Determination of polychlorinated biphenyls in water by CO₂-responsive switchable deep eutectic solvent based...

A homogeneous liquid-liquid microextraction technique based on switchable deep eutectic solvent (SDES-HLLME), combined with gas chromatography-triple quadrupole tandem mass spectrometry (GC-MS/MS), was developed for the extraction and analysis of 16 polychlorinated biphenyls (PCBs) in water samples. CO₂-responsive switchable deep eutectic solvent (SDES), which consists of monoethanolamine (MEA) being used as a hydrogen bond acceptor (HBA) and 3-methoxyphenol (3-MP) being used as a hydrogen bond donor (HBD), was used as the extractant, thus providing an environmentally friendly alternative to conventional toxic organic solvents. The study systematically investigated the effects of various parameters on extraction efficiency, including the type and volume of SDES, vortexing duration, CO₂ bubbling time, centrifugation rate and time, ionic strength. Optimal extraction conditions were identified as follows: 40.0 μL of SDES, vortexing for 40.0 s, CO₂ bubbling for 2.0 min, 5.0 % (w/v) salt concentration, a centrifugation rate of 5000 rpm, and a centrifugation duration of 3.0 min. Under these optimal conditions, the method exhibited a linear range of 0.1-300 ng·mL^-1, with limits of detection (LODs) and quantification (LOQs) ranging from 0.003 to 0.096 ng·mL^-1 and 0.009 to 0.321 ng·mL^-1, while the relative standard deviation (RSD) <7.98 %. Finally, this method was successfully applied to determine the concentrations of 16 PCBs in various environmental water samples, yielding satisfactory recovery rates. This method provides a green, convenient and accurate new idea in the field of HLLME research.