Effervescent-assisted deep eutectic solvent-based dispersive liquid-liquid microextraction of Cr(VI) in aqueous samples

Effervescent-assisted deep eutectic solvent-based dispersive liquid-liquid microextraction (EA-DES-DLLME) was developed for the selective extraction and preconcentration of Cr(VI) in water samples before its spectrophotometric determination. Before using the method, Cr(IV) ions present in the samples were complexed with 1,5-diphenylcarbazide (DPC) in an acidic medium. Experimental parameters that influenced the extraction efficiency of the method including sample pH, volume of DPC, type and volume of DES, type and concentration of effervescent agents, extraction time, stability of the complex, and selectivity were thoroughly investigated. Under optimal conditions, the method showed excellent linearity ranging from 50 to 3200 µg L⁻¹, with a coefficient of determination (R²) of 0.9991. The limits of detection and quantification (LOD and LOQ) of the method were 3 and 10 µg L⁻¹, respectively. Intra- and inter-day precision studies conducted at three concentration levels yielded relative standard deviation (RSD) values of ≤ 3.3 and 7.2, respectively. The method’s robustness, assessed at wavelengths of 535 to 545 nm had RSD < 4.3. The method provided an enrichment factor of 13.52 and recoveries between 81.1 and 111.2%. Overall, the developed method is applicable and selective for the determination of Cr(VI) in aqueous samples. KEY WORDS: Cr(VI), Deep eutectic solvent, Dispersive liquid-liquid microextraction, 1,5-Diphenylcarbazide, Effervescence-assisted extraction, Water samples Bull. Chem. Soc. Ethiop. 2025, 39(7), 1245-1256. DOI: https://dx.doi.org/10.4314/bcse.v39i7.2