Comparison of high-performance liquid chromatography and capillary electrophoresis in the analysis of somatostatin analogue peptides.

HPLC and CE methods were developed for analysis of somatostatin analogue (S-analogue) peptides utilizing triethylammonium phosphate-organic solvent modifier solvents as the CE buffer and HPLC eluent. Acetonitrile, methanol, ethanol and 2-propanol were applied as organic modifiers. The applicability of HPLC and CE systems was evaluated and compared. Optimum conditions for the separation were determined for both methods. Retention (migration) time, elution order and selectivity can be influenced by modifying the composition of the eluent (buffer) with organic solvents not only in HPLC but also in CE. Although the HPLC system reacted to changes in the organic solvent concentration in a much more sensitive way than the CE system did (from the point of view of retention time), CE proved to be a more suitable method for separating the peptides investigated. Baseline separation could be achieved within 6-9 min by CE, a result which was impossible to achieve with HPLC working in the isocratic mode. In CE the effect of the alcohols on migration times proved to be opposite to that of acetonitrile. Whereas ACN decreased, the alcohols increased the migration times in a concentration-dependent way. The results suggest that CE can be applied very advantageously in peptide analysis. Its performance regarding selectivity, resolution, theoretical plate number, duration and cost is comparable or sometimes superior to that of HPLC.