# Preparation of Magnetic Polymers for the Elimination of 3-Isobutyl-2-methoxypyrazine from Wine
## 3 Materials and Methods
### Preparation of Polymers  
Magnetic polymers were prepared by multi-step polymerisation, as shown in Figure 8. Fe\({}_{\mathrm{x}}\)O\({}_{\mathrm{y}}\)@SiO\({}_{2}\)-MPS nanoparticles were prepared first as magnetic bases using commercial iron (II, III) oxide particles instead of preparing through chemical co-precipitation. Surface modification of Fe\({}_{\mathrm{x}}\)O\({}_{\mathrm{y}}\) followed the procedures of [PERSON] et al. [25], with modification of the process of [PERSON] et al. [45], [PERSON] et al. [46], and [PERSON] et al. [47]. The attempted MMIPs were then prepared according to [PERSON] et al. [23] with some modifications. Briefly, MMA (432 \(\upmu\)L, 4 mmol) was added to 'dummy' template molecule 2-methoxypyrazine (98 \(\upmu\)L, 1 mmol) in toluene (12 mL) as a functional monomer. The obtained Fe\({}_{\mathrm{x}}\)O\({}_{\mathrm{y}}\)@SiO\({}_{2}\)-MPS nanoparticles (1 g) were then added and the mixture was stirred for 2 h at ambient temperature. After this time, cross-linker EGDMA (3.8 mL, 20 mmol) was added along with the initiator 2, 2'-azobississobutyronitrile (AlBN, 100 mg). The mixture was degassed in an ultrasonic bath for 15 min and purged with nitrogen, sealed, and placed in a 60 \({}^{\circ}\)C oil bath for 24 h of polymerisation. The obtained bulk polymers were crushed and separated from the round-bottom flask. The polymers were dried under high vacuum and ground in a ball mill (full-directional planetary ball mill (QXQM-1), Tencan, Changsha, China). Ground polymer was passed through a 150 \(\upmu\)m sieve (Retsch test sieve, 200 mm \(\times\) 50 mm, 150 \(\upmu\)m, VWR, Tingalpa, QLD, Australia) and the collected  
\begin{table}
\begin{tabular}{c c c} \hline \hline  & **Australia (Aus)** & **New Zealand (NZ)** \\ \hline Original IBMP (ng/L) & 0.4 \(\pm\) 0.1 & 14.1\(\pm\) 0.4 \\ \hline Spiked with 30 ng/L IBMP & 25 \(\pm\) 3 & 38 \(\pm\) 2 \\ \hline Q\({}_{\mathrm{MMIP}}\) (pmol/g) & 6 \(\pm\) 3 & 10 \(\pm\) 3 \\ Q\({}_{\mathrm{MMIP}}\) (pmol/g) & 3 \(\pm\) 2 & 9 \(\pm\) 2 \\ MMIP adsorption (\%) & 42 \(\pm\) 19 & 45 \(\pm\) 11 \\ MMIP adsorption (\%) & 19 \(\pm\) 10 & 38 \(\pm\) 5 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Adsorption of IBMP (mean \(\pm\) SD, \(n\) = 3) by thermally synthesised MMIP and MMIP in commercial Sauvignon Blanc wines spiked with IBMP.  
Figure 7: Magnetic separation of putative MMIP in white wine samples.  
particles were washed with diethyl ether by Soxhlet extraction until no further 2-methoxypyrazine was detected in the washing solvent by gas chromatography-mass spectrometry (GC-MS) analysis [23]. MNIPs were made by the same protocol without addition of the 2-methoxypyrazine as a template. Other putative imprinted and non-imprinted polymers (i.e., MW MMIPs and MW MNIPs) were prepared in the same way as described above, except that the polymerisation process was completed within 1 h at 60 \({}^{\circ}\)C in a microwave synthesiser (CEM microwave synthesiser, Discover S, DKSH, Melbourne, VIC, Australia). Reactions were performed in a 35 mL sealed reaction vessel (CEM, DKSH). The microwave power was on in dynamic mode with a pressure limit of 150 psi.  
A range of non-magnetic polymers (the MIPs, NIPs, MW MIPs, and MW NIPs) were also prepared in the same way, without the magnetic substrates. All the polymers were prepared in duplicate and gave similar yields of around 92%.