Cadmium in marine sediments: Determination by graphite furnace atomic absorption spectroscopy.

Abstract

Cadmium is one of the most important toxic elements to be determined in environmental samples. Cd has proved, however, to be a difficult element to determine with good precision and relative accuracy. This is shown by the results of recent intercalibration exercises. (a) In the Baltic Sediment Intercalibration Exercise, Brtigmann and Niemisto (1987) found deviations in reported Cd results unacceptable. Relative standard deviations (rsd's) were 48 % and 63 % for for the two intercalibration samples. (b) In the National Research Council of Canada (NRCC) intercalibration (NRC MS1/TM), Berman and Boyko (1985) found that less than one-third of the 35 laboratories submitting Cd values appeared competent in handling samples at the 0.6 mg/kg level. (c) In the ICES First Intercalibration Exercise on the Trace Metals in Marine Sediments (1/TM/MS) report, Loring (1987) found that participating laboratories had difficulty with Cd determinations. Rsd's were 42 %, 39 %, and 53 % for the three intercalibration samples. It is suggested that the poor results are mostly due to the instrumental methods (Jensen, 1987) and inadequate use of reference materials to ensure good relative accuracy of the results. This paper discusses the various parameters that affect the precision and relative accuracy of Cd determinations and describes a simple, straightforward method based on the teflon bomb decomposition of the sample with HF-aqua regia followed by a graphite furnace atomic absorption determination of Cd using an uncoated L'vov platform. The relative accuracy and precision of the method has been confirmed and found to be good by analyses of reference materials and through participation in intercalibration exercises