Ultrasound-assisted deep eutectic solvents microextraction for efficient determination of crystal violet, congo red, and neutral red in water samples

Abstract Industrial effluents release synthetic dyes, which are toxic, persistent, and resistant to conventional wastewater treatment. In the present study a rapid, effective, and environmentally friendly ultrasound-assisted liquid-liquid microextraction (UA-LLME) method based on deep eutectic solvents (DES) was developed to extract crystal violet (CV), congo red (CR), and neutral red (NR) in aqueous samples. Various DES systems were initially screened but choline chloride–glycolic acid exhibited the highest extraction efficiency and was selected for the optimized method. Under optimal conditions, recoveries higher than 95 % were obtained for all three dyes. The linearity of the proposed method was good within the range of 5–30 ppm ( R 2 ≥ 0.992), relative standard deviations were low (<1.6 %), satisfactory limits of detection (84.0–94.2 μg L −1 ), and high enrichment factors (9.75–9.90). The validity of the method was also tested successfully by the standards addition method by analyzing real canal water samples, obtaining recoveries between 95.65 and 97.18 %. The developed DES-based UA-LLME method is much more significant than reported methods in terms of simplicity, short extraction time, high efficiency, and reduced consumption of hazardous organic solvents; consider it a green method of the analysis of dye in environmental water samples.