Aspects of the capillary GC analysis of all-trans- and 13-cis-acitretin

The capillary gas chromatographic (CGC) analysis of the der-matological drug trans-acitretin (Neotigason^R) and its cis metabolite is described. Separation of the methyl ester derivatives can be achieved on a 90% biscyanopropylsiloxane phase. The importance of using cold on-column injection and short, thin film capillary columns is discussed. For patients treated with the prodrug of acitretin, etretinate (Tigason^R), i.e. the ethyl ester of Neotigason, three compounds have to be separated. Selectivity tuning is required for successful CGC separation. An alternative can be found in the selectivity of ion monitoring mass spectroscopy. Analysis of plasma samples involves liquid-liquid extraction, a derivatization step, and HPLC purification.