Deep eutectic solvent based magnetic nanofluid in the development of stir bar sorptive dispersive microextraction: An efficient hyphenated sample preparation for ultra-trace nitroaromatic explosives extraction in wastewater.

A deep eutectic solvent based magnetic nanofluid was coupled with stir bar sorptive dispersive microextraction as a hyphenated sample preparation technique. The neodymium core magnetic stir bar was coated physically with nanofluid of magnetic carbon nanotube nanocomposites and deep eutectic solvents. The prepared nanofluid has magnetic and strong sorbing properties and is compatible with gas chromatography. In this nanofluid, the deep eutectic solvent acts simultaneously as both carrier and stabilizer for magnetic nanotubes. The predominant experimental variables affecting the extraction efficiency of nitroaromatic compounds were evaluated. Under the optimized conditions, the limit of detection and enrichment factor were in the range of 0.2-4.9 ng/L and 852-1480, respectively. The relative standard deviations were between 5.6 and 10.2% (n = 6). Method validation was performed by both spiking-recovery method and comparison of results with other methods. Finally, the proposed method was successfully applied for the extraction and pre-concentration of nitroaromatic explosives in water samples, followed by determination by gas chromatography with micro-electron capture detection.