Subtraction of Blank peak areas from ares in a test sample

<p>Hi,</p><p></p><p>In our Blank chromatogram (sample name <strong>Blank 1</strong>, located on the beginning of a sample set) two small peaks appear (<strong>Peak 1+2</strong>). During our method development it wasn't possible to remove these peaks.</p><p></p><p>In the chromatograms of the following standard and test samples <strong>both peaks</strong>also appear and coelute with two other peaks at the same retention time. Both peaks (Peak 1+2) are listed with the same name in the component table. </p><p>Is it possible to subtract the blank peak areas of this two peaks from the areas of the two peaks in standards and test samples before calibration?</p><p></p><p>I tried to solve this problem with the aid of custom fields and a inter sample calculation, but found no working solution. Neither in the empower help nor in the documents from a custom fields seminar appropriate information to my problem was found.  </p><p></p><p>Any ideas to entries in component table columns and formulas in custom fields?</p>


  • Hi Gerhard

    This can be done with an intersample calculation like the one described in the attachment.

    let me know if you need further advise.

    best regards


  • Hi Rune,

    we carried out the steps shown in your attached pdf-file, but in our column Area_Subtr no subtraction occured. I think it's the best that I first list our basic ideas for this analytics.

    - both peaks that should be subtracted are not located under the standard and internal standard

    - we  need an internal Standard (C17:0, line 6 in the component table)

    - therefore later calculation is running via response

    - our goal is the calculation of the fatty acid profile via standard calibration and obtained amounts (without peaks like Blank, internal standard  or BHT)

    - we are not shure, if our constructed component table is correct (for example column CCompRef1, Curve Reference)

    best regards


  • Hi again

    I think the problem is that you have entered "Don´t process and report" for you blank in the sample set and your calibration and quantitate only works for the labels s and u so the blank injection is never processed. Try and change the processing to normal for the blank and se if this helps.

    Otherwise I think you should contact you local Waters office and get some help from them.

    best regards


  • Hi rune,

    the problem was the entry "Don´t process and report" for our blank in the sample set. We changed the entry to "normal" and all works.

    Thanks for your ideas