[Interlaboratory quality control for the determination of blood lead. Initial experiences in Tuscany]

Results of an interlaboratory precision comparison programme of blood lead determination are presented. The samples consisted of bovine haemolyzed whole blood to which were added in pool small quantities of lead nitrate aqueous solutions to obtain two different concentrations of the metal (i.e. about 30 and 70 micrograms/dl). After each pool was well mixed it was divided into 15 ml portions in screw-top linear polyethylene vials and stored at -25 degrees C. The analytical methods used by the five public health laboratories participating in the programme were based on atomic absorption spectrophotometry. Three laboratories used methods which incorporate discrete sampling techniques (i.e. tantalum boat, electrothermal atomisation) and the remaining two, a method incorporating a sample preconcentration by solvent extraction and flame atomisation. During the six months period of the programme, fifty five results were obtained for each of the two pools of blood. Common statistical methods and the graphic system devised by Youden were used for data analysis. An acceptable agreement among results from the five laboratories has been obtained. The usefulness of this type of programme in improving analytical proficiency has been confirmed.