Atmospheric Pressure Corona Discharge Ionisation and Ion Mobility Spectrometry/Mass Spectrometry study of the negative corona discharge in high purity oxygen and oxygenitrogen mixtures

摘要

Negative ions formed in negative corona discharge in high purity O_2 and O_2/N_2 mixtures have been studied using the Atmospheric Pressure Corona Discharge Ionisation Mass spectrometry (APCDI/MS) and Ion Mobility Spectrometry/Mass Spectrometry techniques (IMS/MS). The primary negative ions have been detected and identified using APCDI/MS technique. The primary ions are fast transformed via ion-molecule reaction with N_2O into ions with m/z=60 (N_2O_2~-). The N_2O is formed in the negative corona discharge in the reaction of O with N_2 (～5ppm). In the case of N_2 admixtures to O_2 from 10 to 80%, additional negative ion m/z=62, NO_3~- appears in the IMS and MS spectra. The mobilities of the negative ions were determined from IMS and mass selected IMS spectra. The m/z=60 (N_2O_2~-) has reduced ion mobility of 2.52±0.05cm~2V~(-1)s~(-1). In O_2/N_2 mixtures, additionally to m/z=60, negative ion with reduced ion mobility of 2.14±0.05cm~2V~(-1)s~(-1) and m/z=62 have been detected and assigned to NO_3~-. Formation of this ion was associated with the presence of NO_2 generated in the negative corona discharge in O_2/N_2 mixtures.