Simultaneous determination of selegiline and desmethylselegiline in human body fluids by headspace solid-phase microextraction and gas chromatography–mass spectrometry

A method for the simultaneous determination of selegiline and its metabolite, desmethylselegiline, in human whole blood and urine is presented. The method, which combines a fiber-based headspace solid-phase microextraction (SPME) technique with gas chromatography–mass spectrometry (GC–MS), required optimization of various parameters (e.g., salt additives, extraction temperatures, extraction times and the extraction properties of the SPME fiber coatings). Pargyline was used as the internal standard. Extraction efficiencies for both selegiline and desmethylselegiline were 2.0–3.4% for whole blood, and 8.0–13.2% for urine. The regression equations for selegiline and desmethylselegiline extracted from whole blood were linear (r2 = 0.996 and 0.995) within the concentration ranges 0.1–10 and 0.2–20 ng/ml, respectively. For urine, the regression equations for selegiline and desmethylselegiline were linear (r2 = 0.999 and 0.998) within the concentration ranges 0.05–5.0 and 0.1–10 ng/ml, respectively. The limit of detection for selegiline and desmethylselegiline was 0.01–0.05 ng/ml for both samples. The lower and upper limits of quantification for each compound were 0.05–0.2 and 5–20 ng/ml, respectively. Intra- and inter-day coefficients of variation for selegiline and desmethylselegiline in both samples were not greater than 8.7 and 11.7%, respectively. The determination of selegiline and desmethylselegiline concentrations in Parkinson's disease patients undergoing continuous selegiline treatment is presented and is shown to validate the present methodology.