质子转移反应飞行时间质谱的建立与性能研究

Development and Validation of Proton Transfer Reaction Time of Flight Mass Spectrometer

介绍了自主研制的质子转移反应飞行时间质谱的基本结构和性能。首先对数据采集卡甄别离子脉冲的阈值电压进行了优化,结果表明当阈值电压为0.33V时,H3^16O^+(m/z 19)与H3^18O^+(m/z 21)的离子计数比约500:1;然后考察了水团簇离子H3O^+H2O(n=0,1,2,3)的分布与漂移管约化电场的关系,结果表明,当约化电场(E/N)为139 Td(1 Td=10^-17 Vcm^2)时,团簇离子得到很好地抑制,质谱观察到的离子主要是H3O^+,其纯度可达99%以上;随后考察了质谱的分辨率,结果表明在m/z=124处,分辨率最好,达到2653;采用不同浓度的乙醇标样对仪器的线性范围和检测限性能进行了测试,结果表明该仪器的线性动态范围可达三个数量级,检测限可达3.8 ppb;最后用该质谱仪检测了实验室空气,得到了实验室空气的质谱图。自主研制的质子转移反应飞行时间质谱可实现对痕量挥发性有机物的实时在线测量,在环境、食品、医学等领域具有重要应用价值.

The construction and the performance of the newly developed proton transfer reaction time of flight mass spectrometer(PTR-TOFMS)are reported.Firstly,the threshold voltage of the discriminator on data acquisition board was optimized.The results show that when the threshold voltage is 0.33 V,the intensity ratio of H3^(16)O^+(m/z 19)and H3^(18)O^+(m/z 21)is about 500:1.Then the relationship between the distribution of water clusters ion H3 O^+(H2 O)(n=0,1,2,3) and the reduced electric field in drift tube was studied.The results show that when reduced-field(E/N)is 139 Td(1 Td=10^(-17) Vcm^2),the water cluster ions are well suppressed,and the purity of the ion H3 O^+is more than 99%.The resolutions at different m/z were also investigated.The results show that the best resolution is at m/z=124 with R(MAX)=2653.The performance of the PTR-TOFMS instrument was tested by using different concentrations of ethanol gas.The results show that the linear dynamic range of the PTR-TOFMS instrument can reach three orders of magnitude,and the detection limit can reach 3.8 ppb.At last,the PTR-TOFMS was used to detect the laboratory air to get a mass spectrum of different volatile organic compounds(VOCs).It is indicated that the newly developed PTR-TOFMS can be used for on-line monitoring trace volatile organic compounds,which will be of great value in the fields of environment,food,medicine and other fields.