Simultaneous determination of β-sitosterol and cholesterol in food samples by using solid phase microextraction fibers based on monolithic moleculary imprinted polymer followed by HPLC–UV

In this paper, an efficient and sensitive analytical method monolithic solid phase microextraction (SPME) fiber on the basis of moleculary imprinted polymer coupled to reverse phase high performance liquid chromatography (RP-HPLC) - UV detection analysis was developed for extraction and determination of β-sitosterol and cholesterol in food samples. Monolithic fiber is provided as follows: Template molecule (β-sitosterol) (2mmol) was dissolved in 30 mL acetonitrile (porogen) and functional monomer (MAA) (30 mmol), cross-linking monomer (EGME) (120 mmol) and intionar (AIBN) (280 mg) were added respectively. Then, 1mL of the mixture was transferred into small glass tube and was deoxygenized for 10 min with nitrogen gas. In order to prepare monolithic fibers, capillary home-made glass tubes as mold were treated according to the following recipe before preparation of monolithic fibers: In order to cut capillaries approximately, 30cm long pieces and windows of about 1 cm were prepared by burning the protecting polymer layer. Then, the capillary was filled with the polymerization mixture and both capillary ends were closed with two small pieces of rubber. The filled capillaries were inserted in an oven and polymerization took place typically at temperature 60 ◦C for 12 hours. Then polymeric monolith was withdrawn from mold by immersed capillaries in solution 40 % hydrofluoric acid for 2 hours .To obtain optimum extraction performance, several extraction parameters including extraction and desorption solvent, starring rate, extraction and desorption time were investigated and discussed. Under the optimized extraction conditions, the limits of detection (S/N = 3) of the proposed method were 0.03 and 0.05μg L−1, for of β-sitosterol and cholesterol respectively. Satisfactory linearity was achieved in the range of 0.1–20μg L−1for analytes with the correlation coefficients (r) above 0.9975. A method precision was performed by Intra-day and inter-day precisions taste which was achieved for the analysis of β-sitosterol and cholesterol in the range of 1.1–1.9%. This procedure was successfully applied with satisfactory results to the determination β-sitosterol and cholesterol in spiked milk, egg yolk and olive oil samples. The relative mean recoveries of oil samples ranged from 92.0% to 101.0%.