Speciation of Chromium by Direct Coupling of Ion Exchange Chromatography With Inductively Coupled Plasma Mass Spectrometry

Abstract

Ion exchange chromatography has been coupled with inductively coupled plasma mass spectrometry (ICP-MS) for the element speciation of chromium. Hydraulic high pressure nebulization was used for sample introduction with high aerosol efficiency. It was the particular aim of this work to exclusively use nitric acid for elution in order to reduce interferences in ICP-MS. Therefore, an anion exchange pre-column IonPac-AG5 (Dionex, Idstein, Germany) with a length of 50 mm and an id of 4 mm has been operated as a mixed-mode column, which shows cation exchange capabilities too. The column was operated at a flow rate of 1.2 ml min^–1 and samples were injected by use of a sample loop with a volume of 100 µl. Both Cr^VI anions and Cr^III cations could be retained on the column, and optimum results concerning chromatographic and mass spectrometric conditions were finally achieved with discontinuous elution in two steps by injection of 0.3 m (pH 0.5) HNO₃ for Cr^VI and subsequently of 1.0 m (pH 0) HNO₃ for Cr^III. Detection limits just above 0.1 µg l^–1 could be realized.