Determination of vitamin E in microsamples of serum by liquid chromatography with electrochemical detection

Abstract

In this procedure for determination of vitamin E by 'high-performance' liquid chromatography with electrochemical detection, 25-μl serum specimens are deproteinized with ethanol. Vitamin E (α-tocopherol), its derivatives (β- and γ-tocopherols), and the internal standard (δ-tocopherol) are extracted into heptane and the extract is evaporated and the residue reconstituted with methanol before injection into the chromatograph. Within- and between-run CVs for an α-tocopherol concentration of 13.6 mg/L were 5.1% (n=28) and 6.0% (n=5), respectively. The standard curve is linear to 100 mg/L; the minimum concentration detectable is 0.1 mg/L. Analytical recovery ranged from 99.8% to 104.8%. In 36 specimens collected from apparently healthy subjects who were not taking vitamin supplements, α-tocopherol as determined by this method ranged from 4.3 to 9.7 mg/L, from 1.8 to 3.9 mg/L for β- and γ-tocopherols. Results by this method (y) and an HPLC-ultraviolet method (x) correlate reasonably (r=0.81):y=0.88x - 0.55 mg/L (n=45). This procedure is adaptable to automated analysis, and the small sample requirement facilitates its applicability to neonates.