高纯亚硝酸钠中杂质测定

分析评价高纯亚硝酸盐中杂质含量是亚硝酸根检测及相关标准物质量值溯源的基础。以高纯NaNO₂为例,采用离子色谱法测定阴离子杂质含量,定性分析主要阴离子杂质为Cl^-、NO^-₃和SO^2-₄;采用电感耦合等离子体原子发射光谱法(ICP-AES)测定K、Ca、Mg含量;采用电感耦合等离子体质谱法(ICP-MS)测定其他阳离子杂质含量(K、Ca、Mg除外),发现其他主要阳离子杂质为B和Sr。结果表明所测杂质在线性范围内,线性相关系数均大于0.9990;Cl^-的检出限为0.001%(质量分数,下同),NO^-₃和SO^2-₄的检出限为0.003%,K的检出限为0.004%,Mg的检出限为0.0009%,Ca的检出限为0.00003%,B的检出限为0.000015%,Sr的检出限为0.0000074%。按照实验方法测定高纯NaNO₂中Cl^-、NO^-₃、SO^2-₄、K、Ca、Mg、B和Sr含量,测定结果的相对标准偏差(RSD,n=10)为1.8%~3.5%,加标回收率为96%~104%。方法用于高纯NaNO₂中杂质含量测定,得到Cl^-、SO^2-₄、NO^-₃、K、Mg、Ca、B和Sr的含量(质量分数,下同)分别为0.0054%、0.037%、0.033%、0.02%、0.0063%、0.0035%、0.00226%和0.000268%。实验方法可为亚硝酸根及亚硝酸盐相关测定及标准物质研制提供技术支持,研制的相关标准物质可保证亚硝酸根的量值溯源。

Determination of impurities in high purity sodium nitrite

The analysis and evaluation of impurity contents in high purity nitrite is the basis of nitrite detection and the traceability of relevant reference materials. The high purity NaNO₂ was selected as an example. The contents of impurity elements were determined by ion chromatography. The qualitative analysis showed that the main anionic impurities were Cl^-, NO^-₃ and SO^2-₄. The contents of K, Ca and Mg were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). The contents of other cation impurity were determined by inductively coupled plasma mass spectrometry (ICP-MS). The results showed that the cation impurities mainly included B and Sr except for K, Ca and Mg. The linear correlation coefficients were all greater than 0.9990 for the tested impurities within the linear range. The limit of detection for Cl^-, NO^-₃, SO^2-₄, K, Mg, Ca, B and Sr was 0.001%, 0.003%, 0.003%, 0.004%, 0.0009%, 0.00003%, 0.000015% and 0.0000074%, respectively. The contents of Cl^-, NO^-₃, SO^2-₄, K, Ca, Mg, B and Sr in high purity NaNO₂ were determined according to the experimental method. The relative standard deviations (RSD, n=10) of determination results were between 1.8% and 3.5%. The spiked recoveries were between 96% and 104%. The proposed method was applied to the determination of impurities in high purity NaNO₂. The measured contents (mass fraction, similarly hereinafter) of Cl^-, SO^2-₄, NO^-₃, K, Mg, Ca, B and Sr were 0.0054%, 0.037%, 0.033%, 0.02%, 0.0063%, 0.0035%, 0.00226% and 0.000268%, respectively. The proposed method could provide technical support for the determination and development of standard materials for nitrites. The developed reference materials could guarantee the traceability of nitrite.