The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Nov. 05, 1996
Filed:
May. 25, 1995
Robert J Cotter, Baltimore, MD (US);
Vladimir M Doroshenko, Reisterstown, MD (US);
The Johns Hopkins University, School of Medicine, Baltimore, MD (US);
Abstract
A method of operation of an ion trap mass spectrometer having a ring electrode and pair of end-cap electrodes in a resonance ejection mode is disclosed. The method includes producing ions from a plurality of biomolecules, applying a trapping RF voltage to the ring electrode, applying an excitation voltage to the end-cap electrodes, scanning the trapping RF voltage in order to sequentially eject the ions, controlling a ration of the amplitude of the trapping RF voltage to the amplitude of the excitation voltage in order that the ratio is generally constant, and determining a ratio of mass to charge of the ejected ions. In one embodiment, a feedback voltage which is proportional to the trapping RF voltage is sensed, and the amplitude of the excitation voltage is controlled as a function of the amplitude of the feedback voltage. In another embodiment, a first value related to the amplitude of the trapping RF voltage and a second value, which is proportional to the first value and related to the amplitude of the excitation voltage, are determined. The amplitude of the trapping RF voltage is modulated employing the first value and the amplitude of the excitation voltage is modulated employing the second value. Preferably, the determined mass-to-charge ratio (m/z) of the ejected ions is equal to a constant (.alpha.) times the trapping RF voltage (V). Associated apparatus and method of calibration are also disclosed.