Purity

This new feature is an enhancement of the Purity calculator script by using the qNMR engine to automatically select the best multiplets in a spectrum and use them to calculate concentration using a number of industry standard approaches. Analysing sample replicates is facilitated.

The workflow would be the expected. We describe the process for a spectrum of Felodipine with TCNB (tetrachloronitrobenzene) as an internal purity reference. Open your dataset with the molecular structure and apply an automatic multiplet analysis (you can download the dataset and the libraries from this link):

Next, follow the menu 'Quantitation/qNMR/Purity' to display this dialog box:

The next step will be to define the settings, by clicking on the applicable button. For this example, we can load the 'Purity_settings.data file (by clicking on the load button highlighted in red in the picture below)

We will also need to define our 'References Library' by clicking on the 'References' button of the 'Purity panel'. From here, you could create your own 'References Library' or click on the 'Load' button to import the 'Purity_References.data' file (From the zip file):

Once the library has loaded, we can click on the 'TCNB' row to use the applicable values. You could also type the reference compound details by hand (instead of loading the settings):

Note that if your purity standard is not in the list, you will have to manually add it. From the References library panel, you could enter the information of your reference compound (Molecular weight, purity, ppm range(s), etc.); next, click on the blue “+” button to add it to the library and finally click on the save button to the keep the changes.

Click on the OK button to fill the 'Purity' dialog box with the information about the 'reference compound'

The next step would be to fill the reference weight (8.182 mg of TCNB for this example), the molecular weight of our compound (384.2538 g/mol) and the sample weight (11.631 mg of Felodipine).

Please bear in mind that if the spectrum was acquired including the sample and the reference details under the 'Comment' field of the 'Parameters Table' (by using the format displayed in the screenshot below: SW for Sample Weight; RW, for Reference Weight, MW: for Sample molecular Weight and CR: for compound reference (or RN or even Reference Name), or even SM: followed by a molecule in smiles format, or NS: for Number of scans), we could parse them just by clicking on the 'Read Parameters' button, so we will not need to manually type them on the Purity panel. If your document contains the molecular structure, the MW will be obtained from there (and not from the comment field).

Finally, click on the 'Calculate’ button to get your purity result (98.3%) and paste the result in Mnova by clicking on the 'Paste Report' button:
 

Clicking on the Results Manager button will display a drop down menu which will allow you to 'Load Results' (in the Purity Results panel) or to 'Open the Results Manager'

Clicking on the Table Setup button will allow you define the number of decimals places:

Advised Calculations

You could also use the 'Advised Calculation' button which will apply an Automatic Multiplet Analysis (Peaks as integral calculation method) with Reference Compound Integration (Peaks as integral calculation method). The 'Advised Calculations' feature will also read the parameters (SW, RW, SW, CR) from the metadata (if they are included in the 'Comments' field of the 'Parameters table'). It will also run an Auto Assignment if a molecule is present; if not, an automatic multiplet analysis will be performed. Finally, it will display the 'Purity results'.

From the settings, you will be allowed you to define the 'Advised Processing' options (Auto Reference and LP) and the integration method (Sum, Peaks or Edited Sum), Peak Picking and Multiplet analysis settings:

Replicates

It is quite often the case that an analysis is performed with replicates: duplicate, triplicate, etc. samples. That is, 2 or 3 samples of the same compound and reference standard are made, and their spectra recorded. In this case the analysis of the replicates is facilitated allowing the user to apply the same analysis on all samples, and determine an average purity for the replicates.

After performing the analysis on the first sample, you could need to create a library of experiments. To do it, just check the 'Experiments box' and click on the 'Open Experiments Library Manager' button and select 'New Library' (which will be saved at the desired folder):

Next click on the 'Create New Experiment' button':

That will save the selected multiplets, ref. compound, compound MWt - things that stay the same from sample to sample in the replicates. When the 2nd, 3rd, etc. sample is active, press "Apply experiment" button to replicate all the qNMR Purity parameters except the weights of sample and reference. In the last replicated sample you will get the averaged purity value.

Clicking on the 'Edit Current Experiment' button, will allow you to change the current experiment:

Clicking on the 'Open Replicates Manager' button will allow you to see (select/deselect/delete) the results obtained:

Here you can find the formulas used for the replicates statistics calculations and for the global results calculations:

Reports

You can easily report your purity results into your Mnova document or export them to a file. Clicking on the 'Settings' button will allow you to customize the 'Basic' and the 'Advanced Reports':

Here you can find an example of a basic report:

You can also create templates for more advanced results:

Clicking on the settings button will allow you to customize the fonts or to use your own layout template:

Here you can find an example of an advanced report:

Please note that the advanced reports will be automatically updated if you change the analysis of your spectrum (for example the selection of your multiplets):

Visit also our blog:

http://mestrelab.com/blog/what-is-qnmr/

http://mestrelab.com/blog/qnmr-the-best-pulse-length-for-acquisition/

http://mestrelab.com/blog/edited-sum-integration-for-qnmr/

http://mestrelab.com/blog/determining-concentrations-when-using-nmr-to-model-chemical-reactions/

http://mestrelab.com/blog/nmr-quantification/

http://mestrelab.com/blog/automating-qnmr/

http://mestrelab.com/blog/qnmr-purity-recipe-book-i/

http://mestrelab.com/blog/qnmr-purity-recipe-book-ii/

http://mestrelab.com/blog/qnmr-purity-recipe-book-iii/

http://mestrelab.com/resources/getting-picky-with-q-nmr/

http://mestrelab.com/blog/new-qnmr-experiments/