Using GSD for multiplets analysis

Exploiting the power of GSD for an improved Multiplet Analysis

By default Mnova uses Global Spectral Deconvolution (GSD) algorithm for automatic peak picking and multiplet analysis.

Multiplet Analysis benefit directly from the exploitation of GSD capabilities to carry out the automatic analysis, with the enhanced peak picking capabilities resulting in much more reliable automatic multiplicity identification and labeling.

Here you can see an example of a triplet which is hidden under the solvent signal:

In order to use this algorithm, make sure that you have the following default options in Mnova.

1 – Defining the GSD level

GSD has different operational levels, ranging from a very fast but inaccurate method to slower but much more accurate levels. In addition, GSD allows the automatic recognition of solvent peaks, impurities, etc. We recommend to use a GSD level of 1 (flash) or 2. This level can be set from Peak Picking/Options as depicted below:

Also, make sure that the Auto Classify option is checked.

From now on Mnova will use GSD when automatic peak picking algorithm is issued (which is the default setting).

2 – Set the Automatic Integration method to GSD

Finally, for Mnova to be able to detect the multiplets regions automatically using GSD, it’s necessary to define the 'peaks' as integral calculation method under the 'multiplet options' (this should be the default setting).

First Order Multiplet Analysis with GSD with Resolution Enhancement

(click here to download the spectrum used)

Consider the following multiplet:

At first sight, this looks like a doublet quadruplet (J = 12.2 x 3, 3.6 Hz) and in fact, this is what some NMR software packages would report if this multiplet were analyzed using based on traditional peak picking algorithms.

Now Mnova Multiplet Analysis is armed with GSD, making the analysis of NMR spectra a more efficient process. Assuming that all Mnova options have been set properly in order to use GSD for multiplet analysis, this is what Mnova would report for this multiplet:

As it can be noticed, Mnova now finds an extra coupling of 11.4 Hz. If we take a closer look at the fine structure of the multiplet once GSD has been applied, we can observe that the 4 peaks in the center of the multiplet are actually split into 8 peaks as illustrated in the figure below: