Simultaneous determination of chromium(III) and chromium (VI) with reversed-phase ion-pair high-performance liquid chromatography

Abstract

A reversed-phase ion-pair high-performance liquid chromatographic method for the simultaneous determination of Cr1I1 and CrV1 in aqueous solution was developed. Chromium(iii) was chelated with ethylenediaminetetraacetic acid (EDTA) prior to the analysis. A CS column was used to separate the CrIl'-EDTA complex from the CrVi ions using an eluent containing acetonitrile and tetrabutylammonium ion. The separated species were monitored at 242 nm using an ultraviolet (UV) detector. The factors affecting complex formation, the chromate stability and prospective interferences were investigated. The proposed method provides a simple analytical procedure for Cr speciation. The detection limits were 0.4 ng for CrIil and 1.6 ng for CrV1 with a 20 pl injection. The relative standard deviations for CriI1 and CrV1 were 0.24 and 1.78%, respectively.

Speciation studies by capillary electrophoresis- Simultaneous determination of chromium(III) and chromium(VI)

“…The effect of changes in the pH at which Cr(III) was complexed was studied carrying out the complexation procedure at different pH in the range of 3.0-8.5. The optimum pH of the sample solution was found to be 6.5-7.0 which corresponds well with that for the Cr (III)-EDTA complex investigated by Jen et al [11]. As demonstrated by an experimental series with different amounts of CDTA added to chromium solutions at pH 6.7, the time necessary for complete formation of the complex without heating the reaction mixture was still very long even when increasing the concentration of CDTA to 20-fold excess (it took about 3 h to reach the maximum peak area under these conditions).…”

“…It can be seen that the peak related to the chromate ion has a longer migration time compared to that of nitrate peak (resulting from the chromium(III) salt). This migration order is in contradiction to the expected one estimated from the ionic equivalent conductances [2] or ion-exchange properties [11] of these ions. It may be explained by the change of the chemical form of the chromate at a pH lower than 6.5 (at pH 3, the predominant form seems to be HCrO\ ).…”

Modification of catalytic adsorptive stripping voltammetric method of hexavalent chromium determination in the presence of DTPA and nitrate

“…According to literature data the complexes of Cr(III) with complexones are formed very slowly at room temperature [16] so usually to shorten the complexation time elevated temperatures were used [17,18,19]. In our study to shorten the time of conversion of the Cr(III)-DTPA complex to a nonactive one (equilibration time) we performed the measurements at elevated temperatures.…”

Speciation Analysis of Chromium by Adsorptive Stripping Voltammetry in Tap and River Water Samples

“…Above pH 7.39 the deprotonation reaction involves carboxylate group exit, followed by entry of hydroxide ion [30]. The conditions affecting formation of the complex between Cr(III) and EDTA, such as solution pH, the temperature and the concentration ratio of Cr(III)/EDTA [14,29,31] in the presented study were investigated.…”