[HPC purity tests for caffeine, theophylline and theobromine].

After giving a survey of the literature of the HPLC methods for the determination of caffeine, theophylline and theobromine two methods are presented for their purity test, i.e. their detection in each other at the trace level.

Ion-pair HPLC study of sulfonamides, barbiturates and antiphlogistic acids on a dynamically modified silica gel stationary phase.

The behaviour of some groups of acidic drugs (barbital derivatives, sulfonamides and antiphlogistic acids) was studied with a reversed-phase ion-pair HPLC method. A methanol-water-posphate buffered (pH = 7) mobile phase containing various concentrations of cetrimide was applied on a silica gel column. The correlations between the migration and the chemical structure within the different groups of compounds are discussed.