Screening analysis for lead in whole blood and urine by Delves cup method using quality control samples. Comparison with the dithizone method.

The use of quality control samples of blood and urine into trays was done upon the basis of the micro-sampling method of Delves for rapid screening determinations of lead in blood and urine by Atomic Absorption Spectrophotometry. For lead in urine this was extended over a range of 12.66 ƒÊmol Pb 1-1 from patients under chelation therapy usually EDTA-Ca without any interference. Thirty-six urine samples with lead concentrations ranging from 0.08 to 12.66 ƒÊmol Pb 1-1 were analysed by colorimetry involving the use of dithiozone. A correlation coefficient of 0.9992 with a 0.995 level of conficence was found. The sensitivity of the method is 0.14 ƒÊmol Pb 1-' per 1 per cent absorption at 283.3 nm with the lowest limit of detection of 0.20 pmol Pb 1-1. In a collaborative test study for blood lead shows that there is a good agreement in interlaboratory variation, and intralaboratory variation. In our intralaboratory experiences we have noted that the mean values are closer to the mean values given for all participants from U.K. External Quality Assessment Scheme (UKEQAS). Considerations were made about precision and accuracy by using two types of absorption tubes as well as the effect of oxidation