Considering the current level of extensive international food trade, food safety has become a significant global issue. Many people are increasingly concerned about chemical residues in their foods. Hundreds of pesticides, including herbicides, insecticides and fungicides, are among the most hazardous chemical compounds extensively applied in agriculture to increase food production. They are intended for destroying and controlling pests, weeds or plant diseases. Pesticide application is strictly regulated to protect consumers and the environment. However, the misuse of pesticides, lack of good agricultural management and/or cross-contamination during food processing, storage or transportation may result in unwanted or even illegal pesticide residues in foods. Some compounds, such as polychlorinated pesticides, have been banned for crop use but they are still present in the environment due to their long-term persistence and can bioaccumulate in the food chain. There is evidence that chronic exposure to pesticides can cause health risks to humans even at trace concentrations, for instance having adverse effects on endocrine system or causing behavior modification.
To control pesticide use and protect the consumers, many national and international regulatory authorities have established maximum residue limits (MRLs) for pesticides in raw and certain processed food commodities. These limits represent the highest concentrations of pesticide residues that are legally permitted as acceptable. MRLs are commonly set by individual countries, such as the United States, the European Union (EU) countries, Japan or China. For example, the EU has established the default MRL of any pesticide in baby foods for infant and young children at 0.01 mg/kg, which has been later adopted as the default limit for pesticides without established MRLs in both the EU and Japan. Consequently, the 0.01 mg/kg (10 ppb) concentration has become the world-wide standard for limit of quantification of analytical methods used for determination of pesticide residues in foods.
Some countries use pesticide residue levels in certain foods as a trade barrier to help protect their domestic production. Such regulations have a great impact on food importers/exporters, especially if their products are found to contain violative residues, such as the recent cases of organophosphate residues in vegetables from Thailand (2010) or unapproved pesticides in rice from Vietnam (2013) imported into the EU market. Disputes sometimes arise if the pesticides in imported foods exceed the MRLs of the importing country but not the exporting one. In some cases, a pesticide may be approved for use in one country but it is illegal in another country. Thus, it is important for food importers and exporters to understand food safety regulations both domestically and internationally and conduct pesticide residue testing in their foods and food ingredients before shipping. This helps to avoid the possible (and very costly) rejection of shipments, destruction of large quantities of products, delay in releasing of products (especially perishable foods) at the port of entry, reduction of trust in the product quality if violations are found repeatedly or loss of a business opportunity.
Without doubt, pesticide residue analysis has become an important part of government food monitoring and enforcement programs, and consequently an indispensable part of routine testing and surveillance programs conducted by the food industry. Modern analytical methods and instrumentation, which have the ability to detect a large number of pesticide residues at very low concentration levels in complex matrices, are necessary to ensure compliance with the strict regulatory limits and support consumer confidence in the food quality and safety.
When it comes to pesticide multiresidue analysis, gas chromatography (GC) and liquid chromatography (LC) are the predominant techniques used for separation of pesticide molecules. Modern analysis employs mass spectrometry (MS) technique for pesticide detection in both GC-MS and LC-MS, typically using tandem mass spectrometry (MS/MS). In particular, advancements in the LC-MS technology have enabled direct and highly selective and sensitive analysis of modern, more polar pesticides and their metabolites which were rather difficult to analyze in the past. MS can detect a wide range of compounds independent of their elemental composition and provide simultaneous quantitation and structural identification of detected analytes. These unique features have made MS the number one choice for detection and identification/confirmation of pesticide residues and other trace-level organic chemical contaminants in modern testing laboratories. State-of-the-art GC-MS/MS and LC-MS/MS instruments are indispensable tools for achieving low detection limits in pesticide multiresidue analysis in complex food matrices because they offer high sensitivity and selectivity and a high degree of confidence in analyte identification even at low concentration levels.
For more information on pesticide testing solutions, visit the Environmental Protection Agency.