DBC-偶氮胂分光光度法测定稀土研究

Spectrophotometric Determination of Rare Earths with DBC-Arsenazo

研究了DBC-偶氮胂（DBC-ASA）与稀土显色反应的最佳实验条件。在pH2.2的HCl-KCl的缓冲溶液中,稀土与DBC-ASA发生显色反应,形成1∶3的蓝紫色络合物。La（Ⅲ）,Ce（Ⅳ）,Eu（Ⅲ）,Y（Ⅲ）络合物最大吸收峰分别为：630nm,632nm,632nm,632nm,络合物表观摩尔吸光系数分别为：εLa（630nm）=1.02×10^5L.mol^-1.cm^-1,εCe（632nm）=9.98×104L.mol^-1.cm^-1,εEu（632nm）=9.60×10^4L.mol^-1.cm^-1,εY（632nm）=9.40×10^4L.mo^l-1.cm^-1,上述络合物在70 min内稳定。镧（Ⅲ）、铈（Ⅳ）、铕（Ⅲ）在浓度为0-1.0μg.mL^-1范围内遵守比耳定律,钇（Ⅲ）在浓度为0.05μg.mL^-1~0.80μg.mL^-1范围内遵守比耳定律,对应线性回归方程分别为：ALa=0.0735C-0.0006,ACe=0.0624C-0.0237,AEu=0.0642C-0.0017,AY=0.0503C-0.0814（C为10mL溶液中所含稀土的μg数）,相关系数分别为γLa=0.9994,γCe=0.9937,γEu=0.9991,γY=0.9913。本法用于直接测定雨水和湖水样品中的稀土总量,获得了满意的结果。方法相对标准偏差分别为2.46%和2.51%,加标回收率分别为97.30%和102.0%。

The optimum experimental conditions of color reaction between DBC- arsenaso and rare earths were studied. In pH 2,2 HCl - KCl buffer solution, the rare earths react with DBC- arsenazo to form 1：3 blue- purple complexes. The maximum peaks of the rare earths lanthanum（ Ⅲ ）, cerium（ Ⅳ ）, europium（ Ⅲ ）, yttrium（ Ⅲ ） complexes are 630nm, 632nm,632nm,632nm, respectively. The apparent molar absorptivities of the complexes are εLa（630nm）=1.02×10^5L.mol^-1.cm^-1,εCe（632nm）=9.98×10^4L.mol^-1.cm^-1,εEu（632nm）=9.60×10^4L.mo^l-1.cm^-1,εY（632nm）=9.40×10^4L.mol^-1.cm^-1. cm^-1, respectively. The above mentioned rare earth complexes remain stable within 70 min. Beer＇ s law is obeyed over the concentration ranges 0 - 1.0μg· mL^- 1, 0 - 1.0μg· mL^- 1, 0 - 1.0μg·mL^- 1,0.05 - 0.8μg·mL^- 1 for lanthanum （Ⅲ ）, cerium （ Ⅳ ）, europium（Ⅲ ）, yttrium（ Ⅲ ）, respectively. The corresponding linear regression equations are ALa = 0.0735C - 0.0006, Ace = 0.0624C - 0.0237, AEu = 0.0642C - 0.0017, Aγ = 0.0503C - 0.0814, C being the amount of μg of rare earth in 10 mL of solution. The correlation correlation coefficients are γLa = 0.9994, γCe = 0.9937, γEn = 0.9991, γY = 0.9913, respectively. The method was applied to the direct determination of total rare eaahs in rain water and lake water samples with satisfactory results. The relative standard deviations and standard addition recoveries of the method were 2.46% and 2.64%, 97.30% and 102.0%, respectively.