Determination of growth hormone-releasing hexapeptide by reversed-phase high-performance liquid chromatography with electrochemical detection

A novel HPLC method with electrochemical detection is described for the det ermination of a growth-hormone-releasing hexapeptide (GHRP-6). HPLC conditi ons, such as the column, mobile phase, and oxidation potential, were optimi zed for sensitivity and selectivity of analysis. GHRP-6 was separated on a reversed-phase CN column with 37% acetonitrile in 100 mM phosphate buffer ( pH 7.0) as the mobile phase. The optimum electrochemical oxidation signal w as obtained at 0.85 V vs. Ag/AgCl in a glassy carbon working electrode due to two electroactive tryptophans and a histidine residue. Solid-phase extra ction using octadecyl cartridges was optimized for sample cleanup of GHRP-6 from serum samples and the method was successfully applied over the concen tration range of 5 to 100 ng/ml of analyte. (C) 2001 Elsevier Science B.V. All rights reserved.