 chit kim loi trong mu t, trm tch. Do , ti cn phi kho st li cc loi acid cho phn hy mu chun ha qui trnh phn tch. S dng cc loi acid nh c trnh by phn 3.2.3.2. Kt qu kho st c biu din trong bng 4.7 v hnh 4.3, 4.4. Bng 4.7: Hm lng kim loi v hiu sut thu hi khi phn hy mu t bng cc acid khc nhau.Acid (mL) HNO3 HCl HF As Hm lng trong mu (mg/kg) Cd Cu Ni Pb Zn As Cd Rec (%) Cu Ni Pb Zn

10 7.5 2.5 2

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9.96

0.06 25.67 25.78 26.33 81.83

72.1 0.0 78.2 78.4 97.3 82.5 85.9 0.0 82.0 88.6 99.9 82.4 94.1 0.0 84.2 92.4 95.4 89.8

11.86 0.00 26.89 29.16 27.03 81.70 12.99 0.00 27.62 30.39 25.82 89.10 13.81 0.00 32.81 32.90 27.07 99.18

46

Hiu sut thu hi ca cc acid chit so vi tng phn hy mu :

Hnh 4.3: So snh hm lng cc kim loi trong mu t thu c i vi cc loi acid khc nhau.

Hnh 4.4: Hiu sut chit cc kim loi khi nn mu t i vi cc acid khc nhau.

47

Nhn xt: - Do mu t dng cho kho st khng cha Cd nn khng th nh gi kh nng chit Cd khi nn mu ca cc dng acid s dng. y l mt trong nhng khuyt im ca ti nghin cu. - i vi Pb, hiu qu chit tt nht i vi hn hp HNO3:HCl (3:1), hiu qu thp nht i vi dung dch HNO3:HCl (1:3). Tuy nhin vi hiu sut chit Pb l 95.4% th dung dch cng thy cng p ng rt tt c mc tiu ca ti. - Dung dch nc cng thy chit c cc kim loi (ngoi tr Cd, Pb) khi nn mu t l tt hn hai dng acid cn li. Hm lng cc kim loi chit tch c bng dung dch cng thy rt gn vi tng hm lng kim loi c trong mu. iu ny c th gii thch do tnh oxi ha mnh ca nc cng thy nn kh nng ha tan cc kim loi tt hn hai dng acid cn li. - Dng acid m ASTM D 5258-02, US EPA 3051A hng dn p dng c hiu qu chit cc kim loi khi nn mu t m ti nghin cu km hn nc cng thy. - Tng hp cc nhn xt nu, trong ti ny chn hn hp nc cng thy-HNO3:HCl (1:3 theo th tch) cho vic chit cc kim loi khi nn t. La chn ny cng ph hp vi kt qu thc nghim ca cc tc gi: M.Bettinelli[23], M. Cheng[25], C.Y. Zhou[58]. 4.4 Kho st chng trnh nhit cho microwave: Kt qu kho st chng trnh nhit cho microwave c th hin trong bng 4.8 v hnh 4.5. Bng4.8 : Hm lng cc kim loi trong mu t thu c vi cc chng trnh nhit khc nhau.Chng trnh nhit A B C D As 12.66 12.79 12.36 10.90 Hm lng trong mu (mg/kg) Cd Cu Ni Pb 0.00 25.73 30.67 25.12 0.00 25.24 30.15 24.18 0.00 25.77 30.60 24.64 0.00 24.86 27.52 24.86 Zn 86.27 92.61 87.55 80.52

48

Hnh 4.5: So snh hm lng cc kim loi thu c vi cc chng trnh nhit khc nhau. Nhn xt: Cc chng trnh nhit A, B, C, D ch khc nhau thi gian ti bc 2 (bng 3.4, phn 3.2.3.3) ln lt tng ng l 10, 15, 20, 30 pht. Nhn chung, kt qu thu c t 3 chng trnh nhit A, B, C gn ging nhau v tt nht l chng trnh B. Kt qu thu c t chng trnh D l xu nht, c bit l vi nguyn t As, Ni, Zn chnh lch nhiu so vi chng trnh B: As gim 16%, Ni gim 10 %, Zn gim 15%. iu ny c th gii thch l do thi gian ti bc 2 ca chng trnh D di gp i thi gian chng trnh B nn dn n tht thot mu phn tch. Thi gian ti u chit cc kim loi l 15 pht. iu ny ph hp vi kt qu kho st ca tc gi C.Y. Zhou[58]. Do , chn chng trnh B p dng cho qui trnh phn tch m ti nghin cu. p dng cc iu kin ti u ca thit b, phng php loi loi tr cn nhiu, acid phn hy mu v chng trnh nhit cho microwave va kho st tin hnh hon thin qui trnh thng qua kho st cc thng s nh LOD, LOQ, hiu sut thu hi, chch, lp li v ti lp.

