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 N1-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 N1-methylnicotinic acid. The calibration graph for N1-methylnicotinamide was linear over the range of 5.0–20.4 pmol using an injection volume of 20–100 μl. The pretreatment of the urine or serum samples consisted of diluting–filtering steps or deproteinizing steps, respectively. The mean recovery of N1-methylnicotinamide from urine and serum was over 95%.