Determination of the pesticide Naptalam, at the ppb level, by FIA with fluorimetric detection and on-line preconcentration by solid-phase extraction on C18 modified silica Original Research Article

The paper describes a method of flow-injection analysis for the determination of the pesticide Naptalam based on its hydrolysis, in an acidic medium, to 1-naphthylamine and the measurement of fluorescence due to this product in an alkaline medium. By direct injection of Naptalam in a carrier of HCl 1.0 M, subsequent heating at 100°C in the reactor and change of the pH with a flow of NH4OH 1.5 M, concentrations >3×10−6 M can be analyzed. The sensitivity of the procedure is greatly increased by using on-line, a column (10 cm length×0.3 cm i.d.) filled with a C18 modified silica packing to retain a large volume of Naptalam. The injection of a very small volume of acetonitrile is enough to elute the pesticide, thus increasing the concentration in the sample zone to a great extent. The method has been successfully applied to the analysis of Naptalam, at the ppb level, in river-water samples.