A mass spectrometry system used for identifying a substance or substances contained in each of a plurality of fractionated samples obtained by separating various substances contained in a sample according to a predetermined separation parameter, comprising:
- a) an identification probability estimation model information memory for storing identification probability estimation model information representing an identification probability estimation model which shows a relationship between peak information values of a plurality of MSn-1 peaks originating from a same kind of sample and a cumulative number of MSn peaks successfully identified through a series of MSn measurements and identifications in which the MSn-1 peaks are sequentially selected as a precursor ion in order of the peak information values thereof, the identification probability estimation model being created by using the peak information values showing information on MSn-1 peaks found by MSn-1 measurements (where n is an integer equal to or greater than two) for a plurality of fractionated samples obtained from a predetermined sample and results of substance identification based on results of MSn measurements using each of the MSn-1 peaks as a precursor ion;
- b) a peak information value obtainer, which, after an MSn-1 measurement for at least one fractionated sample obtained from a target sample to be identified has been completed, obtains a peak information value for each of a plurality of MSn-1 peaks selected as candidates of the precursor ion from among the MSn-1 peaks found by the MSn-1 measurement;
- c) an identification probability estimator for calculating an estimated value of the identification probability of each of the MSn-1 peaks from the peak information values of the MSn-1 peaks obtained by the peak information value obtainer, with reference to the identification probability estimation model derived from the identification probability estimation model information;
- d) an identification probability increment estimator, in which an estimated increment of the identification probability, which shows a degree of increase in the identification probability achieved by performing an MSn measurement for a same MSn-1 peak a plurality of times and accumulating the results of the measurement, is calculated from the estimated value of the identification probability calculated for each of a plurality of MSn-1 peaks selected as the candidates of the precursor ion by the identification probability estimator;
- e) an MSn measurement order determiner for determining an order of priority of the MSn measurements of the plurality of MSn-1 peaks as the candidates of the precursor ion, under the condition that a plurality of MSn measurements are allowed for the same MSn-1 peak, based on the estimated value of the identification probability of each MSn-1 peak calculated by the identification probability estimator and the increment of the identification probability estimated by the identification probability increment estimator;
- f) an MSn spectrum obtainer for obtaining MSn spectra by performing an MSn measurement for each of a plurality of fractionated samples obtained by separating the target sample to be identified according to the predetermined separation parameter and fractionating the sample, using the order of priority determined in the MSn measurement order determiner;
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- g) a substance identifier for identifying a substance contained in each of the plurality of fractionated samples based on the MSn spectra obtained in the MSn spectrum obtainer.