GPC/MDS Triple detection and absolute molecular weight determination

Hello Andreja,

I just wanted to advise that 'data fit limits', have not been set correctly - please see the correct example below:

Hello.

Thank you very much for your answer.

I am now sending the data processing of one sample from start to finish. I hope it's correct. I am interested in what is the criterion for determining the limits (third picture). Do I have to take into account a pair of Mark-Houwink constants from the literature? Can the relative and absolute molecular weights be very different? I will be very grateful for any feedback.

Best regards

Dear Andreja,

The baselines should be set so that the peak to be evaluated is fully included and nothing is cut off in either the high or low molecular weight range. This looks good in your example!

The Mark Houwink constants can be included if they are known. This is especially important for the instrument setup.

Regarding your last question:
Yes, relative and absolute molecular weights can and will differ from each other - sometimes greatly. This depends on the dissolution behavior of the polymer in the solvent compared to the dissolution behavior of the calibration standards in the same solvent. For LS Mw determination, no conventional calibration in the background is needed - you get an absolute molecular weight is measured.

Dear Andreja,

The baselines should be set so that the peak to be evaluated is fully included and nothing is cut off in either the high or low molecular weight range. This looks good in your example!

The Mark Houwink constants can be included if they are known. This is especially important for the instrument setup.

Regarding your last question:
Yes, relative and absolute molecular weights can and will differ from each other - sometimes greatly. This depends on the dissolution behavior of the polymer in the solvent compared to the dissolution behavior of the calibration standards in the same solvent. For LS Mw determination, no conventional calibration in the background is needed - you get an absolute molecular weight is measured.