# Application of Sorbent-Based Extraction Techniques in Food Analysis
## 3 SPE in Food Analysis--Main Fields of Applications
### Pesticide Residues
To increase the production efficiency of olive oil and other vegetable oils, pesticides are commonly used that eliminate or reduce adverse factors for crops. There is much research on the detection and determination of pesticides in complex matrices like vegetable oils. The analysis of vegetable oils for pesticides is difficult due to a large number of co-eluting compounds. SPE with a alumina column or a C18 sorbent is commonly used for that purpose. Lately, this technique has been subjected to some modifications with the utilization of magnetic nanoparticles and MIPs as a new type of sorbents. As a result of the accessibility of novel sorbents, d-SPE is the most popular method so far, used to purify vegetable oil samples before GC or LC analysis [54]. Pesticides used for the protection of wines can be also found in the final product. The range and type of pesticides licensed for use in wine making and their maximum residue levels are determined by law regulations and differ between countries. Optimal conditions for the SPE application for red and white wine samples include the use of hydrophilic-lipophilic balance (HLB) sorbents and a mixture of acetonitrile and methanol as solvents. Extracts were injected into UPLC-MS/MS, which enabled the determination of 50 pesticide residues with a LOQ below 1 ng/mL for 48 of them [55]. Grapevines are prone to a wide range of pests (fruit worm, grapevine moth, vine mealybug) and fungal infections (black mold, grey rot, downy mildew, powdery mildew), which is why they have to be protected by utilizing regulated pesticide formulations. The clean-up stage was performed usingd-SPE with PSA sorbent to remove the effects of the matrix. However, if a tandem MS is available, a sample purification step is less crucial [56]. It is not only foods of plant origin that are exposed to the presence of pesticide residues, since pesticides were also found in fish such as catfish, rainbow trout and shellfish like shrimps. Analysis of pesticides in aquatic species meat requires a clean-up step which is based on a widely applied technique, QuEChers--d-SPE with primary-secondary amine (elimination of interferences such as fatty acids, organic acids, pigments) and C18 sorbents (cleansing from non-polar-constituents like lipids and waxes). Currently, new methods of purification of the sample are studied based on a modification of the sorbent bed, e.g., using multi-walled carbon nanotubes, zirconium-based sorbents or anhydrous salts such as MgSO\({}_{4}\). The purified samples were analyzed by LC-MS/MS [57]. Honey provides a lot of desirable medical properties and it is an analytical challenge due to the complex matrix composed of numerous different types of compounds (amino acids, enzymes, essential oils, flavonoids, organic acids, phospholipids, sugars, sterols, and vitamins) [58]. Pesticides which can transfer into nectar or those that accumulate in the environment are the main pollution of honey. It is possible to determine pesticide residue in a honey sample by utilizing the GC or LC technique; however, in the sample pre-treatment step among which d-SPE with polymerically bonded, ethylenediamine-N-propyl (PSA) sorbent and acetate buffer dominate. It was observed that the purification process with PSA sorbent does not enable sufficient purification efficiency for the honey extract. To remove interferences and maintain the analyte concentration of the honey extracts, the d-SPE method is used with a complex sorbent composed of MgSO\({}_{4}\), florisil, C18, PSA, Z-Sep+ sorbent, and citrate or acetate buffer. The optimal method of purifying a sample of honey turned out to be the use of mixed sorbents varying in clearance mechanism PSA (pH ionic exchanges) with Z-Sep+ (hydrophobic, Lewis acid interactions), MgSO\({}_{4}\), and acetate buffer. The QuEChERS sample preparation technique with modifications enables the analysis of over 200 pesticides in honey [59].