Analytical validity of the determination of mercury in whole blood and urine--results of the German external assurance programme for toxicological analysis in biological materials.

The determination of mercury concentrations in blood and urine is currently the best way of monitoring individual uptake of organic and inorganic mercury. In Germany these determinations must be carried out under the conditions of an external quality assurance programme. The German performance evaluation, based on reference values established by reference laboratories yields success rates in percent for the participants in the intercomparison programme of about 60%. A Canadian evaluation system based on two evaluations scores, yields success rates of 25-50% for "good performance" and of 65-80% for "acceptable performance". The determination of mercury in blood and urine is at present not carried out with the necessary reliability.