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在0.20 mol.L-1盐酸介质中,锆(Ⅳ)与三溴偶氮胂形成1∶1蓝紫色络合物,加入草酸可置换络合物中的三溴偶氮胂,使显色溶液的吸光度升高,草酸的浓度与吸光度升高值成正比。在506 nm波长处,草酸浓度在1.0×10-4~6.5×10-4mol.L-1范围内遵守比耳定律。方法的表观摩尔吸光率5ε06 nm=1.23×103L.mol-1.cm-1,检出限为0.074 mg.L-1。方法已直接用于地下水以及西红柿样品中草酸含量的测定,所得结果与文献[7]的方法结果相符。测定值的相对标准偏差(n=13)均小于2%,所测得的回收率在95.7%~103.9%之间。
In a 0.20 mol.L-1 hydrochloric acid medium, zirconium (IV) forms a 1: 1 blue-violet complex with tribromoarsenazo, oxalic acid displaces the tribromoarsenazo in the complex, causes the color developing solution Of the absorbance increased oxalic acid concentration and absorbance increased in direct proportion. Beer’s law is obeyed at a wavelength of 506 nm with an oxalic acid concentration ranging from 1.0 × 10-4 to 6.5 × 10-4 mol.L-1. The apparent molar absorptivity of the method was 5ε06 nm = 1.23 × 103L.mol-1.cm-1 with a detection limit of 0.074 mg.L-1. The method has been applied to the determination of oxalic acid in groundwater and tomato samples directly. The results are in good agreement with the results from [7]. The relative standard deviations (n = 13) of the measured values were all less than 2%, and the recoveries were between 95.7% and 103.9%.