Elemental speciation by liquid chromatography–inductively coupled plasma mass spectrometry with direct injection nebulization

Abstract

A new version of the direct injection nebulizer (DIN) is used to interface liquid chromatographic (LC) separations with element-selective detection using inductively coupled plasma mass spectrometry (ICP-MS). The DIN injects all of the sample into the ICP and has a dead volume of less than 1 µl. Charged species of arsenic and tin are separated as ion pairs on a micro-scale (1 mm i.d.), packed, reversed-phase column. Detection limits are 0.2–0.6 pg for arsenic and 8–10 pg for tin. For methanol + water eluents, the signal is highest at 25% methanol and stays within 25% of this maximum as the methanol fraction is varied from 20 to 80%. Compared with LC–ICP-MS with conventional nebulizers, the absolute detection limits and chromatographic resolution are substantially superior, and the dependence of analyte signal on solvent composition is somewhat less severe with the DIN.