Determination of 5-methyltetrahydrofolic acid in plasma and spinal fluid by high-performance liquid chromatography,...

Chromatographic conditions for the determination of 5-methyltetrahydrofolic acid in plasma and spinal fluid are described, involving simple pretreatment of the sample. Electrochemical detection was used. The linear range of the method is more than 10(3). Recovery from plasma and spinal fluid is 100%, and the detection limit of the method is 2.10(-9) M, sufficient for the detection of endogenous plasma and spinal fluid levels. The detection conditions are discussed. Endogenous concentrations of the compound in plasma and spinal fluid were determined and correlated with a folate bioassay. Plasma concentrations have been shown after the administration of leucovorin which is used in anticancer therapy.