The electrophoretic mobility of tripeptides as a function of pH and ionic strength: comparison with iontophoretic flux data.

Capillary electrophoresis (CE) is an extremely efficient separations tool which can also be used to determine fundamental molecular parameters, e.g., the electrophoretic mobility of a molecule. We have studied the changes in the CE estimated electrophoretic mobility of thyrotropin releasing hormone (TRH) as a function of pH and ionic strength. Further, we have used CE to estimate the mobilities of two synthetic analogs of TRH to examine the behavior of positive (basic) and negative (acidic) peptides under the conditions of this work. These data were then compared with literature values of iontophoretic flux of these molecules under similar formulation conditions. Our results suggest that CE could potentially assist formulation optimization for the iontophoretic delivery of peptides.