Comparative study of certified reference materials and quality control materials for the quality assurance of blood-lead determination

Abstract

In order to ensure a high standard in the analytical methods used to determine lead in blood, reference materials, quality control materials and several quality assessment schemes exist. However, since 1988 the blood lead level in the European Community has decreased owing to a decline in environmental and occupational exposure; consequently there is a need for certified reference materials (CRMs) at low level. A study of the biological CRMs for blood lead, CRMs 194–196 from the European Community Bureau of Reference (BCR) and the quality control materials STE 901–906 from Nyegaard A/S, and AMI B601–B604 and AMI B701–B705 from the Danish National Institute of Occupational Health (AMI), was made in order to evaluate the control materials AMI B701–B705 against the CRMs 194–196, and to verify the homogeneity and influence of the biological matrix of commercially available blood-lead quality control materials. Internal quality control data were collected and an interlaboratory study was carried out on lyophilized human blood versus lyophilized bovine blood certified for lead. The calculated standard deviations for the BCR CRMs were comparable to the standard deviations for AMI control materials, although the biological matrix was different. No significant difference was demonstrated between the blood-lead levels certified by BCR in 1985 and the levels measured by AMI in 1991, indicating the homogeneity and stability of the lyophilized materials. All analytical results were obtained from selected international laboratories by using atomic absorption spectrometry and anodic stripping voltammetry. The study emphasizes the need for CRMs, control materials and quality assessment schemes for trace elements in biological fluids. Blood-lead concentrations in the range similar to that of the AMI control materials are desirable.