Hydrophobic deep eutectic solvent as a green extractant for high-performance liquid chromatographic determination of tetracyclines in water samples.

A green extractant, hydrophobic deep eutectic solvent was first introduced for extraction of tetracycline, oxytetracycline, and chlortetracycline from environmental water samples prior to high-performance liquid chromatography determination. Deep eutectic solvents consist of methyltrioctylammonium chloride and various medium-chain alcohols/acids, and are easy in preparation, low cost and toxicity, desirably biodegradable, and biocompatible. The overall time required for sample preparation was 6 min and the volume of organic solvent used for extraction was only 400 µL. Under the optimized extraction condition, the present method yielded low limit of detection (0.5-2.0 ng/mL), acceptable precision (relative standard deviations < 9.7%), good linearity from 2.0 to 500 ng/mL (r2  ≥ 0.9991). This optimized procedure was applied for determination of tetracyclines in different water samples with desirable spiked recovery ranged from 77.5 to 87.6%. There is, therefore, a great potential to further expand application of the method for investigation of other ultra-trace analyte(s) in environmental matrixes.