Abstract
A flow chemiluminescence (CL) method combined with a liquid–liquid extraction technique is proposed for the indirect determination of antimony in aqueous samples using rhodamine B (RB). In the liquid–liquid extraction process, the antimony(V) chloro-complex anion, [SbCl6]−, was extracted from an aqueous acidic solution into toluene via ion-pair formation with the protonated RBH+ ion. Upon mixing the extract with a reversed micellar reagent solution of cetyltrimethylammonium chloride (CTAC) in 1-hexanol–cyclohexane/water (0.60 mol dm−3 H2SO4) containing cerium(IV), uptake of the ion-pair by CTAC reversed micelles occurred easily, followed by an oxidation reaction of RB with Ce(IV) in the CL process. The CL signal produced was then measured. Using a flow injection system, the detection limits (DL) of 0.25 μmol dm−3 Sb(III) and 0.20 μmol dm−3 Sb(V), and linear calibration graphs with dynamic ranges from the respective DLs to 16 μmol dm−3 for Sb(III) and Sb(V) were obtained under optimized experimental conditions. The proposed method was successfully applied to a mixture of Sb(III) and Sb(V), where total antimony, Sb(III) + Sb(V), was measured using ceric sulfate as an oxidant to oxidize Sb(III) to Sb(V) prior to extraction, Sb(V) was determined directly without the use of an oxidant, and Sb(III) was calculated by difference.
This work was partially supported by a Grant-in-Aid for Scientific Research, No. 23550097, from the Ministry of Education, Science, Sports, and Culture, Japan.