3493 CHOLINE PROLINE IONIC LIQUID-FUNCTIONALIZED O 4 @SIO 2 FE3FE 43 2 EXPERIMENTAL REAGENTS Anhydrous iron trichloride, ferrous sulfate heptahydrate, polyethylene glycol 400, ammonia, anhydrous ethanol, tetraethyl orthosilicate, choline chloride, proline (Pro), sodium hydrox- ide, hexamethylene bis-isocyanate, potassium bromide, dimethyl sulfoxide, and acetone were purchased from Sinopharm Chemical Reagent Co. Ltd. (Beijing, China). INSTRUMENT The following instruments were used in this study: a constant temperature oscillator (Guohua Electric Co., Ltd. Jintan, China), infrared spectrometer (Bruker, Germany), LC1220 high-performance liquid chromatography (Agilent Technologies, Santa Clara, CA), and DZF-6020 vacuum drying oven (Shanghai Jinghong Experimental Equip- ment Co., Ltd., Shanghai, China). SYNTHESIS OF FE3O4@SIO2 First, FeCl3 (0.02 mol), FeSO4·7H2O (0.01 mol), and polyethylene glycol 400 (30 mL, 10%) were dissolved into 75 mL of deionized water at 80°C. Next, 50 mL of NH3 aqueous was added under vigorous stirring and nitrogen protection. Then, the obtained magnetic nano- ions were separated by a magnet and rinsed three times with deionized water the product was dispersed with 240 mL of ethanol, 60 mL of distilled water, and 15 mL of ammonia water, and sonicated for 20 min. After sonication was completed, 1.7 mL of tetraethyl orthosilicate was added, and the mixture was stirred at 60°C for 12 h. Finally, it was washed twice with water and ethanol to obtain Fe3O4@SiO2 (11). SYN THESIS OF CHOLINE PROLINE IONIC LIQUID ([CH][PRO]) Ref erring to the synthesis method of [Ch][AA] reported in the literature, [Ch][AA] was obtained by ion exchange and neutralization reaction, and the brief steps are as follows: fi rst, [Ch]OH was obtained by passing [Ch]Cl through a ion exchange column. Then, [Ch][Pro] solution was obtained by a simple neutralization reaction between [Ch]OH and Pro. Last, the solution was dried to obtain [Ch][Pro] (12). SYN THESIS OF FE3O4@SIO2@[CH][PRO] A m ixture of Fe3O4@SiO2 (0.2 g), [Ch][Pro] (0.4 g), and dimethyl sulfoxide (40 mL) was dispersed ultrasonically for 1 h in a 250-mL three-necked fl ask and transferred to a water bath and stirred at 70 °C for 2 h then, 1.0 mL of hexamethylene diisocyanate was added, and stirring was continued for 48 h. After the reaction, the product was separated with a magnet, and washed with distilled water and anhydrous ethanol three times. Finally, the product was dried at room temperature for 48 h to afford Fe3O4@SiO2@[Ch][Pro]. EXTR ACTION PROCEDURE The extraction of allura red was carried out in a 10-mL tube. A mixture of 1.0 mL of 100 μg/mL allura red standard solution and 2.0 mL buffer (pH = 5.0) was diluted with

350 JOURNAL OF COSMETIC SCIENCE 4 deionized water to a fi nal volume of 10.0 mL. 8.0 mg Fe3O4@SiO2@[Ch][Pro] nanopar- ticles was added in the tube and stored at room temperature for 5 min, and the nanopar- ticles were separated in a magnetic fi eld and washed with 6.0 mL of KBr/acetone (KBr: acetone = 2:1, v:v KBr: 2 mol/L). Finally, nanoparticles were separated again with an external magnet, and 20.0 μL of the upper solution was taken for HPLC determination. CHROMA TOGRAPHIC CONDITION The al lura red was separated in an Apollo C18 (150 × 4.60 mm, 5 micron, Shanghai Evans & Trade Co., Ltd., Shanghai, China) the mobile phase was a mixture of 0.02 M ammonium acetate and methanol (70:30, V/V). The fl ow rate was 1 mL/min, and the injection volume was 20 μL. The detector was programmed at 502 nm. RESULTS AND DISCUSSION CHARACTE RIZATION OF FE3O4@SIO2@[CH][PRO] Figure 2 showed the FT-IR spectra of Fe3O4@SiO2, [Ch][Pro], and Fe3O4@SiO2@ [Ch] [Pro](curves a, b, c). From Figure 2, (i) the peaks around 582 cm-1 and 1,042 cm-1 in a F igure 2. FT-IR spectra. (A) Fe3O4@SiO2, (B) [Ch][Pro], and (C) Fe3O4@SiO2@[Ch][Pro].