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1 Introduction

Production of food produces are seriously affected by insect pests and diseases. Due to plant pests and diseases, 20–40% of the crop yields are reduced globally [1]. To overcome these situations farmers are using different kind of pesticides. Pesticides play a key role to control the insect pests and diseases and hence protect and promote production [2]. However, pesticides and pesticide residues in foods may cause several adverse effects on human health and the environment [3,4,5].

Nowadays food safety is a major concern to the consumers [6]. The percentage of food containing pesticide residues has increased in the last 10 years. In order to ensure the supply of safe food, pesticides should be used following Good Agricultural Practices (GAP). Monitoring of pesticide residues in the food is the essential tool to ensure GAP. To monitor pesticide residues in the commercial produces, reliable multi-residue analytical methods are required. Multi-residue analytical methods, which allow the quantification of residues of different analytes simultaneously in a single run, are used advantageously for monitoring purposes. This chapter will briefly discuss different extraction, and analytical detection techniques of pesticides residues in foods.

2 Pesticide Residue Analysis

Concern about pesticide residue analysis is increasing day by day due to the consumers demand for safe food and to serve the trade related obligations [7]. Methods to analyze pesticide residues involve two steps: (a) extraction and clean-up of the target analytes from the matrix, and (b) determination of the target analytes.

2.1 Extraction and Clean-Up

The sample preparation methods to detect pesticide residue in food matrices involve: extraction of target analytes from the bulk of the matrices and partitioning of the residues in an immiscible solvent, and/or clean-up of the analytes from the matrix co-.extractives. Complex samples like meat and meat products require two step clean-up which combines different chromatographic techniques [8].

Different techniques are used to extract and clean-up of pesticides from different food matrices, such as: liquid-liquid extraction (LLE), super critical fluid extraction (SFE), microwave-assisted extraction (MAE), solid phase extraction (SPE), solid phase micro extraction (SPME), stir-bar sorptive extraction (SBSE), and QuEChERS extraction etc.

2.1.1 Liquid–Liquid Extraction (LLE)

Liquid–liquid extraction is an important separation technique, which is also known as solvent extraction and partitioning. It is widely used in the modern process industry and it is a basic technique in the chemical laboratories. This extraction technique is mainly based on different degrees of solubility of components in two immiscible, or partially miscible, liquids. It is a separation technique of a substance from one liquid into another liquid phase. Both of the liquids are thoroughly contacted and subsequently separated from each other again.

2.1.2 Supercritical Fluid Extraction (SFE)

Supercritical fluid extraction is a technique where supercritical fluids are used as the extracting solvent to separate one component or to separate desired analytes (pesticides) from the matrix. Usually CO2 is used as a supercritical fluid. This technique is more effective for the solid matrix but it can also be used to separate desired analyte from the liquid matrix. This extraction process is used for analytical purposes to extract the analytes from the matrix, and to strip unwanted material from a product (decaffeination) or collect a desired product (e.g. essential oils).

2.1.3 Solid-Phase Extraction (SPE)

Solid phase extraction (SPE) is a rapid, reliable, and selective sample preparation technique. Solid phase extraction technique is used to extract the analytes from different matrices such as urine, blood, water, beverages, soil, and animal tissue [9]. In the analytical laboratories, this extraction technique is used to concentrate and purify samples for analysis using HPLC, GC, GC-MS and LC-MS/MS. It extends the lifetime of chromatographic systems and improves the qualitative and quantitative analysis.

2.1.4 Solid-phase microextraction (SPME)

Solid-phase microextraction is a fast, solvent-free extraction technique that involves the use of a fiber coated with an extracting phase, which can be a liquid or a solid [10]. Different kinds of analytes including volatile and non-volatile compounds from different kinds of media are extracted by this extraction technique [11]. SPME is compatible with analyte separation/detection by GC or HPLC, and provides a very good result for wide concentrations of analytes.

2.1.5 Stir Bar Sorptive Extraction (SBSE)

Stir-bar sorptive extraction (SBSE) belongs to a group of techniques which was first developed for sampling in liquid phase and is based upon sorption of the investigated analytes or fraction onto a very thick film of PDMS coated onto a glass-coated magnetic stir bar (commercially known as Twister, Gerstel GmbH, Muelheim, Germany).

2.1.6 Microwave-Assisted Extraction (MAE)

Microwave-assisted extraction is an efficient method that involves deriving natural compounds from raw plants. MAE technique allows organic compounds to be extracted more rapidly, with similar or better yield as compared to conventional extraction methods.

2.1.7 QuEChERS Extraction

One of the latest extraction and clean-up techniques for pesticide residue analysis in food matrices is the QuEChERS (quick, easy, cheap, effective, rugged and safe) technique, which was first introduced by Anastassiades et al. [12] in 2003. QuEChERS employs a novel and much quicker dispersive solid phase extraction (dSPE) cleanup. This technique was modified by several research groups (AOAC Official methods, 2007.1; the European Committee for Standardization (CSN) Standard Method, CSN EN 15662, 2008) [13, 14]. Because of high analyte recoveries, the low organic solvent consumption, and the low cost per sample, QuEChERS technique is gradually gaining popularity compared to other existing technique.

