Abstract
A simple and accurate extractive spectrophotometric procedure for the chemical speciation of chromium(III,VI) species in aqueous media has been developed. The method is based upon the extraction of the complex ion-associate formed between the chloro chromate (CrO
3Cl
−) anion and the ion-pair reagent tetraphenylarsonium chloride (TPAs
+Cl
−) or tetraphenylphosphonium bromide (TPP
+Br
−) at pH
≤
0 in chloroform followed by direct spectrophotometric measurement at 355
nm. The optimum concentration range evaluated by Beer–Lambert's law, Ringbom's plot, the molar absorptivity, the Sandell's sensitivity, the extraction and stability constants (
K
D,
K
ex and
β), the stoichiometry and the extraction equilibria of the produced complex ion-associates have been determined and gave a convenient applications of the investigated system for analytical purposes. Chromium(III) was also determined by the proposed procedure after prior oxidation to chromate with H
2O
2 in alkaline solution. The method has been applied successfully for the analysis of chromium(VI) and total chromium(III,VI) in industrial wastewater of electroplating plant.