Optimized and validated HPLC methods for compendial quality assessment .1. Methylxanthine derivatives

The HPLC method suggested here is suitable for the detection and quantitative determination of 0.1-1 % caffeine, theobromine and theophylline impurities in each of these methylxanthine derivatives. The system optimization includes organic modifier content. ionic strength, eluent flow rate and concludes to the use of a simple C-18/methanol-water 1:4 (I = 0.1) chromatographic system. The limit of impurity detection was found to be 15 ng (theobromine. theophylline) and 30 ng (caffeine). The range of quantitation extends from 31.25 to 250 ng. The accuracy (percentage of recovery) and precision (repeatability) of the method are tabulated. The method, considering validation requirements of USP XXIII. demonstrates the suitability of HPLC for selective compendial purity tests.