Effervescence assisted dispersive liquid-liquid microextraction for spectrophotometric determination of chromium (VI) in water, tannery effluent, milk, and orange juice samples

In this paper, effervescence-assisted dispersive liquid-liquid microextraction was proposed for selective extraction and preconcentration of Cr (VI) prior to its quantitative determination by UV-Vis spectrophotometry. Before employing the method, Cr (VI) ions available in the samples were complexed with 1,5-diphenylcarbazide in an acidic medium. Experimental parameters influencing the performances of the method including pH, the concentration of the complexing agent, type and volume of both extraction solvent and effervescent agent, stability of the complex, and effect of extraction time were thoroughly studied and optimized. Calibration curve plotted from 0.005-2.0 mg L-1 demonstrated good linearity (R-2 = 0.9992). The limits of detection and quantification of the method were 0.001 and 0.005 mg L-1, respectively. The method provided an enrichment factor of 21.4. Precision studies in terms of repeatability, intermediate precision, and reproducibility were conducted at three concentration levels and their RSD values were <6.2. The ruggedness of the method studied at different wavelengths (535-545 nm) had RSD values <3.3. The recoveries of the method were from 83.0-117.6%. Finally, the proposed method was successfully applied for the determination of Cr (VI) from various matrices including tap, well, and river water; tannery effluent; milk; and orange juice samples.