Molecular mass and location of the most abundant peak of the molecular ion isotopomeric cluster.

The location of the most abundant peak of the molecular-ion pattern often differs from the molecular mass published in scientific databases. The location is also distinct from the value expected from average atomic masses. The cause of this phenomenon is a large number of atoms of carbon, sulfur, chlorine, bromine, silicon and boron. This due to the natural isotope abundances of some elements forming organic compounds. A parameter called location of the most abundant peak of an isotopometric cluster (LAPIC) denotes the location of the most abundant (the main) peak of an isotopomeric cluster, which is determined, e.g., by mass spectrometry and can be important for medium- and high-molecular mass compounds. The equations for LAPIC calculation are presented for elements usually observed in organic compounds. The LAPIC with elemental formula helps effectively, e.g., in mass spectra interpretation since the prediction of LAPIC allows the correct connection of the main peak of the investigated ion with the expected ion formula and the mass of the ion considered. This solution can be a substitute for the much more complex method of isotopometric analysis applied in mass spectra interpretation. [Figure: see text]. Differences of the most abundant peak location (Delta LAPIC(C)=f(n)) for carbon aggregates C(n).