ANALYTICAL EVALUATION OF A TUNGSTEN COIL ATOMIZER FOR CADMIUM, LEAD, CHROMIUM, MANGANESE, NICKEL AND COBALT DETERMINATION BY ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

The analytical performance of an unenclosed tungsten coil atomizer operating in Ar-H-2 (90:10) was assessed by electrothermal atomic absorption spectrometry (ETAAS) for the determination of pg to ng levels of Cd, Co, Cr, Mn, Ni and Pb in liquid samples. A three-steps low power unit provided the heating programme for the tungsten coil with dry, pyrolysis and vaporization-atomization as sequential steps, and shortlived absorption signals (100-250 ms) were produced with an analysis time of 100 s. parameters studied were the current applied to the coil; temperatures and duration of the three heating steps; purge gas flow rate; coil alignment in the radiation beam; and sample volume. Under optimized conditions, linear working ranges extended between 0-2.0 mu g l(-1) for Cd and 0-100 mu g l(-1) for Ni and Pb, and characteristic masses were between 0.3 pg (Cd) and 14 pg (Pb). Within-day reproducibility (relative standard deviation) of measurements varied between 2.2% (Cr) and 7.5% (Pb), and between-day was < 8% (Ph) in the analyte's linear working ranges, being acceptable for manual sample introduction used in this atomizer. Detection limits (3 sigma(Bl)) were in the range 0.6 pg (Cd)-23 pg (Pb).