Abstract: To provide a method for controlling a liquid chromatograph mass spectrometer by which contamination of a mobile phase solvent caused by a foreign substance can be detected without using an internal standard substance. The method for controlling a liquid chromatograph mass spectrometer according to the present disclosure includes: calculating a first ratio of signal intensities at a first time point and a second time point when measurement is performed using a first mobile phase solvent; calculating a second ratio of signal intensities at the first time point and the second time point when measurement is further performed using a second mobile phase solvent; and determining whether or not the second mobile phase solvent is contaminated according to an absolute difference between the first ratio and the second ratio.

Abstract: To provide a mass spectrometer in which a mass axis deviation can be prevented by having a relatively inexpensive configuration. The mass spectrometer includes: a mass filter including rod electrodes, a holder for holding the rod electrodes, a holder support base on which the holder is placed, and a leaf spring configured to press the holder with an elastic force to fix the holder to the holder support base; a temperature sensor; and a control unit configured to control, based on a measurement signal of the temperature sensor, a voltage value of a high frequency voltage applied to the rod electrodes, in which the temperature sensor is fixed to the leaf spring.

Abstract: An object of the present disclosure is to provide a method for controlling a mass analyzer. According to the method, sensitivity reduction in a high ion concentration region can be prevented without changing a dwell time for each data point. In the method for controlling a mass analyzer according to the present disclosure, starting collecting data is executed at the same time interval, and a time length for collecting the data varies depending on a degree of space charge generated in a prefilter or a degree of sensitivity reduction of the mass analyzer caused by the space charge.