Chromatographic method for the determination of conditional equilibrium constants for the carbamate formation reaction from amino acids and peptides in aqueous solution

Abstract

A novel and sensitive method has been developed and evaluated for the study of carbamate formation equilibria of amino acids and peptides in aqueous solution. The method is based on reversed-phase liquid chromatography with cetyltrimethylammonium bromide. The reliability of the method was established by comparing the results determined from the present study with the few data in the literature. The relaxation rate of the carbamate reaction was shown to be faster than the chromatographic distribution relaxation rate (seconds). As a result, the retention time of amine solutes is increased in the presence of CO 2 . Carbamate formation constants and mole fractions of carbamates at physiological pH of eleven L-α-amino acids and peptides were determined. No correlation between the formation constant and the ammonium pK a was found