Enhancing sensitivity by Triton X-100 in extractive spectrophotometric determination of chromium via transforming the formed binary complex ion associate between chromate and rhodamine 6G into an adduct

摘要

The reaction of chlorochromate anion (CrO3Cl-) with rhodamine 6G hydrochloride dye (RG(+)) results in the formation of complex ion associate [RG(+)center dot CrO3Cl-] in non-aqueous medium. This study aimed to use t-octylphenoxypolyethoxyethanol polymer (Triton X-100) in [RG(+center dot)CrO(3)Cl](org) extraction system to enhance the sensitivity of Cr(VI) under the optimized conditions. The produced highly electron deficient system in the binary complex ion associate [RG(+)center dot CrO3Cl] of Cr(VI) transforms into an adduct [(CrO3Cl-center dot RG(+))center dot TX-100 center dot nS](org) in the presence of Triton X-100 (TX-100). This transformation enhanced the analytical response of the produced adduct specie in the organic phase by over 75%. The adduct formation via ether oxygen of TX-100 and the possible existence of H-bonding between NH of RG(+) and ether oxygen of TX-100 are directly related to the increase in the molar absorptivity and this phenomenon was monitored by UV-Vis spectrophotometric measurement at lambda(max) = 534 nm. The current study discusses the role of different surfactants and its influence on the extraction of Cr(III) & Cr(VI) species. A detailed proposed mechanism, structure, stoichiometry, and extraction equilibria for the produced adduct is presented. Cr(III) species after oxidation with H2O2 in KOH media were also determined by the proposed procedure. At optimal conditions, the method exhibited a wide linear range 0.0245-1.5 mu g mL(-1) with detection and quantification limits of 0.0073 mu g mL(-1) and 0.025 mu g mL(-1), respectively. This enhancement principle in the extraction systems could be extended to other class of surfactants and/or nano materials. (C) 2018 Elsevier B.V. All rights reserved.