Fluorometric determination of N1-methylnicotinamide in human urine and serum by liquid chromatography postcolumn photoirradiation with a mobile phase containing 18-crown-6

For the determination of N-1-methylnicotinamide in human urine and serum, liquid chromatography (LC)-postcolumn photoirradiation using a mobile phase containing 18-crown-6 has been developed. The mobile phase consisted of 35 mmol l(-1) potassium dihydrogenphosphate containing 5 mmol l(-1) hydrogen peroxide and 25 mmol l(-1) 18-crown-6. Addition of 18-crown-6 to the mobile phase led to peaks having a good shape, earlier elution and increased sensitivity. Moreover, the assay succeeded in separation of N-1-methylnicotinic acid. The calibration graph for N-1-methylnicotinamide was linear over the range of 5.0-20.4 pmol using an injection volume of 20-100 mu l. The pretreatment of the urine or serum samples consisted of diluting-filtering steps or deproteinizing steps, respectively. The mean recovery of N-1-methylnicotinamide from urine and serum was over 95%. (C) 1998 Elsevier Science B.V.