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

This paper describes the development and validation of a novel GC-FID method for the determination of a-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 a-tocopherol in human plasma, an aliquot of the plasma sample was deproteinized with ethanol. alpha-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 mu g ml(-1) (for standard solutions and solutions without endogenous alpha-tocopherol in plasma) and 5-34 mu g ml(-1) (for solutions with endogenous alpha-tocopherol in plasma). Absolute recovery, precision, sensitivity and accuracy assays were carried out. The analytical recovery of alpha-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 mu g.ml(-1) and 0.30 mu g.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 alpha-tocopherol. The endogenous alpha-tocopherol amounts in blood of twelve healthy volunteers with no vitamin drug usage were measured with this method. (c) 2006 Elsevier B.V. All rights reserved.