Molecules can be analyzed by converting components of a sample into rapidly moving gaseous ions and separating them on the basis of their mass-to-charge ratio (m/e or m/z, dividing an atomic or molecular mass of an ion by the number of charges that the ion bears). This analytical technique provides qualitative and quantitative information about analytes in complex mixtures and aids in identifying the structures of complex molecular species and isotopic ratios of atoms in samples. This technique is called mass spectrometry (MS).
A mass spectrum typically displays the relative abundance vs. the mass-to-charge ratio of the ions. In this program, the number of ions is plotted vs. m/e. The signal in the spectrum that arises simply from an ionized molecule is called the parent peak. The parent ion can lead to a number of peaks due to the various isotopes of the ion's constituent elements. The comparison of these peaks is particularly useful in analyzing the spectrum of a compound.
This module simulates a mass spectrometer, yet it generates only the base peak region, which contains peaks due to the base molecules at masses for the various combinations of elemental isotopes.
INSTRUCTIONS
1. Select the molecule type to analyze by clicking on the
Molecule Type menu and then click on a molecule type.
2. Set the number of atoms of each element in the parent ion
by adjusting the scroll bars for each element. The formula of
the ion changes as the scroll bars are calibrated. For increments of
numbers of atoms, click just above or below the scroll button.
3. Click on the Calculate button to generate the spectrum.
Each vertical line on the spectrum indicates ions of that mass hitting the detector and the size of the peak is proportional to the number of ions of that particular mass. This peak intensity reflects the relative number of ions composed of a particular combination of isotopes. A table of relevant isotopes is available that lists the isotopes of the elements as well as their abundance in nature. This can be accessed by clicking on the Table of Isotopes button.
