Liquid chromatographic determination of nalidixic acid in pharmaceutical preparations.

A simple, rapid, and environmentally safe liquid chromatographic (LC) method was developed for the qualitative and quantitative determination of pharmaceutical preparations of nalidixic acid. The new method was applied to commercial preparations of tablets and a suspension of nalidixic acid and found to be satisfactory for both quantitative and qualitative determinations. Previous LC methods either used chloroform to extract, which we were trying to eliminate, or used a mobile phase of about pH 2.5, which will destroy the column coating. The LC system for the new method uses sulfanilic acid as internal standard, a mu-Bondapak C18 column, and a mobile phase of methanol, 0.0045M dibasic potassium phosphate, and 0.0072M hexadecyltrimethylammonium bromide. The detection wavelength is 254 nm. The sample is dissolved in methanol, and an aliquot is injected through a 20 microL injection loop. Average recoveries ranged from 99.4 to 101.3%.