Pharmaceutical samples spiked with several heavy metals were prepared for ICP-MS analysis using microwave digestion following the protocols in proposed USP chapters <232> and <233>. The results of the spike recovery study are discussed.

Current USP Method 231 "Heavy Metals" was introduced in 1905 for determining heavy metal impurities in pharmaceutical drug products. The procedures of the method have several limitations, which produce results that are nondiscriminatory, difficult to reproduce, and qualitative, or at best, semi-quantitative.