Microfluidic paper-based analytical devices and electromembrane extraction; Hyphenation of fields towards effective analytical platforms.

Herein, the applicability of electromembrane extraction (EME), as an efficient and paper-compatible separation technique, was envisaged over customized microfluidic paper-based analytical devices (µPADs). The utility of EME was assessed on 2D planar and 3D origami structures using different types of electrodes including stainless steel and paper-based electrodes. The overall separation procedure was integrated to colorimetric detection demonstrated for copper ions as the model analyte. According to the obtained results, EME based on 3D design of µPADs could effectively be performed under low applied voltage. Using 3D architecture, the analyte could be quantified within the range of 40.0-1500.0 µg L-1 with limit of detection down to 20.0 µg L-1 using smart phone camera as signal read-out. The proposed platform showed remarkable compatibility with direct analysis from untreated real samples of human blood and spring water.

Microfluidic-enabled versatile hyphenation of electromembrane extraction and thin film solid phase microextraction.

In the present study, a versatile combination of electromembrane extraction (EME) with thin film solid phase microextraction (TF-SPME) was introduced using a microfluidic chip device. The device consisted of two single channels on two separate layers. The upper channel was dedicated to donor phase flow pass, while the beneath channel was used as a reservoir for stagnant acceptor solution. A slide of fluorine doped tin oxide (FTO) was accommodated in the bottom of the acceptor phase channel. A thin layer of polyaniline was electrodeposited on the FTO surface to achieve the required thin film for TF-SPME. A stainless-steel wire was embedded in the donor phase channel and another wire was also attached to the FTO surface. The channels were separated by a piece of polypropylene membrane impregnated with 1-octanol and the whole chip was fixed with bolts and nuts. The driving force for the extraction was an 8 V direct current (DC) voltage applied across the supported liquid membrane (SLM). Under the influence of the electrical field, analytes immigrated from sample towards the acceptor phase and then adsorbed on the thin film of the solid phase. Finally, the analytes were desorbed by successive movement of a desorption solvent in the acceptor phase channel followed by injection of the desorption solution to HPLC-UV. The applicability of the proposed device was demonstrated by the determination of four synthetic food dyes: Amaranth, Ponceau 4R, Allura Red, and Carmoisine, as the model analytes. The effective parameters on the efficiency of the both EME and TF-SPME were investigated. Under the optimized conditions, the microchip provided low LODs (1-10 µg L-1), and a wide linear dynamic range of 10-1000 µg L-1 for all analytes. The system also offered RSD values lower than 5.5% and acceptable reusability of the thin film for multiple extractions.