Effect of nonaqueous buffer modifiers on the capillary electrophoresis-mass spectrometry analysis of peptides.

The effect of the addition of nonaqueous modifiers in capillary electrophoresis at varying concentrations was determined using synthetic peptides as model compounds. The electroosmotic flow is compared in each of the binary solvent systems and, in all cases, an increase in the concentration of organic solvent resulted in a decrease in the electroosmotic flow. The electrophoretic mobilities of each peptide were calculated and, in the case of acetonitrile, little or no change was observed in the peptide mobilities. In general, a decrease in the electrophoretic mobilities of the peptides was observed for increasing concentrations of methanol and N-methylformamide. The compatibility of each modifier at 25% (vol/vol) for use with mass spectrometric detection was evaluated. From our data, the addition of acetonitrile to the CE buffer appears to be the most compatible with mass spectrometry due to shorter analysis times and increased sensitivities in comparison to methanol and N-methylformamide.