REDUCTION OF BACKGROUND ABSORPTION IN THE MEASUREMENT OF CADMIUM, LEAD AND SELENIUM IN WHOLE-BLOOD USING IRIDIUM-SPUTTERED GRAPHITE TUBES IN ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

The thermal behaviour during pyrolysis and of the vapour phase during atomization for Cd, Pb and Se in acid-digested whole blood using Ir-sp uttered tubes is described, The performance of Ir as a permanent modif ier was affected unfavourably by the complex matrix compared with conv entional modifiers. Background absorption was measured using an atomic absorption spectrometer in addition to a diode-array spectrometer and compared with the background obtained in pyrolytic graphite-coated gr aphite tubes, Both methods of measurement indicated that the backgroun d was much reduced in the Ir-sputtered tubes. The decrease in backgrou nd absorption improves conditions for the measurement of these element s, Background molecular absorption was also measured as a function of time, Molecular species such as NO were detected in the vapour phase u sing pyrolytic graphite-coated tubes, whereas CS and CO were detected using Ir-sputtered tubes.