Membrane-protected molecularly imprinted polymers: Towards selectivity improvement of liquid-phase microextraction

Sample preparation is still considered the bottle-neck of the whole analytical process. Nowadays, several sample preparation techniques are available, however all of them suffer from lack of the selectivity. At this regard, molecularly imprinted polymers (MIPs) are considered excellent materials able to perform selective extractions. Recently, new objectives in sample preparation have been set, including to use smaller initial sample sizes; to facilitate automation; and, to minimize the amount of glassware and organic solvents needed. MIP incorporation to other microextraction techniques offers a new strategy in order to fulfil current sample preparation requirements. However, even using MIPs, the complexity of the sample can affect recoveries of target analytes, negatively affecting the analytical method precision and accuracy. The use of a porous membrane, as a protective sleeve, is one of the simplest approaches to circumvent the difficulties mentioned above in the analysis of complex and “dirty” samples. Accordingly, the present paper pretends to provide an overview of micro-extraction approaches developed during last years based on the use of membrane-protected MIPs and how such approaches have open new pathways in the development of liquid phase micro-extraction methods with improved analytical characteristics. Advantages, drawbacks and future expected trends are also critically assessed.