A new structural design for fabricating four types of ionic liquids was successfully adapted, which was based on changing the anion of 1-vinyl-3-octylimidazolium bromide (VOIm⁺Br⁻) with benzene sulfonic acid (BenSO₃⁻), 2-naphthalene sulfonic acid (NapSO₃⁻), 1-anthraquinonesulfonic acid (AQSO₃⁻) and 1,2-naphthoquinone-4-sulfonic acid (NQSO₃⁻). Then, designed ionic liquids were directly modified on the surface of magnetic graphene oxide reduced nanoparticles (Fe₃O₄@SiO₂@G) and used as a novel magnetic adsorbent for the determination of preservatives in vegetables via ultra-high performance liquid chromatography-triple quadrupole/linear ion trap mass spectrometry (UPLC-MS/MS). In this study, the specific adsorption capacity of the four types of functional ionic liquid–magnetic graphene adsorbents was investigated. The adsorption abilities of the as-prepared novel magnetic adsorbents towards 34 preservatives were investigated. The adsorbent comprising functional ionic liquid 1-vinyl-3-octylimidazole-2-naphthalene sulfonate (VOIm⁺NapSO₃⁻) combined with Fe₃O₄@SiO₂@G adsorbent had better adsorption capacity than the other adsorbents due to the following factors: the structure of the ionic liquid with two benzene rings could produce an appropriate intensity of π–π conjugation; lower steric hindrance enabled the facile combination with preservatives; the imidazole ring and the hydroxyl groups provided the possibility of formative hydrogen bonding. The detailed chemical and microstructural features of the hybrid nanomaterials were studied via SEM, VSM, FTIR and XPS analyses. Under the optimal conditions, the satisfactory detection limits (LOD) of this method were in the range of 0.01–0.15 μg L⁻¹. This study reveals the potential of the VOIm⁺NapSO₃⁻ attached Fe₃O₄@SiO₂@G nanomaterial composite as a novel adsorbent for pretreatment applications.