ONLINE THERMOSPRAY CONTINUOUS VOLATILIZATION OF COBALT, ALUMINUM AND CHROMIUM VOLATILE CHELATES AND DETERMINATION BY HEATED QUARTZ TUBE ATOMIC-ABSORPTION SPECTROMETRY

A thermospray of 24 cm in length and 0.5 mm inner diameter is used for on-line gas sample introduction of Co, Cr and Al chelate compounds into a heated quartz tube followed by atomic absorption spectrometric determination. The chelates are initially synthesised by means of flow injection (flow rate 6.5 ml min-1, injection volume 0.5 ml and reactor length 2 m) and transported to the vaporizer by an air flow [60 psi (1 psi = 6895 Pa)]. The optimum heating temperature of the vaporizer is 10-degrees-C higher than the volatilization temperature of the particular chelate, The sensitivity values obtained (Co, 0.05; Al, 0.07; and Cr, 0.03 mug ml-1 show an improvement of 3- and 20-fold, linearity showing a similar improvement, although the reproducibility is lower, when compared with values obtained using a pneumatic nebulizer. The presence of other elements that also form chelates can interfere with the determination of the analytes.