High pressure liquid chromatographic determination of sulfisoxazole in dosage forms: collaborative study.

A reverse phase high pressure liquid chromatographic method for the determination of sulfisoxazole in tablets, solution, and ointment dosage forms was collaboratively studied by 7 laboratories. The method uses a C18 column, an acetonitrile-acetic acid-water mobile phase, sulfadimethoxime as the internal standard, and photometric detection at 254 nm. Collaborators were supplied samples of 2 commercial tablets, 1 synthetic tablet powder, 1 commercial and 1 synthetic ophthalmic solution, and 1 commercial ophthalmic ointment. Mean recoveries of sulfisoxazole from the synthetic tablet powder and ophthalmic solution were 99.9 and 100.0%, respectively. Mean coefficients of variation for all samples analyzed were less than 2%. The method was adopted interim official first action.