Determination of Lead in Evaporated Milk by Atomic Absorption Spectrophotometry and Anodic Stripping Voltammetry: Collaborative Study

Abstract

Abstract A method for the determination of lead in evaporated milk was successfully collaborated by 11 laboratories. Five laboratories used both atomic absorption spectrophotometry (AAS) and anodic stripping voltammetry (ASV) for the determination, 5 used only the atomic absorption method, and 1 used only the polarographic method. Each collaborator received 12 samples, 2 at each of the 5 different levels (0.06–0.95 ppm) and 2 practice samples with a known lead content. Both AAS and ASV were equally suitable for the determination of lead in the concentration range studied. The pooled variation between duplicate determinations was 0.0010 and 0.0016 for the AAS and ASV methods, respectively. For the AAS determinations the coefficients of variation (random error components) decreased from 43% at the lowest Pb level to 4% at the highest level. Although the ASV results did not show the same regularity of decreasing coefficients of variation with increasing Pb level, the coefficients of variation were acceptable: 28% at the 0.06 ppm level and 6% at the 0.22 ppm level. The AAS method has been adopted as official first action and the ASV method as interim official first action.