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4.5 nh tr phng php th: 4.5.1 Khong tuyn tnh: Kho st khong tuyn tnh cho kt qu nh c biu din trong bng 4.9. Bng 4.9: Khong tuyn tnh.Nguyn t As Cd Cu Ni Pb Zn Khong tuyn tnh tnh theo dung dch chun (mg/L) 0.020 - 5.0 0.005 2.5 0.020 - 5.0 0.020 - 5.0 0.020 - 5.0 0.020 - 5.0 Khong tuyn tnh tnh theo hm lng trong mu (mg/kg) 2.5 - 625 0.62 - 312 2.5 - 625 2.5 - 625 2.5 - 625 2.5 - 625

4.5.2 Gii hn pht hin, gii hn nh lng: LOD, LOQ ca cc kim loi trong nn t c trnh by trong bng 4.10. (S liu kho st c trnh by trong ph lc D). Bng 4.10: Gii hn pht hin, gii hn nh lng ca cc kim loi trong nn mu t.Nguyn t As Cd Cu Ni Pb Zn LOD (mg/kg) 0.73 0.15 0.80 0.28 0.73 1.64 LOQ (mg/kg) 2.42 0.51 2.67 0.69 2.43 2.80

4.5.3 Hiu sut thu hi, chch, lp li v ti lp: Kho st hiu sut thu hi ca cc kim loi trn mu thm chun ti 3 mc hm lng nh sau: 1.85 mg/kg; 6.2 mg/kg; 12.4 mg/kg i vi Cd. 3.7 mg/kg; 12.4 mg/kg; 24.8 mg/kg i vi As, Cu, Ni, Pb, Zn.

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T cc d liu thu c s tnh ton c hiu sut thu hi, chch, lp li v ti lp ca qui trnh phn tch nh c biu din trong bng 4.11 v 4.12. (Bng s liu v cch tnh ton c trnh by trong ph lc E1 n E4 v F1 n F2). Bng 4.11: Kt qu xc nh cc kim loi trong mu thm chun ti 3 mc hm lng khc nhau.Mc hm lng 1 (mg/kg) Hm lng Hm lng thm vo tm c Mc hm lng 2 (mg/kg) Hm lng Hm lng thm vo tm c Mc hm lng 3 (mg/kg) Hm lng Hm lng thm vo tm c

Nguyn t

As Cd Cu Ni Pb Zn

3.70 1.85 3.70 3.70 3.70 3.70

3.34 0.71 1.82 0.13 3.61 0.54 3.52 0.30 3.49 0.44 3.26 0.55

12.40 6.20 12.40 12.40 12.40 12.40

11.2 2.6 6.14 0.43 13.2 2.0 12.28 0.98 11.7 1.4 11.4 1.9

24.80 12.40 24.80 24.80 24.80 24.80

22.8 4.8 11.53 0.81 25.5 3.8 23.0 1.8 23.0 2.8 22.1 3.9

Bng 4.12: Hiu sut thu hi, chch, lp li v ti lp ca kim loi trong mu thm chun ti 3 mc hm lng khc nhau.Mc hm lng 1Nguyn t Rec (%) Bias (%) r (%) R (%)

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As Cd Cu Ni Pb Zn

90.2 98.4 97.6 95.0 94.4 88.1

-9.8 -1.6 -2.4 -5.0 -5.6 -11.9

7.8 3.0 11.7 8.8 3.9 28.1

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-9.7 -1.8 6.0 -0.99 -5.4 -9.3

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-8.0 -7.8 2.7 -7.3 -7.3 -10.9

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Nhn xt:-

Hm lng tm c tha mn vi hm lng tnh ton l thuyt ti 3 mc hm lng thm chun trn nn mu t. Hiu sut thu hi t 88% 106%v chch nh hn 12% cho cc nguyn t m ti kho st. lp li v ti lp ti 3 mc hm lng thm chun kh tt cho hu ht cc nguyn t (di 12%) ngoi tr Zn ti mc hm lng 1c lp

