## 1 Introduction  
Molecularly imprinted polymers (MIPs) are macromolecular materials with a specific recognition function for template molecules. The synthesis of molecularly imprinted polymers is a process of combining template molecules with functional monomers under the action of initiator and cross-linkingagent, and then the template molecules are eluted from the polymers. Water-soluble redox initiator is commonly used in emulsion polymerization. The initiator decomposes under the condition of illumination or heating to generate free radicals. The active free radicals to initiate the polymerization reaction, and the template molecules are combined with the functional monomers under the action of the cross-linking agent to form molecularly imprinted polymers. The detailed synthesis process is as follows. Firstly, the functional monomers and the template molecules are pre-polymerized, and the pre-polymerization time is generally 12 h. In order to improve the pre-polymerization effect, ultrasonic assistance can be used. Then, cross-linking agents and initiators are added to carry out a polymerization reaction under suitable conditions. The cross-linking agent generally requires reduced pressure distillation before use. Finally, the obtained polymers are eluted under appropriate conditions to elute the template molecules. Thus, molecularly imprinted polymers with imprinted holes matched with the size, shape, and functional groups of the template molecules are obtained [1; 2]. [PERSON], a famous scholar, put forward the theory of antibody formation in the 1940s, which laid a theoretical foundation for the generation of molecular imprinting technology [3]. In 1972, [PERSON] et al. successfully prepared an MIP for the first time [4]. Today, molecular imprinting technology is widely used in solid-phase extraction [5; 6], chromatographic separation [7; 8], bionic sensing [9], membrane separation [10], the food industry [11; 12], natural drug separation [13], medicine [14], and environmental monitoring [15], among other applications. The methods of the synthesis of MIPs include bulk polymerization, solution polymerization, dispersion polymerization, suspension polymerization, and emulsion polymerization. MIPs obtained by different polymerization methods have different morphologies and adsorption effects. The conventional bulk polymerization method and solution polymerization method produce block MIPs, which need to be pulverized and ground; therefore, the polymer ultimately obtained is not uniform in shape or size. Additionally, the imprinted holes are buried in the polymer and directly affect the adsorption effect [16]. The emulsion polymerization method can directly synthesize spherical MIPs, and it does not require complicated post-treatment processes such as subsequent grinding or screening, thus reducing the probability of the destruction of imprinted holes. Spherical polymers synthesized by the emulsion polymerization method have a uniform particle size and high use efficiency. The emulsion polymerization method is fast and has a stable dispersion system, and it can realize continuous production. Additionally, water is used as a dispersion medium, which is beneficial to heat transfer and temperature control, a safe production process, and the reduction of environmental pollution [17; 18]. Solanesol (SSO) is an important pharmaceutical intermediate and an irreplaceable natural raw material for the synthesis of coenzyme Q10 and anti-ulcer and anti-cancer drugs [19]. Crude solanesol cannot be directly used as a medicinal raw material, so it is necessary to separate and purify it. In recent years, it has been reported that molecular imprinting technology can be used to purify solanesol. [PERSON] [20] synthesized spherical solanesol molecularly imprinted polymers (SSO-MIPs) in a size range of 250-350 \(\upmu\)m via suspension polymerization, which was used to purify solanesol via rapid chromatography.