Simultaneous determination of low plasma concentrations of retinol and tocopherols in preterm infants by a high-performance liquid chromatographic micromethod.

A method for the simultaneous determination of low concentrations of retinol and tocopherols from 100 microliters plasma using isocratic reversed-phase HPLC is described. Retinol is quantified with a programmable UV-Vis detector, whereas tocopherols are quantified by fluorescence detection using tocol as the internal standard. Intra- and inter-assay precision are 3.7 and 4.3% for retinol and 2.3 and 6.1% for alpha-tocopherol, respectively. The accuracy as determined with standard material from the US National Institute of Standards and Technology with low, medium and high concentrations is in the range of 0.2-6.0% bias for retinol and of -3.0 to 5.5% for alpha-tocopherol, respectively. This method is highly sensitive and selective and has a good precision and accuracy for measuring low concentrations of vitamins in small plasma volumes.