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li v ti lp kh ln. i vi Zn ti mc hm lng 1 c th do d b nhim bn nn kt qu kho st c s phn tn rng. Chng ti cng thc hin so snh kt qu thu c bng ICP-OES ti mc nng 2 vi k thut hp thu nguyn t . Kt qu so snh c trnh by nh bng 4.13. Bng 4.13: Kt qu xc nh cc kim loi trong mu thm chun ti mc nng 2 vi ICP-OES v AAS.Hm lng thm vo (mg/kg) Hm lng tm c (mg/kg) ICP-OES 11.2 6.14 13.2 12.28 11.7 11.4 AAS 9.91 11.39 10.92 9.66 10.04 Hiu sut thu hi (%) ICP-OES 90.3 98.2 106.2 99.1 94.6 91.7 AAS 79.9 91.9 88.1 77.9 81.0

Nguyn t

As 12.40 Cd 6.20 Cu 12.40 Ni 12.40 Pb 12.40 Zn 12.40 (-: khng thc hin)

K thut chi tit s dng xc nh cc nguyn t vi AAS nh sau: Nguyn t As Cd Cu Ni Pb Zn K thut xc nh HG-AAS F-AAS F-AAS F-AAS F-AAS

Theo kt qu c biu din trong bng 4.13 cho thy rng : - Ch c Cu cho kt qu tng thch gia ICP-OES v AAS. Vi Cd, ti mc nng kho st khng th nh lng trc tip c vi F-AAS do hn ch v nhy. Vi As, mc d dng k thut HG-AAS nhng hiu sut thu hi vn thp hn ICP-OES do nn mu qu phc

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tp dn n nh hng hiu sut vic to hydride. Cc kim loi cn li cng cho hiu sut thu hi thp do thnh phn nn mu v nn chun khng ging nhau a n hiu sut phun sng ca dung dch mu v chun vo bun phun sng khc nhau. - ICP-OES c th xc nh ng thi cng mt lc cc nguyn t nhng vi F-AAS phi xc nh ring l tng nguyn t. Mt khc, vi As v Cd th k thut phn tch F-AAS thng thng khng th xc nh c do hn ch v nhy. khc phc nhc im ny phi s dng k thut c nhy cao hn (v d: HG-AAS, GF AAS) dn n tiu tn nhiu thi gian, ha cht, nhn lc...cng nh phi trang b thm cc thit b ph tr. - V tng qut cho thy s dng ICP-OES c nhiu u th trong phn tch mu hn so vi AAS. 4.5.4 khng m bo o: khng m bo o m rng c tnh ton ng vi mc tin cy 95%, h s ph k=2 c trnh by bng 4.14. Bng 4.14: khng m bo o ca cc nguyn t trn nn t.Nguyn t As Cd Cu Ni Pb Zn khng m bo o (%) (mc tin cy 95%, k=2) 21 7 15 8 12 17

(Cch c lng khng m bo o c minh ha trong ph lc D1, D2 v G).

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4.6 p dng qui trnh phn tch mu tht: Cc dung dch chun s dng cho phn tch mu tht c nng nh trnh by hnh 4.6

Hnh 4.6: Cc dung dch chun dng cho phn tch mu. Trong khong thi gian t 22/7/2010 n 18/8/2010, p dng phng php c nh tr xc nh cc kim loi trong 26 mu t phc v cho mc ch trng trt. Mi l mu thc hin mt mu thm chun vo nn mu bit trc hm lng - mu QC kim sot qu trnh chun b mu. Kt qu xc nh cc kim loi thu c nh bng 4.15. (ng chun v ph ca cc nguyn t c minh ha trong ph lc C1 n C6. Hm lng nguyn t gy nhiu ch yu l Al, Fe trong cc mu tht c trnh by ti ph lc H).

