Accurate analysis of your NMR spectra with Chenomx NMR Suite requires preparing good samples and acquiring high-quality spectra.
Preparing your samples properly helps you get the best possible results from your analyses with Chenomx NMR Suite.
Your samples must contain an internal standard for accurate quantification using Chenomx NMR Suite. The internal standard solution recommended for use with Chenomx NMR Suite contains the following components:
To prepare the Chenomx-recommended internal standard solution:
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To the desired volume of 99.9% D2O, add 5 mM 2,2-Dimethyl-2-silapentane-5-sulfonate (DSS) as a chemical shape indicator (CSI) and 0.2% w/v sodium azide (NaN3) to inhibit bacterial growth.
Remember that DSS is hygroscopic in the solid form. For accurate concentrations from a Chenomx NMR Suite analysis, you must determine the final DSS concentration accurately.
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For optional pH measurement in Processor, add one or more of 100 mM imidazole, 100 mM creatinine and 20 mM DFTMP.
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Adjust the resulting solution to about pH 6.5.
Add the internal standard as a 1 in 10 (10% v/v) spike to each of your samples. For example, add 70 μL of the internal standard to 630 μL of a sample to be analyzed for 700 μL of spiked sample.
Tips and Tricks
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Instead of DSS, you may use 3-trimethylsilylpropionate (TSP or TMSP) or formate as a CSI. However, we do not recommend TSP or formate, as their chemical shifts are sensitive to pH.
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For accurate sample analysis with Chenomx NMR Suite, the pH of your samples should be between 4 and 9, and ideally close to 7 for manual analysis.
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Spectra that are poorly collected or collected from samples that are poorly prepared may be difficult or even impossible to convert, process, and analyze accurately.
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If you choose not to add any pH indicators to your samples, you still need to supply a measured pH value for proper analysis with Chenomx NMR Suite (see “Calibrate pH”). More accurate pH values for your samples allow you to make better use of pH-sensitive signatures to profile spectra of the samples.