Research on Automatic Tuning of Quadurpole Mass Resolution in Quadurpole-Liner Ion Trap Tandem Mass Spectrometry

In order to achieve quadrupole mass resolution and precision automatic tuning of a radial excitation mode quadrupole ion trap tandem mass spectrometer, a set of algorithms was developed that can freely set the target peak width at half maximum and automatically adjust instrument parameters. This algorithm gradually increased the mass-to-charge ratio of quadrupole screening ions, scanned the ion trap to obtain the target ion intensity, and plotted the relationship curve between the mass-to-charge ratio of quadrupole screening and the target ion signal intensity, thereby reconstructing the quadrupole mass spectra. This method solves the problem of being unable to directly obtain quadrupole mass spectra due to ion trap storage and enrichment. Quadrupole mass resolution and mass accuracy data can be obtained via this method, and the quadrupole mass resolution can be tuned by using automatic adjustment of mass resolution in quadrupole mass spectrometry. Then the quadrupole mass accuracy was calibrated based on the tuning results of mass resolution. Multiple samples were used to test the accuracy and stability of the algorithm. The test results showed that when the target half width is within the range of 1-50 u, the deviation of both the measured half-width and mass-to-charge ratio in the experiment are less than 10% of the target half-width. There is a linear relationship between the intercept of the quadrupole mass axis and the mass resolution. The significance of this study lies in the fact that the algorithm enables automatic tuning of quadrupole mass resolution and mass accuracy on quadrupole-liner ion trap tandem mass spectrometry (Q-LIT MS), allowing free setting of the required quadrupole mass resolution, meeting more mass resolution requirements, and ensuring mass accuracy under different mass resolution conditions. The method effectively improves the accuracy of instrument mass resolution tuning and mass accuracy correction, and reduces the technical requirements for operators. Regarding with the shortcomings, firstly, because the signal intensity decays rapidly with the decrease of the set target half-width, the case of FWHM<1 has not been studied. Increasing the time of ion implantation during the tuning process may solve this problem, but it may also lead to the generation of space charge effect, which will affect the spectral quality of the reconstructed peak and reduce the tuning success rate. In the future, automatic gain control technology can be used to regulate the ion implantation time during calibration to solve the influence of space charge effect.