###### Abstract  
A novel magnetic nanomaterial with Fe\({}_{3}\)O\({}_{4}\) as the core, PS-DVB as the shell layer, and the surface modified with C18 (C18\(-\)PS\(-\)DVB\(-\)Fe\({}_{3}\)O\({}_{4}\)) had been synthesized by seeded emulsion polymerization. C18\(-\)PS\(-\)DVB\(-\)Fe\({}_{3}\)O\({}_{4}\) retains the advantages of the chemical stability, large porosity, and uniform morphology of organic polymers and has the magnetic properties of Fe\({}_{3}\)O\({}_{4}\). A simple, flexible, and efficient magnetic dispersive solid phase extraction (Mag-dSPE) method for the extraction of preservatives, sweeteners, and colorants in river water was established. C18\(-\)PS\(-\)DVB\(-\)Fe\({}_{3}\)O\({}_{4}\) was used as an adsorbent for Mag-dSPE and was coupled with high-performance liquid chromatography (HPLC) to detect 11 food additives: acesulfame, amaranth, benzoic acid, tartrazine, saccharin sodium, sorbic acid, dehydroacetic acid, sunset yellow, allura red, brilliant blue, and erythrosine. Under the optimum extraction conditions, combined with ChromCoreTMAQC18 (5 um, 4.6 \(\times\) 250 mm), 20 mmol/L ammonium acetate aqueous solution and methanol were used as mobile phases, and the detection wavelengths were 240 mm and 410 nm. The limits of detection (LODs) of 11 food additives were 0.6-3.1 ug/L with satisfactory recoveries ranging from 86.53% to 106.32%. And the material could be reused for five cycles without much sacrifice of extraction efficiency. The proposed method has been used to determine food additives in river water samples, and results demonstrate the applicability of the proposed C18\(-\)PS\(-\)DVB\(-\)Fe\({}_{3}\)O\({}_{4}\) Mag-dSPE coupled with the HPLC method to environment monitoring analysis. M 202429367530 June 20  
food additives, causing serious food safety accidents [9]. In addition, in the production, processing, packaging, transportation, and storage of food additives, food additives will flow into the environment due to improper operation [10]. Benzoic acid, which is often used for food preservation, was detected in groundwater at concentrations of 10-27,500 ug/L [11]. Acesulfame is used to improve the taste of food, and the concentration detected in surface water can be as high as 21 ug/L [12]. In addition, allura red, which is used for food coloring, was detected in natural water samples at concentrations ranging from 9.9 to 77.5 ug/L [13]. Therefore, the adsorption removal and enrichment detection of food additives in environmental water samples is an urgent problem to be solved. In the production, processing, packaging, transportation, and storage of food additives, food additives will flow into the environment because of improper operation. In addition, many synthetic food additives are difficult to degrade in the body, and they are released into the environment through excretion. The ultimate destination of these food additives would be transferred to the surface water. And the decomposition of a variety of aromatic amines display carcinogenicity. Therefore, it is worth studying to establish a simple and feasible method for the detection of food additives in environmental water samples [14; 15; 16; 17]. At present, the detection methods of food additives include liquid chromatography [18; 19; 20; 21; 22], gas chromatography [23], and colorimetric methods [24]. However, the composition of the sample is very complex, and the sample needs to be pretreated before the instrument detection. Solid phase extraction (SPE) is the most widely used pretreatment technique. It includes solid phase microextraction (SPME), dispersed-solid phase extraction (d-SPE) [25], and molecularly imprinted solid phase extraction (MISPE) [26; 27; 28]. SPE minimizes matrix effects, improves selectivity and recovery, and the detection limit of the instrument is greatly reduced [29]. In 2022, a novel molecularly imprinted polymer was used as an adsorbent for MISPE to remove sodium sacchar from the sample. The detection limit was 7.0 g/L [30].