A simple micro method for determination of plasma levels of alpha tocopherol (Vitamin E) in Pakistani normal adults

A relatively simple spectrophotometeric method has been developed for the determination of α tocopherol in human plasma. Method is modification of a previous micromethod base on oxidation of α tocopherol by ferric chloride. The complex of ferrous ions (generated in this reaction) with bathophenanthroline is determined spectrophotometrically at 536 nm. The absorbance of this colored complex is directly proportional to concentration of α tocopherol. The method involves extraction of α tocopherol from human plasma using nhexane which is relatively less toxic than xylene. The assay is sensitive enough to detect as little as 0.2 μg of vitamin. The recovery of α tocopherol from the plasma using n-hexane was in the range of 75% - 100%. The mean values of intra-assay and interassy coefficient of variation were found to be 5.3% and 13%, respectively. The assay was used to monitor α tocopherol levels in plasma samples of 81 normal healthy adults. Mean concentration of plasma α tocopherol in these normal healthy adults was found to be 9.45±2.64 μg/ml. Sixteen percent of adults had low levels of α tocopherol. The method is rapid, convenient, reproduciable and relatively less hazardous compared to methods using xylene for the extraction of vitamin E. It can be routinely used to analyze as many as 20 plasma samples in about 2 hours time.