Predictive model for capillary electrophoretic peptide mobility in 2,2,2-trifluoroethanol-water solution

Using capillary electrophoresis (CE) on a set of 21 peptides with a molecular mass ranging from about 350 to 1850 Da, the Stokes radii at different protonation stages and the acidic dissociation constants in water and in a 2,2,2‐trifluoroethanol (TFE) water mixture (30% v/v) were determined. These results permitted us to establish separately the reliability of semiempirical models utilized for the prediction of peptide size and charge at different acidic pHapp (pHapp range: 2.00–4.25). The data obtained on size and charge were utilized in order to provide suitable mobility predictions on the basis of the charge‐to‐size ratio. The best predictive conditions for size and charge were found at the most acidic range of pHapp studied (2.00–2.25), either in water or a TFE‐water mixture, and reliable predictive equations for peptide mobility were established at this pHapp.