Comparison of methods for determining penicillamine in bulk drug and formulations.

The mercuric acetate method (Method I) cited in the Code of Federal Regulations (CFR) as the official method for determining the penicillamine content of a drug was compared with a nonaqueous amine titration (Method II), a nonaqueous acid titration (Method III), and a hydroxylamine assay (Method IV). Quantitative determinations were made for 3 types of penicillamine samples: commercial lots of bulk drug, capsules, and test solutions containing known amounts of penicillamine and EDTA. Method III proved unsatisfactory in the bulk drug determinations. Method II, although slightly less precise than Method I, gave generally satisfactory results for the bulk drug and capsule samples. Method IV was the only method to give satisfactory results in the presence of EDTA.

High pressure liquid chromatographic method for probenecid in flavored oral suspensions containing ampicillin: collaborative studies.

A high pressure liquid chromatographic method for determining probenecid in oral suspensions of amoxicillin was applied to the determination of probenecid in oral suspensions of ampicillin. Three preparations containing various known amounts of probenecid in synthetic mixtures of ampicillin oral suspensions were analyzed by 5 chemists in an intralaboratory study, with satisfactory results. Blind duplicates of 3 prepared oral suspensions were sent to 12 collaborators, who were instructed to analyze the samples in a fixed random order. The standards showed a satisfactory linear response. Average recoveries of probenecid in the interlaboratory study for the 6 mixtures ranged from 95.2 to 99.1%, and the coefficients of variation ranged from 1.63 to 4.9%.