Micellar liquid chromatographic determination of nicotinic acid and nicotinamide after precolumn Konig reaction derivatization

In the Konig reaction, the heterocyclic nitrogen of a pyridine derivative reacts with cyanogen bromide and is afterwards coupled with an arylamine to give a polymethine dye. In the previous work, this reaction was automated using a flow injection system, and in this study we have coupled this system to a chromatograph to determine nicotinic acid and nicotinamide, after precolumn derivatization, using the Konig reaction. First, we checked the micellar chromatography behavior of the polymethines using a C 18 column, a flow of I mL min(-1) and detection at 440 nm. After modeling, the composition of the selected mobile phase was 150 mM sodium dodecyl sulfate (SDS)-6% (v/v) pentanol pH 3. In this mobile phase, the analysis time was below 17 min, the calibrations were lineal in the range 0.05 to 50 mug mL(-1) with regression coefficients above 0.999, and intra- and inter-day imprecision were below 5%. The method developed here was applied to the determination of nicotinamide and nicotinic acid in pharmaceuticals, serum and urine samples and the amounts determined were similar to those obtained using a reference method. (C) 2004 Elsevier B.V. All rights reserved.