Protocols for extraction of pesticide residues

Abstract

Over the past few years, the presence of pesticides in foods has received growing attention as one of the main food safety problems. Many countries and health organizations have dictated increasingly stringent regulations on the maximum residue limits for pesticides in foodstuffs, which are based on sensitive and trustworthy methods for pesticide residue analysis. Pesticides can also reach surface water through runoff from treated plants and soil, contaminate groundwater, soil, ground and grass and be toxic to non-target organisms. Therefore, it is necessary to develop highly selective methods of analysis that can ensure accurate and precise results with sufficiently low detection limits for a wide range of pesticides. Due to the large number of pesticides on the current market, multiclass and multiresidue methods are certainly the best way to address the problem of pesticide analysis and, in recent years, the general tendency has been the development of increasingly sensitive, accurate, precise and rapid methods. Despite the enormous progress made in the development of highly efficient analytical instrumentation for pesticide determination in samples of a very different nature, in most cases a pretreatment of the sample is still required to extract, isolate and concentrate the target compounds since it is generally not possible to directly manipulate the sample. Sample preparation often includes a cleanup step in order to remove non-specific matrix co-extractives, especially for analysis of very complex matrices such as foodstuffs and environmental samples, which also brings the analytes to an appropriate concentration level. Conventional sample treatment techniques are efficient, but they entail drawbacks such as the employ of toxic organic solvents that cause environmental contamination and additional operational costs for waste treatment, complicated procedures that require a lot of time, and difficulty in automation. Therefore, in recent years a lot of techniques have been developed in order to miniaturize and simplify the sample treatment, and reduce the amount of organic solvents used for meeting the requirements of green chemistry. Nevertheless, the pesticide residue analysis is an ongoing challenge mainly due to low concentration of pesticides, as well as the large quantities of compounds in the matrix that can be co-extracted, often giving rise to errors and damage to analytical instrumentation. In this chapter, the main classical and advanced methodologies available for the treatment of food and environmental samples for analysis of pesticide residues are summarized and explained. These techniques include: liquid-liquid extraction, Soxhlet extraction, supercritical fluid extraction, microwave-assisted extraction, pressurized liquid extraction, gel permeation chromatography, solid-phase extraction, matrix solid-phase dispersion, solid-phase microextraction, QuEChERS, stir bar sorptive extraction, and liquid-phase microextraction. Their advantages, drawbacks and future perspectives are also discussed.