# Application of Sorbent-Based Extraction Techniques in Food Analysis
## 3 SPE in Food Analysis--Main Fields of Applications
### Processing Contaminants  
As mentioned earlier, food can be contaminated by various paths and from different sources. Impurities arise during processes and thermal reactions as well as cleaning, disinfecting, sterilization and other preservation techniques. The analysis of processing contaminants is demanding because they most often occur in trace amounts in complex matrices, hence a sample pre-treatment stage is required to concentrate the analyte and eliminate interference from the matrix [67]. PAHs are widely known as carcinogenic compounds that are primarily produced during the thermal treatment of food (combustion, roasting, and smoking of organic matter). The most known compound in this class is benzo[a]pyrene, which is classified in category 1 according to the International Agency for Research on Cancer. Any smoked or thermally processed food may contain PAHs even in roasting raw materials like coffee beverages or dark beer. To clean the samples of coffee and dark beer, silica-gel cartridges were used; however, recovery was low in contrast to alumina-N SPE cartridges, which turned out to be suitable for this matrix. For the determination of PAHs, GC-MS, LC with a variety of detection methods (UV, FLD, MS) and, currently gaining recognition, supercritical fluid chromatography with carbon dioxide, which is suitable for low-polarity analytes and provides a shorter analysis time, were applied [68]. Edible oils are consumed in large quantities as part of our diet. Through the lipophilic nature of edible fats and their origin, they are highly exposed to toxic PAH pollutants. The main problem in the analysis is a matrix that consists of high-molecular-weight compounds (triglycerides); therefore, it is necessary to separate the analyte from the matrix and adequately clean the sample. To achieve a satisfactory sample, which can be analyzed by GC-MS/MS, the d-SPE was used. A modern multi-walled carbon nanotube sorbent was applied for selective extraction, which replaced the habitually used time-consuming techniques [69]. Meat, particularly smoked, is subjected to strict controls, using the SPE method. A recent study indicated a deficiency in the optimal extraction methods for different bovine tissues because of the unsatisfactory sensibility of the methods. Sufficient recovery values, LOD and LOQ were obtained by utilizing matrix solid-phase dispersion extraction before sample pre-treatment by SPE with a nucleoside silica C18 sorbent. The results obtained enable the monitoring of food samples because the method provides sufficient sensitivity below the permitted levels [70]. Derivatives of furan (2-methyl furan, 2-furaldehyde, 5-methyl-2-furaldehyde) form a group of organic heterocyclic compounds called forans. Nevertheless, in the literature, the term \"furans\" also refers to polychlorinated dibenzofurans, which commonly appear with dioxins as environment impurities. Typically, furan derivatives are not found naturally in food and are formed during fermentation, pathogen disinfection or preservation (pasteurization, thermal processing or UV light treatment). The presence of furans was found in a wide diversity of foods such as apple cider, bakery products, brandies, bread, coffee, fruit juices, honey, tequilas, vinegar, and wines. For the determination of furan derivatives, the SPE technique with polymer-based LiChroult EN cartridges was used to purify the sample, as well as to isolate and concentrate the VOCs from liquid samples. The high diversity oforbents creates many possibilities for extraction from lipophilic and hydrophobic matrices, which enables obtaining a satisfactory LOD [71]. Acrylamide is formed as a result of thermal processes (baking, grilling, frying) in foods with a high carbohydrate content based on the Maillard reaction mechanism [72]. As reported by the International Agency for Research on Cancer, acrylamide has several potential adverse health properties (carcinogenic, genotoxic, mutagenic); therefore, it is subject to specific controls and law regulations.