Research On New Operation Mode Of Quadrupole Mass Spectrometry

Mass spectrometry is a kind of prosperous scientific instruments and is widely used in many fields. The recent development of mass spectrometry is characteristic by new ionization source (DESI DART), new mass analyzer (Orbitrap), tandem MS, and portable MS. For some reasons, China has been left behind in mass spectrometry field. It is significant to research mass spectrometry instruments with independent intellectual property right. Currently used commercial quadrupole MS are all driven by sinusoidal RF voltage with stable frequency and the filter of ion is realized by changing of amplitude of RF voltage. Some scholars engaged in study of quadrupole MS driven by sweep frequency sinusoidal voltage. Driving quadrupole trap and quadrupole MS with rectangular wave has been proposed and simulation or experiment results have been presented by some scholars.The focus of the thesis is to study quadrupole MS with new operation mode. Sweep frequency rectangular power supply is developed to replace traditional power supply. Frequency sweep operation mode is used to substitute traditional voltage-scanning operation mode and mass spectrograms with new operation mode are attained for the first time. DDS technology is used to produce sweep frequency signal which drives power switching devices to switch DC voltage to produce sweep frequency rectangular wave. The range, stepped frequency and dwell time of sweep frequency could be set by software. Calculating principle of DDS parameters is presented. Requirements for driving MOSFET in bridge circuit are analyzed. Gate-driving and interference suppression problems of bridge circuit are solved. Designing principle and designing procedure are described. Quadrupole MS driven by frequency-sweeping rectangular wave is studied. The effects of electric parameters to resolution are analyzed. A conclusion that increasing of U and V is favorable to resolution is made.Data acquisition system with new interface is designed and is used to obtain raw mass spectrum data. Data acquisition system is constituted by USB interface chip cy7c68013a and AD converter Max115. Firmware program and application program are complied. Real-time acquisition of spectrum data is realized.