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

MarkoG

<p>Dear all,</p><p></p><p>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.</p><p></p><p>Does someone know how I exactly have to set up the processing method?</p><p></p><p>Thanks in advance!</p><p>Marko</p>

HeatherLongden

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

MarkoG

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

HeatherLongden

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

rune

Hi Marko

The attached Technote might be useful.

best regards

Rune

MarkoG

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

rune

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