Histidine as a dipolar eluent in ion chromatography of aliphatic amines

Summary Acidified L-histidine was found to be a suitable eluent in membrane-suppressed cation chromatography for the separation of aliphatic mono-amines (methyl, ethyl, trimethyl, triethyl, tripropylamines). Based on the protonation equilibrium of amines with the histidine eluent, a simplified separation method was developed, in which the eluent can act as a source of diprotic cations and analytes as monoprotic amines. On detection, the suppressor converts the eluent by deprotonation to its dipolar form with minimum conductivity at the pH of the isoelectric point of histidine, (pl 7.56). Efficient separations were observed under isocratic development with an eluent concentration of C_HIS≤2 mM and a pH below 2.0. The effect of eluent concentration and number of carbon atoms in the aliphatic chain on the retention and the resolution was determined. Selectivity data of the separation system are also presented. Presented at Balaton Symposium '01 on High-Performance Separation Methods, Siófok, Hungary, September 2–4, 2001