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

Abstract

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 (∼5 ppm). 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 ± 0.05 cm 2 V −1 s −1. In O 2/N 2 mixtures, additionally to m/ z = 60, negative ion with reduced ion mobility of 2.14 ± 0.05 cm 2 V −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.