Recent trends in microextraction techniques employed in analytical and bioanalytical sample preparation

Sample preparation has been recognized as a major step in the chemical analysis workflow. As such, substantial efforts have been invested in recent years to simplify the overall sample preparation process. Major focusses of these efforts include, miniaturization of the extraction device; minimizing/eliminating toxic and hazardous organic solvent consumption; eliminating sample pre-treatment and post-treatment steps; reducing the sample volume requirement; reducing extraction equilibrium time, maximizing extraction efficiency etc. All these attributes corroborate with the Green Analytical Chemistry principles. Classical sample preparation techniques such as solid phase extraction (SPE) and liquid-liquid extraction (LLE) are being rapidly replaced with emerging miniaturized and environment friendly techniques including Micro Extraction by Packed Sorbent (MEPS), Fabric Phase Sorptive Extraction (FPSE), Dispersive Liquid-Liquid Micro Extraction (DLLME). In addition to the development of many new generic extraction sorbents, a large number of molecularly imprinted polymers (MIPs) based on different template molecules have also enriched the large cache of microextraction sorbents. Application of nanoparticles as high performance extraction sorbents has undoubtedly elevated the extraction efficiency and method sensitivity to a new level. Incorporating magnetic nanoparticles with many microextraction sorbents has opened up new possibilities to extract target analytes from sample matrices containing high volume of matrix interferents. The aim of the current review is to critically audit the progress of microextraction techniques in recent years, which has indisputably transformed the analytical chemistry practices, from biological and therapeutic drugs monitoring to environmental field, from foods to phyto-pharmaceuticals applications