Quantitative determination of alpha-, beta-, gamma- and delta-tocopherols in human serum by high-performance liquid chromatography and gas chromatography-mass spectrometry as trimethylsilyl derivatives with a two-step sample preparation

Using a two-step sample preparation with Extrelut and silica gel extraction in Pasteur pipettes it is possible to quantify all tocopherols in human serum samples by means of normal-phase HPLC with fluorescence detection (lambda(ex) 295 nm, lambda(em) 330 nm) or by GC-MS of their trimethylsilyl (TMS) derivatives. The method has been used in pharmacoepidemiological studies concerning the exposition with vitamin E-containing drugs in Germany. The recovery for all tocopherols is 98% and the limit of detection is 50 pg for alpha-tocopherol in the HPLC and 40 pg for all TMS-tocopherols in the GC-MS method using the selected ion monitoring mode with a well-tuned GCQ system. Linearity of calibration is excellent for both methods over the full physiological relevant range. Due to the low sample amount needed, the method is suitable for epidemiological and paediatric research.