系列水分活度标准物质的研制  

Development of a Series of Certified Reference Materials of Water Activity

作　　者：郑涵 王海峰[1] 张艾蕊[1] 李佳[1] ZHENG Han;WANG Hai-feng;ZHANG Ai-rui;LI Jia(National Institute of Metrology of China,Beijing 100029,China)

机构地区：[1]中国计量科学研究院,北京100029

出　　处：《化学试剂》2024年第3期105-111,共7页Chemical Reagents

基　　金：国家市场监督管理总局能力提升项目(31-ANL1814)。

摘　　要：水分活度的准确测定对食品安全具有重要意义。水分活度仪急需水分活度标准物质进行校准。研制了氯化钠(NaCl)溶液和氯化锂(LiCl)溶液水分活度标准物质。采用质量平衡法和电位滴定法测定LiCl的纯度。采用重量法制备LiCl溶液,利用LiCl和水的质量以及LiCl纯度计算LiCl的质量摩尔浓度(m)。将m代入德拜-休克尔方程,计算得到渗透系数(?)。根据物理化学基本原理,由m和φ计算得到水分活度的标准值。另外,还采用NaCl纯度标准物质制备了NaCl溶液水分活度标准物质,并计算出其水分活度标准值。7种标准物质的标准值分别为0.250、0.500、0.762、0.797、0.850、0.900和0.950,它们的扩展不确定度(U,k=2)不超过0.007。以德拜-休克尔方程表示的?的标准数据,由美国标准局(NBS)统计并发布。该系列水分活度标准物质可用于水分活度仪的校准和水分活度测量方法的验证。Accurate determination of water activity is essential for food safety.The water activity meter needs the certified reference materials(CRMs)for water activity calibration.The CRMs of sodium chloride(NaCl)solution and lithium chloride(LiCl)solution for water activity were developed.The purity of LiCl was determined using the mass balance method and the potentiometric titration.The LiCl solution was prepared using the gravimetric method and its molarity(m)was calculated using the mass of LiCl and water,and the purity of LiCl.m was introduced into the Debye-Hückel equation,and then the corresponding osmotic coefficient(∅)was calculated.The certified value of a was calculated usingφand m according to physical chemistry basic theory.Furthermore,the CRMs of NaCl solution for water activity calibration were prepared using the CRM of NaCl for purity,and then their water activities were calculated.The certified values of seven CRMs were 0.250,0.500,0.762,0.797,0.850,0.900,and 0.950,respectively.The reference value of φ expressed in the Debye-Hückel equation was published by the National Bureau of Standards(NBS)of the USA after the statistics and analysis.Their uncertainty(U,k=2)was less than 0.007.This series of CRMs can be used in the calibration of instruments and validation of analytical methods.

关 键 词：水分活度 标准物质 渗透系数 氯化钠 氯化锂 不确定度 

分 类 号：O657.12[理学—分析化学]