The problem of background correction in the determination of chromium in urine by atomic absorption spectrometry with electrothermal atomisation

Abstract

A previously described positive interference in the determination of chromium in urine was ascribed to the failure of the deuterium arc background correction system to correct fully for background absorption. In this work, it is shown that the interference is dependent on the gain setting of the photomultiplier and on the atomisation temperature. At temperatures below 2400 °C the interference is absent, but on increasing the atomisation temperature from 2400 to 2700 °C the interference increases in severity. The interference is thought to be emission caused by chromium together with potassium and sodium in the matrix. Lowering the atomisation temperature to 2400 °C allows the determination of chromium in urine without significant interference using conventional deuterium arc background correction.