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

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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.

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