Quantitation in GPC?

[Jaries]

We have been using GPC for a while now to measure Molecular weights of polymers. My question now is there a way to quantitate a compound via GPC. My understanding is that GPC is to measure Molecuar wieghts and not quantitate like in HPLC. I am trying to see basically if i can quantitate 2 different polymers that have different retention times(hence different Molecular Weights) when they are in a mixture. is this even possible via GPC and if so can you please explain ? Thank you so much!

[Bruce Hamilton]

As long as you have standards that match the components fo the samples, it's possible to quantitate.

In our case, we found for RI detection that the standards must be chemically identical and have a molecular size distribution very similar to the components of the mixture. For some reason, we got poor results when we used a set of closely-related MW standards - probably some RI difference in the polymer.

In one case we added a small amount of a narrow range polymer of the same type as an internal standard to improve precision, because we know that the total area response was lower than expected.

We just used the total area of each peak, and prepared some calibration mixtures at different concentrations and ratios.

Please keep having fun,

Bruce Hamilton

[Jaries]

Thanks Bruce!!


So we have this mixture of 2 polymers at different quantity 40:60 and 50:50. I am trying to see if i can quantitate this by GPC. GPC as I know is for determining Molecular weight from the Cal curve, however i was thinking if i can take the raw data of integrated peak value and use it for quantitation. That is considering I did a calibration curve of 30:70, 40:60, 50:50, 60:40, 70:30. Does this seem like a novel ideal or am I just making it easier than it should be?

[Bruce Hamilton]

If it works, do it.

Howver ( isn't life full of that word ) ...
- if the polymers give different area responses for the same mass injected, your calculations willquickly become more complicated.
- if you injections are not consistent the areas will change, even though the ratios may not.
- if you samples vary, the injected volume may vary

Adding an internal standard, and generating a calibration curve against the area of that IS peak for each polymer would improve precision and help overcome the above issues.

Please keep having fun,
Bruce Hamilton
“Aim high, there is little virtue in easy victoryâ€