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Bng 4.15: Kt qu xc nh kim loi trong mt s mu t.L mu (Ngy thc hin) 1 (22/7/2010) K hiu mu T1 T2 QC 1 T3 2 (26/7/2010) T4 QC 2 T5 3 (28/7/2010) T6 QC 3 T7 4 (29/7/2010) T8 QC 4 T9 5 (30/7/2010) T 10 QC 5 T 11 6 (5/8/2010) T 12 QC 6 T 13 7 (7/8/2010) T 14 QC 7 T 15 8 (8/8/2010) T 16 QC 8 T 17 9 (11/8/2010) T 28 QC 9 T 19 10 (12/8/2010) T 20 QC 10 T 21 11 (15/8/2010) T 22 QC 11 T 23 12 (17/8/2010) T 24 QC 12 T 25 13 (18/8/2010) T 26 QC 13 99/2008/Q-BNN (*) ND: < LOD Hm lng (mg/kg) As 10.7 2.2 16.7 3.5 12.0 2.5 10.4 2.2 16.0 3.4 12.5 2.6 13.8 2.9 9.7 2.0 12.3 2.6 2.64 0.56 0.88 0.19 11.9 2.5 25.3 5.3 16.1 3.4 11.7 2.4 N.D N.D 11.9 2.5 N.D N.D 12.0 2.5 N.D N.D 11.6 2.4 N.D N.D 11.6 2.4 N.D N.D 12.0 2.5 N.D N.D 12.4 2.6 N.D N.D 11.9 2.5 N.D N.D 12.2 2.6 12 Cd N.D(*) N.D 1.87 0.13 N.D N.D 1.80 0.13 N.D N.D 1.73 0.12 N.D N.D 1.86 0.13 N.D N.D 1.87 0.13 N.D N.D 1.82 0.13 N.D N.D 1.76 0.12 N.D N.D 1.86 0.13 N.D(*)

Cu 110 15 107 15 15.6 2.2 70.5 9.9 89 12 15.6 2.2 76 11 79 11 15.7 2.2 9813 17.0 2.4 14.9 2.1 36.6 5.1 32.4 4.5 15.1 2.1 86 12 112 16 15.8 2.2 92 13 17.9 2.5 15.8 2.2 39.8 5.6 117 16 15.8 2.2 100 14 72 10 15.6 2.2 84 12 42.1 5.9 15.2 2.1 84 12 49.4 6.9 15.1 2.1 34.54.8 101 14 15.4 2.2 60.0 8.4 38.5 5.4 15.4 2.1 50

Ni 35.9 2.9 30.2 2.4 21.6 1.7 31.0 2.5 29.0 2.3 22.1 1.8 33.5 2.7 33.0 2.6 22.2 1.8 4.94 0.40 0.880 0.070 21.9 1.8 33.1 2.6 30.7 2.4 21.1 1.7 33.1 2.6 47.9 3.8 21.0 1.7 40.8 3.3 39.9 3.2 21.3 1.7 34.3 2.7 41.1 3.3 21.5 1.7 45.4 3.6 40.1 3.2 21.7 1.7 35.1 2.8 7.41 0.59 21.8 1.7 11.86 0.95 9.47 0.76 21.9 1.7 8.50 0.68 13.0 1.0 21.4 1.7 8.79 0.70 43.1 3.4 21.6 1.7 -

Pb 26.0 3.1 20.3 2.4 14.2 1.7 20.9 2.5 18.9 2.3 14.5 1.7 26.7 3.2 23.5 2.8 14.2 1.7 149 18 8.8 1.0 14.2 1.7 24.6 3.0 21.2 2.5 14.4 1.7 58.6 7.0 57.9 6.9 14.0 1.7 41.9 5.0 8.4 1.0 14.8 1.8 21.7 2.6 79.8 9.6 14.6 1.8 68.0 8.2 39.6 4.8 14.3 1.7 45.7 5.5 43.9 5.3 14.6 1.7 59.2 7.1 39.6 4.7 14.3 1.7 21.2 2.5 86 10 14.1 1.7 35.2 4.2 5.19 0.62 14.2 1.7 70

Zn 98 17 102 17 17.2 2.9 82 14 81 14 16.5 2.8 88 15 89 15 17.7 3.0 428 73 27.3 4.6 16.3 2.8 138 23 126 21 16.6 2.8 199 34 277 47 16.9 2.9 198 34 60 10 17.5 3.0 104 18 256 43 17.1 2.9 230 39 215 37 17.5 3.0 201 34 44.9 7.6 17.6 3.0 106 18 71 12 17.2 2.9 71 12 152 25 16.7 2.8 76 13 107 18 16.8 2.8 120

N.D 1.70 0.12 N.D N.D 1.82 0.13 N.D N.D 1.81 0.13 N.D N.D 1.73 0.12 N.D N.D 1.72 0.12 2

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Theo kt qu c biu trong bng 4.15, mt s mu t c kho st trong lun vn ny c hm lng vi nguyn t vt mc cho php (c t m) so vi quy nh 99/2008/Q-BNN ca B Nng nghip v Pht trin nng thn v yu cu t trng theo chun VietGAP. Tnh ton hiu sut thu hi ca cc mu kim sot cht lng (mu QC) trong tng l mu, th hin kt qu ln biu kim sot cht lng nh gi mc tin cy ca kt qu t c nh trnh by ti chng 5.

