Determination of N-methylcarbamate pesticides in environmental samples by an automated solid-phase extraction and liquid chromatographic method based on post-column photolysis and chemiluminescence detection

Abstract

An automated solid-phase extraction–high performance liquid chromatography method has been developed to determine trace concentration of N-methylcarbamate pesticides in water and fruits. The method is based on the post-column conversion of the pesticides into methylamine by irradiation with UV light. The resultant methylamine was subsequently detected by chemiluminescence using tris(2,2′-bipyridyl)ruthenium(III), which was on-line generated by photo-oxidation of the ruthenium(II) complex with peroxydisulfate. Factors affecting the rate of the reactions were optimized so that their contribution to the total band-broadening was negligible. This detection system was used to determine bendiocarb, carbaryl, promecarb and propoxur, which were separated on an ODS C 18 column. The mobile phase consisted of water and acetonitrile using a gradient elution. A linear relationship between peak area and concentration was obtained for all pesticides ( r 2 > 0.999). Intra- and inter-day precision values of about 0.64–1.3% RSD ( n = 10) and 2.2–2.8% RSD ( n = 15), respectively, were obtained. N-Methylcarbamate pesticide residues at ultratrace levels could be determined in environmental samples when an automated solid-phase extraction device was coupled on-line with the HPLC system. Detection limits were within the range 3.9–36.7 ng l −1 for water samples and 0.5–4.7 μg kg −1 for fruits.