A new experimental approach for liquid-liquid extractive spectrophotometric determination of chromium(VI) in tannery wastewater and alloy samples

In this research work, a new approach is developed for the extractive determination of chromium. The principle of this approach is based on the complexation reaction between 4-(4'-chlorobenzylideneimino)-3-methyl-5-mercapto-1,2,4-triazole (CBIMMT) in dichloromethane as a complexing reagent and chromium(III) in presence of potassium iodide to form a yellow coloured complex at room temperature. The 1:2:2 [Cr(III)-CBIMMT-iodide] ternary complex was quantitatively extracted in dichloromethane from 2.5 mol L-1 of hydrochloric acid medium which showed maximum absorption intensity at lambda(max) 411 nm and was stable for more than 72 h. The values of molar absorption coefficient and Sandell's sensitivity of the complex were found to be 0.7019 x 10(4) L mol(-1) cm(-1) and 0.00748 mu g cm(-2), respectively. The system adheres to Beer's law from 1.5 to 6.0 mu g mL(-1); however, Ringbom's plot suggests optimal concentration range was 1.8-5.8 mu g mL(-1.) The limit of detection and limit of quantification of the approach is 0.26 and 0.79 mu g mL(-1). This approach was successfully used for the determination of chromium from wastewater effluents from the tannery industries (Kolhapur, MS, India), alloy samples and for separation of it from synthetic mixtures. The present experimental approach is apparently much simpler than the conventional method comprising multistep processes.