Candidate BCR reference materials for arsenic and selenium determinations in human serum and urine

摘要

The pilot production of candidate reference materials for the quality assurance and statistical control of methods to determine toxic trace elements in biological samples is described. In the initial phase the project concerns a lyophilized human blood material containing Cd and Pb, a lyophilized human urine material containing As, Cd, Co and Cr, and a liquid human serum material with Al, Se and Zn at three different levels, representative of environmental and occupational exposure. The homogeneity and stability of the pilot batches were investigated by determining Al and Zn in serum, As in urine, Cd and Pb in blood at the medium level. The pilot batches produced were deemed to be homogeneous with respect to all the trace elements tested, and there was no indication of thermal instability except that the arsenic levels decreased significantly with time at 200 dec, 370 deg and 450 deg. Thirty-two laboratories from 12 different countries participated in an intercomparison round organized to test the suitability of the reference material and validate the methodological approaches for certification purposes. Focusing on the neutron activation results, the outcome of this first intercom-parison exercise demonstrates that the comparability of the calibration standards needs improvement. There fore, for the certification round stronger efforts will be undertaken to document the spiked concentrations and to reduce their uncertainties, and the laboratories will be required to meet defined quality criteria for the checking and documentation of traceability.