Development of Real-Time Analysis System of Selenium Ion in Solutions by Using Microextraction and Fluorescence Microscopy

Abstract

The development of advanced analytical methods for trace amounts of selenium (Se) ions in wastewater become a matter of great importance in avoiding biological and environmental burdens due to Se pollution. In this study, a simple microanalytical methodology was developed, enabling the rapid and highly efficient extraction, real-time monitoring in situ, and extraction kinetic analysis of Se­(IV) ions. The microscale extraction and analysis was verified by means of fluorescence intensity changes of fluorogenic complex 4,5-benzopiazselenol (BPS) consisting of the coordination of Se­(IV) with 2,3-diaminonaphthalene (DAN). After the optimal BPS formation conditions, including pH, temperature, and Se­(IV)/DAN concentration ratio, were examined, the microscale extraction of BPS was carried out under aqueous and organic two-phase parallel flow regimes in Y-shaped microchannels. The fluorescence intensity profiles of BPS in the organic phase were scanned in situ along the flow direction in the microchannel by a fluorescence microscope. The residence time dependence of the BPS concentrations could be precisely detected in real time. The results show that the developed microsystem has not only a detection limit of a submicromolar level for Se­(IV), which is sufficiently lower than the permeable limit concentration of selenium in wastewater, but also a large apparent extraction rate constant of approximately 0.3 s–1 and a short time to reach equilibrium of approximately 20 s, compared to those of bulk-scale extraction. This would indicate a valuable technique for elucidating microfluidic extraction kinetics and for applying real-time, environmentally friendly monitoring of toxic selenium ions.

Design optimization of microfluidic-based solvent extraction systems for radionuclides detection

“…From a practical perspective, the implementation of an actual µTAS will require consideration of a number of practical details not taken into account in this computational study. For instance, materials for the microchannels that withstand the radioactivity must be chosen [5,[41][42][43][44]. Similarly, the sample volumes and the method to pump the liquids into the µTAS must be properly decided.…”

“…It is important to mention, however, that PTFE is a sensitive type of plastic and not suitable for applications involving long exposure to radiation. An actual µTAS system will preferably be made from glass or metallic materials [5,[41][42][43][44]. In any case, once segmented flow is established, the channel material is not relevant in terms of performance.…”