Development of Some Electrochemical Systems for Detection of Arsenic in Drinking Water

Traces of arsenic in environmental water affect human health and the World Health Organization (WHO) has fixed the threshold limit of arsenic in drinking water up to a maximum of 10 parts per billion (ppb). Presently various techniques are available to detect arsenic in drinking water. Some of the techniques are atomic absorption spectrometry, gas chromatography and suppressed ion chromatography etc. However these methods require expensive instrumentation, cannot be employed for on-site analysis and most of them cannot detect arsenic below 10 ppb. We have developed three electrochemical sensing systems for measurement of arsenic in drinking water and compared the results with that obtained by standard estimation procedures such as spectrophotometric estimation and stripping voltammetry using hanging mercury drop electrode (HMDE). The first sensing system utilized the consumption of ammonium molybdate by arsenate and the rest of the ammonium molybdate was reacted with hydrazine sulphate and detected amperometrically. In this procedure arsenate concentration was inversely proportional to the amperometric response. A potentiometric determination of arsenate by complexation with catechol was accomplished in the second method. In the third sensing protocol, arsenic (total) was first converted to arsine gas and the same was detected by amperometric response through reduction of mercuric bromide using (i) polymer hydrogel transducer (ii) screen-printed electrode. All procedures gave response well below 10 ppb and thus could be used as alternatives to standard methods.