Ion Selective Apertures for Mass Spectrometry

DESCRIPTION (provided by applicant): The objective of the present project is the development of commercial technologies to eliminate the significant inefficiencies associated with sampling of ions from atmospheric pressure into the mass spectrometer. A typical commercial ionization source will have an efficiency of less than 0.01%. One (1) ion in 10,000 actually reaches the detector with most atmospheric pressure interfaces; including, electrospray (ES), atmospheric pressure chemical ionization (APCI), and atmospheric pressure matrix assisted laser desorption ionization (AP-MALDI). This project will focus on the weakest link in mass spectrometry, the conductance aperture from atmospheric pressure into vacuum where the majority of losses occur. Ion transmission will be enhanced through the use of novel laminated "ion selective" apertures, tubes, and array assemblies. We will evaluate the use of delayed (or eliminated) ion dispersion within the conductance aperture from atmospheric pressure into the first pumping stage. Simulations of ion motion under the influence of electrostatic and viscous forces predict increase in the effective conductance aperture by factors of 10 to 100. This will have a direct impact on improving the sensitivity and quality of mass spectral data in all areas of atmospheric pressure ion sampling including proteomics and pharmaceutical development. This will be accomplished by eliminating effects from field dispersion by incorporating laminated conductance apertures, tubes, and arrays that are designed to account for all force vectors (field and flow) throughout the entire ion transmission pathway. In order to achieve the precise control of both electric field and flow within the dimensions of typical conductance apertures [micron range] we will be required to evaluate state-of-the-art microfabrication processes to maintain surface quality and dimensional tolerances. Preliminary studies show a 16-fold transmission improvement with microfabricated laminated arrays. By coupling our existing atmospheric pressure optics to these conductance arrays we predict system level sensitivity enhancements of factors of 100 to 1000. Conductance and optical assemblies with these figures-of-merit will become standard components in most research and product mass spectrometer in pharmaceutical biomedical analysis.