| Abstract
| - Contamination of water resources by organochlorinepesticides (OCPs) continues to receive widespread attention because of the increasing concern regarding theirhigh persistence and bioaccumulation. These organicpollutants are not amenable by liquid chromatography(LC) coupled to atmospheric pressure ionization-massspectrometry, which represents the method of choice forthe characterization of pesticide residues in water. Gaschromatography−mass spectrometry provides excellentresponse for OCPs, but it falls short when complex,multiresidue analyses are required. As recently demonstrated, an efficient EI-based LC−MS interface can generate very good spectra for an extremely wide range ofsmall−medium molecular weight molecules of differentpolarity and can represent a valid tool in solving theanalytical challenge of analyzing OCPs by LC−MS. Basedon this assumption, we present a new approach for thedetermination of 12 OCPs in water samples. The methodrequires a solid-phase extraction preconcentration stepfollowed by nanoscale liquid chromatography coupled toa direct-electron ionization direct interface (Direct-EI).Direct-EI is a miniaturized interface for efficiently couplinga liquid chromatograph with an EI mass spectrometer.The capability to acquire high-quality EI spectra in a widerange of concentrations, and to operate in selected ionmonitoring mode during analyses, allowed a precisequantification of the OCPs. Without sample injectionenrichment, limits of detection of the method span from0.044 to 0.33 μg/L, corresponding to an instrumentaldetection limit of 120−850 pg. In addition, a carefulevaluation of the matrix effect showed that the responseof the Direct-EI interface was never affected by sampleinterferences. From our knowledge, the proposed methodrepresents the first application of LC−MS in the analysisof organochlorine pesticides.
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