Flexible dispersive liquid–liquid microextraction for on-site sample pre-concentration

Abstract

ABSTRACT In recent years, more and more interest has been focused on the on-site sample preparation. Dispersive liquid–liquid microextractions without centrifugation or toxic organic solvent were developed and proved suitable for on-site extraction. In this study, a flexible dispersive liquid–liquid microextraction was developed for on-site water sample pre-concentration. A device containing a phase separation filter was prepared. By means of the phase separation filter packed with hydrophobic nonwoven polypropylene fibre, extraction phase and aqueous phase of the emulsified system were separated by manual filtration, which avoided the electric devices usually required in dispersive liquid–liquid microextractions. Combining the device with ionic liquid-based in situ dispersive liquid–liquid microextraction, a totally electricity-free procedure was developed. During the procedure, the extraction phase 1-hexyl-3-methylimidazolium bis[(trifluoromethane)sulfonyl]imide was formed through an ion exchange reaction, and then separated with water by filtration. After filtration, the extraction phase was eluted and submitted to high-performance liquid chromatography-variable wavelength detector for analysis. Parameters affecting the extraction performance were investigated and optimised. The optimised procedure achieved extraction recoveries of 75–89%. The intra-device, inter-device, intra-day and inter-day relative standard deviations were less than 4.6%. Good linearity (r2 > 0.9992) was obtained over the calibration range from 2 to 1000 µg L−1. The limits of detection of the method were in the range of 0.41–0.65 µg L−1. Because electric devices and organic dispersants are not required, the present approach is proved green, fast, and extremely flexible for on-site preparation of water sample. The proposed device is also expected to make other dispersive liquid–liquid microextractions transform into the on-site procedure.