Hint: This is the first of only a few keyboard commands you will have to learn. If you edit a yellow marked peak it will turn red after editing. Please note, that all edited names are always marked with a red arrow in the chromatogram. The little grey cross in the lower left corner allows you to delete the currently selected entry from the list box. You may double-click on any list box entry to accept that label. The list box offers all previously used labels for your convenience, so if you frequently find the same unidentified peaks it is easy to repeatedly assign the same labels. If the scan already had a name assigned, the input box will display the current text and let you edit it. Enter any text you like and press return or click OK. Please press the letter 'n' as mnemonic for name and a input dialog box will pop up. However, you may also edit the name of any GC scan manually if desired. MassFinder performs assignments conveniently with only one mouse click and gives reasonable names to identified peaks or informative text to unknowns. Step 6: Editing the names of unknown peaks
MASS FINDER DIOPITT HOW TO
All marks and assignments can be saved with the chromatogram as well as exported in graphical or text form to document the assignments (you will learn how to do this later). We recommend to assign and mark all interpreted peaks to avoid repeating the identification process when opening the GC/MS run the next time. You can turn assigned scans to unknown scans just by clicking on the highlighted scan and vice versa. If you want to undo the assignment, just click again on the same scan. This gives a name to the unknown spectrum containing helpful information for discussing the peak (base peak, possible molecular ion, retention index) and marks the unknown peak with a red arrow and its retention time in the chromatogram. To mark such interesting scans as unknown, just click anywhere on top of the highlighted scan (center spectrum in left panel). discovering novel constituents or handling compounds not covered by the library. Naturally, there are cases where no perfect library match exists, e.g. You may scroll through different library entries while being in butterfly mode. If you click the butterfly icon a second time the normal view is restored. You need to try for yourself whether this is true for you. Many people feel butterfly presentations facilitate comparing spectra with each other. If you click on this icon, the current target GC/MS mass spectrum and the current library entry are displayed head-to-tail (top = library, bottom = scan). Please note the little icon in the upper left corner of the highlighted library entry it is called the butterfly icon. In the status bar at the bottom of the window MassFinder displays how many library matches were found. Please again play around navigating through the GC/MS and this time more closely watch the right panel displaying the library search results. On the previous tutorial page you learned how to navigate through the GC/MS and you probably enjoyed the instantaneous library hits displayed on the right side.
Compare the adjacent scans and their respective search results. Check how closely the retention indices match. Always consider not only the first library hit, but also the next few hits.MassFinder is only a tool to make this process as reproducible, reliable and convenient as possible and it supports and facilitates the documentation and presentation of your assignments. The scientist as user of MassFinder is solely responsible for identifying and assigning spectra. In summary, please note the two important points: If the compound is not in the library, MassFinder suggest similar spectra as possible matches. in case of mixtures of compounds in co-eluting peaks, overloaded spectra, bad low-intensity spectra or wrong retention indices due to mismatched temperature programs in gas chromatography can make an identification difficult or misleading. However, there are many cases, where the first library hit MassFinder presents is not the correct identification, e.g. MassFinder 4 has a powerful and reliable search engine and employs the two-dimensional algorithm considering both spectrum similarity and retention index. 9 Step 8: A first glance on the value of retention indices.7 Step 6: Editing the names of unknown peaks.3 Step 2: Assign names to identified peaks.
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