Faster determination of chromium in urine by electrothermal atomisation atomic absorption spectrometry

Abstract

Omission of the ashing stage in the determination of chromium in urine by electrothermal atomisation atomic absorption spectrometry (ETA-AAS) led to an increase in the background absorbance, but the values found were still within a range which a deuterium-arc background correction system is capable of correcting. Rapid three-stage furnace programmes omitting the ashing stage were developed for two systems: one for an instrument with deuterium-arc background correction using an uncoated tube and the other for a Zeeman-effect system using a pyrolytically coated tube. Cycle times of 53 and 70 s, respectively, were achieved for these methods which were developed for monitoring occupational exposure. Small matrix effects were overcome by adding a surfactant, Triton X-100, to the diluent. Samples and standards were diluted 1 + 1 with 1%V/V HNO₃ and 0.25%V/V Triton X-100. Results obtained by the two methods agreed well (r= 0.997) and also with those obtained by a slower method using an ashing stage (r= 1.000). It was concluded that Zeeman-effect background correction was unnecessary for this determination and that faster and more precise results could be obtained with the simpler system using deuterium-arc background correction.