Development Of PTR-MS Key Components And Research Of The Breath Acetone Measurement

Breathing gas carries important physiological information. Detection of breathing gas technology has become a research focus for the advantages of nondestructive sampling, convenient operation and simple components. Proton transfer reaction mass spectrometry(PTR-MS) plays an irreplaceable role because of the advantages of high sensitivity, fast response and good specificity.This paper is based on and supported by the national key scientific instrument and equipment development project “PTR-MS instrument development and application”, and takes research from analysis simulation and experiment to achieve the research and design on of PTR-MS key components: drift tube and ion source. Based on the principle and theory of PTR-MS, a depth research about proton transfer reaction in the drift tube and hollow cathode effect in the ion source are presented. The movement state and focusing properties of ions in drift tube with different structure are simulated by using the ion optics analysis software Simion. The uniformity of electric field distribution and focusing properties of ions are improved. The PTR-MS ion source is developed, and the influence of cone interface on concentration of reagent ions and contaminating ions is analyzed. The preliminary platform of PTR-MS is built.The sampling device of PTR-MS instrument is designed. Acetone mixture gas with different carbon dioxide concentration and relative humidity are prepared by syringe method in Tedlar bags and measured by PTR-MS based on the designed ion source and drift tube. The influences of carbon dioxide concentration,relative humidity, oxygen ions concentration and nitric oxide ions concentration are investigated. The results show that carbon dioxide concentration and humidity do not influence the counts per second of acetone ions, but enhance the concentration ratio of protonated water clusters to protonated water in the drift tube. The oxygen ions enhance the acetone fragment ions concentration, which influence the measurement accuracy of breath acetone by PTR-MS. The nitric oxide ions concentration is so low that the influence on the result could be negligible. Finally, the concentration correction expression is deduced.