甲烷中四氢噻吩标准气体定值方法研究

Study on the concentration determination of tetrahydrothiophene in methane reference gas

甲烷中四氢噻吩标准气体是保证天然气中加臭剂准确分析的计量基础。采用感量为0.1mg的质量比较仪,使用称量法进行甲烷中四氢噻吩的称量并定值,同时对比了使用分压法制备,以氮中的H_2S为分析标准,使用总硫定值的方法。由于四氢噻吩与气瓶之间的作用,称量法的定值结果与实际样品中的四氢噻吩浓度存在偏差。而使用分压法制备,总硫定值的方法由于四氢噻吩与气瓶的作用达到平衡后进行定值,定值结果与其他机构研发的四氢噻吩标准气体之间的差值在标准物质不确定度接受范围内。分压法制备,总硫定值的方法可以作为较为适宜的甲烷中四氢噻吩定值研发方法。

Tetrahydrothiophene in methane reference gas is the metrological foundation of natural gas odour analysis. Tetrahydrothiophene in methane reference gas is prepared by mass comparator with 0.1 mg sensitivity using gravimetric method. Because of the interaction between tetrahydrothiophene and the inner-side of the cylinder, the actual tetrahydrothiophene concentration and the result of gravimetric data exhibit some differences. Another method use manometric method to prepare reference gas and determine the concentration by total sulfur comparison. Because of the dynamic balance between tetrahydrothiophene and the cylinder, the determined concentration of tetrahydrothiophene has an uncertainty acceptable difference with the comparative result. The second method is more statistically accurate.