阻抑动力学光度法测定催化剂中铈

摘要

在弱酸条件下，痕量铈(Ⅳ)对于亮绿SF和十六烷基三甲基溴化铵（CTMAB）的褪色反应有阻抑作用，由此建立了一种动力学光度法测定铈的新体系。考察了缓冲溶液种类和用量、亮绿SF和CTMAB用量、试剂加入顺序、温度和时间等因素对反应的影响，建立的最佳测定条件为：在25 mL 比色管中加入1.0 mL CTMAB溶液、2.0 mL 醋酸‐醋酸钠缓冲溶液、2.0 mL 亮绿SF溶液，室温反应60 min ，测定波长为630 nm。实验表明，在Ce(Ⅳ)质量浓度为0～80 ng／mL时，吸光度的改变量ΔA与Ce槑质量浓度有良好的线性关系，相关系数为0.9943，检出限为7.1 ng／mL ，表观摩尔吸光系数为3.73×105 L · mol－1· cm －1。实验方法用于含铈催化剂中铈含量的测定，其测定结果与硫酸亚铁铵滴定法基本一致，5次测定结果的相对标准偏差RSD≤4.0％。%A sensitive method for the determination of cerium (Ⅳ) was established based on its inhibitory effect on the reaction of hexadecyl trimethyl ammonium bromide(CTMAB) with light green SF in the me‐dium of weak acid. The influence of buffer solution ,amount of CTMAB and light green SF ,addition order of reagents ,reaction temperature and time were studied and the optimum condition was founded as follows :1.0 mL of CTMAB solution ,2.0 mL of HAc‐NaAc buffer solution and 2.0 mL of light green SF solution were added in a 25 mL colorimeter tube ,after reaction for 60 min at room temperature ,the determination was performed at wavelength of 630 nm. The results showed that the absorbance variation (ΔA) showed good linear relationship to the mass concentration of Ce (Ⅳ) in range of 0‐80 ng/mL .T he correlation coeffi‐cient was 0.994 3 .The detection limit was 7.1 ng/mL .The apparent molar absorptivity was 3.73 × 105 L · mol-1 · cm -1 .The experimental method was applied to the determination of cerium content in cata‐lyst .The found results were basically consistent with those obtained by ammonium ferrous sulfate titration method .The relative standard deviation (RSD ,n=5) was less than 4.0% .