56

CHNG 5: KIM SOT CHT LNG TH NGHIM5.1 Mc ch: Nhm m bo qui trnh th nghim cung cp c mt kt qu khch quan, tin cy cao v truy sut c nguyn nhn khi c s c. 5.2 Phng thc kim sot: Thc hin vic kim sot cht lng thng qua kim sot tnh trng thit b, dng c phc v cho php th, ha cht, qui trnh vn hnh trn thit b v p dng biu kim sot cht lng. 5.2.1 Kim sot thit b, dng c, cht chun: Cc thit b chnh lin quan n qui trnh th nghim nh ICP-OES, microwave, cn phn tch, cc pipet, bnh nh mc cn phi c k hoch kim tra, hiu chun nh k m bo cc thit b, dng c p ng tt v mt k thut. K hoh ny phi c tun th v thc hin nghim ngt. Cht chun phi c h s ghi chp r rng v vic pha ch chun, c m nhn din tng dung dch c th truy sut c ngun gc chun. 5.2.2 Kim sot qu trnh vn hnh thit b: Khi phn tch mu trn thit b cn tun theo theo mt qui trnh kim sot cht ch thng qua cc dung dch kim sot (dung dch QC) nhm kim sot tri ca thit b, s nhim bn cho, s ph hp ca ngun chun v cc yu t cn nhiu. Cc dung dch cn thit, cch s dng v yu cu i vi cc dung dnh ny c miu t trong bng 5.1.Bng 5.1: Cc dung dch, cch s dng v cc yu cu cho vn hnh ICP-OES. Tn dung dch ICB (Initial calibration blank) Cc dung dch chun. - Dng ng chun. - Chun cao nht c o li kim tra nhim bn cho v tri ca thit b. Mc ch - Zero thit b. Yu cu - Dung dch 2% HNO3. - o trc cc dung dch chun. - o sau ng chun, kt qu tng nguyn t MDL/5. - Matrix 2% HNO3. - Dng hi qui tuyn tnh, h s tng quan 0.995. - Kt qu tng nguyn t trong chun cao nht sai lch 10% so vi nng bit.

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Bng 5.1: Cc dung dch, cch s dng v mc chp nhn khi vn hnh ICP-OES (tip theo). Tn dung dch ICV(*) Mc ch Yu cu

(Initial calibration verification)

- Kim tra li ng - Matrix 2% HNO3. - Nng cc nguyn t khong gia ng chun chun. - o sau khi dng ng chun v trc cc dung dch mu th. - Kt qu cc nguyn t sai lch 10% so vi nng bit.

- Kim tra cn nhiu. - Matrix 2% HNO3. - Nng kim loi 25% chun cao nht. - Hm lng cht cn nhiu tng ng matrix 2 (phn 3.2.2.2). (Interference check - o t nht 2 ln, trc v sau cc dung dch standards) mu th. - Kt qu cc nguyn t sai lch 20% so vi nng bit. ICkS CCV (Continuing calibration verification) - Kim tra tri - Matrix HNO3 2%. - Nng cc nguyn t khong gia ng ca thit b. chun. - o trc v sau cc dung dch mu th v theo chu k t nht 10mu/1ln. - Kt qu cc kim loi sai lch 10% so vi nng bit.

CCB (Continuing calibration blank)

- Kim tra tn hiu - Dung dch 2% HNO3. Blank v nhim bn - o sau CCV v ICks. - Kt qu cc nguyn t MDL/5. cho.

(*) ICV: chun b t dung dch chun gc khc vi chun gc ca chun lm vic ( khc l sn xut hoc nh sn xut).

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Qu trnh phn tch mu vi ICP-OES phi tun th theo trnh t c ch nh nh bng 5.2 Bng 5.2: Trnh t phn tch mu trn ICP-OES.Cc bc thc1hin 2 3 4 5 6 7 8 9 10 11 12 13 14 Tn dung dch ICB Cc dung dch chun ICB ICV Chun lm vic cao nht CCB ICkS CCB CCV CCB Cc dung dch mu th nghim CCV CCB Cc dung dch mu th nghim ICkS CCB 15 CCV CCB Kim tra tuyn tnh ca ng chun Kim tra cn nhiu Kim tra nhim bn cho Kim tra tri ca thit b Kim tra nhim bn cho Bt u phn tch mu Ti a 10 dung dch Kim tra tri ca thit b + nhim bn cho Ti a 10 dung dch Kim tra cn nhiu + nhim bn cho Kim tra tri ca thit b + nhim bn cho Lp li bc 11-15 (nu s mu > 20) Kt thc phn tch mu Xc nhn ng chun Mc ch Xy dng ng chun

Cc dung dch kim sot phi t c yu cu nh bng 5.1, nu khng p ng c th thc hin hnh ng khc phc nh bng 5.3.

