# Application of Sorbent-Based Extraction Techniques in Food Analysis
## 3 SPE in Food Analysis--Main Fields of Applications
### Pesticide Residues  
The development of agriculture in recent years has led to the use of pesticides that are sprayed on crops mainly for economic purposes. It is estimated that the use of these chemicals contributes to the protection of approximately 30% of crops by deterring pests and insects [45]. The use of pesticides not only increases crop yields but also involves risks to human health due to the extensive use of these resources without legal restrictions. Residues of pesticides can be detected in soil for several decades and effectively reduce its quality. Furthermore, many pesticides show bioaccumulation and biom magnification in concentration, which is harmful to human health [46]. Pesticide residue may be found in a wide range of food products (e.g., fatty animal-origin foods like eggs, fish, meat, milk, and poultry [47; 48], and plant origin-food such as citrus essential oil, fruits and vegetables, and wines) which is an analytical challenge considering the pesticide contaminants in the complex matrix are present usually in low concentrations [49]. Focusing on the analysis of multi-residue pesticides in plant samples, it can be noticed that they have a wide range of matrix properties that cannot be omitted by choosing the optimal method for sample preparation (acidity, basicity, neutral, polar, non-polar). There are many techniques for extracting pesticides--liquid-liquid microextraction, LLE, liquid-phase microextraction, SPE, SBSE, supercritical fluid extraction, and QuEChERS--with d-SPE as the most often used one method [50]. The conventional method used to detect and quantify the number of pesticides in samples is based on chromatographic methods (GC or HPLC) with various detectors [51], but the sample preparation process is usually matrix specific. The cinnamon used in medicine and as a spice is grown in a hot and humid climate, which makes it particularly prone to bacteria, fungi, and pests. Application of herbicides may cause not only high productivity but can also generate residues in cinnamon bark. Spices such as black pepper, paprika, and turmeric were reported as matrices that are difficult to analyze and induced a suppression effect as a result of complex chemical composition (essential oils, fatty acids, pigments, sugars) and excess water [52]. To eliminate co-extracted compounds, d-SPE with diverse types of sorbents was proposed. Primary-secondary amine (PSA) sorbents can be successfully used to reach substantial retention of fatty acids, organic acids, pigments and sugars instead of C18, which is applied to maintain the hydrophobic nature of the sample. Graphitized carbon black sorbent is effective against colored compounds like chlorophyll but it keeps other targeted composites. Satisfactory results for the analysis of spices are obtained by the combination of d-SPE with repetitive d-SPE with HPLC-MS/MS [52]. Apple, broccoli, shallot, and tea are examples of polyphenol-rich food products which may contain pesticide residues. Polyphenol compounds cause analytical problems as a result of interferences at the ionization step. The necessary step for determining pesticides in food with a high content of polyphenols is, therefore, clean-up. The sample pre-treatment stage included the precipitation of polyphenols by d-SPE with polyvinylpolypyrrolidone (PVPP) before dilution of the sample to eliminate the influence of the matrix. This made it possible to analyze 8 neonicotinoid insecticides and the further optimization and use of UPLC-MS/MS led to the determination of multiple classes (e.g., neonicotinoid, an organophosphate) of 20 different pesticides with a wide range of polarity. A high yield of the sample purification and reduced matrix effects were obtained without significant dilution of the cleaned-up fractions. This technique in combination with ESI-HPLC-MS/MS provides sufficient recoveries and satisfactory limits of quantification (LOQ) values to a wide range of pesticide residue [53].