Comparison of methods for determining probenecid in tablets and flavored oral suspensions containing ampicillin

Several methods for quantitating probenecid were compared: USP XIX method for probenecid in tablets, a modified USP extraction method for probenecid in tablets, a new column extraction method for probenecid in tablets and oral suspensions containing ampicillin, and a high pressure liquid chromatographic (HPLC) method for probenecid in tablets and oral suspensions containing antibiotics. The first 3 methods were satisfactory for probenecid in bulks and tablets but proved unsatisfactory for oral suspeonsions containing flavors. The flavors gave positive interference for probenecid in oral suspensions. The HPLC method, although more time-consuming, separated probenecid from excipients, thus eliminating positive interference from flavors.