Rhoderick G, Chu P, Dolin E, Marks J, Howard T, Lytle M, McKenzie L, Altman D
National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
Fresenius J Anal Chem. 2001 Aug;370(7):828-33. doi: 10.1007/s002160100883.
An EPA Voluntary Aluminum Industrial Partnership (VAIP) program has been formed to help US primary producers focus on reducing the emissions of two perfluorocarbons (PFCs), tetrafluoromethane (CF4) and hexafluoroethane (C2F6), during the production of aluminum. To ensure comparability of measurements over space and time, traceability to national sources was desirable. Hence, the EPA approached the NIST to develop a suite of primary standards to cover a mole fraction (concentration) range of 0.1 to 1400 micromol mol(-1) for CF4 and 0.01 to 150 micromol mol(-1) of C2F6. A total of eight gravimetric PFC gas standards were prepared with relative expanded uncertainties of < or = 0.52% (approximately 95% confidence level). These primary standards were ultimately used to assign values to a series of secondary gas standards at three mole-fraction levels with relative expanded uncertainties ranging from +/- 0.7% to 5.3% (approximately 95% confidence level). This series of secondary standards was used within the aluminum industry to calibrate instruments used to make emission measurements. Assignment of values to the secondary standards was performed by use of gas chromatography with flame-ionization detection (GC-FID) and Fourier transform infrared spectrometry (FTIR). Real time pot-line and stack samples from a local aluminum plant were also obtained and sub-samples sent to each participating facility for analysis. The data generated from each facility were sent to NIST for analysis. The maximum difference between the NIST and individual facilities' values for the same sub-sample was +/- 26%.
美国环境保护局（EPA）已组建了一个铝工业自愿合作项目（VAIP），以帮助美国原生铝生产商专注于减少铝生产过程中两种全氟化碳（PFCs）——四氟甲烷（CF4）和六氟乙烷（C2F6）的排放。为确保空间和时间上测量结果的可比性，溯源至国家标准是很有必要的。因此，EPA与美国国家标准与技术研究院（NIST）合作，开发了一套主要标准，涵盖CF4的摩尔分数（浓度）范围为0.1至1400微摩尔每摩尔（-1），以及C2F6的摩尔分数范围为0.01至150微摩尔每摩尔（-1）。总共制备了八种重量法PFC气体标准，其相对扩展不确定度≤0.52%（约95%置信水平）。这些主要标准最终用于为三个摩尔分数水平的一系列二级气体标准赋值，其相对扩展不确定度范围为±0.7%至5.3%（约95%置信水平）。这一系列二级标准在铝行业内用于校准用于进行排放测量的仪器。通过使用带有火焰离子化检测的气相色谱法（GC-FID）和傅里叶变换红外光谱法（FTIR）为二级标准赋值。还从当地一家铝厂获取了实时电解槽生产线和烟囱样品，并将子样品送至每个参与机构进行分析。每个机构生成的数据被发送至NIST进行分析。对于同一样子样品，NIST与各机构测量值之间的最大差值为±26%。
