title: Determination of chlormequat and mepiquat in pear, tomato, and wheat flour using on-line solid-phase extraction (Prospekt) coupled with liquid chromatography-electrospray ionization tandem mass spectrometry.
abstract: A sensitive and selective method is presented for the simultaneous analysis of the pesticides chlormequat and mepiquat at trace levels in tomato, pear, and wheat flour. The method entails direct injection of the food extract onto an on-line solid-phase extraction (SPE) instrument (Prospekt) using a strong cation-exchange resin. Analyte separation and detection is done by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS-MS). Surrogate standards (d9-chlormequat, d6-mepiquat) are employed to compensate for recovery losses and potential MS-MS signal suppression. The method achieves a limit of quantification for both cationic analytes at or below 5 microg/kg, and good intra- and inter-assay precision with mean variability values <7% over a concentration range up to 195 microg/kg. This study also addresses potential analyte carry-over in an SPE on-line system, as well as the robustness of the procedure and its applicability in routine quality control operations.
authors.affiliation: Department of Quality and Safety Assurance, Nestle Research Center, Nestec Ltd, Lausanne, Switzerland.
authors.forename: Sonja
authors.initials: S
authors.lastname: Riediker
authors.forename: Heinrich
authors.initials: H
authors.lastname: Obrist
authors.forename: Natalia
authors.initials: N
authors.lastname: Varga
authors.forename: Richard H
authors.initials: RH
authors.lastname: Stadler
mesh_terms: D002138:Calibration; D002716:Chlormequat / Q000032:analysis*; D002853:Chromatography, Liquid / Q000379:methods*; D005638:Fruit / Q000737:chemistry*; D010880:Piperidines / Q000032:analysis*; D010937:Plant Growth Regulators / Q000032:analysis*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D014908:Triticum / Q000737:chemistry*
chemical_list: D010880:Piperidines; D010937:Plant Growth Regulators; D002716:Chlormequat; C049449:mepiquat