Separation and Determination of Chromium (III) Chromium (VI), Gold (III) and Arsenic (V) by Capillary Zone Electrophoresis Using 2-Acetylpyridine-4-phenylthiosemicarbazone as Complexing Reagent

Capillary zone electrophoretic procedure has been developed for the speciation of Cr (III) and Cr (VI) along with separation from Au (III) and As (V) as chelate compounds of 2-acetylpyridine-4-phenylthiosemicarbazone (APPT). APPT reacts with Cr (III), Cr (VI), Au (III) and As (V) to form water-methanol soluble chelates which absorb maximally within 360 418 nm with molar absorptivity of 3.2 x 10(3) to 1.2x10(4) L mol(-1)cm(-1). Off line pre-capillary complexes of the cations prepared were introduced onto uncoated fused silica capillary of 54 cm effective length with 75 mu m id by auto-sampler and separated with background electrolyte (BGE) system of oxalate buffer at pH-4 at an applied voltage of + 15 kV. Photodiode array detection was carried out at 241 nm. Linear calibrations were obtained within 1-80 mu gmL(-1) for all the cations. The separation and quantitation was repeatable in terms of migration time and peak height with relative standard deviation (RSD) within 2% (n=4). The limit of detection (LOD) measured were 0.125 mu gmL(-1), 1.0 mu gmL(-1), 0.2 mu gmL(-1) and 0.1 respectively for Au(III), As(V), Cr (III) and Cr(VI). The limits of quantitation (LOQ) were in the range of 0.375-3.0 mu gmL(-1). The method was applied for the determination of Cr (III) from tap water, Cr (VI) from industrial effluents and Au (III) and As (V) from pore water of coal mines with RSD within 4%. The results of analysis were supported by standard addition method and rechecked by atomic absorption spectrometry (AAS).