Liquid-chromatographic monitoring of 5-methyltetrahydrofolate in plasma.

The liquid-chromatographic measurement of 5-methyltetrahydrofolate in biological fluids is described. The sensitivity of the spectrophotofluorometric detector used allows direct evaluation of basal concentrations of the compound in plasma. Because it is resolved from the other common folates and from methotrexate, the procedure is suitable for monitoring it in plasma of patients receiving high-dose therapy with methotrexate.