Shodex Column Selection for High Molecular Weight Polyacrylamide (Aqueous SEC/GPC)

Record: 563

Category: Column Selection
Product: SB-807 and SB-806
Sample: Polyacrylamide 

Question
A customer needs to analyze partially hydrolyzed polyacrylamide (aqueous) to measure molecular weight distribution (polydispersity index) using GPC.

Sample conditions:
Polymer concentration: 1000 ppm
Sodium carbonate: 5000 ppm
Molecular weight range: 2–20 million Da

What Shodex columns are recommended?

Answer
For aqueous size exclusion chromatography (SEC/GPC) of high molecular weight polyacrylamide, Shodex OHpak SB series columns are the recommended choice. These polymer-based columns are designed for water-soluble polymers and provide separation across a wide molecular weight range.

Given the very high molecular weight range (2–20 million Da), selection of appropriate pore size is important. Larger pore size columns such as SB-807 HQ are more suitable for very high molecular weight species, while SB-806 HQ can be used to extend separation toward lower molecular weight fractions.

In many cases, a combination of columns may be used to cover a broad molecular weight distribution. However, the optimal configuration depends on the actual distribution of the sample. If the sample contains a significant portion of lower molecular weight components, inclusion of smaller pore size columns may be beneficial.

If additional information on the molecular weight distribution is available, column selection can be further optimized.

Recommended Applications:

• Polyacrylamide (SB-805 HQ)
• Polyacrylamide – Comparison of SB-807 HQ and SB-806 HQ

Additional Comments

For high molecular weight polymers, it is recommended to use lower injection volumes and appropriate sample concentrations to avoid overloading effects, which can lead to peak distortion and reduced accuracy in molecular weight determination.

The presence of sodium carbonate (5000 ppm) should also be considered. Salt is commonly used in aqueous SEC to minimize secondary interactions, but the sample and mobile phase should be matched as closely as possible to ensure stable and reproducible results.

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