小型质子转移反应质谱仪离子源的设计与优化

Design and optimization of the ion source for miniature proton transfer reaction mass spectrometer

作为一种快速、高灵敏的挥发性有机物(VOCs)检测技术,质子转移反应质谱(PTR-MS)被越来越多地应用于环境、医学、公共安全等领域。作为PTR-MS的关键部件之一,空心阴极辉光放电离子源对仪器性能具有重要影响。本文通过有限元仿真优化了空心阴极结构,在阴极内径为20 mm、阳极与阴极间隙为4 mm时,离子源放电效果较好。将优化后的空心阴极辉光放电离子源与便携式质谱仪联用,并测试了离子信号与放电气压和放电电流的关系。结果表明,最佳放电气压约为200 Pa,最佳放电电流为9~13 m A。采用乙腈样品测试了仪器性能,系统响应时间在10 s以内,乙腈检出限约为10^(-9)(V/V),线性范围为50×10^(-9)~350×10^(-9)(V/V),线性相关系数R^(2)=0.991。利用该装置检测了苹果发酵过程中产生的VOCs随时间的变化,证明了该仪器可用于实际样品检测。

As a rapid and highly sensitive technique for volatile organic compounds(VOCs)detection,proton transfer reaction mass spectrometry(PTR-MS)is increasingly used in environment,medical,and safety fields.As a key component of PTR-MS,the hollow cathode glow discharge ion source has very important effect on the performance of the instrument.In this work,the hollow cathode structure was optimized by finite element simulation,and the best discharge effect had been achieved with a cathode at inner diameter of 20 mm and a gap of 4 mm between anode and cathode.The hollow cathode glow discharge ion source was coupled to a portable mass spectrometer.The effects of pressure and discharge current on ion signals were verified experimentally.The results showed that the optimum discharge pressure was 200 Pa and the discharge current was between 9 and 13 mA.The instrument performance was tested with acetonitrile samples.The results showed that the response time of the system to acetonitrile was within 10 s,the limit of detection was about 10^(-9)(V/V),and the linearity range was 50×10^(-9)~350×10^(-9)(V/V),with the correlation of R2=0.991.Finally,the device was used to detect the variation of VOCs released during apple fermentation over time,demonstrating that the instrument can be used for actual samples analysis.