The document discusses two new methods for detecting parts-per-billion (ppb) levels of arsenic (As) in water using simpler and less costly techniques than traditional spectroscopic methods. The methods are photoionization detection (PID) and electrochemical detection (ECD). Both methods were evaluated to determine their detection limits, linear ranges, and suitability for quantifying As in water samples. The PID showed lower detection limits down to 2 ppb and was determined to be an ideal, low-cost detector for ppb levels of As in water. The ECD also provided low-cost detection down to 10 ppb.

1. J.N. Driscoll, PID Analyzers,
D. Lewis, R. Kipp, Julie Ann, Heidi Hu,
Chemistry Dept., Suffolk University
Pittsburg Conference 2006
Orlando, FL
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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
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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
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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
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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
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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
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8. 8

9. 9

10. 10

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
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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
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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%
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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
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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
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