High-performance liquid chromatographic analysis of penicillin V benzathine oral suspensions.

A rapid high-performance liquid chromatographic assay for penicillin V content of penicillin V benzathine bulk drug and oral suspensions is described. Dilution of the oral suspension with methanol containing 1,3,5-trimethoxybenzene as the internal standard allowed for direct analysis on a reversed-phase column with a mobile phase of 53% methanol in 0.05 M aqueous pH 3.5 phosphate buffer. A relative standard deviation of less than 1% was obtained on commercial formulations, and the system was linear over a range 10-40 microgram injected.