Analysis of Purity and Uncertainty for 1, 2, 3, 4-Tetrachlorobenzene with the Mass Balance Method
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摘要: 采用可溯源的质量平衡法对1，2，3，4-四氯苯标准物质纯度定值，评价了此方法的不确定度。其中非挥发性杂质用气相色谱串联质谱(GC-MS)进行定性，经标准添加的方式确认杂质为1，2，3，5-四氯苯，并用气相色谱电子捕获检测器(GC-ECD)对杂质准确定量；水分含量和灰分含量分别采用卡尔费休库伦法和马弗炉灼烧的方法测量，溶剂残留采用顶空GC-MS分析，确认1,2,3,4-四氯苯中的残留溶剂是乙醚。纯度定值结果为98.79%，扩展不确定度为0.20%(k=2)。同时对分装的500瓶样品抽取10瓶进行均匀性检验，F检验和T检验结果表明在95%置信范围内样品均匀性良好；按短期稳定性(1个月)和长期稳定性(12个月)分别进行稳定性检验，结果表明在20℃条件下1,2,3,4-四氯苯的稳定期不少于12个月。
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关键词:
- 质量平衡法 /
- 1,2,3,4-四氯苯 /
- 标准物质 /
- 纯度分析 /
- 不确定度评定
Abstract: A traceable method is presented, to study the purities of certified reference material of 1,2,3,4-tetrachlorobenzene with the assessment of uncertainties. The purities of 1,2,3,4-tetrachlorobenzene were determined by the mass balance method. The qualitative analysis of main non-volatile impurities was identified as 1,2,3,5-tetrachlorobenzene with Gas Chromatography-Mass Spectrometry (GC-MS) and standard addition. The quantitative analysis for the impurities was measured by Gas Chromatography-Flame Ionization Detector (GC-FID). The content of water and ash in 1,2,3,4-tetrachlorobenzene were respectively measured by Karl-Fischer titrator and ignited at 900℃ in a muffler roaster. The residuals of solvent were confirmed as ethyl ether by Headspace Gas Chromatography-Mass Spectrometry. The certified result with the mass balance method was 98.79% and the expanded uncertainty was 0.20% (k=2). The good homogeneity result in the 95% confidence interval was validated by F-test and t-test statistical methods with samples from 500 different bottles. The stability inspection was carried out on short-term (one month) and long-term (12 months) tests, and the results indicate that the stability period for 1,2,3,4-tetrachlorobenzene of storage is no less than 12 months at 20℃. -
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图 1 1,2,3,4-四氯苯的总离子流图和质谱图
Figure 1. Total ion chromatograms and mass spectra of 1,2,3,4-tetrachlorobenzene
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图 2 1,2,3,4-四氯苯和异辛烷空白的GC-FID放大叠加色谱图
Figure 2. The GC-FID chromatogram of 1,2,3,4-tetrachloro-benzene and iso-octane (blank)
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图 3 1,2,3,4-四氯苯和1,2,3,5-四氯苯的GC-FID色谱图及叠加图
(a)—1,2,3,5-四氯苯GC-FID色谱图； (b)—1,2,3,4-四氯苯候选物GC-FID色谱图； (c)—1,2,3,4-四氯苯候选物溶液添加1,2,3,5-四氯苯的标准添加GC-FID叠加色谱图。
Figure 3. The GC-FID chromatograms of 1,2,3,4-tetrachloro-benzene and 1,2,3,5-tetrachlorobenzene
表 1 非挥发性杂质、水分与溶剂残留的含量及质量平衡法、GC-FID与GC-ECD纯度定值结果
Table 1 Analytical results of non-volatile impurities, water and residual solvents and purity of 1,2,3,4-tetrachlorobenzene by mass balance method, GC-FID and GC-ECD
测量次数 质量平衡法wB/% 质量平衡法纯度
w(1,2,3,4-四氯苯)/%面积归一化法w(1,2,3,4-四氯苯)/% 1,2,3,5-四氯苯 水分 乙醚 GC-FID GC-ECD 1 1.12 0.10 0.0061 98.775 99.094 98.883 2 1.21 0.09 0.0067 98.694 98.802 98.932 3 1.05 0.10 0.0060 98.845 98.801 99.017 4 1.11 0.12 0.0065 98.765 98.779 99.025 5 1.07 0.08 0.0057 98.845 98.880 99.053 6 1.11 0.09 0.0052 98.794 98.760 99.084 7 1.08 0.10 0.0062 98.815 98.812 99.057 平均值 1.11 0.097 0.0061 98.791 98.847 99.007 标准偏差 0.052 0.013 0.0005 0.053 0.12 0.073 RSD/% - - - 0.054 0.13 0.07 
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表 2 1,2,3,4-四氯苯标准物质均匀性测定结果
Table 2 The results of homogeneity test for 1,2,3,4-tetrachlorobenzene certified reference materials
测定次数 w(1,2,3,4-四氯苯)/% 瓶间均匀性 瓶内均匀性 1 98.87 98.91 2 98.85 98.96 3 98.78 98.87 4 98.94 98.88 5 98.97 98.90 6 98.83 98.89 7 98.88 98.91 8 98.96 98.87 9 98.85 98.92 平均值 98.88 98.90 标准偏差(SD) 0.064 0.029 RSD/% 0.065 0.029 F检验 F=s12/s22 2.23 F0.05(8，9) 3.38 F＜F0.05(8，9) 样品均匀 t检验 t=|x1-x2| 0.002 
0.029 t≤ta 样品均匀
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表 3 1,2,3,4-四氯苯标准物质稳定性检测结果
Table 3 The results of stability test for 1,2,3,4-tetrachloro-benzene certified reference materials
序号 短期稳定性
w(1,2,3,4-四氯苯)/%长期稳定性
w(1,2,3,4-四氯苯)/%-10℃ 4℃ 20℃ 70℃ 检验时间 4℃ 20℃ 1 98.94 98.94 98.90 98.78 2011年1月 98.77 98.88 2 98.85 98.93 98.90 98.27 2011年2月 98.93 98.83 3 99.00 98.82 98.80 97.93 2011年3月 98.97 98.92 4 99.02 99.00 98.79 98.36 2011年5月 98.88 98.79 5 99.02 98.92 98.92 98.20 2011年7月 99.03 98.95 6 98.92 99.00 98.78 97.81 2011年9月 98.89 98.82 7 98.90 98.86 98.91 98.41 2011年11月 98.96 98.90 平均值 98.95 98.93 98.86 98.25 平均值 98.90 98.87 标准偏差 0.067 0.067 0.064 0.322 标准偏差 0.086 0.055 RSD/% 0.067 0.068 0.065 0.327 RSD/% 0.087 0.055 t检验 t=0.003＜tα=0.028
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表 4 质量平衡法不确定度评定结果
Table 4 The uncertainty results of mass balance method
评定项目 质量平衡法 扩展不确定度U(k=2) 0.20% 标准不确定度uc 0.1 u(I水分) 0.04 u(I灰分) 0.003 u(I溶剂) 0.02 u(I非挥发) uc(I杂质)＝0.07 uA＝0.06 uB＝0.03
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