Thursday, 14 January 2010

On integrating overlapped peaks

Following up from the integration problem raised in my previous post and before I delve into Line Fitting, I would like to give you a quick update on some progress we have recently done in Mnova to facilitate the accurate integration of peaks in those cases in which a multiplet is contaminated by one or several extraneous peaks (e.g. a solvent peak).
Consider the following spectrum predicted using NMRPredict Desktop

As expected (this is a perfect synthetic spectrum and therefore noise-free with no phase or baseline distortions and enough separation between the 3 multiplets) the relative integrals are in agreement with the structure, 1:2:1.
I will now modify this spectrum by adding an extra peak in the H-5multiplet

As a result, the multiplet corresponding to H-5 will show a relative integral of 2 instead of 1. This problem can be tackled by using, for example, some signal suppression algorithm to get rid of this extra peak or by deconvolving the multiplet and then summing up the individual deconvolved peaks without the extra peak.
The aim of this post is to let you know that we have just automated all this process via the powerful GSD algorithm (more about this in a later post) so that dealing with this kind of problems has become much easier than before. As I will describe in depth once the new version with this functionality is released, the user just has to select which peak or group of peaks needs to be excluded for the integration and the program will do the rest. This is illustrated in the figure below where the extra peak (in red) is not used for the integral calculation

Even though this new functionality is not available in the current official release of Mnova, it’s already fully operative in our internal version (alpha). Anyone interested in trying this new feature out is more than welcome. Just drop me a line (support at ) and I will give more detail.

No comments: