Determination Of Arsenic In Water At Ppb Levels
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Transcript of Determination Of Arsenic In Water At Ppb Levels
J.N. Driscoll, PID Analyzers,J.N. Driscoll, PID Analyzers,D. Lewis, R. Kipp, Julie Ann, Heidi Hu, D. Lewis, R. Kipp, Julie Ann, Heidi Hu,
Chemistry Dept., Suffolk University Chemistry Dept., Suffolk University Chemistry Dept., Suffolk University Chemistry Dept., Suffolk University
Pittsburg Conference 2006Pittsburg Conference 2006
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Orlando, FLOrlando, FL
Many of the municipal laboratories that will be Many of the municipal laboratories that will be Many of the municipal laboratories that will be Many of the municipal laboratories that will be required by EPA to monitor As in drinking water are required by EPA to monitor As in drinking water are smallsmall
Traditional methods that have been used to detect ppb Traditional methods that have been used to detect ppb ad t o a et ods t at ave bee used to detect ppb ad t o a et ods t at ave bee used to detect ppb levels of As in water include: AA, ICP, ICPlevels of As in water include: AA, ICP, ICP--MS… MS…
There is a definite need for simpler and less costly There is a definite need for simpler and less costly techniques for the water labs to keep the water rates techniques for the water labs to keep the water rates q pq pfrom rising significantlyfrom rising significantly
We will evaluate two new methods for the detection of We will evaluate two new methods for the detection of ppb levels of As in water; both are simpler and less ppb levels of As in water; both are simpler and less pp ppp pcostly than the spectroscopic methods described abovecostly than the spectroscopic methods described above
These methods are: photoionization (PID) and These methods are: photoionization (PID) and electrochemistry (ECD) detectorselectrochemistry (ECD) detectors
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Determine the detection limits and linear range gfor both the PID and ECD
Simplify the equipment (electronics) needed f d ifor detection
Evaluate a manual and automated method for the determination of Asthe determination of As
Determine the best method for quantitation of the method: peak height, integrated peak area, p g , g p ,headspace (PH) …
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Food Food –– 70%; Fish70%; Fish Food Food 70%; Fish70%; Fish TypeType-- organic (less toxic)organic (less toxic)
Water 29%Water 29%%% TypeType-- mixturemixture
Air Air –– 1%1% Cigarettes Cigarettes
Type mixture/resultType mixture/result-- lung cancer lung cancer yp /yp / gg
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1. Aqueous sample (containing AsAqueous sample (containing As+3+3) is injected ) is injected into hydride generatorinto hydride generator
AsAs+3+3(aq) (aq) As HAs H33(g) (g) in the presence of reducing agent (NaBHin the presence of reducing agent (NaBH44 + HCl)+ HCl)
2. The AsH2. The AsH33(g) produced is swept into the (g) produced is swept into the analyzer with nitrogenanalyzer with nitrogeny gy g
AsHAsH33 (g) + hv (g) + hv AsHAsH33+ e+ e--
3 The AsH3 The AsH produced is proportional to the produced is proportional to the 3. The AsH3. The AsH3 3 produced is proportional to the produced is proportional to the arsenic concentration in the water samplearsenic concentration in the water sample
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4. Analysis via a Photoionization Detector oror 4. Analysis via a Photoionization Detector oror 5. Analysis via an Electrochemical Detector 6 Detection by headspace method with peak 6. Detection by headspace method with peak
detection oror 7. Detection by PeakWorks Data Software 7. Detection by PeakWorks Data Software
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The equipment for arsenic determination includes: A hydride generator that contains a reducing agent A carrier gas such as perpurified nitrogen with an in-line flow
controller A glass wool filter (in-line) for moisture
A high input impedence preamplifier for the PID; a preamp for the electrochemical detector
A photoionization detector with a 10.6 eV lamp or an electrochemical detector for arsine
A 16 bit ADC smart meter that integrates the signal and di l h l 2 li 16 h LCD di ldisplays the results on a 2 line x 16 character LCD display
A PC with windows XP & PeakWorks software
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Calibration Curve As in Water- PID
y = 29.427x - 25.0181500
2000
g R2 = 0.9983
500
1000
1500
3 R
eadi
ng
0
500
0 10 20 30 40 50 60
AsH
3
-5000 10 20 30 40 50 60
ug/L As in water
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Calibration Curve As in Water- ECD
y = 3 1782x + 3 2148200
r y = 3.1782x + 3.2148R2 = 0.9971
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150
L A
s in
Wat
er
0
50
0 10 20 30 40 50 60
ug/L
AsH3 Reading
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PID PID20 ug/L +/- 16.9%
50 ug/L +/- 5.3%g/ / %
ECD ECD 30 ug/L +/- 24.6% 60 ug/L +/- 8 2% 60 ug/L +/- 8.2%
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Type Det. Limit (ug/L) Cost $Type Det. Limit (ug/L) Cost $ Type Det. Limit (ug/L) Cost $Type Det. Limit (ug/L) Cost $ICP-MS 1.4 200,000ICP-AES 8 80 000ICP AES 8 80,000GFAA 0.5 80,000GHAA 0 5 60 000GHAA 0.5 60,000ASV 1.0 30,000PID 2 12 000PID 2 12,000ECD 10 9,000
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The PID is an ideal detector for ppb (down to The PID is an ideal detector for ppb (down to 2) levels of As in water. The electronics and the method are simpler than any of the complex spectroscopic methods. The cost of the PID is a fraction of the cost of an AA
The ECD will detection As down to 10 ppb levels in water. The cost of this detection systems is also a fraction of the cost of an AAsystems is also a fraction of the cost of an AA
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