Calibration of a quadrupole ion trap for particle mass spectrometry

Abstract

A quadrupole ion trap (QIT) is calibrated for microparticle mass spectrometry by confining φ{symbol} = 2.02 μ m dye-labeled polystyrene microspheres and measuring their secular oscillation frequencies and fluorescence spectra. A particle's absolute mass and charge are found by measuring its secular oscillation frequencies within the QIT while initiating charge steps through photo-ejection of electrons. The radius of the same microsphere is determined by analyzing the fluorescence emission spectrum, which is dominated by optical cavity resonances, employing Mie theory. The mass of the microsphere is calculated from the radius using the density of bulk polystyrene. For nine particles originati..