CHIRAL SEPARATIONS USING HEPARIN AND POLYELECTROLYTE MULTILAYERS IN CAPILLARY ELECTROPHORESIS

Abstract

Reports on the use of heparin as a chiral additive show widely different separation conditions and inconsistent results. A systematic evaluation of the separation of pheniramine enantiomers using heparin as a chiral selector suggested that heparin was interacting with the capillary surface at acidic pH. Further testing confirmed the interaction between heparin and the capillary surface at acidic pH causing an increase in the electroosmotic flow (EOF). Polyelectrolyte multilayer (PEM) was chosen as a potential means to eliminate the interaction between heparin and the capillary surface. Generation of the PEMs on a bare capillary was monitored by measuring the changes in EOF following the deposition of each polyelectrolyte layer; deposition provided consistent EOF intensities and facilitated control over EOF direction. Results from this study indicated that a stable PEM system could be generated, which prevents the interaction of heparin with the capillary surface. This PEM system showed excellent reproducibility, with only a slight loss of resolution due to the increased interactions between the analyte and the charged capillary wall.