摘要
用直接进样差量气相色谱法测定非甲烷总烃(NMHC)量。实验研究了分析条件、气源和定量方式等对NMHC定量准确度的影响。综合考虑较低基线响应和较高灵敏度等,选择合适的氢气和空气流速,测得NMHC方法检出限为0.03 mg/m3(以碳计),该法可保证低浓度样品分析的准确度。实验结果表明,标准气中CH4和C3H8遵从碳数响应规律,其配比不会影响定量的准确性,可根据样品总烃和甲烷比例适当配制;对于低浓度样品,以空气为底气的总烃响应灵敏度低于氮气为底气的总烃响应灵敏度,采用以氮气为底气的标准气来定量空气中总烃的含量时,测定结果将产生较大偏差,甚至可能产生负值,应该用以除烃空气为底气的标准气来定量空气样品;某些样品测定过程中,总烃不只出一个峰,需要调节相关条件再进行测定。
A method of determination of non-methane hydrocarbons （ NMHC ） in air by gas chromatography was established. The effects of analysis condition, gas supplies and quantification mode on quantification accuracy in the determination of NMHC by GC were studied. In the experiment, from overall consideration of lower baselines and higher sensitivities, suitable flow rate of H2 and air was selected and the method detection limit of NMHC was 0.03 mg/m3 （by carbon）. From the results, it was found that CH4 and C3H8 comply with carbon number responses, the ratio of CH4 and C3Hs in the standard gases won＇ t affect quantification accuracy, and the ratio of CH4 and C3H8 in the standard gases can be determined by the ratio of total hydrocarbon and methane in the samples. About low concentration gases, the response sensitivity of total hydrocarbon in air was lower than that in nitrogen, so that if standard gases in nitrogen was used to quantify total hydrocarbon in air samples, it may produce large deviations, even negative values. Standard gases in air without hydrocarbon should be used to quantify total hydrocarbon in air samples. Total hydrocarbons responses of some samples may appear not only one peak, so that it needs to adjust some measurement conditions, and then measure them again.
出处
《化学分析计量》
CAS
2013年第4期95-98,共4页
Chemical Analysis And Meterage
关键词
非甲烷总烃
甲烷
气相色谱法
负值
non-methane hydrocarbons
methane
gas chromatography
negative value
