Concurrent analysis of plasma retinol and alpha-tocopherol by isocratic HPLC

A simple, rapid and reliable method is described for simultaneous determination of plasma retinol and alpha-tocopherol. Plasma is deprotenized with 100% ethanol which contains retinyl acetate as internal standard and later extracted with HPLC grade n-hexane. The evaporated organic layer is reconstituted with methanol; diethyl ether (75:25 v/v) and injected onto a 250 x 4.6 mm column of zorbax CIS ODS C18 at a 1.5 ml/min flow rate. The system is monitored at 280 nm for both retinol and alpha-tocopherol. Intrabatch CVs were 3.9% for retinol and 1.8% for alpha-tocopherol respectively. Interbatch CVs over a 8-12 weeks period were about 9.48% for retinol and 6.7% for alpha-tocopherol. Our results agree well with those of retinol and alpha-tocopherol in quality control samples. This method should prove useful for routine analysis in clinical and epidemiological work.