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Bng 5.3: nh gi kt qu cc dung dch kim sot v hnh ng khc phc.Tn dung dch - ICV - Dy chun lm vic - ICV - Chun lm vic cao nht - ICkS - Gim khong nng ca dy chun lm vic v o li ng chun. - o li ICkS, nu vn khng tha iu kin th chun b li ICkS, o li. - ICkS vn b li th thay i cc thng s phn tch trn thit b, o li ng chun. S thay i phi c ghi li. - Gim nng cht cn nhiu nu vic o dung dch mu th cho thy cht cn nhiu khng hin din vi nng cao nh chun b ICkS. S thay i phi c ghi li. - Xc nh li cc mu nm trong khong gm mt ICkS t yu cu v mt ICkS khng t yu cu . - o li CCV n khi t yu cu. - Nu vn khng tha iu kin th dng li ng chun, o li CCV. - Xc nh li cc mu nm trong khong gm mt CCV t yu cu v mt CCV khng t yu cu . - Tng thi gian ra gia cc mu, o li CCB. Nu gi tr CCB t yu cu th tip tc qui trnh phn tch. - Nu vn khng t yu cu th Zero li thit b, sau o CCV-CCB - Xc nh li cc mu nm trong khong gm mt CCB t yu cu v mt CCB khng t yu cu . M t li Hnh ng khc phc - Chun b li cc dung dch chun v o li cc chun ny.

Kt qu o ca cc dung dch khng tha iu kin ct Yu cu ca Bng 5.1 - CCV

- CCB

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5.2.3 p dng biu kim sot cht lng: a) Xy dng biu kim sot cht lng: xy dng biu kim sot cht lng, c th s dng mu CRM hoc mu c thm chun. Thc hin phn tch mu CRM hay mu thm chun 10 ln c lp. Cc gi tr cn tnh ton: Hiu sut thu hi trung bnh, cho ng trung tm (Mean). lch chun SD . Gi tr gii hn cnh bo trn (UWL) = Mean + 2*SD Gi tr gii hn cnh bo di (LWL) = Mean - 2*SD Gi tr gii hn hnh ng trn (UAL) = Mean + 3*SD Gi tr gii hn hnh ng trn (LAL) = Mean - 3*SD Biu kim sot cht lng c dng nh hnh 5.1

Hnh 5.1: Biu kim sot cht lng. Trong lun vn ny, chn nng xy dng biu kim sot cht lng cho As, Cu, Ni, Pb, Zn l 12.4 mg/kg v cho Cd l 1.85 mg/kg. (Cch xy dng biu kim sot cht lng c minh ha trong ph lc I).

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b) p dng biu kim sot cht lng trong phn tch mu:Mi mt l mu, thc hin mt mu kim sot cht lng - mu QC. Hm lng ca mu QC ging hm lng ca mu xy dng biu kim sot cht lng. Trong lun vn ny, mu QC c chun b bng cch cn khong 0.4 g mu (chnh xc n 0.001 g) bit trc hm lng cc nguyn t (trnh by ph lc E 1) vo ng cha mu ca microwave. Thm 5.0 mL chun hn hp c nng As, Cu, Ni, Pb, Zn l 1 mg/L; nng Cd l 0.15 mg/L. Thm 10 mL nc cng thy v tin hnh phn hy mu QC cng vi cc mu th bng thit b microwave theo chng trnh nhit ti u. Tnh ton kt qu mu QC v th hin ln biu kim sot cht lng nh gi v x l kt qu phn tch theo cc trng hp sau: Trng hp 1: Phng php c kim sot tt, kt qu th nghim t khi tha mn: - Gi tr mu QC nm trong khong gii hn cnh bo trn v gii hn cnh bo di. - Mt gi tr nm trong vng gia gii hn cnh bo v gii hn hnh ng nhng c 2 gi tr lin tip trc nm trong khong gii hn cnh bo. Trng hp 2: Phng php c kim sot, kt qu th nghim t, tuy nhin v mt thng k khng hon ton tha mn. Cn phi lu kim sot li cc yu t nh: cht chun, nhim bn...khi: - Lin tc 7 gi tr nn trong khong gii hn cnh bo nhng xu hng tng dn hoc gim dn. - Lin tc 10 trong 11 gi tr trong khong gii hn cnh bo nhng nm mt bn trc. Trng hp 3: Phng php khng kim sot c, kt qu th nghim khng t, phi dng th nghim v tm hiu nguyn nhn trc khi p dng li qui trnh phn tch: - Gi tr mu kim sot nm ngoi khong gii hn hnh ng.

