## 4 Conclusions  
In this study, the magnetic polystyrene microspheres with good morphology were prepared by improved microemulsion polymerization with nano-sized magnetic microspheres Fe\({}_{3}\)O\({}_{4}\) as carriers, and styrene, divinylbenzene and triallyl isocyanate as polymerization monomers. The Fourier transform infrared spectroscopy results showed that there were Fe\({}_{3}\)O\({}_{4}\) nanoparticles, styrene and a sulfonic acid group in these microspheres. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results showed that these magnetic polystyrene microspheres had good sphericity and the average particle size was less than 10 um. The vibrating sample magnetometer (VSM) results showed that the saturated magnetization of magnetic polystyrene microspheres was 3.225 emu/g, which was superparamagnetic. The X-ray diffraction (XRD) spectrum analysis results showed that Fe\({}_{3}\)O\({}_{4}\) nanoparticles would not destroy the crystal structure of ferrite during modification, and would also not change the crystal structure of ferrite during suspension polymerization. At the same time, typical amorphous polystyrene diffraction peaks appeared at 20 = 20\({}^{\circ}\). Moreover, these magnetic polystyrene microspheres were functionalized by chlorosulfonic acid. The infrared spectrum analysis results showed that the magnetic polystyrene microspheres were successfully grafted with sulfonic acid groups. The results, based on an organic element analyzer, showed that the loading amount of Fe\({}_{3}\)O\({}_{4}\)@SPS microspheres was 2.185 mmol/g. The actual sample test and HPLC-MS/MS results showed that Fe\({}_{3}\)O\({}_{4}\)@SPS microspheres had strong adsorption properties for melamine, clenbuterol, ratcopamine and salbutamol. In summary, based on the work of [PERSON] et al. we obtained satisfactory magnetic composite microspheres by optimizing the ratio of initiator and magnetic microspheres, the reaction time and the pH of the reaction system as a prerequisite for the experiments conducted in this paper. By reviewing the literature and comparing the experiments, the selection of a sulfonation reagent, the control of sulfonation time and the adjustment of the ratio, we finally decided to choose chlorosulfonic acid as the sulfonation agent; the molar ratio of \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Description of** & **Concentration** & \multirow{2}{*}{\(\beta\)-Agonists} & **Average Value of Results** & **Average Recovery** & **Relative Standard** \\
**Sample** & **(ug/kg)** & & **(ug/kg)** & **Rate (\%)** & **Deviation (\%)** \\ \hline \multirow{4}{*}{Pork} & \multirow{4}{*}{0.5} & Clenbuteral & 0.478 & 95.7 & 3.6 \\  & & Salbutamol & 0.478 & 95.7 & 4.1 \\ \cline{1-1}  & & Ractopamine & 0.498 & 99.7 & 3.9 \\ \cline{1-1}  & & Clenbuteral & 0.485 & 97.0 & 2.8 \\ \cline{1-1} \cline{2-5} Mutton & \multirow{2}{*}{0.5} & Sallbutanol & 0.473 & 94.7 & 5.8 \\ \cline{1-1}  & & Ractopamine & 0.470 & 94.0 & 3.3 \\ \cline{1-1}  & & Clenbuteral & 0.482 & 96.3 & 4.2 \\ \cline{1-1}  & & Salbutamol & 0.470 & 94.0 & 3.0 \\ \cline{1-1}  & & Ractopamine & 0.472 & 94.3 & 4.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Precision and recovery rate of standard addition samples of three \(\beta\)-agonists at the standard addition concentration of 0.5 ug/kg. chlorosulfonic and magnetic composite microspheres was 1:1, and the optimal sulfonation time was 5 min. [PERSON], [PERSON] and [PERSON] designed and performed the experiments, analyzed the data, and wrote the manuscript; [PERSON] and [PERSON] conceived the idea, reviewed, and edited the paper. All authors have read and agreed to the published version of the manuscript. This research was funded by Jiangsu Graduate Research and Practice Innovation Program (NO.SJCX22-0478) and National Key R&D Program (2018 YFC1602800). Not applicable. Data Availability Statement: Data is contained within the article. This work was supported by National Light Industry Quality Supervision and Inspection Nanjing Station.