Download - De Cuong Thuc Nghiem

8/2/2019 De Cuong Thuc Nghiem

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CHNG 2: KHO ST PH HP THU V CC YU TNH HNG NQU TRNH XC NH NG BNG PHNG PHP TRC QUANG VITHUC THDIETYL DITHIOCACBAMAT

2.1 Kho st ph hp thu gia ng v thuc thdietyl dithiocacbamat

xc nh hm lng ng bng phng php trc quang, trc tin ta phi kho

st bc sng ti u nht (max) ca phc ng vi dithizone.

- Pha dung dch chun ng t 1000ppm xung 100ppm ri tip tc pha longxung nng lm vic

- Chun b2 bnh nh mc 50ml, ln lt ht 5ml dung dch ng chun, 5mlthuc thdithizone, nh mc n vch.Chit dung dch tpha nc sang pha

hu c

- yn 5 pht v em o quang. Kho st v qut bc sng t 300900 nm2.2 Kho st hm lng thuc thdietyl dithiocacbamat

Xc nh hm lng ng bng phng php trc quang, ta phi tin hnh kho stlng thuc th dietyl dithiocacbamat, bit lng thuc th thm phi m bocho qu trnh to phc gia ng v dietyl dithiocacbamat.

- chun b7 bnh nh mc

- cnh dung dch ng chun 5ml

- ln lt thay i thtch lng thuc th thm vo t 1ml, 3ml, 5ml, 7ml,10ml, 12ml, 15ml.

- nh mc bng nc ct

2.3 Kho st nh hng ca pH n phc mu

PH ca dung dch nh hng n cc dng tn ti ca cc hp cht tham giaphn ng. Nu pH ca dung dch thay i c th slm thay i tc ca phnng. V vy, vic kho st pH ti u trong h phn ng l cn thit. Ta chun bmu nh bng v sau o quang bc sng thch hp.

- chun b7 bnh nh mc


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- ht 5ml dung dch ng tiu chun

- ht 5ml thuc th NaDDC

- cho ln lt cc th tch khc nhau (2, 4, 6, 8, 10, 12, 15ml) ca dung dch

axit NH3

- nh mc bng cloroform.

yn 5 pht ri em o quang

2.4 Kho st nh hng ca thi gian n vic to phc

kho st hm lng ng bng phng php trc quang, ta phi tin hnhkho st snh hng ca thi gian n khnng bn mu ca phc mu gia

ng vi thuc th dietyl dithiocacbamat. Ta thc hin cc bc sau:

- chun b5 bnh nh mc

- ht 5ml dung dch ng tiu chun

- thm vo 5ml dung dch thuc th

- nh mc bng cloroform, sau em o quang cc khong thi gian khcnhau (5, 10, 15, 20, 25, 30 pht)

2.5 Kho st cc ion l

Trong mi trng c cha amoniac, xitrat v complexon, a s cc kim loai khc

khng gy cn cho vic xc nh ng bng phng php ny, ch c bitmut, bc v thy

ngn vn phn ng vi DDC v c th b chit cng vi phc ng.Tuy nhin trong 3

phc ch c phc ca bitmut c mu vng l nh hng, cn cc phc ca bc v thy

ngn khng mu hp th nh sng trong vng t ngoi, nn thc t khng nh hng n

vic xc nh ng.

kho st nh hng ca ion nu trn, ta tin hnh ly 6 bnh nh mc

50ml to phc mu vi 5ml dd Cutiu chun, 5ml thuc th dietyl dithiocacbamat,


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thm ion cn kho st vo cc bnh tr bnh th nht (nng tng dn). nh mc

n vch. i 10 pht em o quang bc sng thch hp

2.6 Kho st khong tuyn tnh LOL

kho st khong tuyn tnh ca ng ta tin hnh thay i th tch cadung dch ng chun sau ta thc hin cc bc sau:

- chun b7 bnh nh mc

- ht cc th tch khc nhau ca dung dch ng chun lm vic (0.1ml, 0.5ml,1ml, 5ml, 10ml, 20ml, 30ml.

- thm 5ml thuc th dietyl dithiocacbamat

- nh mc bng cloroform v yn 5 pht sau em o quang.

2.7 Kho st LOD v LOQ

LOD: gii hn nh nht ca phng php m my c th pht hin c.

Gii hn nh lng ca phng php:l gi tr nh nht m snh lng tin cy c,

c gi tr bng 10 ln S/N.

Trong :

Cmin: nng ti thi im xt S v N.

S: mt quang ca mu c nng Cmin.

N: mt quang trung bnh ca mu trng.

kho st LOD v LOQ, tin hnh mt quang A vi mu trng lp li sau miln o mu.

2.8Kho st hiu sut thu hi ca phng php phn tch mu

minmin

C SLOD = 3 = 3C (10 > T = 3)

T N

N

S

min

min

C SLOQ =10 =10C (10 > T = 3)

T N

N

S


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kho st hiu sut thu hi ca phng php chng ti tin hnh thm mt lngng ng vi nng ca ng 50ppm, 100ppm, 200ppm, vo cc mu xc nh.Tin hnh phn tch mu thm chun v khng thm chun theo phng php kho st.


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