Measurement of alpha-, beta-, and gamma tocopherol in serum by liquid chromatography.

A liquid-chromatographic assay for alpha, beta, and gamma-isomeric tocopherols in human serum is reported. The tocopherols and the internal standard (tocol) are absorbed into a silica gel column and are eluted in less than 10 min with n-hexane/isopropanol (99.4/0.6, by vol) at a flow rate of 1 mL/min. The complete analysis requires no longer than 30 min. Within-day precision (CV) was 1.4% (mean = 13.18 mg/L, n = 24), 7.4% (mean = 0.214 mg/L, n = 14), and 1.3% (mean = 1.01 mg/L, n = 14) for alpha-, beta-, and gamma-tocopherol, respectively. Day-to-day precision (CV) was 4.4% (mean = 9.85 mg/L, n = 10) for alpha-tocopherol, 9.1% (mean = 0.222 mg/L, n = 20) for beta-tocopherol, and 3.8% (mean = 1.00 mg/L, n = 20) for gamma-tocopherol. Extraction recoveries for alpha-, beta-, and gamma-tocopherol averaged 92.4 +/- 2.9% (n = 5), 91.4 4/- 7.6% (n = 5), an 92.0 +/- 4.1% (n = 4), respectively. The smallest injected amount detectable is estimated to be 0.03 micrograms for alpha-, and 0.04 micrograms for beta- and gamma-tocopherol.