More confident pesticide screening in complex food matrices

Food stocks are being stretched due to growing populations, the use of some crops in biofuel production, and regular adverse weather conditions. Farmers are therefore under intense pressure to get the maximum value out of their land. Crop pests and diseases can significantly impact yield rates, and pesticides play a key role in minimizing their impact. However, a steady buildup in resistance to pesticides in crops means that both advances in crop protection science and the discovery of new active compounds are critical.
Maximum residue levels (MRLs) are set in the EU for 315 fresh products (and for the same products after processing) for around 1100 pesticides by Regulation EC 396/2005. Under this legislation, the European Food Safety Authority (EFSA) assesses MRL applications for new pesticides. As new pesticides are introduced, the task for food safety labs to ensure MRLs for an ever broader range of chemical analytes is becoming more complex.

Analytical techniques evolve

This increasing demand of screening for contaminants in food requires an efficient and sensitive analytical technique. High-resolution GC/Q-TOF has emerged as a tool to fit this purpose for GC-amenable analytes. The latest technology from Agilent – the 7250 GC/Q-TOF – optimizes screening for targets, suspects, and unknowns all at once. Full-spectrum accurate mass data enables the confident identification of analytes and accurate quantification addresses stringent MRL requirements. The addition of low-energy electron impact (EI) ionization enhances the possibility to preserve or confirm molecular ions in EI mass spectra, aiding in the study of unknowns.

Comprehensive screening for pesticides in food matrices is greatly empowered with the new Agilent 7250 GC/Q-TOF’s untargeted acquisition and high resolution spectral libraries.

        

A) The GC/Q-TOF data presented here shows 120 pesticides spiked into three different food matrices, including avocado and salmon. The repeatability (RSD %) values for spiking levels of 5 ng/mL and 10 ng/mL show excellent analytical performance, with two examples of detected characteristic ion replicates shown.

B) Quantitative accuracy at 10 ng/mL for rapid comparison against MRLs is shown for six food matrices ranging in complexity. Even for complex matrices like avocado and salmon, quantitative accuracy complies with SANTE/11945/2015 guidelines (± 20% versus standard) for over 97% of the pesticide:food pairs for each commodity tested.

Key features of the new system that provide some of these particular benefits in pesticide screening include:

High resolution and mass accuracy

High resolution is necessary to separate analytes from interferences. But, to provide the most analytical utility, this performance characteristic must be usable under challenging conditions, like complex matrices and trace level analytes. The example shown here represents such a challenging scenario: analyzing the insecticide Thiamethoxam at 5 ppb in avocado, a complex matrix with significant background levels. Even under these conditions, characteristic mass peaks are separated from background with mass accuracy that complies with SANTE/11945/2015 guidelines on compound identification. What’s more, this level of spectral performance is achieved regardless of acquisition speed or mass range. The 7250 GC/Q-TOF delivers maximum spectral utility for the most challenging GC/MS applications.

Wide in-spectrum dynamic range

A wide in-spectrum dynamic range enables confident detection of trace level analytes in the presence of abundant background or other co-eluents. The 7250 GC/Q-TOF typically provides four orders of magnitude of in-spectrum dynamic range, even in heavy matrices. This performance allows for confident detection of targets, suspects, and unknowns simultaneously while minimizing the concerns and limitations of other analytical techniques. When unknowns are detected, they can be interrogated with MS/MS product ion spectra, generated from a putative molecular ion. Using powerful Molecular Structure Correlator software, analyte structure possibilities and likelihoods based on fragment ion data from the unknown compound can be proposed to narrow the range of possibilities.

Low energy EI

Based on the revolutionary High Efficiency Source (HES) proven in the Agilent 5977B HES GC/MSD and 7010B GC/TQ, the 7250 GC/Q-TOF features a Low Energy optimized Electron Ionization (EI) source. A paradigm shift in GC/MS soft ionization is enabled by proprietary technology found on no other platform. Preserved or enhanced molecular ions are possible with Low Energy EI to assist in the identification of unknowns, while conventional 70 eV ionization produces reference-quality spectra for library searching. GC/MS laboratories can rely on simplified spectra without the need for on chemical ionization or other specialty techniques to give them more powerful identification and elucidation capabilities.

Agilent provides the expertise, supplies, and tools needed to generate results confidently and reproducibly with ease across a wide range of food matrices. For more information about the new system, visit the new 7250 GC/Q-TOF page.

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