Rubidium and Lead Content of Market Milk

Market milk samples collected on a quarterly basis from various cities in the United States were analyzed for rubidium (Rb) and lead (Pb) content by atomic absorption spectrophotometry. The average Rb content of milk varied between 0.57 and 3.39 ppm. Statistical analysis of the data showed that the Rb content of milk varied significantly from one city to another at a-0.01; in addition, milk from cities in southeastern United States showed significant differences., from one sampling period to another. In general, the Rb content of milk sold in cities in inland states was small and that in cities of coastal states large.