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- Mt gi tr nm gia vng gii hn cnh bo v gii hn hnh ng nhng c t nht 1 hoc 2 gi tr lin tip trc trong trong khong gii hn cnh bo v gii hn hnh ng. c) p dng vo phn tch mu tht: p dng mu QC trong mi l mu tht, hiu sut thu hi c biu din trong bng 4.16. Bng 4.16: Hiu sut thu hi ca cc mu QC.Ngy thc hin 22/7/2010 26/7/2010 28/7/2010 29/7/2010 30/7/2010 5/8/2010 7/8/2010 8/8/2010 11/8/2010 12/8/2010 15/8/2010 17/8/2010 18/8/2010 L mu 1 2 3 4 5 6 7 8 9 10 11 12 13 K hiu mu QC 1 QC 2 QC 3 QC 4 QC 5 QC 6 QC 7 QC 8 QC 9 QC 10 QC 11 QC 12 QC 13 Rec (%) As 88.9 93.8 91.0 88.3 88.8 90.3 90.8 86.0 86.5 89.1 89.1 91.5 93.1 Cd 100.0 96.8 93.3 99.4 100.2 99.2 94.6 100.5 93.6 98.0 97.0 95.4 94.6 Cu 104.3 105.4 106.2 103.0 101.2 108.5 106.1 107.2 106.8 101.9 100.4 105.8 105.2 Ni 97.8 103.1 103.3 101.0 94.5 95.3 96.1 98.4 101.7 100.2 100.6 99.1 100.9 Pb 92.5 95.1 93.4 92.8 94.4 92.9 97.6 97.1 95.2 95.7 93.1 94.4 94.9 Zn 90.0 85.0 94.7 83.1 85.9 89.5 92.6 90.1 94.7 93.4 90.2 88.5 89.1

Th hin hiu sut thu hi ca cc mu QC ln biu kim sot cht lng ca tng nguyn t nh cc hnh 5.2.(a); (b); (c); (d); (e); (f). Kt qu mu QC cho thy cc l mu thc hin u t yu cu kim sot cht lng.

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(a)

Hnh 5.2.(a): Biu kim sot cht lng ca As.(b)

Hnh 5.2.(b): Biu kim sot cht lng ca Cd.(c)

Hnh 5.2.(c): Biu kim sot cht lng ca Cu.

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(d)

Hnh 5.2.(d): Biu kim sot cht lng ca Ni.

(e)

Hnh 5.2.(e): Biu kim sot cht lng ca Pb.

(f)

Hnh 5.2.(f): Biu kim sot cht lng ca Zn.

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CHNG 6: TM TT QUI TRNH6.1 Nguyn tc ca qui trnh: Cc nguyn t c chit khi nn t vi hn hp nc cng thy HCl:HNO3 (3/1, v/v) bng k thut microwave. Xc nh hm lng cc kim loi trong dch chit bng phng php quang ph pht x ghp cp cao tn cm ng ICP-OES. 6.2 Thit b - Ha cht Cc dung dch chun: 6.2.1 Thit b - Ha cht: Nh phn 3.1, chng 3. 6.2.2 Cc dung dch chun: a. Dung dch HNO3 2%: 200 mL HNO3 m c, nh mc vi nc kh ion thnh 1L. b. Dung dch Blank: 2mL HNO3 m c, nh mc vi nc kh ion thnh 100 mL. c. Dung dch chun trung gian hn hp 1: pha long thch hp t chun gc bng cn phn tch, trn ln cc chun n vi nhau, thm 6.2.2.a v cn thnh 100g c cc nng : 100 mg/L vi cc nguyn t As, Cu, Ni, Pb, Zn v 50 mg/L vi Cd. d. Dung dch chun trung gian hn hp 2: chun b ging 6.2.2.b nhng c nng 100 mg/L vi cc nguyn t As, Cu, Ni, Pb, Zn v 15 mg/L vi Cd. e. Dung dch chun trung gian hn hp 3: chun b ging 6.2.2.b nhng t cc chun gc khc l sn xut. f. Dung dch chun lm vic: pha long thch hp t chun 6.2.2.b, thm 6.2.2.a v cn thnh 100g c cc nng : 0.025, 0.05, 0.50, 1.0, 2.0 (mg/L) vi cc nguyn t As, Cu, Ni, Pb, Zn. 0.005, 0.0125, 0.025, 0.25, 0.50, 1.0 (mg/L) vi Cd. g. Dung dch CCV: pha long thch hp t chun 6.2.2.c, thm 6.2.2.a v cn thnh 100g c cc nng : 0.50 mg/L vi As, Cu, Ni, Pb, Zn v 0.25 mg/L vi Cd.

