Sample preparation is commonly considered a key step to achieve selective, sensitive, and reliable chemical analyses, particularly those involving complex matrices. Although the application of electric fields to improve the speed and efficiency of sample preparation methods has been proven, this approach is still considered to be state-of-the-art; hence, further development is necessary to improve future applications. This review describes the fundamentals, advances, applications, and perspectives of using electric fields to enhance sample preparation techniques such as liquid-liquid and solid-liquid extractions in conventional and microscale devices.

Electric field-assisted solid phase extraction using syringe type cartridges (E-SPE) is a recent approach with a high capacity to obtain differential selectivity and/or recovery in comparison with conventional solid phase extraction (SPE). In this work, E-SPE was employed for the extraction of the anionic dye sunset yellow. During the washing step the electric field was evaluated with the top electrode negatively (E-SPE(–/+)) or positively charged (E-SPE(+/–)) and the results were compared with conventional SPE to understand how the electrochromatographic parameters can influence the recovery of the dye. Using the E-SPE(–/+) the electric field can increase the elution of the dye from the cartridge by over 57-fold. This notable result can be attributed to the electrophoretic velocity of the dye in the direction of the flow rate of the eluent. These results demonstrated that E-SPE is an interesting approach to elute ionic compounds with reduced volumes of eluent or less amount of organic solvent.