GPC/SEC peak integration - OpenLab CDS Rev. C.01.04(51) and Agilent GPC/SEC Software version 1.2 Build 3182.29519

Hi RedRidingHood,

Peaks are best interpreted baseline separated. Anything that is not part of the polymer peak should be excluded (impurities, system peaks, etc.). If you are not sure what your system peak is, blank injections can help. If the signal does not return to the baseline level after the peak, e.g. because the system peak has already started, you must be setting the baseline incorrectly. In this case, a column with a smaller particle and/or pore size will help to better separate smaller molar masses. Please also note that anything outside the calibrated range cannot be evaluated. For better comparability, the baseline criteria should always be applied in the same way.
In your case, this looks good. The peak at 10.5 min is already a system/solvent peak? Then you will have to set the baseline end at the minimum before that.

B rgds,

Anne

Hello,

thank you for your prompt reply. I suppose you commented point 3. The system solvent is THF, characteristic peak begins at approx. 12 min. The peak before is probably remaining solvent from polymer synthesis or monomers. In accordance with this where is the end point of baseline? Do I have first recognize the peak at 10.5 min? If it's solvent (not necessary THF) then the baseline end point is at the minimum before that peak? And if it's monomer then the baseline end point is at the minimum (maximum) before THF peak?

Thank you.

Best regards

Andreja

HI,

Correct, I commented on peak 3. If you are unsure whether it is a monomer rest or solvent rest from the reaction medium, you could also inject the monomer and reaction solvent as a sample and overlay the elugrams to identify it. Concerning your consideration: Whether it is solvent or monomer, you should exclude that peak from your baseline settings, because even monomer rests are somehow impurities that will falsify your results. You could also try to evaluate in both ways and see the difference in Mn/Mw.

Best,

Anne

Is that way now correct? No matter how many peaks are there? I have to orient on the last peak before "impurities", right? 

Next question: where is the first point of baseline estimated from the picture above? How could I know that? 

What about manually integration: can I choose 2 points of x-axis to do the integration (7th icon below)?

Thank you very much.

Regards

Andreja

Hi,

Yes it is right, please orientate on the last peak before the impurities start.

The exact baseline settings can be seen when enabling the peak information section below the analysis view (highlighted in green):

Manual integration limits can be set with the icon (highlighted in green):

Best,

Anne

Hi,

Yes it is right, please orientate on the last peak before the impurities start.

The exact baseline settings can be seen when enabling the peak information section below the analysis view (highlighted in green):

Manual integration limits can be set with the icon (highlighted in green):

Best,

Anne