How to calculate ratio of two different wavelength for peak(s) in given sample - Any Suggestion

I have two different wavelengths collected in given sample that has more than single peak, need to find the ratio of wavelength1/wavelength2 for all the peaks in the sample.
Any suggestion appreciated.

Best Answers

  • Accepted Answer
    This Empower Tip of the Week may also help.  It was written about QDa but should be similar for PDA.
  • Accepted Answer

    Dan you are correct, the ratioplot will only give a visual of the peaks when displayed as a ratio, and not peak area.If you want that, you need a peak real cf and include the channel names in your formula. For instance, derive 2 channels with the fixed wavelengths and call them 250nm and 210nm. Then your cf formula is U%.%.250nm(Area)/U%.%.210nm(Area) and this will display the peak area ratio from the 2 wavelengths presuming your unknown samples are labelled as U...etc.

    Or you could try MarcNoble idea.


  • Are you using a PDA? If so, In the method set used to acquire the data, create a derived channel called Ratioplot. Open your method set, right click on Derived Channel< New Derived Channel and pick Ratioplot, pick your Numerator wavelength, your denominator wavelength and a minimum value, call the derived channel something like Ratio and assign a processing method beside it when it appears in the Channels table.

    Save all changes, open up some raw data, apply method set and in the 2D channels tab, your Ratio should be populated with each peak value of 1 wavelength divided by another.

  • Of course, if you're after the ratio of peak areas for the same peak(s) collected at different wavelengths, that's a completely different question from what the derived channel will yield... you'll need a CF that calls out the peaks by channel description or ID to get there.
  • @ Empower2019:
    I have tried your option with using method set used for acquire data, but I don't find the option for Derived channel with RatioPlot, but if I do new MS it has option for "RatioPlot".
    I have to try MarcNoble suggestion.
  • I have tried the article provided by MarcNoble, it works fine and no additional Cfs required. It gets more complicated, if we have more than one peak makes in a given sample.
    Also, I have tried extracting derived channels using acquisition method set with two different channels and processed new Cf as channel1/channel2, It provides the same results as Peak Ratios output. 
    Thank you Both.
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