聚乙烯醇存在下耐尔蓝－铈钼、钪钼杂多酸体系连续光度测定铈和钪

Successive Spectrophotometric Determination of Cerium and Scandium with Nile Blue─Molybdoceric or Molybdoscandic Acid Systeim in the Presence of Polyvinyl Alcohol

在聚乙烯醇（ＰＶＡ）存在下，耐尔蓝（ＮＢ）与铈钼、钪钼杂多酸络阴离子形成离子缔合物，其最大吸收均位于５８５ｎｍ，表观摩尔吸光度分别为εｃｗ＝３．５２×１０６和εＳｃ＝３．５９×１０＿５Ｌ·ｍｏｌˉ１·ｃｍˉ１，铈和钪服从比耳定律的浓度范围分别为０～０．８μｇ／２５ｍｌ和０～２．０μｇ／２５ｍｌ，测定极限分别为１．３ｎｇＣｅ／ｍｌ（ｎ＝１０）和３．０ｎｇＳｃ／ｍｌ（ｎ＝７），对于０．０２μｇＣｅ／ｍｌ或０．０４μｇＳｃ／ｍｌ测定的相对标准偏差分别为２．７％（ｎ＝９）和２．８％（ｎ＝１０），离子缔合物的摩尔比分别为Ｃｅ：Ｍｏ：ＮＢ＝１：６：４和Ｓｃ：Ｍｏ：ＮＢ＝１：１２：３。本法用于地质标样分析，结果满意。

A successive spectrophotometric determination of cerium and scandium has been reported. The method is based on that heteropoly molybdoscandic acid or heteropoly molybdoscandic acid and nile blue (NB) are added to form the ion-association complexes in the presence of polyvinyl alcohol(PVA). The absorption maxima are at 585 nm for cerium or scandium systems. The apparent molar absorptivities of ion─association complexes was found to 3. 52×10_6 L. mol-1. Cm-1for cerium system and 3.59×10_5L. mol-1. Cm-1for scandium system. Beer's law was obeyed and the contratians were over the ranges 0～0. 8μg/25 ml for cerium and 0～2.0 μg/25 ml for scandium.The limits of detection were 1.3 μg/ml for cerium (n=10) and 3.0 μg/ml for scandium (n=7) respectively.A 0.02 μg/ml for cerium or 0.04 μg/ml for scandium were analysed,the relative standard deviation were 2.7%(n=9) and 2. 8%(n=10) respectively. The molar compositions or ion-association complexes were found to be Ce:Mo:NB=1:6:4 and Sc:Mo:NB=1:12:3. This method has been applied to the geological samples analysis with satisfactory results.