Effects of ageing of pyrolytically coated tubes on the determination of refractory elements by electrothermal atomisation atomic absorption spectrometry

Abstract

The quality of the pyrolytic coating of graphite tubes is shown to be of prime importance in the electrothermal atomisation atomic absorption spectrometric determination of refractory elements in complex matrices. For molybdenum in a plant matrix the shortcomings due to progressive degradation of the coating can be circumvented by signal integration. The problems encountered with chromium in several matrices are related to the irreproducible quality of the coating between different sets of tubes supplied by the same manufacturer. For the determination of barium in sea water, pyrolysis at 1800 °C efficiently eliminates background absorption. With an increase in tube porosity, due to degradation of the coating, there is a drastic increase in the background signal that can be corrected only with a Zeeman device.