Automated solid-phase extraction and high-performance liquid chromatographic determination of nitrosamines using post-column photolysis and tris(2,2′-bipyridyl) ruthenium(III) chemiluminescence

Abstract

A sensitive and selective post-column detection system for nitrosamines is described. The principle upon which the detector works is that UV irradiation of aqueous solutions of nitrosamines leads to cleavage of the N NO bond. The amine generated is subsequent detected by chemiluminescence using tris(2,2′-bipyridyl) ruthenium(III), which is on-line generated by photo-oxidation of the ruthenium(II) complex in the presence of peroxydisulfate. Factors affecting the photochemical and chemiluminescent reactions were optimized to minimise their contribution to the total band-broadening. This detection system was tested for N-nitrosodimethylamine, N-nitroso-diethylamine, N-nitrosomorpholine, N-nitrosopiperidine and N-nitrosopyrrolidine, which were separated on an ODS column by isocratic reversed-phase chromatography with acetonitrile–water containing 5 mM acetate buffer at pH 4.0. A linear relationship between analyte concentration and peak area was obtained within the range 0.13–500 μg l −1 with correlation coefficients greater than 0.9995 and detection limits of between 0.03 and 0.76 μg l −1. Intra- and inter-day precision values of about 1.2% RSD ( n = 11) and 2.5% RSD ( n = 10), respectively, were obtained. The sensitivity may increase from 9 to 280 times with respect to UV detection, depending on the nitrosamine in question. An automated solid-phase extraction (SPE) system was used in conjunction with HPLC to determine nitrosamine residues in waters. Detection limits within the range 0.10–3.0 ng l −1 were achieved for only 250 ml of sample.