Problems about Detect Negative Peak

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rigol
Posts: 75
Joined: Wed Aug 19, 2009 8:44 am

Problems about Detect Negative Peak

Post by rigol »

Dear sir:
I have some difficulty in seting detection inteval of Detect Negative Peak.In case the Detect Negative operation is active,I set Time A equals to 0.0,Let Time B equals to different values, and sometine these values differ only in 0.01,But we will get different results. Why is that?
Thank you !
negative-peak-1.jpg
negative-peak-2.jpg
Last edited by Daniel Mentlik on Mon Oct 24, 2011 10:42 am, edited 1 time in total.
Reason: EDIT: Added the screenshots

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Daniel Mentlik
DataApex Support
DataApex Support
Posts: 354
Joined: Fri Mar 27, 2009 3:15 pm

Re: Problems about Detect Negative Peak

Post by Daniel Mentlik »

Dear Daniel,
the images were not attached to the original post, most probably due to the image size. Please, send us both the images (with the graph and Integration table visible) and also the chromatogram file by email to support@dataapex.com . We will look into the matter.
Daniel Mentlí­k
DataApex

rigol
Posts: 75
Joined: Wed Aug 19, 2009 8:44 am

Re: Problems about Detect Negative Peak

Post by rigol »

OK,Thank you very much! I will send the email to support@dataapex.com .

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Daniel Mentlik
DataApex Support
DataApex Support
Posts: 354
Joined: Fri Mar 27, 2009 3:15 pm

Re: Problems about Detect Negative Peak

Post by Daniel Mentlik »

Dear Daniel,
I have added the screenshots from your e-mail to the first post in the topic. Also, as other people may find this topic helpful in the future, I will copy the answer by Ivan Vinš here:

The recommended procedure for this chromatogram is to optimize the global integration parameters first using the Global Peak Width and Global Threshold tools.
In your chromatogram, the peak width is set to the low molecular weight components, the threshold is set approximately twice the suggested value. Then set the detect negative only to the interval where negative peaks should be detected.
The integration of negative peaks in combination with positive ones is sometimes difficult. In some cases it is useful to specify separate (discontinuous) integration intervals for areas, where the positive or negative peaks should be integrated and apply detect negative for the desired areas only.
negative-peak-3.jpg
Please note we are working on a more user-friendly behaviour of integrating alternating positive and negative peaks, which may be present in some of the next releases of Clarity.

Best Regards,
Daniel
Daniel Mentlí­k
DataApex

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