AbstractsChemistry

The determination of the pKa's of several organic acids and bases using chromatography was investigated. Normal-phase buffer-impregnated paper chromatography was found to be unsuitable. TLC plates impregnated with mineral oil were examined as a possible reversed-phase method, with poor results. The use of XAD-2 copolymer as the stationary phase in a simple HPLC method gave good results. Experimentally determined pKa values were confirmed using UV spectrophotometry with the identical solvents and buffers used in the HPLC method. Statistical comparisons using both pKa and Ka values were performed. The advantage of using a computer method involving the second derivative to determine pKa was illustrated.