Novel mobile phase for separation of Cr6+ from Cr3+ and associated heavy metal cations by high-performance thin-layer chromatography

Eleven heavy metal cations have been chromatographed on silica gel high-performance thin-layer chromatography plates with pure organic, mixed organic, and mixed aqueous-organic mobile phases. Mobile phases such as methanol-dimethylamine, 8:2 (v/v), and methanol-dimethylamine -formic acid, 8:8:2 (v/v), were found most suitable for rapid separation and identification of mixtures of Cr6+ and Cr3+ and of Cr6+, Ni2+, and Co2+, respectively. The effect of impurities such as inorganic ions, phenols, and surfactants on the separation of Cr6+ and Cr3+ was examined. Mutual separation of Cr6+, Ni2+, and Co2+ was investigated at different sample solution pH. The limit of detection for Ni2+, Co2+, Cu2+, and Pb2+ on HPTLC plates was evaluated and semiquantitative determination of Cr6+ and Ni2+ by spot-area measurement was attempted. The proposed method was successfully used for identification of Cr6+, Cr3+, Ni2+, and Co2+ and for mutual separation of Cr6+ from Cr3+ and of Cr6+ from Ni2+ and Co2+ from a variety of industrial wastewater samples.