Rapid drop-to-drop liquid–liquid microextraction by help of surface acoustic wave

A novel drop-to-drop liquid–liquid microextraction method is presented, by which a liquid–liquid microextraction is greatly accelerated. A pair of interdigital transducers (IDTs) with 27.5 MHz center frequency is fabricated on a 128° yx-LiNbO3 substrate. Once a RF signal is applied to an IDT, surface acoustic wave is generated and then radiated into drops to be extracted on the acoustic path. The surface acoustic wave radiation, leading to rapid movement of droplets in original position, enhances the microextraction. An ionic liquid and an organic dye aqueous solution are used for extraction experiments and extraction kinetics is studied using an image-based concentration measurement technique. Extraction experiments show that a drop-to-drop liquid–liquid microextraction process can be finished within 100 s when the RF signal power applied to the IDT is 26.9 dBm, and the extraction time is decreased with RF signal power applied to the IDT.

► Fabrication process of the microextraction device was described.
► A principle of surface acoustic wave enhancing microextraction was described.
► Extraction kinetics was studied using an image-based concentration measurement technique.
► The effect of RF signal power applied to an IDT on microextraction was studied.
► The microextraction method was demonstrated by extracting acid green-25 solutes from aqueous solution to IL drop.