DETERMINATION OF ARSENIC, CHROMIUM, SELENIUM AND VANADIUM IN BIOLOGICAL SAMPLES BY INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY USING ONLINE ELIMINATION OF INTERFERENCE AND PRECONCENTRATION BY FLOW-INJECTION

A method of matrix elimination has been developed that facilitates the determination of analytes such as arsenic, chromium, selenium and van adium in biological matrices by inductively coupled plasma mass spectr ometry (ICP-MS) without interference from polyatomic ions. The method involves the retention of the analytes as anions on activated alumina (acidic form) in a microcolumn using an on-line flow injection system, with simultaneous matrix removal. Analysis of certified reference mat erials [NIES (National Institute of Environmental Studies) 9 Sargasso, Tort-1 Lobster Hepatopancreas, Dorm-1 Dogfish Reference Muscle and Do lt-1 Dogfish Liver Tissue] yielded results in good agreement with the certified values, although a photolysis step was used for determinatio ns of arsenic in animal based samples in order to destroy organoarseni c compounds. Tests showed close to 100% recovery for all analytes. The limits of detection (3sigma(n-1)) using a 200 mul sample loop were 1. 2, 6.0, 9.0 and 65 ng ml-1 for vanadium, chromium, arsenic and seleniu m, respectively. A preconcentration system was developed for selenium because of the relative insensitivity of ICP-MS to this element. This yielded a detection limit of 1.0 ng ml-1 at m/z 78.