Measurement of vitamin E in serum and plasma by high performance liquid chromatography with electrochemical detection

A deficiency of vitamin E has been associated with a wide variety of pathological conditions, many of them involving neonates. Previously published methods for the quantitation of vitamin E require large sample volumes as well as extensive extraction and concentration procedures. The present work describes a method for the quantitation of vitamin E in small volumes (less than or equal to 50 microliters) of serum or plasma without the need for extraction or concentration of the sample. With further optimization, even smaller volumes (less than or equal to 10 microliters) can be employed. Sample preparation consisted of precipitation of plasma proteins with absolute ethanol. After centrifugation, a small volume (10 to 50 microliters) of the supernatant was injected directly onto the high performance liquid chromatography (HPLC) column. A dual channel electrochemical detector was used for quantitation of the vitamin E. Pooled serum or plasma was used to determine within-day (8.43 +/- 0.19 mg/L) and between-day (8.49 +/- 0.34 mg/L) precision. Analytical recovery of added vitamin E (4-16 mg/L) averaged 102 +/- 7.0%. No interfering peaks were observed. Linearity was demonstrated over 0.5 to 800 ng. Vitamin E acetate is not detected by this method. HPLC with electrochemical detection is a highly sensitive and specific method for the quantitation of vitamin E in plasma or serum. This procedure is rapid and simple, and can be performed with very small sample volumes.