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Analysis of urine samples by electrothermal atomisation--atomic-absorption spectrometry: a comparison of natural and control material.

Biological matrices, especially human urine, vary considerably in their composition so that matrix effects in electrothermal atomisation-atomic-absorption spectrometry (ETA-AAS) may become unpredictable. This may lead to difficulties in the calibration procedure, which makes the usefulness of control and reference materials questionable. In this work we systematically investigated these problems for the direct determination of cadmium in urine. Background structures of natural and control materials are compared and the advantages of using a graphical display of the corrected, the uncorrected and/or the non-specific signals are presented. The efficiency of background compensation and the usefulness of control materials for quality control in routine analysis are discussed.