Ionization Characteristics of Atmospheric Pressure Ionization by Corona Discharge

Abstract

Ionization characteristics of Atmospheric Pressure Ionization(API)by corona discharge are investigated in relation to total discharge current and needle electrode position. Cluster ions produced in the ionization region are dissociated into molecular ions by a collision induced dissociation method. Calibration curves relating nitrobenzene molecular ion intensity and injected sample size are obtained for wet nitrogen carrier. Ion intensity is found to increase linearly for sample sizes up to 2ng/sec., however, saturation occurs in a large sample size region. Ionization efficiency is found to increase as the needle electrode approaches the aperture electrode. It is close to 100% when the needle position is 3mm from the aperture electrode.