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Field kits have been used extensively to test for arsenic in groundwater, and in many cases, it is the only assay applied. The current baseline methodology involves a variety of technologies that are all variations of the “Gutzeit” method, developed over 100 years ago. These assays have been applied almost exclusively to water samples, although they may be applied to testing solid waste and soil, using either an acidic extraction or an acidic oxidation digestion of the sample.
The “Gutzeit” method procedures:
1. treat the water sample with a reducing agent that transforms the arsenic compounds present in the water into arsenic trihydride (arsine gas).
2. Arsenic is separated from the sample
3. The arsenic trihydride diffuses out of the sample where it is exposed to a paper impregnated with mercuric bromide.
4. The reaction with the paper produces a highly colored compound.
5. The concentration of the arsenic can be approximated using a calibrated color scale.
Advantages:
- inexpensive
- minimally trained personnel can readily perform it and read the results in the field.
Disadvantage:
- sulfur, selenium, and tellurium compounds have the potential of interfering with this assay.
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