Arsenic speciation in natural waters by cathodic stripping voltammetry

• Published in: Analytica chimica acta Vol. 662; no. 1; pp. 1 - 8
• Main Authors: Gibbon-Walsh, Kristoff, Salaün, Pascal, van den Berg, Constant M.G.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 03-03-2010; Elsevier
• Subjects: Adsorption; Analysis methods; Analytical chemistry; Applied sciences; Arsenic; Arsenic - analysis; Arsenic - chemistry; Arsenic speciation; Cathodic stripping voltammetry; Chemistry; Deposition; Drinking water; Electrochemical methods; Electrochemistry - instrumentation; Electrochemistry - methods; Electrodes; Environmental Monitoring - instrumentation; Environmental Monitoring - methods; Exact sciences and technology; Gold - chemistry; Groundwater; Hydrogen-Ion Concentration; India; Mathematical analysis; Natural water pollution; Pollution; Speciation; Surface Properties; United Kingdom; Vibrating electrode; Voltammetry; Water Pollutants, Chemical - analysis; Water Pollutants, Chemical - chemistry; Water treatment and pollution; Arsenic speciation; Vibrating electrode; Arsenic; Groundwater; Cathodic stripping voltammetry; Drinking water; Water supply; Time; Chemical enrichment; Arsenic V; Reduction; Detection limit; Test method; pH; Deposition; Monitoring; Speciation; Ground water; Gold; Sample; Use; Anodic stripping voltammetry; Ultratrace compound; Digestion; Contamination; Adsorption; Preparation; Arsenic III; Water pollution
• ISSN: 0003-2670; 1873-4324
• DOI: 10.1016/j.aca.2009.12.038

Contamination of groundwater with arsenic (As) is a major health risk through contamination of drinking and irrigation water supplies. In geochemically reducing conditions As is mostly present as As(III), its most toxic species. Various methods exist to determine As in water but these are not suitable for monitoring arsenic speciation at its original pH and without preparation. We present a method that uses cathodic stripping voltammetry (CSV) to determine reactive As(III) at a vibrating, gold, microwire electrode. The As(III) is detected after adsorptive deposition of As(OH)
3
0, followed by a potential scan to measure the reduction current from As(III) to As(0). The method is suitable for waters of pH 7–12, has an analytical range of 1
nM to 100
μM As (0.07–7500
ppb) and a limit of detection of 0.5
nM with a 60
s deposition time. The As speciation protocol involves measuring reactive As(III) by CSV at the original pH and acidification to pH 1 to determine inorganic As(III)
+
As(V) by anodic stripping voltammetry (ASV) using the same electrode. Total dissolved As is determined by ASV after UV-digestion at pH 1. The method was successfully tested on various raw groundwater samples from boreholes in the UK and West Bengal.