Expert Insight: Advanced GPC Technology as a Part of Solving Complex Polymer Problems: Exclusive Webinar Highlights

28 Nov 2014

Discover how the Waters ACQUITY Advanced Polymer (APC™) system enables improved efficiency and characterization of the analysis of problematic polymers, such as low molecular weight polymeric materials.

Scott D. Hanton (General Manager, Intertek Allentown), and Tanya Tollifson (Senior Marketing Manager, Waters Corporation), describe the advantages of APC technology over traditional GPC techniques. A wide range of applications areas are highlighted, such as synthesis, regulatory and R&D analyses. A summary of the question and answer session is provided below. To watch the webinar on-demand, click here.

1. Is APC molecular weight always higher than GPC?
Scott: Not necessarily, we have shown cases where it has been higher and some lower. The most common is a slightly higher value for APC, but this does not always occur.

2. How do you decide on the mobile phases for various sample types?
Scott: Solubility is a key problem with size exclusion chromatography and it is very important to ensure the polymeric material has fully dissolved before injection into the instrument. In our lab, we see understanding the solubility of the sample as a separate initial step, prior to GPC analysis.

3. Have you tried using a multi-angle light scattering (MALS) detector with APC? If not, do you think MALS would be able to reconcile the MW differences observed between traditional GPC and the APC?
Scott: The short answer is no, but we really want to try it! We are in discussion with the market place to find a MALS that will have the size components necessary to link with the APC hardware. The particular construction of the detector is crucial in order to retain the benefits we see from the APC and we are currently exploring this further.

4. Where can I find the APC selection tool?
Tanya: The APC selection tool is available on the Waters website. If you look-up either APC columns or APC system, there will be a link to the selector tool.

5. Can an organic APC column tolerate some water?
Tanya: Yes, we have multiple customers that use different additives, which may be aqueous, and add these to their main organic solvent. It is possible to use aqueous solvents on both the XP chemistry and the AQ chemistry systems.

6. Is APC available for high temperature operation, such as trichlorobenzene as solvent at 150 °C?
Tanya: The APC system is targeted at room temperature applications. It has a column compartment that goes up to 90 °C, but the sample compartment only goes up to 40 °C. The temperature in the column compartment is targeted for dealing with viscosity, such as solvents that are much more viscous at the flow rates selected. So no, there is no compatibility with the high temperature solvents.

7. I'm very interested in the potential for HFiP work. What is the trade-off for time vs. flow rate for total solvent consumption per analysis? Are there potential materials of construction problems for the APC hardware?
Scott: We are at the beginning of our exploration with HFiP, but we do know of other labs that are doing it. Firstly, we know it is possible because others have done it, plus, the columns and hardware are compatible enough with HFiP to get the benefits. There are two clear benefits to the APC system; lower solvent consumption, and the speed of the experiments. We are working with Waters regarding preventative maintenance when using solvents such as HFiP.

8. You probably know that Wyatt Corporation already has suitable flow cells for MALS and DRI?
Scott: Yes we are aware and we are in discussion with them currently.

9.Is sample concentration and injection volume the same with APC and GPC?
Scott: Yes they are similar. If anything we may reduce the volume slightly for APC, but not by much.

10. Could APC be used with other low dispersion RI detectors?
Tanya: It is possible to use other detection techniques with the system. At Waters we offer RI, tunable UV detection, photodiode array detection and evaporative light scattering. If you needed another technique there are other suppliers that can provide them.

11. What is the maximum working pressure of the column?
Tanya: The APC system is able to manage system backpressures of up to 15,000 psi. In terms of the columns we have ratings on them based on flow rate and the viscosity of the solvent. When using the larger pore size columns you will need to reduce the flow rate to ensure the columns remain stable.

12. How long does it take to change solvents systems? How many times can you change the solvent before the column deteriorates?
Tanya: The columns can equilibrate into another solvent very quickly (approx. 15 minutes). If you have an RI detector in the system, which is very sensitive to the change in eluent it can take up to 3 hours to equilibrate. Other labs regularly change solvent and do not see degradation from changing the solvents. It is possible to have a long lifetime of the column even with multiple solvent changes.
Scott: We have seen some solvent contamination from samples we have injected. However, we have never seen any issues due to changing of solvents.

13. Is it possible to use GPC columns on a APC system?
Tanya: Yes, absolutely.

14. What have you noticed in terms of polymers reacting with the columns? Have you seen any polymers that degrade the column particularly harshly?
Tanya: No. But, if you have a polymer that interacts with a GPC column it is just as likely to interact with an APC column. You may need to add some additives to reduce interactions with the surface chemistry.
Scott: Amines are a good example here, where they do not degrade the columns but can cause contamination by sticking to the column.