| 摘要 |
Fine structures of isotopic peak clusters of substances are determined using ultrahigh resolution mass spectrometry, e.g, FT-ICR mass spectrometry. Resolved individual peaks in the fine structure of the non-monoisotopic peak clusters of organic substances usually contain the additional elemental isotopes 13C, 15N, 17O, 18O, 2H, 33S, 34S, and combinations thereof. In each of a series of experiments, one of the non-monoisotopic peak clusters is isolated and the corresponding fine structure spectrum acquired. Abundances of the resolved fine structure peaks and their positions on the mass scale are recorded and, after measuring some or all of the isotopic peaks, the atomic composition of the measured substance is calculated. By excluding the monoisotopic peak and isolating only one isotopic peak cluster at a time, the number of ions in the FT-ICR cell is kept low, which avoids resolving power losses due to space charge effects and ion-ion interaction phenomena. |
| 主权项 |
1. A method for the determination of an unknown elemental composition of a sample substance measured by ultrahigh resolution Fourier Transform (FT) mass spectrometry, comprising:
a. acquiring a mass spectrum of the sample substance with a full isotopic pattern using an FT analyzer cell; b. isolating a non-monoisotopic peak cluster in the vicinity of a monoisotopic peak, wherein the isolation includes allowing only one selected non-monoisotopic peak cluster, comprising a plurality of unfragmented peaks, to be in the analyzer cell; c. acquiring a narrowband mass spectrum of the isolated non-monoisotopic peak cluster, which allows resolution of an isotopic fine structure of the isolated non-monoisotopic peak cluster; d. determining relative abundances and mass values of mass peaks corresponding to individual isotopes and isotope combinations of elements in the non-monoisotopic peak cluster; e. isolating another non-monoisotopic peak cluster and repeating the procedures described in steps (c) and (d), and continuing until a predetermined minimum abundance of the non-monoisotopic peak clusters is reached; and f. determining the elemental composition by calculation from the isotopic fine structures using the relative abundances of the individually acquired non-monoisotopic peak clusters, wherein the mass values and the relative abundances of one non-monoisotopic peak cluster are cross-correlated to those of at least one other non-monoisotopic peak cluster. |
