When creating a compound, you can adjust its fit style by using the “Compound Details” dialog. By default all compounds use the peak-based fit style, which allows you to fit the exact areas and lineshapes of individual compounds while you are profiling an NMR spectrum. These peak-based compounds can be used to quickly and easily deconvolve (break down) overlapping regions in your spectrum and generate accurate profiled concentration values.
Sometimes, however, you may prefer to assign the region-based fit style to a newly created compound. Region-based compounds will automatically fit themselves to your spectrum as you are profiling, ignoring the shape of their own individual peaks and instead fitting the entire region around each of their clusters. This fit style is ideal for compounds whose individual peak shapes are not modelled accurately enough to provide a good fit.
Using the region-based fit style allows you to create new compounds very quickly and without worrying too much about how they are affected by changes to pH, magnet frequency, and other acquisition variables. But it has disadvantages, too.
For example, region-based compounds cannot overlap with other region-based compounds. Also, they are not associated with a sample concentration, so Profiler will never report a concentration value for them. Instead, Profiler calculates the area of a region-based compound by summing up the areas of your spectrum within each of the compound's cluster regions. This total area is proportional to the real underlying concentration of the compound, so it can still be used for various kinds of analysis.
Region-based compounds can also used for simple compound identification.
How do change the fit style of a compound?
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Click Compound Details.
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Choose region-based fits or peak-based fits on the General tab.
Tips and Tricks
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You don't have to worry too much about the exact shape of each cluster in your region-based compounds. Just make sure that the peaks are far enough apart to capture each cluster's entire area.
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The “Generate Cluster for Region” and “Optimize Selected Peak Shapes” features provide a quick and easy way to generate and fit cluster shapes for your region-based compounds.