title: Application of internal quality control to the analysis of quaternary ammonium compounds in surface and groundwater from Andalusia (Spain) by liquid chromatography with mass spectrometry.
abstract: A method has been developed for the simultaneous determination of paraquat (PQ), deiquat (DQ), chlormequat (CQ) and mepiquat (MQ) in water samples by liquid chromatography (LC) coupled with electrospray ionization mass spectrometry (MS). The LC separations of the target compounds, as well as their MS parameters, were optimized in order to improve selectivity and sensitivity. Separation was carried out in a Xterra C8 column, using as mobile phase methanol-heptafluorobutyric acid (HFBA) in isocratic mode. The molecular ion was selected for the quantitation in selected ion monitoring (SIM) mode. Off-line solid-phase extraction (SPE) was applied with silica cartridges in order to preconcentrate the compounds from waters. Detection limits were in the range 0.02-0.40 microg l(-1). Recovery range varied between 89 and 99.5% with precision values lower than 6%. The method has been applied successfully to the analysis of both surface and groundwater samples from agricultural areas of Andalusia (Spain), using well defined internal quality control (IQC) criteria. The results revealed the presence of deiquat and paraquat in some samples.
authors.affiliation: Research Group: Analytical Chemistry of Contaminants, Department of Analytical Chemistry, University of Almería, 04071 Almería, Spain. jlmartin@ual.es
authors.forename: J L Martínez
authors.initials: JL
authors.lastname: Vidal
authors.forename: A Belmonte
authors.initials: AB
authors.lastname: Vega
authors.forename: F J Sánchez
authors.initials: FJ
authors.lastname: López
authors.forename: A Garrido
authors.initials: AG
authors.lastname: Frenich
mesh_terms: D002851:Chromatography, High Pressure Liquid; D006812:Humic Substances / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D013058:Mass Spectrometry; D010573:Pesticide Residues / Q000032:analysis; D011786:Quality Control; D000644:Quaternary Ammonium Compounds / Q000032:analysis*; D012015:Reference Standards; D015203:Reproducibility of Results; D012997:Solvents; D013030:Spain; D013048:Specimen Handling; D021241:Spectrometry, Mass, Electrospray Ionization; D013501:Surface-Active Agents / Q000032:analysis; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014881:Water Supply / Q000032:analysis*
chemical_list: D006812:Humic Substances; D010573:Pesticide Residues; D000644:Quaternary Ammonium Compounds; D012997:Solvents; D013501:Surface-Active Agents; D014874:Water Pollutants, Chemical