A Green Fieldable Analyzer for Measuring Arsenic In Environmental Samples

Over the past three decades, occurrence of high concentrations of arsenic in drinking-water has been recognized as a major public-health concern in several parts of the world, including USA. This element is included in the U.S. Environmental Protection Agency's list of priority and it is designated as group A carcinogen by IARC. Apart from drinking water, soil, food is also considered to be a major source of arsenic exposure for people residing in the arsenic affected areas. Chemical speciation of arsenic is important because of the diverse toxicity of various forms of arsenic.

Analytical methods of choice thus far involved atomic and mass spectrometry for total As measurement and coupling with high-performance liquid chromatography (HPLC) for its species detection. While these can provide very good detection limits, the systems are expensive, bulky, require expensive consumables and compressed gases, and are not particularly conducive to use by arsenic researchers in South Asia where arsenic has become an enormous problem.

We have developed a simple, inexpensive and highly sensitive detection technique based on gas phase chemiluminescence (GPCL) method for trace measurement of arsenic and its species in wide variety of samples includes water, soil, dust and food. The principle is based on the reduction of inorganic As to AsH3 which reacts with O3 to produce chemiluminescence which is being detected by a photo multiplier tube. For detecting arsenic species a postcolumn reaction (LC-GPCL) involving chromatographic separation followed by photooxidisation to arsenate, conversion to arsine and finally detected by GPCL.

We compare parallel measurements for soil and dust samples extracts for total As by induction coupled plasma mass spectrometry (ICP-MS) and the results were highly correlated with GPCL and LC-GPCL results (r2 = 0.9935 and 1.0000, respectively) with limit of detection in sub ppb levels.