离子置换色谱法测定亚氯酸钠纯度及其杂质阴离子的含量

以常规的抑制型离子色谱仪为基础,在抑制器之后和紫外检测器之前,依次串联两根自制的离子置换柱,第一根为Li+型阳离子置换柱,第二根为IO3-型阴离子置换柱。IC测定中用Dionex IonPac AS18阴离子交换柱为分离柱,以30mmol·L^-1氢氧化钠溶液为流动相。在测定亚氯酸钠的纯度及其杂质阴离子含量时,样品溶液(0.100 0g样品溶于水中,定容至50.0mL,分取部分溶液定量稀释100倍)在经过离子置换柱的过程中,亚氯酸根及其他待测阴离子均被定量地置换成同一的碘酸根离子,并通过紫外检测器,在波长210nm处予以测定。结果表明:亚氯酸根及其他4种杂质离子的浓度在一定范围内与其对应的峰面积呈线性关系,检出限(3S/N)在6.09～19.66μg·L^-1之间。按标准加入法进行回收试验,回收率在96.0%～101%之间,测定值的相对标准偏差(n=6)在1.1%～3.0%之间。

Determination of Purity of Sodium Chlorite and Its Anion Impurities by Replacement-Ion Chromatography

As an attachment to the conventional suppression ion chromatograph,two self-prepared ion replacement columns were installed in series between the suppressor and the UV-detector successively.The former is a cation replacement column of Li+-type and the latter is an anion replacement column of IO3--type.Dionex IonPac AS 18 anion exchange column was used for separation in IC analysis,and 30 mmol·L^-1 NaOH solution was used as mobile phase.In the determination of purity of sodium chlorite and its impurityanions,when the sample solution(prepared by dissolving 0.100 0 g of the sample in water,making its volume to 50.0 mL,and still-further by diluting an aliquot of the solution 100 times quantitatively)was separated through the anion-exchange column and then passed through the 2 ion-replacement columns,the anions,i.e.,ClO2- and the other 4 anions,were all replaced to the same anion of IO3-,and determined at the wavelength of 210 nm by the UV-detector.As shown by the results,linear relationships between values of peak area and concentration of chlorite and other impurity ions were obtained in definite ranges,with detection limits(3 S/N)in the range of 6.09-19.66μg·L^-1.Test for recovery was made by standard addition method and the values of recovery were found in the range of 96.0%-101%,with RSDs(n=6)ranged from 1.1% to 3.0%.