High-performance liquid chromatographic and capillary electrophoretic determination of free nicotinic acid in human plasma and separation of its metabolites by capillary electrophoresis.

Two methods are described based on high-performance liquid chromatography and capillary electrophoresis that provide the selective and sensitive determination of nicotinic acid in human plasma. Moreover, the capillary electrophoresis system was used for the separation of nicotinic acid, nicotinamide, nicotinamide N-oxide, N'-methylnicotinamide, 6-hydroxynicontinic acid, nicotinuric acid and barbital (internal standard). The extraction procedure is simple; no gradient elution or derivatization is required. Both methods can be useful for clinical and biomedical investigations.