A Green Fieldable Analyzer for Arsenic

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Professor Purnendu Dasgupta of Texas Tech University is supported by the Analytical and Surface Chemistry program to develop a new environmentally friendly tool for the analysis of various arsenic species in groundwater samples and drinking water sources. Most fieldable arsenic detectors involve the use of the toxic chemicals lead and mercury. Further, most test kits are not suitable for analyzing arsenic below 10 microgram/L (the current acceptable level set by WHO), and the method developed in this work will improve this sensitivity. The instrument is based on sequential injection (for speciation), zone fluidics (for hydride generation), and gas phase chemiluminescence (for detection). The integrated arsenic analyzer includes concentration and separation of arsenic species with ion exchange cartridges, electrooxidation of As(III) to As(V), electroreduction of As(V) to arsine with an electrolytic arsine generator, membrane-based electrodialytic salt splitter, and enhanced ozone generation by electrical discharge and oxygen feed. It only requires the use of NaCl and electricity to enable analysis of arsenic at the sub-microgram/L levels. With a preliminary setup, the PI achieved detection limits of around 0.1 ppb using only a 2 mL sample. By adjusting acidity, he can distinguish between arsenic(III) and arsenic(V), and he can detect organic arsenic species. The project includes undergraduates who work on semester-long research modules.Millions of wells around the world may contain high levels of arsenic. However, many of these wells have not been tested. Besides its acute toxicity, it is a known carcinogen, especially arsenic(III). Hence, it is important to monitor the arsenic species, both in groundwater and drinking water treatment facilities. The method being developed here would be applicable to field work, even in rural areas of India and Bangladesh devastated by arsenic poisoning.