Domestic Status Quo and Quantity Value Verification of Certified Reference Materials for Electrolytic Conductivity
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摘要: 电导率标准物质是保证电导率测量结果准确一致的关键。本文从标准物质的定值方法、适用范围等方面综述了国内现有电导率标准物质的现状,深入分析了现有标准物质的特点及其不足。针对我国现有电导率标准物质中有超过50%标准物质的定值采用比较测量方法的现状,采用电解质溶液电导率国家计量基准对这些标准物质进行了量值核查。量值核查结果表明:采用比较测量方法对标准物质的量值进行定值准确性差、质量堪忧(总体合格率58%,较低量值标准物质合格率20%),亟需加强标准物质复制过程中的市场监管;比较测量方法对标准物质进行定值时,几个重要技术环节值得重点关注,即所使用电导率仪的准确度等级、实验室二级水电导率的准确测定、质量称量时空气浮力的正确修正、溶液定容时的准确定容以及标准物质定值不确定度的科学合理评定。Abstract: The certified reference materials (CRMs) for electrolytic conductivity are crucial to ensuring accurate and consistent conductivity measurement results. In this paper, the current situation of existing conductivity CRMs in China is reviewed in terms of their characterization methods and scope of application, and the characteristics of existing CRMs and their shortcomings are analyzed in depth. In view of the current situation that more than 50% of the existing conductivity CRMs in China are characterized by comparative measurement methods, the primary standard for the conductivity of electrolyte solutions was used to verify the values of these CRMs. The results of the verification show that: the accuracy and quality of the comparative measurement method for the characterization of the CRMs are poor (overall pass rate of 58%, the rate of CRMs with lower characterization values is 20%), and there is an urgent need to strengthen the market regulation in the process of replication of the reference materials. When the comparative measurement method for the characterization of the CRMs is being applied, several important technical aspects deserve attention, namely, the accuracy level of the conductivity meter used, the accurate determination of the conductivity of type II water in the laboratory, the correction of the air buoyancy when weighing the mass, the accurate fixing of the solution volume, and the scientific and reasonable assessment of the uncertainty of the characterization of the CRMs.
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表 1 中国计量科学研究院电解质电导率标准物质信息
Table 1. Information of conductivity CRMs developed by the National Institute of Metrology
研制单位 标准物质编号 标准值
(μS/cm)不确定度
(%,k=2)中国计量
科学研究院GBW13120 146.5 ~ 111330 0.10 GBW13121 21.08 1.2 GBW13122 51.13 0.50 GBW13123 12858 0.10 GBW13124 111330 0.10 GBW(E)130106 146.5 ~ 111330 0.25 GBW(E)130107 1409 0.25 GBW(E)130108 147.5 0.25 NIM-RM2092 84.00 0.25 NIM-RM2651 5.15 1.2 NIM-RM2652 9.33 1.2 NIM-RM2653 1.21 2.5 注:所列标准物质的标准值对应的温度为25℃。 表 2 量值核查标准物质列表
Table 2. List of CRMs for quantity value verification
标准物
质代码批次
编号标准值
(μS/cm)扩展不确定度
(%)采购
数量A1 201902 1411 0.25 3 A2 201902 147.6 0.25 3 B1 190506 111300 0.25 2 B2 190506 12850 0.25 2 B3 190419 1409 0.25 2 B4 190419 147.4 0.25 2 C1 009031901 1408 0.25 2 C2 009041901 146.5 0.25 2 D1 190603 12846 0.3 1 D2 190530 1408.2 0.3 1 D3 190513 146.48 0.3 1 D4 190513 84.00 0.3 1 注:出于非技术因素考虑,表2中以标准物质代码代替标准物质编号。 表 3 标准物质量值核查结果
Table 3. Results of quantity value verification for CRMs
标准物
质代码y
(μS/cm)U
(μS/cm)y0
(μS/cm)U0
(μS/cm)$\left|E_n\right| $ A1 1411 4 1411.8 3.6 0.16 A2 147.6 0.4 148.34 0.37 1.41 B1 111300 279 111240 279 0.15 B2 12850 33 12851.2 32.1 0.03 B3 1409 4 1408.4 3.6 0.12 B4 147.4 0.4 147.53 0.37 0.25 C1 1408 4 1406.9 3.6 0.22 C2 146.5 0.4 147.79 0.37 2.5 D1 12846 39 12844.7 38.5 0.02 D2 1408.2 4.3 1422.5 4.3 2.4 D3 146.48 0.44 148.78 0.44 3.7 D4 84.00 0.26 84.70 0.26 2.0 -
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