Comparison of gas chromatography with NPD, MS, and tandem MS-MS in the multiresidue analysis of pesticides in environmental waters

Gas chromatography (GC) with nitrogen-phosphorus detection (NPD) and mass s pectrometry (MS), in full scan and tandem (MS-MS) modes have been used to d etermine eleven pesticides in aqueous samples. Preconcentration of 500 mL w ater with C-18 cartridges enabled the determination of pesticides at ng L-1 levels. The best precision and sensitivity were obtained from GC-NPD and G C-MS-MS. The limits of detection were between 4 and 44 ng L-1 for NPD and 1 and 40 ng L-1 for MS-MS. The application of this methodology to the determ ination of pesticides in real samples was tested by analyzing wetland sampl es from province of Almeria (Spain). The results obtained were compared and the advantage of MS-MS over NPD for highly selective quantitative determin ation of pesticides in complex matrices is discussed.