Contents
- Index
- Previous
- Next
Match
Following an autofragmentation, one of the buttons on the Autofragment Results window is labeled Compare Spectrum. If you click this button, the Spectrum window will open and additional options will be present at the bottom of the Spectrum window. You can then open a mass spectrum for comparison with the autofragmentation results. You can choose to allow either 1 or 2 hydrogen transfers by clicking on the appropriate button at the bottom of the window, or to not allow any by unchecking the Allow H transfers box. This essentially determines the match criterion in which a match is recorded if the autofragment mass is identical to a spectrum mass, or differs by a maximum of 1 or 2 amu.
Clicking on Compare will then analyze the spectrum and redraw in red each spectral line that has a "matching" mass in the autofragmentation results, within the range specified by the number of H transfers allowed. There will be two additional menu items present on the Spectrum window labeled Isotope Match and Summary. Clicking Isotope Match will analyze the results to determine whether the expected molecular ion is present and how well the observed isotopic cluster agrees with the calculated values. Summary will present a brief description of the number and percentage of "matched" ions with an overall match index.
The Summary results are provided for general information only. This analysis is based completely on brute force fragmentation of all bonds in the structure with a prediction of what masses could result. There is certainly no assurance that a "matched" fragment would ever be formed, is actually representative of a fragment from the target molecule, or even that it has the same elemental composition. Therefore these results should be viewed with appropriate caution.
If the NIST Library and Mass Spec Interpreter are available, you can analyze the results further by clicking on the NIST MS Interpreter item on the Evaluate menu.