Introduction
The international trade in food commodities has enabled a wide variety of fruits and vegetables to be made available year round. However, this also creates a challenge for food safety regulators who seek to ensure a safe food supply chain, particularly with regard to the potentially hundreds of different pesticides in use across the globe. The European Union (EU) has some of the most stringent pesticide residue regulations. In 2008, it implemented regulation EC No. 396/20051, which sets default maximum residue levels (MRLs) at 10 μg/Kg for all pesticide/commodity combinations for which no substantive MRL had been set. Further to this, in 2009, the pesticide safety review EU 91/414/EEC2 led to the approval of approximately 250 pesticides and effectively set the permissible level for all other pesticides to the default limit (10 μg/Kg). Recently, at the beginning of 2016, the latest version of the SANTE/11945/2015 guidance document on analytical quality control and validation procedures for pesticide residues in food and feed took effect.3 This document describes the method validation and analytical quality control (AQC) requirements to support the validity of data reported within the framework of official controls on pesticide residues and used for checking compliance with maximum residue levels (MRLs), enforcement actions, or assessment of consumer exposure. It is intended for use by Official control laboratories in Europe, but in practice it is used by pesticide laboratories worldwide. Implementation of the stringent requirements present a major challenge to testing laboratories who seek to provide an accurate and cost competitive services.
Pesticide residue testing requires detection using both liquid and gas chromatographic techniques typically coupled with triple quadrupole mass spectrometers. These analytical techniques can cover the range of compounds that need to be monitored with the required sensitivity and selectivity. However, they are limited to detecting pesticides that are measured at the time of acquisition and require careful method optimization and management to ensure selected ion monitoring windows remain viable. In recent years, high-resolution Orbitrap mass spectrometry has provided an alternative to MS/MS techniques with additional analytical advantages.4 With high-resolution mass spectrometry (HRMS), the default acquisition mode is untargeted (full-scan) making it simple to manage and potentially allows for an unlimited number of pesticides to be monitored in a single injection. In addition to this, full-scan data analysis provides access to supplementary identification points such as spectral matching and enables retrospective interrogation of samples to additionally search for emerging pesticides or other contaminants that were not considered at the time of acquisition.
In this study, the quantitative performance of the Thermo Scientific™ Exactive GC Orbitrap™ mass spectrometer was evaluated for the routine analysis of GC-amenable pesticides in fruits and vegetables following SANTE/11945/2015 guidelines using full scan acquisition. The Exactive GC-MS system provides routine high-mass resolving power up to 60,000 (m/z 200) full width at half maximum (FWHM) with scan speeds suitable for GC peaks to facilitate the detection of trace compounds in the presence of high matrix components.
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