Direct determination of cadmium in soil slurries by micro-sampling cup atomic absorption spectrometry

Abstract

A method is described in which finely ground soil (0.5 g) is slurried with 25–50 ml of water and 50-µl aliquots of the slurry are pipetted into nickel cups. After drying, the samples are injected into an air-acetylene flame and the transient absorbance signals are recorded. No other sample treatment is necessary. Deuterium-arc background correction is needed to remove any small non-specific absorption interferences, and to prevent the base-line shift which otherwise occurs when the cup is placed in the flame. Calibration by standard additions gives quantitative recoveries of Cd compared with slurry electrothermal atomisation atomic absorption spectrometry (slurry ETA-AAS) and flame atomic absorption spectrometry with acid digestion. The method is less precise than slurry ETA-AAS but offers a cheaper alternative for rapid and sensitive analysis.