Abstract: Method and system for characterising an isolation profile of a mass spectrometer, the method comprising obtaining data of an, or at least one ion species transmitted by a mass spectrometer forming an isolation profile of the mass spectrometer. Normalizing the obtained data. Providing the normalized data to a deep neural network trained using a plurality of previous isolation profiles. Generating from the deep neural network a set of fit parameters of a curve representing a fit to the normalized data. Providing as an output, data representing the curve. The method may also be used as part of a calibration procedure for the mass spectrometer.