At present QuEChERS technique is widely used for the extraction and clean-up of the extracts of fruit and vegetable matrices [1, 15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40], dairy and fatty matrices [41,42,43,44], matrices of grains, nuts and seeds [38, 45,46,47,48,49], and matrices of baby foods [50,51,52,53,54,55,56,57,58,59,60].

2.2 Pesticide Residue Determination

Gas Chromatography (GC), Gas Chromatography associated with Mass Spectrometry (GCMS), High Performance Liquid Chromatography (HPLC), and Liquid Chromatography associated with Mass Spectrometry (LC-MS) are the most commonly used techniques to detect pesticides and pesticide residues in foods.

2.2.1 Gas Chromatography (GC)

A gas chromatograph (GC) is an analytical instrument that measures the content of various components in a sample. There are different detectors, with different types of selectivity, can be used in gas chromatography. Flame ionization detector (FID) is feasible for most of the organic compounds. Thermal conductivity detector (TCD) is a universal detector. Electron capture detector (ECD) is used for halides, nitrates, nitriles, peroxides, anhydrides, organometallics etc. Nitrogen-phosphorus detector (NPD) is normally used for nitrogen, phosphorus and the Flame photometric detector (FPD) is used for sulphur, phosphorus, tin, boron, arsenic, germanium, selenium and chromium. Till date, GC technique with different detectors are used for the quantification of pesticide residues from different food matrices [81, 87,88,89,90,91,92,93,94].

2.2.2 Gas Chromatography–Mass Spectrometry (GC–MS)

In GC-MS, pesticides are identified by retention time and specific ions, and quantified by selected ion monitoring (SIM) mode using the target and qualified ions. SIM mode provides adequate quantification at low concentration. However, the accuracy may be reduced if the selected ions are affected by matrix effect. Besides using the MS/MS it is possible to decrease the matrix effects, may achieve a higher selectivity levels and lower detection limit [51, 76]. GC-MS/MS with triple quadrupole [76, 77] and ion trap mass spectrometers [77] has been used for pesticide residue analysis on fatty food. To analyze multiple pesticide residues from food matrices using GC-MS, acquisition mode, multiple reaction monitoring (MRM) [76], and the selected reaction monitoring (SRM) [78] mode have been used. Several single and multiresidue methods using GC-MS have been developed for the analysis of pesticides from different classes [79,80,81,82,83,84,85,86,87,88].

2.2.3 Liquid Chromatography-Mass Spectrometry (LC-MS)

In recent years, LC-MS has been used to determine pesticide residues in fruit and vegetable extract. LC-MS is an effective technique that generally reduces the excessive clean-up steps, exhibits little chance of false-positive findings, and reduces the analysis time and cost [61]. The high sensitivity of LC-MS technique makes it useful in many applications. Different mass analyzers are used in LC-MS, including single quadrupole, triple quadrupole, ion trap, and time of flight mass spectrometry (TOF-MS). LC-MS/MS with electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) source are used widely to analyze multiple pesticide residues from a wide variety of matrices [2, 21, 62,63,64,65,66,67,68,69,70,71,73]. A wide range of pesticides can be analysed by both GC-MS and LC-MS techniques. However, LC-MS is considered to cover a wider scope than GC-MS [74]. LC-MS/MS with ESI (electrospray ionization) and APCI (atmospheric pressure chemical ionization) source have improved the feasibility of the identification of pesticides of different chemical structures in food at concentrations comparable to those obtained by GC-MS [75].

2.2.4 High Performance Liquid Chromatography (HPLC)

High Performance Liquid Chromatography (HPLC) has been used for manufacturing (e.g. during the production process of pharmaceutical and biological products), legal (e.g. detecting performance enhancement drugs in urine), research (e.g. separating the components of a complex biological sample, or of similar synthetic chemicals from each other), and medical (e.g. detecting vitamin D levels in blood serum) purposes. Nowadays, HPLC is mostly used for the purity analysis of pesticides. It is also used for single pesticide residue analysis of different food matrices [15, 89].

The commonly used detectors for pesticide residue analysis are UV-VIS Detector, Photo Diode Array Detector (PDA) and Fluorescence Detector. UV-VIS Detector is the most commonly used detector. The response of UV-VIS Detector is specific to a particular compound or class of compounds depending on the presence of light absorbing functional groups of eluting molecules. Fluorescence detector gives higher sensitivity than a UV-VIS detector. Photo Diode Array Detector (PDA) helps to monitor simultaneous determination of more than one absorbing component at different wavelengths.

3 Conclusion

Analytical methods discussed in this chapter play an important role for the qualitative and quantitative detection of pesticide residues in food matrices. Prior to analyze the sample, the analytical methods should be validated in terms of accuracy, precision, limit of detection (LOD), limit of quantification (LOQ), and linearity [95].