How to use noise of a fixed RT range for S/N determination

Dear all,I am using Empower 3 and want to calculate S/N based on the noise of a blank run. Deviating to USP, EP or JP I want to determine the noise in a fixed retention time range (13-18 min, not averaged) and use this noise for S/N calculations of all peaks. I managed to define the blank runs but for me it looks like the software is not exactly doing what I want it to do.Does someone know how I exactly have to set up the processing method?Thanks in advance!Marko

Comments

  • I think you are trying to use a mix of the new EP S/N   (going to a designated blank run) but without the X * Peak width based around Peak RT that EP uses.

    I think you will have to use the old fashiioned Noise calculations, but with an inter sample custom field to get that noise from a region in the correct blank peak ( using regular labels).

    Heather

  • Dear Heather,

    thanks for your advise. I know it is kind of unusual but this is exactly what I want to do. I am just getting used to Empower and don´t know all commands yet. Can you please tell me the full "Calculated Field Formula"?

    I think it should be something like "2*Height*Scale to µV/(Blank.1.SAME(Peak to Peak Noise))" but how can I configure the retention time window?

    Marko

  • Marko

    I am a bit out of touch with these, but I think you don't want the SAME as that refers to a peak name, and there will be no peak in the blank.

    The noise is a result level field as you specify the kind of noise and the region in the NOISE AND DRIFT tab in the processing method. I think you might be able to just skip the SAME part of the custom field  ie Blank..(PeaktoPeak Noise)

    Heather

  • Hi Marko

    The attached Technote might be useful.

    best regards

    Rune

  • Dear Heather, dear Rune,

    The informations you provided are very welcome. Now I understand Empower much better than before. Nevertheless I was not able to perform the calculations I need. I am validating a HPLC method and my protocol says that I have to determine the noise of the blank run in the fixed interval between 13.00 and 17.00 min. This noise has to be used for s/n calculation of all peaks of interest measured in the whole validation sequence. I also have to report the noise itself to allow my reviewers to check if the calculations were done correctly. Unfortunatelly I do not have the privilidge to use customs fields and I am very afraid that I will not be able to do it without it.

    Thanks again for your so far given advise.

    Marko

  • Hi Marko

    I am afraid that you will have to use custom fields if you want to calculate the way you described. The noise interval from 13-17 is set in the noise and drift tab of the processing method so this is no problem. The noise valu can be reported or viewed in review.

    best regards

    Rune

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