Pulsed micro-discharge ambient ionization mass spectrometry

Abstract

A method named pulsed micro-discharge ambient ionization mass spectrometry (PMD-AIMS) was developed for direct surface analysis with simple apparatus. In PMD-AIMS, micro-discharges is generated between a copper plate and a tungsten needle with pulsed high voltage applied, in which the analyte on the surface of copper plate is desorbed and ionized, then drawn to the inlet of the mass spectrometer. In this experiment, the tungsten needle was fabricated via an electrochemical method with sharp apex to reduce the volume of the discharge. The experimental parameters were optimized to achieve a high sensitivity and high spatial resolution for mass spectrometry imaging. LOD (S/N = 3) was determined to be 20 ng/ml for atrazine on the yam and 1 ng/ml for atrazine on the copper plate with a lateral resolution of 60 μm. The PMD-AIMS technique was further applied for the rapid detection of the residual herbicide on epidermis. The distribution of the herbicide in plant tissue was investigated with mass spectrometry imaging. The results indicate that PMD-AIMS is a sensitive analytical technique with the capability of mass spectrometry imaging.