ISOTOPE RATIO DETERMINATION USING MASS SPECTROMETRY

摘要

To address the problems of inaccuracies introduced into isotope ratio measurements by the space charge effects.SOLUTION: Mass spectra of ions are obtained by generating ions, guiding the ions through a device having a mass transfer function that varies with ion current, providing at least some of the ions to a mass analyzer to obtain a mass spectrum of the ions, and determining the current of the ions provided to the mass analyzer. An isotope ratio of the ions is determined for each mass spectrum. Using the determined isotope ratio and ion current determined for each mass spectrum, a calibration relationship is determined that characterizes variation of the determined isotope ratios and the measured ion currents across the mass spectra. Then, a measured isotope ratio obtained at a determined ion current is adjusted using the calibration relationship to adjust the measured isotope ratio to an adjusted isotope ratio corresponding to a selected ion current.SELECTED DRAWING: Figure 1A