Arsenic speciation in natural and contaminated waters using CZE with in situ derivatization by molybdate and direct UV‐detection

Abstract

A simple and sensitive procedure for simultaneous determination of arsenate, arsenite, monomethylarsonate and dimethylarsinate (DMA) ions in waters using CZE with chemical derivatization in situ and UV-detection at 250 nm was developed. The separation was performed in a fused-silica capillary using solution containing sodium molybdate and sodium perchlorate as electrolyte. Molybdate forms heteropolycomplexes with arsenic species in low acidic media, while sodium perchlorate masks silicate ion. The analysis conditions were optimized; the best results were achieved with the electrolyte consisting of 10 mM Na(2)MoO(4) and 10 mM NaClO(4) at pH 3.0 using negative voltage and pneumatic injection of the sample. Nevertheless, the signal of arsenite ion was not detected, probably because of its instability. Arsenite ion was quantified as a difference between arsenate ion contents after and before oxidation by bromine water. The detection limits for the fresh water at the level of 5.0 microg/L for As(III) and As(V), 16 microg/L for DMA and 20 microg/L for MMA were achieved. The reproducibility varied in the range of 0.06-0.25 relative units. To reduce the interferences of the sample salinity an addition of organic substances and isotachophoretic effect were used.

Potential molecular mechanisms for combined toxicity of arsenic and alcohol

“…Combined with oxygen, chlorine, and sulfur, arsenate (As 5+ ) and arsenite (As 3+ ) represent the most common forms of inorganic arsenic [16]. Dimethylarsinic acid (DMA) is a major form of organic arsenic in the environment and has been used as a general herbicide or pesticide for many years.…”

Arsenic Speciation Analysis by Ion Chromatography - A Critical Review of Principles and Applications

“…For the most common As-species, DL of 5-17 μg/L were reached [117], detecting with a high sensitivity UV-cell and high sample volume stacking. In situ heteropolyacid formation with molybdate and UV-detection gave similar DL [118]. Without sensitivity enhancement in UV-detection, DL between 0.1 and 1.2 mg/L have been reported [119] in aqueous soil extracts.…”

A study of complex phosphovanadomolybdates [PV x Mo12−x O40]−(3+x) by reversed-phase HPLC and capillary zone electrophoresis

“…It can be seen that, for the studied mixture, a relatively low resolution of peaks 1 and 2 (R s1,2 = 1.5), substantially lower com pared to the expected efficiency (approximately 60000 TP), was observed. The probable reason for this phenomenon can be the expanded tailing edge of the peaks of components, the formation of which in its turn is associated with the adsorption of heteropoly compound anions on the walls of the quartz capillary [27].…”