Separation of Type I and III Isomers of Copro- and Uroporphyrins Using Affinity Capillary Electrophoresis

Abstract

Naturally occurring 8- and 4-carboxylic porphyrin I and III isomers are separated using a run buffer consisting of bovine serum albumin (BSA) and phosphate as the electrolyte. The method requires the use of deactivated capillaries to minimize protein-wall interactions. The uroporphyrin isomers are resolved in 15 minutes while the separation of the coproporphyrin isomers requires 28 minutes. Retention times are largely characteristic of the number of carboxylic acid side chains as well as the relative affinity for BSA. The binding of porphyrins to BSA is supported by a wavelength maxima red shift in the soret region when using BSA in the run buffer.