Selective Extraction of Cholesterol from Dairy Samples Using a Polypyrrole Molecularly Imprinted Polymer and Determination by Gas Chromatography

A novel molecularly imprinted polymer (MIP) was prepared by chemical oxidation of pyrrole through applying FeCl3 and was used as a sorbent for selective batch extraction of cholesterol (CHO) in dairy samples. Gas chromatography coupled with flame ionization detector was performed to analyze the samples without any saponification and derivatization treatments. MIP particles were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy techniques. The selectivity of MIP for CHO under competitive adsorption with structurally steroid analogous compounds was investigated and developed polymer showed selectivity toward CHO. The various parameters, such as desorption solvent, the amount of sorbent, pH, and ionic strength, that affect the extraction efficiency of the imprinted polymer were evaluated to optimize the method. Under the optimized conditions, the developed method showed a good linearity in range of 3.75–7000 ng/mL through a correlation coefficient of 0.9952 and 10–120 μg/mL through a correlation coefficient of 0.9921, while good CHO recoveries of 87.3–92.4 % and the limit of detection and the limit of quantification were, respectively, obtained 1.25 and 4.2 ng/mL. The polypyrrole-MIP showed a high extraction efficiency toward CHO compared to the non-imprinted polymer and was successfully used for the determination of CHO in dairy products.