Defining a lowest level of reliable measurement for lead in foods

Procedures are outlined for defining and demonstrating a lowest level of reliable measurement for Pb in foods. The method of analysis studied was a dry ash sample mineralization with quantitation by differential pulse anodic stripping voltammetry at a hanging mercury drop electrode. Past experience with analyses for Pb in foods indicated that the lowest measurement of Pb in foods was limited by the Pb contributed from the reagents, apparatus, and laboratory environment. The magnitude of contamination from these 3 sources was investigated. Once a specific source of contamination was identified, attempts were made to eliminate or minimize the amount of Pb it contributed to the analysis. After contamination was controlled to the degree our facilities would allow, low level Pb determinations were performed on infant formula.