Problems of chromium analysis in biological materials

Detailed results are presented for all analytical quality-control samples distributed by the IAEA including a new animal muscle intercomparison material of very low chromium content, and an attempt is made to draw some conclusions regarding likely sources of analytical error. The report is largely a catalogue of failures. Most of the results of chromium analysis reported to IAEA in recent years must have been subject to significant sources of error of which the analysts were presumably unaware. With sufficient care, the analytical blank can probably be reduced to a satisfactorily low level. Similarly, interfering nuclear reactions in activation analysis, specifically the interference arising from iron in the sample, can be evaluated and, where appropriate, a correction applied. The loss of chromium during sample drying, however, is a more intractable problem. More work is required first to verify that the problem really exists. Activation analysis using a low temperature irradiation facility, in which fresh biological material can be activated, appears at present to be the best way of investigating this problem. (T.G.)