## 5 MIP Applications for the Extraction of Antibiotics in Milk
### Amphenicols
CAP-MIPs were prepared by sol-gel synthesis in four steps. In the first step, a self-assembled complex between CAP and the sol-gel precursors was obtained by mixing CAP (250 mg), (3-aminopropyl)triethoxysilane (APTES) (0.8 g), triethoxypphenylsilane (TEPS) (0.8 g) and isopropanol (4 mL). The mixture was sonicated for 30 min and incubated at room temperature for 6 h. In the second step, TMOS (2.5 mL) was mixed with isopropanol (20 mL) and the mixture was vortexed for 5 min. HCl solution (0.1 M, 750 \(\mathrm{\SIUnitSymbolMicro L}\)) was added to the mixture that was retained in a silicon oil bath at 50 \({}^{\circ}\)C for 12 h, until the cross-linker was completely hydrolyzed. In the third step, the mixtures obtained in the first two steps were combined and vortexed for 5 min. The resulting mixture was retained in a silicon oil bath for 4 h, until a transparent gel is formed, and for additional 24 h until the three-dimensional sol-gel network was developed. Finally, the developed MIPs were washed tenfold with methanol (10 mL) with subsequent sonication for 30 min or centrifuging at 1900g for 30 min and dried at 50 \({}^{\circ}\)C for 30 min. CAP-MIPs (30 mg) were packed into a syringe barrel, preconditioned with methanol (2 mL) and deionized water (2 mL), retained for 15 min and loaded with defatted and deproteinized spiked milk extract. The analytes were eluted with methanol (500 \(\upmu\)L) and the eluate was injected directly for analysis. In comparison with the respective NIP, MIP adsorption capacity for CAP was higher, with maximum adsorption capacity of 2300 \(\upmu\)g/g, while imprinting factors were 5 for CAP, 1.9 for TAP and 1.8 for FFC. Furthermore, the MIPs could be used for six consecutive extraction cycles with no adsorption capacity loss [50]. A MISPE-high-performance liquid chromatography-diode array detection (HPLC-DAD) method was developed for the determination of CAP in honey and milk samples. Acrylamide-grafted chitosan was used as the matrix in MIP synthesis. Acrylamide (AM) (0.4 g) and CAP (0.1 g) were dissolved in ethyl acetate (10 mL), EGDMA (1 mL) was added and the mixture was stirred for 30 min. 1.5% Chitosan solution (30 mL) dissolved in 2% acetic acid aqueous solution and liquid paraffin (50 mL) that contained sorbitan oleate (0.3 mL) were added and the mixture was stirred at 40 \({}^{\circ}\)C for 30 min. The mixture was adjusted to pH 9.0 by adding NaOH solution (2 M), 50% glutaraldehydehyde (0.8 mL) was added and the mixture was stirred for 3 h. The template was removed by Soxhlet extraction with methanol-acetic acid (9:1, \(v/v\)) for 10 h. CAP-chitosan-MIPs (100 mg) were packed into a SPE cartridge, loaded with deproteinized spiked milk extract (5 mL) and washed with 10% methanol. The analytes were eluted with 10% acetic acid in methanol. In comparison with the respective NIP, MIP adsorption capacity for CAP was higher, with Q\({}_{\text{max}}\) values of 4400 and 59,850 \(\upmu\)g/g, while imprinting factors were 7.43 for CAP, 1.29 for erythromycincin (ERY) and 1.83 for tetracycline (TC) [51]. A MISPE-LC-MS/MS method was developed for the determination of FFC. FFC (0.358 g) and AM (0.284 g) were dissolved in dimethyl sulfoxide (10 mL) and the mixture was stirred in dark for 1 h. EGDMA (4 mL) and styrene (1 mL) were added and the mixture was stirred for 30 min. The upper phase was collected, mixed with water (50 mL) that contained sodium dodecyl sulfate (150 mg) and stirred for 600 rpm for 25 min. The emulsion was placed inside a high-pressure microwave vessel at 70 \({}^{\circ}\)C for 1 h. The template was removed with methanol-acetic acid (80:20, \(v/v\)) and ultrasound application. The MIP particles were washed with water and dried at 60 \({}^{\circ}\)C. FFC-MIPs (100 mg) were packed into a syringe barrel, preconditioned with methanol (3 mL) and water (3 mL), loaded with milk extract and washed with acetonitrile-water (50:50, \(v/v\); 2 mL).