# Application of Sorbent-Based Extraction Techniques in Food Analysis
## 2 The Introduction to SBE Methods  
Among all SBE methods, solid-phase extraction (SPE) is the most often used technique in the food chemistry field, due to both its long history as well as the broad fields of application resulting from the selectivity of sorbents used in SPE. The ability of solid surfaces to bind organic compounds has been known for years and the first experiments were performed with activated carbon, which was used among other applications in the closed-loop stripping analysis with all its benefits and drawbacks (i.e., irreversible adsorption, varying recoveries, etc.). The developments in SPE in the 1960s and 1970s and the use of Amberlite XAD resins, Tenax, and finally bonded silica cemented the popularity of SPE [12; 13]. In particular, modification of silica with alkyl or aryl groups (C2, C8, C18, diol, cyanopropyl, phenyl) resulted in the success of this technique in food analysis. In 2002, a new chapter in SPE applications opened, especially in pesticide residues and veterinary drugs analysis, when [PERSON] et al. [14] developed an effective method of the extraction of especially polar and basic compounds. This method is named QuECHERS (for Quick, Easy, Cheap, Effective, Rugged and Safe) and it is dispersive SPE (d-SPE), revolutionized sample preparation in pesticide residue analysis. The success of QuECHERS in terms of popularity is reflected in many published reports and also in a database for recoveries for over 650 pesticides and metabolites (www.eurl-pesticides-datapool.eu (accessed on 10 November 2022)). The purpose of dispersive SPE clean-up is the removal of organic acids, sugars, lipids, and pigments, mainly carotenoids and chlorophylls. The most often analyzed samples using QuECHERS for which AOAC methods are developed are fruits and vegetables, even those with fats, waxes, and pigments [15]. The second popular SBE method is solid-phase microextraction (SPME), which was developed by [PERSON] in 1990 [PERSON] (1990). The idea behind integrating the sorption of analytes into fused silica fiber coating and subsequent desorption into the injection port of a gas chromatograph (GC) in syringe-like fiber/holder simplified sampling and analysis of volatile organic compounds (VOCs). Due to the complexity of food matrices, SPME is usually performed from the headspace (HS-SPME). This approach enables the analysis of compounds in solid matrices without solvents and in a shorter time. However, recently, some attention was focused on the direct extraction from liquid food samples since it was proven that it is a more effective way to extract polar compounds ([PERSON] et al., 2018). Additionally, the next direction of SPME, still not sufficiently explored for food analysis, but used for biological fluids is the combination of SPME with LC-MS ([PERSON] et al., 2018). Another new era is using SPME with an ambient MS, without chromatographic separation ([PERSON] et al., 2018). This area of SPME application is still under investigation; nevertheless, results achieved so far indicate that it might be a technique of choice in the future. Several methods using needle-based extraction were developed afterwards, among them solid-phase dynamic extraction (SPDE), where sorbent is on the inner wall of a needle mounted in a gas-tight syringe, needle-trap devices (NTD) or in-needle capillary adsorption trap (INCAT) ([PERSON] et al., 2018). Extraction techniques based on similar principles followed SPME development, such as stir bar sorptive extraction (SBSE) or high-capacity sorbent extraction (HCSE), which also found many applications in food analysis. Molecularly imprinted polymers (MIPs) are used frequently in the sample preparation of food. Very high selectivity is possible by tailoring MIPs for specific compounds, enabling highly sensitive and selective analyses of veterinary drugs and other contaminants in food ([PERSON] et al., 2018).