DETERMINATION OF LEAD CONCENTRATION AND LEAD-ISOTOPE RATIOS IN CALCIUM SUPPLEMENTS BY INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY AFTER HIGH-PRESSURE, HIGH-TEMPERATURE DIGESTION

The presence of lead as a contaminant in calcium supplements has arous ed considerable public health interest in recent years. In this invest igation lead and lead isotope ratios were determined by ICP-MS in ten brands of calcium supplements after high pressure/temperature digestio n. Calcium supplements (200 to 250 mg) were digested in 2 mt of nitric acid at 230 degrees C and at a pressure of 1770 psi (1.2 x 10(4) kPa) . Lead concentrations were determined by matrix-matched lead standards prepared in a high-purity calcium carbonate matrix. Good recoveries o f lead and calcium were obtained for certified animal bone reference m aterial. High levels of Pb (8 to 28 mu g Pb per g of calcium) were fou nd in calcium supplements that contain dolomite or bone meal. Chelated and refined calcium supplements had lower Pb levels (0.8 to 0.9 mu g Pb/g Ca). Application of lead isotope ratios to distinguish the origin of calcium sources was also explored.