Monolithic Material Prepared with Nanodiamond as Monomer for the Enrichment of β-Sitosterol in Edible Oil

In this paper, a hybrid monolithic column with modified nanodiamond and 1-dodecene as co-monomers was prepared and applied to the online enrichment and purification of β-sitosterol in edible oil. The obtained monolithic column was characterized by scanning electron microscopy (SEM) and nitrogen adsorption–desorption isotherm measurement, which indicated that the monolith possessed characteristics of porous structure and high permeability. Under the optimum conditions for extraction and determination, the linear regression coefficient for β-sitosterol was 0.998; the limit of detection (LOD) and the limit of quantitation (LOQ) were 3.0 μg mL−1 and 10.0 μg mL−1, respectively; the relative standard deviation (RSD) of intra-day and inter-day assays for four edible oils were 2.33–6.58% and 3.24–6.94%, respectively. The recovery was in the range of 89.6–105.5%. The results showed that the hybrid monolithic column with high selectivity and good permeability were successfully used as online solid-phase extraction (SPE) column for determination of β-sitosterol in edible oil.