Deep Eutectic Solvent Based Liquid-Liquid Microextraction of Mercury in Water, Hair and Fish with Spectrophotometric Determination: A Green Protocol

Mercury (Hg) is a toxic heavy metal discharged into the environment by many human and natural sources. Therefore, the precise and accurate determination of trace mercury in samples is of immense importance. In this regard, a spectrophotometric method has been developed for the quantification of Hg (II) in water, hair, and fish using deep eutectic (choline chloride, ChCl + decanol) solvent-based liquid-liquid microextraction (DES-LLME). All of the relevant parameters, including pH (9), volume of 1-(2-pyridylazo)-2-naphthol (PAN) (300 µL), ratio of choline chloride and decanol (1:1), volume of DES (400 µL), volume of tetrahydrofuran (THF) (400 µL), and sample volume (40 mL) were optimized. The low limits of detection (LOD) (0.09 µg L−1) and quantification (LOQ) (0.325 µg L−1) demonstrate that the developed approach is highly sensitive. High preconcentration (PF) and enhancement factors (EF) of 50 show that the developed protocol is highly efficient. The relative standard deviation (RSD) is 6.32%, indicating that the method is reproducible. The method was validated by the analysis of TMDA-53.3 water and NCSZC81002B hair certified reference materials with high recoveries of 97% and 93%, respectively. The method was also employed for the analysis of tap water, dam water, river water, hair, and tuna fish with satisfactory recoveries from 95% to 102%. The developed approach was compared with literature methods on the basis of the limit of detection.