Thiomalic acid/ferric chloride-based deep eutectic solvent for microextraction of chromium in natural water samples prior to FAAS analysis

Deep eutectic solvents have become interested green materials for microextraction applications. In this study, a novel deep eutectic solvent have been formed by combination of thiomalic acid and ferric chloride in ethylene glycol medium, which then used for liquid–liquid microextraction of trace chromium from water samples. The microextraction process is donated the name of deep eutectic solvent-liquid liquid microextraction (DES-LLME). The microextraction procedure was optimised by evaluating the effect of pH, amount of deep eutectic solvent and sample volume. The optimum recoveries for chromium were achieved at pH 7.0, 200 µL of deep eutectic solvents, and sample volume up to 40 mL, with limits of detection and quantification of 1.18 µg·L−1 and 3.54 µg·L−1 respectively. By validating the DES-LLME with TMDA-53.3 fortified water reference materials, the chromium recovery was 99%.