BayCEER Workshop 2008

Application of capillary electrophoresis in the analysis of heavy metals

Determination of heavy metals in environmental samples is important due to their ecotoxicological relevance. Capillary electrophoresis is an interesting alternative to the conventional atomic absortion spectroscopy as the former technique allows speciation of metal ions in short time and at low costs. Taking into consideration that the electrophoretic mobilities of metal cations with equal charge are similar, it is required to improve their resolution using complexes with different stability. In this work, the application of α-hydroxyacids for the separation of Cd²⁺, Cu²⁺, Ni²⁺, Pb²⁺, and Zn²⁺ was studied. Nine α-hydroxyacids (glycolic, lactic, 2-hydroxybutyric, 2-hydroxyisobutyric, 2-hydroxyisovaleric, 2-hydroxy-2-methylbutyric, 2-ethyl-2-hydroxybutyric, 2-hydroxycaproic and 2-hydroxyisocaproic acid) were tested as to their ability to resolve these ecotoxicologically relevant heavy metals. The electrophoretic conditions using an uncoated fused silica capillary (effective length: 50 cm, i.d.: 75µm) were: background electrolyte (pH 4.2) 4-aminopyridine 10 mmol/L and complexing acid 15 mmol/L, indirect UV detection at 254 nm and hydrodynamically injection. Best results, i.e. complete resolution of all metals, were achieved with glycolic and lactic acid.