Determination of Heavy Metal Ions by Capillary Electrophoresis with Contactless Conductivity Detection after Field-amplified Sample Injection

Abstract

A method has been developed for determining of heavy metal ions by field-amplified sample injection capillary electrophoresis with contactless conductivity detection. The effects of the 2-N-morpholinoethanesulfonic acid/histidine (MES/His) concentration in the sample matrix, the injection time and organic additives on the enrichment factor were studied. The results showed that MES/His with a low concentration in the sample matrix, an increase of the injection time and the addition of acetonitrile improved the enrichment factor. Four heavy metal ions (Zn²⁺, Co²⁺, Cu²⁺ and Ni²⁺) were dissolved in deionized water, separated in a 10 mM MES/His running buffer at pH 4.9 and detected by contactless conductivity detection. The detection sensitivity was enhanced by about three orders of magnitude with respect to the non-stacking injection mode. The limits of detection were in the range from 5 nM (Zn²⁺) to 30 nM (Cu²⁺). The method has been used to determine heavy metal ions in tap water.