Simultaneous Determination and Enrichment of β-Sitosterol From Edible Oil Samples Using Poly(NMA-ST-co-TAIC-co-EDMA) Monolith as Sorbent with On-line SPE-HPLC

A poly(NMA-ST- co -TAIC-EDMA) monolithic column was prepared by redox initiation method using N -methylolacrylamide (NMA) and styrene (ST) as co-monomers. The composite monolith was characterized by scanning electron microscopy (SEM) and nitrogen adsorption–desorption isotherm and was used as a solid phase extraction (SPE) absorbent for enrichment of β -sitosterol by high performance liquid chromatography (HPLC). Under the optimum conditions for extraction and determination, the calibration equation was y  = 1.02247 x  + 0.1766; the linear range was 0.015–0.75 mg mL −1 and the linear regression coefficient was 0.998. The limit of detection (LOD) and the limit of quantification (LOQ) were 0.006 mg mL −1 and 0.02 mg mL −1 , respectively. The spiked recoveries of β -sitosterol in edible oil samples were 83.60–103.88%; precisions for intra-day and inter-day assays presented as relative standard deviations were less than 6.0% and 6.2%, respectively. The enrichment factor of β -sitosterol was 60 and the results showed that the monolithic column had high selectivity and good permeability as an on-line SPE absorbent for the enrichment and determination of β -sitosterol from edible oils.