Simple GC-FID method development and validation for determination of α-tocopherol (vitamin E) in human plasma

This paper describes the development and validation of a novel GC-FID method for the determination of α-tocopherol concentration in human plasma which does not requires derivatization. The standard solutions and the plasma working solutions were prepared in absolute ethanol. To determine the concentration of α-tocopherol in human plasma, an aliquot of the plasma sample was deproteinized with ethanol. α-tocopherol was extracted with a mixture of hexane and dichloromethane (9:1). GC separation was performed using a HP-5 capillary column. Nitrogen was used as carrier gas at a flow-rate of 2 ml min− 1. Calibration curves were linear over the concentration range 1–30 μg ml− 1 (for standard solutions and solutions without endogenous α-tocopherol in plasma) and 5–34 μg ml− 1 (for solutions with endogenous α-tocopherol in plasma). Absolute recovery, precision, sensitivity and accuracy assays were carried out. The analytical recovery of α-tocopherol from plasma averaged 97.44%. The limit of quantification (LOQ) and the limit of detection (LOD) of method for standard samples were 0.35 μg.ml− 1 and 0.30 μg.ml− 1, respectively. Within-day and between-day precision, expressed as the relative standard deviation (RSD) were less than 4%, and accuracy (relative error) was better than 8%. This novel method, developed and validated in our laboratory, could be successfully applied to the in-vivo determination of α-tocopherol. The endogenous α-tocopherol amounts in blood of twelve healthy volunteers with no vitamin drug usage were measured with this method.