Development of molecularly imprinted poly(methacrylic acid)/silica for clean-up and selective extraction of cholesterol in milk prior to analysis by HPLC-UV

Abstract

In the present paper the assessment of a novel molecularly imprinted polymer, poly(methacrylic acid)/silica, for clean-up and selective extraction of cholesterol in milk samples is described. The relative selectivity coefficient (k) values for cholesterol/5-α-cholestane and cholesterol/7-dehydrocholesterol systems were found to be 5.08 and 6.08, respectively, thus attesting the selectivity of the MIP for cholesterol under competitive adsorption with structurally analogous steroid compounds. The milk analysis was initially based on saponification followed by liquid-liquid extraction with n-hexane. Then, the protocol of molecularly imprinted solid phase extraction (MISPE) was carried out by loading the milk hexanic extract through 200 mg of MIP or NIP (non-imprinted polymer) packed into SPE cartridges at a flow rate of 0.6 mL min(-1). The washing step was performed by using n-hexane followed by further elution with ethanol and HPLC-UV analysis at 208 nm. From the breakthrough curve the maximum adsorption capacity of the MIP towards cholesterol was found to be 29.51 mg g(-1). The precision of the MISPE protocol was assessed as intra- and inter-days yielding RSD (relative standard deviations) lower than 4.10%. Cleaner HPLC chromatograms were obtained for milk samples submitted to the MISPE protocol in comparison to the solid phase extraction using the NIP or modified octadecyl silica (C18). Recoveries varying from 96.6 up to 102.2% for milk samples spiked with cholesterol were achieved, thus ensuring the accuracy of the proposed method.

Molecularly imprinted solid‐phase extraction coupled with LC–APCI–MS–MS for the selective determination of serum cholesterol

“…A 2 mL aliquot of human serum hexanolic extract was applied to the organic and hybrid MIP and NIP to find the optimized MISPE protocol . Some solvents and mixtures were evaluated as washing solvents: (i) n‐hexane, (ii) chloroform, (iii) toluene, (iv) n‐hexane:toluene (1:1, v/v), and (v) n‐hexane:chloroform (1:1, v/v).…”

Electrochemical sensing of methyl parathion on magnetic molecularly imprinted polymer

“…After separation of the magnetic-MIP, the supernatant was measured at maximum absorption wavelength of each compound (λ max = 270, 230, 274, 312) for methyl parathion, malathion, phenol and 4-nitrophenol, respectively. The distribution coefficient (K d, mL g −1 ), selectivity (α), imprinting factor (I) and the relative selectivity coefficient (β) were calculated by the following equations (Clausen et al, 2014;Tarley et al, 2005).…”

Evaluation of a new water‐compatible hybrid molecularly imprinted polymer combined with restricted access for the selective recognition of folic acid in binding assays

“…It has been very well documented that these organic−inorganic hybrid materials fabricated by incorporation of template molecules into rigid inorganic or inorganic organic networks give rise to materials with complementary properties to that observed by isolated organic or inorganic phase. Some characteristics of these materials can be cited, such as superior thermal stability, high hardness, good textural and morphological features and uniform particle sizes . In this study, folic acid was chosen as target molecule considering its relatively large size, incipient data on literature regarding synthesis of MIP for this molecule, and due to its great clinical importance to human health as a water soluble vitamin.…”