The choice of paper and thin-layer chromatographic systems for the analysis of basic drugs

Thirty-seven paper and thin-layer chromatographic systems in general use for the analysis of basic drugs have been examined. Their discriminating powers were measured, both individually and when used in combination. The better systems were found to be thin-layer systems of silica gel sprayed with 0·1n NaOH, dried and run using one of the following solvents: (1) chloroform-methanol (90:10), (2) cyclohexane-toluene-diethylamine (75:15:10) and (3) acetone. A thin-layer cellulose system using n-butanol-water-citric acid (87:13: 0–48) was suitable if speed was not a requirement and a reversed phase paper system run with an aqueous buffer solution (pH 4·58) at 95† was the fastest system examined. Any of these five systems could be used in combination since their correlation coefficients were never higher than 0·61.