66

h. Dung dch ICV: pha long thch hp t chun 6.2.2.e, thm 6.2.2.a v cn thnh 100g c cc nng : 0.50 mg/L vi As, Cu, Ni, Pb, Zn v 0.25 mg/L vi Cd. i. Dung dch CCB: 2 mL HNO3 m c, nh mc vi nc kh ion thnh 100 mL. j. Dung dch ICkS: pha long thch hp t chun 6.2.2.b v cc chun gc ca Al, Fe, Ca, K, Mg, Na, Si. Thm 6.2.2.a v cn thnh 100g c cc nng : 0.10mg/L vi cc nguyn t As, Cu, Ni, Pb, Zn. 0.05mg/L vi Cd. Al, Fe: 500 mg/L. Ca, K, Mg, Na, Si: 50 mg/L. k. Chun QC: pha long thch hp t chun 6.2.2.e, thm 6.2.2.a v cn thnh 100g c cc nng : 1.0 mg/L vi As, Cu, Ni, Pb, Zn v 0.15 mg/L vi Cd. l. Dung dch Y 10mg/L: cn 1g chun gc Y 1000mg/L , thm 6.2.2.a v cn thnh 100g. 6.3 Chun b mu: 6.3.1 Chun b s b mu th: Chun b s b mu th theo phn 3.2.3.1, chng 3. 6.3.2 Phn hy mu bng microwave: Mu th nghim: cn khong 0.4g mu t ( c chun b nh phn 6.3.1) vo ng cha mu ca microwave. Mu c thc hin th nghim song song. Mu kim sot cht lng- mu QC: cn khong 0.4g mu t bit trc hm lng vo ng cha mu ca microwave. Thm 5mL chun 6.2.k. Mu Blank: khng cn mu th vo ng cha mu ca microwave. Thm 10 mL nc cng thy vo tt c cc mu trn, yn qua m. Sau phn hy mu bng microwave vi chng trnh nhit B nh sau:

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Chng trnh Bc 1 B 2 3

Cng sut (W) 250 1000 0

Nhit (0C) Thi gian 25-180 (pht) 8 180 15 15

ngui dung dch, lc b cht khng tan, thm 5mL ni chun 6.2.l, nh mc thnh 50 mL. 6.4 Phn tch trn thit b: iu kin vn hnh thit b ICP-OES nh sau: Cng sut RF (W) Kh auxilay (L/pht) Kh plasma (L/pht) Kh nebulizer (L/pht) Dng nebulizer Dng spray chamber Tc bm mu (mL/pht) Cch ly tn hiu Cch x l tn hiu 1400 0.4 15 0.6 Cross flow-gem tip Double pass 1.3 Axial Peak Area: As, Cu, Ni, Pb, Zn. MSF : Cd.

Cc bc sng ca nguyn t c s dng nh sau: Nguyn t As Cd Cu Ni Pb Zn Bc sng (nm) 188.979 214.440 327.393 231.604 220.353 202.548 Trng thi kch thch I (nguyn t) II (ion) I II II II

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Bt plasma khong 30 pht trc khi tin hnh phn tch. Trnh t phn tch mu nh trnh by bng 5.2, cch khc phc li nh trnh by trong bng 5.3 ca chng 5. 6.5 Tnh kt qu: Hm lng kim loi X trong mu c tnh theo cng thc:C X (mg/kg) =f x * (C1,x C o,x ) m * Vdm

Trong : C1,x : hm lng kim loi X c trong dung dch mu th (mg/L). C0,x : hm lng kim loi X c trong mu Blank (mg/L). Vdm : th tch nh mc ca dung dch mu th (mL). m fx : khi lng mu th (g). : h s pha long i vi kim loi X (nu c).

Hiu sut thu hi nguyn t X trn mu Qc c tnh theo cng thc:

Trong : RecX : hiu sut thu hi ca nguyn t