Solid phase extraction is routinely used in many different areas of analytical chemistry. Some of the main fields are environmental, biological, and food chemistry, where cleaning and pre-concentration of the sample are important steps in the analytical protocol. Molecularly imprinted polymers (MIPs) have attracted attention because they show promise as compound-selective or group-selective media. The application of these synthetic polymers as sorbents allows not only pre-concentration and cleaning of the sample but also selective extraction of the target analyte, which is important, particularly when the sample is complex and impurities can interfere with quantification. This review surveys the selectivity of MIPs in solid phase extraction of various kinds of analytes.
As shown in the past years, SPE based on molecularly imprinted polymers (MIPs) may provide significant enhancement of selectivity in sample preparation and analyte preconcentration. The objective of this work was the fabrication of MIPs for the specific adsorption of rutin and quercetin. The two flavonoids were used as the template molecules for the preparation of MIP phases in a self-assembly (noncovalent) approach. The produced MIPs were validated with regard to the imprinting efficiency as media for LC and SPE. The retention behavior of several flavonoid compounds was studied using as stationary phases imprinted, control nonimprinted polymers, and commercial silica-based materials. MIPs were applied as materials for the selective SPE and preconcentration of the flavonoids from white and red wine, orange juice, and tea. The collected fractions were analyzed by high-pressure LC. MIP-SPE facilitated specific analyte isolation and effective sample clean-up. The results show that molecularly imprinted SPE can be a useful tool for the simple, selective, and cost-effective pretreatment of samples containing natural antioxidants.
A molecularly imprinted polymer (MIP) was synthesized and evaluated to selectively extract ephedrine from human plasma. The MIP synthesis was performed in chloroform with methacrylic acid as a functional monomer and the target alkaloid as a template molecule. The resulting MIP was applied to the selective extraction of ephedrine from a pure aqueous medium. A recovery about 74% was obtained using the MIP with only 7% on the nonimprinted polymer (NIP). A very straightforward selective SPE procedure was then successfully applied to the direct extraction of ephedrine from spiked human plasma with a high extraction recovery (68%) on the MIP with no recovery on the NIP. Moreover, the MIP was used for the selective extraction of catecholamine neurotransmitters, i.e. adrenaline and noradrenaline.
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