## 5 Analysis of Template-Monomer Functional Interactions
### Proton-Nuclear Magnetic Resonance (\({}^{1}\)H-Nmr)  
\({}^{1}\)H-NMR can be used for the analysis of complex formation during pre-polymerization; this method is commonly used to obtain optimal MIP preparation with the appearance of non-covalent compounds (hydrogen interactions, electrostatic interactions, and hydrophobic interactions) [117; 118; 119]. Studies by [PERSON] et al. [120] have demonstrated the use of \({}^{1}\)H-NMR on the significance of hydrogen bonding in achieving imprinting effects, while work by [PERSON] et al. [121] showed how NMR investigations of monomer-template dissociation constants can predict MIP binding capacities. During the formation of hydrogen bonds, there is a downfield shift caused by the reduced electron density around the hydrogen nucleus [83]. The reduction in \({}^{1}\)H-shielding correlates with the shortening of the distance between the donor and acceptor of the hydrogen bond. The \({}^{1}\)H-shielding value of hydrogen bonding protons is determined by the reduced electron charge density around the hydrogen atom. The greater the deshielding proton, the shorter the hydrogen bond distance [119]. The downfield shift of the NMRsignal of the bridging proton in a hydrogen bond is divided into two phenomena. First, the formation of hydrogen bonds due to polarization and charge transfer leading to deshielding. Second is the presence of proton-accepting groups, where the response to an external magnetic field and electron density causes an effect on the position of the proton bridge, exclusive of any H-bonding phenomenon [122]. The interaction between template molecules and functional monomers will be stronger along with the significant chemical shift [83]  
The research of [PERSON] et al. [83] reveals the hydrogen bond interaction between and AM from the chemical shifts in the single AM spectra compared to the DM-AM complex spectra. In the AM spectra, the peak of the amino hydrogen atom, which was at 3.10 ppm, was shifted to 2.89 ppm in the DM-AM complex spectra. The hydrogen bond of the carbonyl group in DM with the amino group in AM causes the electron density around the AM amino hydrogen atom to decrease so that a downfield shift occurs. This indicates that the DM template and AM functional monomer are successfully conjugated [83, 123]  
[PERSON] et al. [55] investigated the interaction between template cocaine hydrochloride (COCH) and functional monomers methacrylate acid (MAA) and ethylene dimethacrylate (EDMA). The investigation was carried out by varying the molar ratio in the range 0.3-3.0 between COCH: MAA and COCH: EDMA, then comparing the chemical shift disturbance caused by certain functional groups present in the template and functional monomers. The result is a chemical shift at 2.84 ppm COCH (H from the protonated COCH), 1.89 ppm MAA (H close to the acid group in MAA), and 4.36 ppm EDMA (H close to the ester groups in EDMA). This shift occurs due to the interaction of the amino group hydrogen bonds in COCH with oxygen in the acid group (MAA) and oxygen in the ester group (EDMA) [55]. [PERSON] et al. [99] also investigated the intermolecular interactions between the oblongifolia C (OC) template derived from the fruit extract of Garcinia yunnenensis Hu and the functional monomer AM. The molar ratio used is OC:AM = 1:4. When the single spectrum of OC was compared to the mixed spectrum of OC:AM, the proton -OH peak at 9.912 ppm experienced a downfield shift to 9.916 ppm. When the single spectrum of AM was compared to the mixed spectrum of OC:AM, the -NH\({}_{2}\) proton peak at 7.509 ppm underwent a downfield shift to 7.513 ppm. When the spectrum of the \({}^{13}\)C-NMR mixture (OC:AM = 1:4) was compared with the AM spectrum, the -C=O group at 166.33 ppm experienced a downfield shift to 166.35 ppm. The results of this chemical shift confirm the occurrence of intermolecular interactions between OC and AM in the form of hydrogen bonds [99].