Predicting electrospray response from chromatographic retention time

The relationship between electrospray ionization response and HPLC retention time was explored. For the series of small peptides studied, higher ESI response was observed for analytes with longer reversed-phase HPLC retention times. This correlation existed for both experimentally measured retention times and those calculated from amino acid retention coefficients. This study is useful to ESI users since it provides a way to predict and understand anomalies in ESI response with a readily accessible experimental parameter (chromatographic retention time). In addition, the ability to correlate ESI response with chromatographic partitioning lends validity to the equilibrium partitioning model, which explains differences in ESI response on the basis of partitioning between the surface and interior phases of the ESI droplet.