INCORPORATION OF HYDROPHOBIC SELECTIVITY IN CAPILLARY ELECTROPHORESIS- ANALYSIS OF RECOMBINANT INSULIN-LIKE GROWTH-FACTOR-I VARIANTS

A highly selective electrophoretic system employing differential hydro phobic interaction was evaluated for the quantitative determination of recombinant insulin-like growth factor I (IGF-I) variants. The system consisted of mixed aqueous-organic buffers containing suitable amount s of a zwitterionic detergent. In addition, a neutral hydrophilic coat ing was attached to the wall of the capillary to minimize analyte adso rption and electroosmotic flow. The zwitterionic detergent acted as a hydrophobic selector, allowing independent optimization of the electro phoretic and hydrophobic selectivities in the separation system. The e xtent of hydrophobic interaction was conveniently adjusted by varying the type and amount of organic modifier. Complete resolution of a mixt ure of IGF-I variants with closely related mass-to-charge ratios was a chieved. Quantitative analysis of IGF-I process samples agreed well wi th HPLC results. Finally, the approach was found to be compatible with on-line capillary electrophoresis-mass spectrometry.