Quantitative determination of small amounts of L-penicillamine in D-penicillamine after desulfurization with Raney nickel.

Commercially available D-penicillamine is desulfurized with Raney nickel at room temperature in aqueous solution. L-Valine derived from contaminating L-penicillamine is determined colorimetrically by the amino acid oxidase/peroxidase reaction, using 2,2'-azino-di-[3-ethyl-benz-thiazoline-sulfonate(6)] (ABTS). The procedure assures the quantitation of L-penicillamine contaminating D-penicillamine down to the level of 0.1%.