Matrix effects in pesticide multi-residue analysis by liquid chromatography-mass spectrometry.

Multiresidue liquid chromatography tandem mass spectrometry determination of 52 non gas chromatography-amenable pesticides and metabolites in different food commodities☆

Residue determination of cyromazine and its metabolite melamine in chard samples by ion-pair liquid chromatography coupled to electrospray tandem mass spectrometry

Liquid chromatography–tandem mass spectrometry (LC–MS2) is an excellent technique for the determination of polar pesticides and transformation products in water. On-line trace enrichment by solid-phase extraction (SPE)-LC in combination with MS2 satisfies most analytical demands of modern laboratories for pesticide-residue analysis, with respect to sensitivity (limits of detection and limits of quantification at sub-μg/L levels), selectivity, reliability and rapidity, and all with very little sample manipulation. However, several obstacles have to be overcome when developing SPE-LC–MS2 multi-residue and confirmative methods. The different physicochemical characteristics and wide polarity range of pesticides and their transformation products make their simultaneous preconcentration, chromatographic separation and determination difficult. Also, for the correct confirmation of the identity of compounds, it is necessary to increase the number of monitored MS transitions, which normally leads to a loss in sensitivity. This may hamper confirmation at low concentrations in a single chromatographic run (i.e., when a second analysis is not performed).

In this article, we discuss different strategies for developing sensitive multi-residue methods for pesticides in water, able to correctly quantify and confirm compounds detected in samples. We discuss the use of different analyzers, triple quadrupole and hybrid quadrupole time-of-flight and compare their performances for screening purposes, and for the quantification and confirmation of positive samples. We present several practical cases of water samples, including some positive findings that would result in false positives if no criteria were applied for unequivocal confirmation of the identity of detected compounds.

Strategies for quantification and confirmation of multi-class polar pesticides and transformation products in water by LC–MS2 using triple quadrupole and hybrid quadrupole time-of-flight analyzers

Liquid chromatography-mass spectrometry (LC-MS) has become an invaluable technique for the control of pesticide residues to ensure food safety. After an introduction about the regulations that highlights its importance to meet the official requirements on analytical performance, the different mass spectrometers used in this field of research, as well as the LC-MS interfaces and the difficulties associated with quantitative LC-MS determination, are discussed. The ability to use practical data for quantifying pesticides together with the option of obtaining structural information to identify target and non-target parent compounds and metabolites are discussed. Special attention is paid to the impact of sample preparation and chromatography on the ionization efficiency of pesticides from food. The last section is devoted to applications from a food safety point of view. (c) 2006 Wiley Periodicals, Inc.

Control of pesticide residues by liquid chromatography-mass spectrometry to ensure food safety

This paper describes a new method for the sensitive and selective determination of fosetyl-aluminum (Al) residues in vegetable samples. The method involves extraction with water by using a high-speed blender and subsequent injection of the 5-fold diluted extract into the liquid chromatograph. Fosetyl-Al is determined by liquid chromatography with electrospray tandem mass spectrometry after the addition of tetrabutylammonium acetate as the ion-pairing reagent. The method has been used to assay lettuce samples spiked at 2 and 0.2 mg/kg. Recoveries were satisfactory, with mean values of 98 and 106%, respectively, and relative standard deviations were <10%. The limit of quantitation was 0.2 mg/kg, and the limit of detection was as low as 0.05 mg/kg. Matrix-matched calibration was used for quantitation, and the addition of an internal standard improved repeatability. The developed method allows the accurate and rapid determination of low levels of fosetyl-Al residues in lettuce with very little sample handling and good sensitivity; it was shown to be robust by the analysis of almost 100 samples.

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Carme Villaplana

Papers

Rapid determination of fosetyl-aluminum residues in lettuce by liquid chromatography/electrospray tandem mass spectrometry.