Patent ID: 8067729

Claim:
A method for determining a valence of each ion peak and identifying one or more monoisotopic peaks in a mass spectrum by analyzing mass spectrum data obtained by a mass analysis, comprising the steps of: a) creating centroid data based on profile data obtained as the mass spectrum data; b) specifying a peak on the centroid data, in order of descending peak intensity, as a standard peak for identifying the isotopic cluster; c) comparing an emerging pattern of peaks near the standard peak and an emerging pattern of peaks of an isotopic cluster within a predetermined valence range, and determining, a valence of the isotopic cluster including the standard peak and for determining peaks belonging to the isotopic cluster, in a case where an emerging pattern of the standard peak and the peaks near it corresponds to the emerging pattern of peaks of the isotopic cluster as a result of a comparison; d) determining the valence of the isotopic cluster identified in the step c) as a valence of the peaks belonging to the isotopic cluster; and e) identifying a peak having a smallest mass-to-charge ratio in the isotopic cluster as a monoisotopic peak.