SOLID-PHASE MICROEXTRACTION (SPME) FOR SA MPLE PREPARATION DURING DRUG-METABOLISM STUDIES

Within the scope of the investigation of drug metabolism in keratinocy tes solid phase microextraction (SPME) was investigated as a suitable method for sample preparation. The application of SPME is based on the fact, that a amount of analyte is absorbed by the polymer fiber at eq uilibrium, and the fiber is localized on a tip of a GC-syringe. The st able nitroxyl radical TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) and its apolar metabolite 2,2,6,6-tetramethylpiperidine were analyzed by SPME and subsequent GC using thymol as internal standard. By means of the headspace-technique and an apolar fiber the recovery rate of TEMPO and the metabolite was nearly 100% and the precision was high. Howeve r, the results of the direct SPME were unsatisfactory. In comparison w ith conventional liquid/liquid extraction and solid phase extraction S PE the SPME proved the best results with regard to recovery rate and p recision. Furthermore, the main advantages of SPME are the renunciatio n of organic solvents, the saving of time, the possibility to reuse th e fiber about 100-150 times and the option for a complete automatisati on of the extraction procedure.