铬(Ⅲ)-溴邻苯三酚红-乙基紫体系水相显色反应的研究

Chromogenic Reaction on the Ion-associate Complexin Water-Chromium (Ⅲ )-BromopyrogallolRed-Ethyl Violet System

本文系统探讨了聚乙烯醇(PVA-124)存在下,铬(Ⅲ)-溴邻苯三酚红(BPR)-乙基紫(EV)体系产生的协同显色反应。在pH4.8～5.5 HAc-NaAc缓冲介质中,Cr(Ⅲ)-BPR-EV形成[EV]^-·[Cr(BPR)]型离子缔合物,λ_(max)=535 nm,ε_(535nm)=1.1×10~5L·mol^(-1)·mol~_(-1)·Cm^(-1),铬(Ⅲ)含量在0～7μg/25ml范围内吸光度遵从比尔定律,反应选择性好,用于污水中铬的测定得满意结果。根据络合物组成探讨了反应机理。

Chromium( Ⅲ ) ion can form a colour ion-associate complex with both bromopyrogallol red (BPR)and ethyl violet (EV) in a HAc-NaAc medium (pH 5. 0). The composition of the complex was found to be Cr: BPR : EV = 1 : 1 : 1 with the apparent molar absorptivity of 1. 1 × 105 L · mol-1cm-1. Beer's law is obeyedover the range of 0-7 μg/mi for chromium. This method has been applied to the determination of chromiumin water with good precision and accuracy.