Photometric measurement of trace As(III) and As(V) in drinking water

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• 作者：Dasgupta ; Purnendu K. ; Huang ; Huiliang ; Zhang ; Genfa ; Cobb ; George P.
• 关键词：Light-emitting diode ; Photometric method ; Phosphate ; Flow injection analysis
• 刊名：Talanta
• 出版年：2002
• 出版时间：August 16, 2002
• 年：2002
• 卷：58
• 期：1
• 页码：153-164
• 全文大小：161 K

文摘

A simple, fast and sensitive light-emitting diode (LED)-based photometric method for the differential determination of ppb–ppm levels of As(III) and As(V) in potable water in the presence of ppm levels of phosphate was developed. The detection chemistry is based on the well-known formation of arsenomolybdate, followed by reduction to heteropoly blue. The front-end of the measurement system is configured to selectively retain P(V) and As(V), based on the considerable difference of the pK_a of the corresponding acids relative to As(III). Thus, it is As(III) that is injected into the medium, oxidized in-line with KBrO₃ to As(V) and forms Mo-blue that is detected by an LED-based detector. Only As(III) is measured if the sample is injected as such; if all As in the sample is prereduced to As(III) (by the addition of cysteine, in a provided in-line arrangement), the system measures As(V)+As(III). In the present form, limit of detection (LOD) (S/N