Determination of glycine and threonine in topical dermatological preparations

In the present study, a single HPLC method was developed for the determination of glycine and threonine in cicatrizants. Two different preparations Of a Cream and an ointment, and the corresponding bandages, onto which the formulations were applied, were Studied. The method involved Matrix solubilisationn with dichloromethane, liquid-liquid isolation of gly and thr with aqueous 1N NaOH, and derivatization with phenylisothiocyanate. Reversed-phase HPLC separation was carried Out by gradient elution with 20mM aqueous NaClO4 and acetonitrile (from 90% to 30% aqueous NaClO4 in 10min) on a LiChrospher (R) 100 RP-18 cartridge (125mm x 4.6mm). Analytes were determined with a UV detector set at 245nm. Quantitation was accomplished by internal standardization with methionine. Linearity was studied in the range 60-120% of the concentrations expected for gly and thr (viz. for gly from 200 to 400 mu g ml(-1), and for thr from 100 to 200 mu g ml(-1)). In reference aqueous samples, linear correlation (r)was better than 0.99 for gly and thr, while in spiked matrix samples r ranged from 0.97 to 0.98. Recoveries were in the 95-105% interval, and precision (CV%, N=6) was better than 5% for both analytes either in cream, ointment or bandages. The method was successfully used for the quality control of topical dermatological preparations. (C) 2008 Elsevier B.V. All rights reserved.