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Determination Of Arsenic In Water At Ppb Levels
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Determination Of Arsenic In Water At Ppb Levels

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  • 1. J.N. Driscoll, PID Analyzers, D. Lewis, R. Kipp, Julie Ann, Heidi Hu, Chemistry Dept., Suffolk University Pittsburg Conference 2006 Orlando, FL 1
  • 2.  Many of the municipal laboratories that will be required by EPA to monitor As in drinking water are small  Traditional methods t at have been used to detect ppb ad t o a et ods that ave bee levels of As in water include: AA, ICP, ICP-MS… ICP-  There is a definite need for simpler and less costly techniques for the water labs to keep the water rates q p from rising significantly  We will evaluate two new methods for the detection of pp ppb levels of As in water; both are simpler and less p costly than the spectroscopic methods described above  These methods are: photoionization (PID) and electrochemistry (ECD) detectors 2
  • 3.  g Determine the detection limits and linear range for both the PID and ECD  Simplify the equipment (electronics) needed for d f detection i  Evaluate a manual and automated method for the determination of As  Determine the best method for quantitation of the method: peak height, integrated p p g , g peak area, , headspace (PH) … 3
  • 4.  Food – 70%; Fish  Type- Type- organic (less toxic)  Water 29% %  Type- Type- mixture  Air – 1%  Cigarettes  Type mixture/result- lung cancer yp mixture/result- / g 4
  • 5.  1. Aqueous sample (containing As+3) is injected into hydride generator As+3(aq) As H3(g) in the presence of reducing agent (NaBH4 + HCl)  2. The AsH3(g) produced is swept into the analyzer with nitrogen y g AsH3 (g) + hv AsH3+ e-  3. 3 The AsH3 produced is proportional to the arsenic concentration in the water sample 5
  • 6.  4. Analysis via a Photoionization Detector or  5. Analysis via an Electrochemical Detector  6. 6 Detection by headspace method with peak detection or  7. Detection by PeakWorks Data Software 6
  • 7.  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 displays the results on a 2 li x 16 character LCD di l di l h l line h display  A PC with windows XP & PeakWorks software 7
  • 8. 8
  • 9. 9
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  • 11. Calibration Curve As in Water- PID 2000 y = 29.427x - 25.018 1500 AsH3 Reading g R2 = 0.9983 1000 500 3 0 0 10 20 30 40 50 60 -500 ug/L As in water 11
  • 12. Calibration Curve As in Water- ECD 200 y = 3.1782x + 3 2148 3 1782x 3.2148 ug/L As in Water r 150 R2 = 0.9971 100 L 50 0 0 10 20 30 40 50 60 AsH3 Reading 12
  • 13.  PID 20 ug/L +/- 16.9%  50 ug/L g/ +/- 5.3% / %  ECD  30 ug/L +/- 24.6%  60 ug/L +/- 8 2% 8.2% 13
  • 14.  Type Det. Limit (ug/L) Cost $ ICP-MS 1.4 200,000 ICP AES ICP-AES 8 80,000 80 000 GFAA 0.5 80,000 GHAA 0.5 05 60,000 60 000 ASV 1.0 30,000 PID 2 12,000 12 000 ECD 10 9,000 14
  • 15.  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 AA 15