Cadmium Determination of Frozen Cod: An Interlaboratory Comparison

Results of analyses of cod portions by eight laboratories indicate that a substantial lack of agreement exists among laboratories and methods for cadmium analysis. Consistent result for cod samples of low Cd content (biologically bound) were reported by only three of eight participating laboratories. These laboratories reported a mean Cd content of 0.323 ppm with a coefficient of variation of 38%. Results were better when cod samples were spiked with Cd acetate at the 78 ppm level. Six of the eight laboratories correctly reported that Cd content at the 78 ppm level (mean 71.2 ppm with a coefficient of variation of 13%). Lack of consistency in determining biologically bound cadmium in cod tissue is attributed in part to loss of Cd during dry ashing of tissue. Laboratories utilizing atomic absorption spectrophotometry or neutron activation analysis generally reported more accurate results than the laboratory utilizing argon plasma atomic emmission spectrometry.