In the European food industry, pesticide analysis remains a central component of food safety and compliance with statutory maximum residue limits (MRLs). At the same time, the focus is increasingly shifting from pure detection toward interpretation, methodology, and risk-based monitoring. We spoke with a laboratory expert about how modern pesticide analyses are conducted and evaluated in practice today.
Athanasios Nitsopoulos – Managing Director of Labor Friedle GmbH
The biggest change has been the shift from single-substance analyses to comprehensive multi-residue screenings. Whereas in the past individual pesticides were specifically tested, today we routinely analyze several hundred active ingredients in a single measurement. This is primarily done using LC-MS/MS and GC-MS/MS, which allow even very low concentrations to be reliably detected.
This development has significantly improved food safety, but it also brings with it greater complexity. Each method must be comprehensively validated, and matrix effects, interferences, and measurement uncertainties must be taken into account for each matrix group.
The matrix is a decisive factor. A pesticide behaves differently in a high-fat avocado than in a dry spice sample or a water-rich vegetable. These differences influence the signal in the mass spectrometer—so-called matrix effects.
For this reason, laboratories use matrix-matched calibration as well as recovery corrections using isotope-labeled internal standards (ILIS). These allow for the correction of losses or signal amplification during the analysis. Without these corrections, results could be distorted, posing a significant risk to the accurate assessment of compliance.
A common mistake is to view results in isolation without considering the analytical context. A measured value must always be evaluated in relation to the MRL, but also taking into account parameters such as measurement uncertainty and the LOQ (limit of quantification).
A value just above or below the limit may, from an analytical standpoint, fall within the uncertainty range. A purely binary “compliant/non-compliant” assessment is therefore often insufficient. This is precisely why close collaboration between QA and the laboratory is crucial for correctly interpreting results.
Trend analysis is also becoming increasingly important. A single instance of exceeding a limit must be evaluated differently than a recurring pattern within a supply chain.
There is a clear shift from standardized testing programs toward risk-based strategies. Not every product and not every supplier requires the same testing frequency. Risk assessment is increasingly based on origin, crop type, previous results, and the stability of the supply chain.
This makes monitoring more efficient and targeted. Instead of relying exclusively on reactive testing, preventive screening approaches and supplier evaluations are being used more frequently. Analytical data thus serves not only for control but increasingly also for prevention.
Sampling is one of the most critical—and at the same time most frequently underestimated—steps in pesticide analysis. Even the most advanced analytical methods are only as good as the sample that arrives at the laboratory. Pesticide residues are often distributed unevenly in food—depending on the surface, peel, degree of ripeness, or state of processing. A non-representative sample can therefore either lead to an underestimation of actual residue levels or to apparent exceedances.
It is crucial that sampling be standardized, traceable, and conducted in accordance with recognized guidelines. This includes not only the correct sample size and number of subsamples but also aspects such as transport conditions, homogenization, and storage. Errors made at this early stage cannot be corrected later in the analytical process.
From a laboratory perspective, close coordination with QA and procurement is particularly important. Only when it is known where, when, and how a sample was taken can analytical results be interpreted correctly from a technical standpoint. Sampling thus forms the foundation of any reliable assessment and is an essential component of risk-based and legally compliant supply chain monitoring.
A key driver is high-resolution mass spectrometry (HRMS), particularly in the context of non-target and suspect analytics. While traditional routine analyses focus primarily on known active ingredients, HRMS enables the detection of unknown or unexpected substances regardless of their specific nature.
Thanks to its high mass resolution and precise mass accuracy, HRMS allows for the narrowing down of molecular formulas, the evaluation of isotope patterns, and the use of fragmentation information for structural classification. In practice, this is particularly relevant for previously unlisted degradation products, new active ingredients, or impurities.
HRMS also allows analytical data to be re-evaluated retrospectively when new substances or research questions arise. As a result, the instrument is used not only for traditional monitoring but, above all, for elucidating unexplained findings and analyzing root causes within the supply chain. Overall, HRMS expands pesticide analysis from the mere testing of target substances to a structure-elucidating, knowledge-generating approach.
This collaboration is crucial. The laboratory provides the analytical data, but the QA department makes risk-related decisions based on this data. Without correct interpretation, even the best analysis can lead to incorrect decisions.
QA managers must therefore understand how results are generated, what methodological limitations exist, and how measurement uncertainties are factored into the assessment. Only in this way can analytical data be reliably translated into well-founded decisions regarding food safety throughout the entire supply chain.
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