Simultaneous derivatization and air–assisted liquid–liquid microextraction based on solidification of lighter than water deep eutectic solvent followed by gas chromatography–mass spectrometry: An efficient and rapid method for trace analysis of aromatic amines in aqueous samples

Highlights: • A deep eutectic solvent based SFO–AALLME followed by GC-MS has been developed. • Lighter than water deep eutectic solvent was synthesized for the first time. • Deep eutectic based microextraction solvent based method was used in derivatization process. • Simplicity, low cost, and effective sample preparation are advantages of the method. - Abstract: In the present work, a simultaneous derivatization and air–assisted liquid–liquid microextraction method based on the solidification of deep eutectic solvent coupled with gas chromatography–mass spectrometry has been developed for the determination of some aromatic amines in various aqueous samples. In this work, choline chloride and n–butyric acid are mixed at a suitable molar ratio and after heating, a deep eutectic solvent of low density compared to water is formed. The prepared extraction solvent is mixed with ethyl chloroformate as a derivatization agent and injected into an alkaline aqueous solution containing the target analytes adjusted at elevated temperature. The resulting mixture is drawn into a syringe via a needle and pushed out into a test tube several times. As a result, a cloudy solution consisting of the fine droplets of the extraction solvent containing the derivatized aromatic amines is obtained. Then, the solution is placed into an ice bath and the extraction solvent is solidified and collects on the top of the solution after centrifugation. Then the solidified extraction solvent is removed by a spatula and transferred to a microtube and dissolved in 10 µL acetonitrile. A portion of the obtained mixture is injected into the gas chromatography–mass spectrometry. Under optimum conditions, limits of detection and quantification were obtained in the ranges of 1.8–6.0, and 6.0–23 ng L^-1, respectively. The extraction recoveries, enhancement factors, and enrichment factors of the selected aromatic amines ranged from 79–94%, 2498–3422 and 790–940, respectively. The relative standard deviations were =5.3% for intra– (n = 6) and inter–day (n = 4) precisions at a concentration of 100 ng L^-1 of each analyte.