How can I reference spectra that contain no CSI?
8 February 2016 Comments Off on How can I reference spectra that contain no CSI? FAQ - Processing Spectra
We recommend that you add a supported CSI to all samples intended for use with Chenomx NMR Suite (currently, we support DSS, TSP and formate). You should consider adding a CSI to any new samples that you intend to analyze using Chenomx NMR Suite. That being said, you can still extract some information from existing spectra of samples with no CSI.
When you open a spectrum of a sample that contained no CSI, you can now choose “none” as a CSI option. The software will try to automatically determine the best location for reference.
Although, we suggest that you still calibrate the spectrum manually to no CSI by referencing the ppm location to a known peak in the spectrum. In Processor, load your spectrum and calibrate your CSI. While calibrating, you can drag the x-axis at any ppm location that you wish to reference to.
When you have manually referenced spectra using this technique, please remember:
- Absolute compound concentrations measured in Profiler will be inaccurate, but relative concentrations will still be reasonably accurate. For example, if you measure acetate at 1 mM and alanine at 2 mM, those numbers will not necessarily reflect the ‘real’ concentrations of those compounds in the sample. However, it would be fair to say that alanine is present at twice the concentration of acetate.
- The transform windows may not be optimal for all compounds; you may not be able to move a cluster to exactly where you would like it to be. To fine tune your manual referencing, you can click Jump to Processor, tweak the CSI position in the CSI Editor, and then click Jump to Profiler to continue profiling.