薄层树脂相吸光光度法同时测定痕量Fe(Ⅲ)和Co(Ⅱ)的研究

Study on the determination of trace iron(Ⅲ) and cobalt(Ⅱ) by thin layer resin phase spectrophotometry

在0.2mol/L的盐酸介质中,Fe(Ⅲ)和Co(Ⅱ)能与硫氰酸盐生成稳定的配合物[Fe(SCN)6]3-和[Co(SCN)4]2-,此二种配阴离子能被碱性717型阴离子交换树脂定量交换缔合,形成阴离子交换树脂(R+)金属离子(M+)硫氰酸盐(SCN)-三元配合缔合体系,该三元配合缔合体系最大吸收波长分别为490nm和630nm,与二元水相最大吸收波长相同,通过制作薄层,用光度法测定了水中Fe(Ⅲ)和Co(Ⅱ)含量。εFe(Ⅲ)490=2.4×105L·mol-1·cm-1,比水相光度法提高48倍;εCo(Ⅱ)630=2.1×105L·mol-1·cm-1,比水相光度法提高19倍。实测了天然水中Fe(Ⅲ)和Co(Ⅱ)含量,并与AAS法测定结果作了比较。

A new method for the determination of Fe（ Ⅲ ） and Co （ Ⅱ ） by thin layer resin phase speetrophotometry in acidic medium was investigated. Fe （ Ⅲ） and Co （ Ⅱ ） could associate with SCN- to form [Fe（SCN）6]^3- and [Co（SCN）4]^2- respectively. Both anion complexes could quantitatively exchange with anion exchange resin 717^# （R^＋ ）, in the form of （R^＋ ）-Fe（ Ⅲ ）- （SCN） - and （ R^＋ ）-Co（ Ⅱ ）-（SCN） - respectively. The maximum absorption wavelength of （R^＋ ）-Fe （ Ⅲ）-（ SCN）- was 490nm,and that of （R^＋ ）-Co（Ⅱ ）-（SCN）- was 630nm, the same as in water phase. The sensitivity of the thin layer resin phase spectrophotometry method was improved,the molar absorptivities of （ ε490^Ee（Ⅲ） ） 2.4 × 10^5L· mol^- 1 · cm^- 1 and （ε630^Co（Ⅱ）） 2.1 × 10^5L · mol^- 1 · cm^- 1, which were about 48 and 19 times higher than those in water phase, respectively. Fe （Ⅲ ） and Co（ Ⅱ ） in natural water have been determined. Beer＇s law was obeyed in the range of 0 - 10μg /25mL for Fe（ Ⅲ）, and 0 - 16μg/25mL for Co（ Ⅱ ）. The detection limits of Fe（ Ⅲ ） and Co（ Ⅱ ） were 0.12μmol· L^- 1 and 0.15μmol·L^- 1 ,respectively.