Carbamate and Carbamoyloxime Insecticides: Single‐Class, Multiresidue Analysis of

Abstract

Large quantities of modern pesticides such as the N ‐methyl‐ and carbamoyloxime carbamates (over 1000 t of the N ‐methylcarbamate carbaryl) are used for agricultural as well as for nonagricultural purposes. The European Union (EU)‐permitted concentration levels of these insecticides and their related transformation products in drinking water is 0.1 µg L −1 , and the maximum for the total pesticide content has been set to 0.5 µg L −1 . Many analytical procedures, focusing on sample pretreatment, column chromatographic separation, and sensitive detection, have been reported for the trace‐level determination of these compounds. This article surveys the application of these techniques, and their potential with regard to recovery, resolution, sensitivity, and robustness is discussed. For example the reproducibility of results with a variety of carbamates from water samples or pretreated biological/soil samples is an essential criteria during the development of extraction procedures. The percentage of recovery influences the sensitivity of the total analytical method. Good results with solid‐phase extraction (SPE) are obtained with a C 18 /OH phase which is used on a routine basis by various analytical laboratories for the analysis of surface waters and vegetables. This technique is superior to liquid–liquid extraction (LLE) for reasons explained in this article. Chromatographic resolution is most effective, when gas chromatography (GC) is used. Unfortunately, thermal degradation of some carbamates in the injector takes place, making liquid chromatography (LC) the separation technique of choice despite the fact that some carbamates cannot now be separated. Capillary electrophoresis (CE) offers better separation efficiency but is still not a robust technique. Another way to solve the coelution problem is the application of mass spectrometry (MS). Utilizing the selected ion monitoring mode, coeluting compounds can be quantified. MS adds an extra separation step because ionized compounds are separated by the mass‐to‐charge ratio. Application of the ionspray (ISP) and the heated nebulizer (HN) interfacing techniques makes possible the quantification of carbamates at trace levels as low as 0.1 ng L −1 in drinking water, without any sample preconcentration. Furthermore, MS also offers the ability to confirm the identity of the compounds. On‐line SPE in combination with liquid chromatography/mass spectrometry (LC/MS) or, better, liquid chromatography/tandem mass spectrometry (LC/MS/MS) is the best method for the quantification and structural confirmation of carbamate pesticides at concentration levels of 0.1 ng L −1 or lower.