INFLUENCE OF ANALYTE STEREOCHEMISTRY AND BASICITY ON PEAK SHAPE OF BASIC COMPOUNDS IN HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH REVERSED-PHASE COLUMNS, USING PYRIDINE AND ALKYL-SUBSTITUTED DERIVATIVES AS PROBE COMPOUNDS

Column efficiency, peak asymmetry and retention factor of a series of sixteen compounds comprising pyridine and some alkyl-substituted derivatives, with pK(a) values ranging from 5.17 to 6.74 is reported on a RP-HPLC column previously shown to be especially suitable for the analysis of basic compounds. Compound stereochemistry in close vicinity of the basic group is found to influence peak shape strongly: however, stereochemistry at more remote positions is also of some significance. The effect of pK(a) on peak shape is discussed in the light of measurements of the degree of protonation of the compounds in the methanolic mobile phase as well as water.