Image Credit: Jordi Labs
Gel Permeation Chromatography (GPC) is an effective method that offers direct quantification of molecular weight, a crucial feature in characterizing synthetic and natural polymers.
No universal GPC system exists that can differentiate every polymer based on size alone, so how does one select the correct column customized directly to the sample in question?
Choosing a mobile phase
The mobile phase is the starting point for this process. What is the sample polymer soluble in? An insoluble polymer cannot be measured by GPC, making the choice of solvent important. For a fast GPC separation based only on size, the ideal solvent must be sufficiently strong to reduce the sample-column interaction.
Don’t sacrifice on resolution
It is crucial to decipher the required resolution level for the standards and samples when selecting GPC columns.
The golden rule must be considered: separation efficiency and resolution are increased directly with the volume of the column. The internal diameter (ID) and length of each column must be carefully observed before buying any column set. Jordi Labs suggests the following:
- Utilize a column that is longer, or use several columns in series (two 30 cm in series compared to one 30 cm column)¹
- Select a column that has a bigger internal diameter (22 mm compared to 7.8 mm)
Including an extra column in addition to the existing system is a beneficial solution to poor resolution. “Free resolution” can be acquired by selecting the ideal injection volume/concentration for the system or by increasing the temperature of the column.
Pore size matters
A non-interactive stationary phase, comprising a porous network, is used by GPC, which enables an elution order established on decreasing molecular size. There are various pore sizes, and each pore size is suited for separating a particular range of molecular weight (Table 1).
For unknown or routine sample analyses, the Mixed Bed packing is highly recommended, which is a linear column. The pore size of the column should be selected depending on the estimated molecular weight range of the polymer being studied.
“It’s just a phase…”
To summarize the findings from this article:
- The pore size is based on the predicted MW range of the sample
- The chromatographic eluent depends on the solubility of the sample
- The amount of dimensions and columns is based on the required resolution
To learn more, please contact a member of the Jordi Labs team today with any queries regarding gel permeation chromatography or choosing a GPC column.
¹This would produce a 2-fold increase in pore volume, based on a column length increase.
About Jordi Labs
Jordi Labs provides the highest quality contract analytical services and polymer HPLC columns to some of the world’s leading consumer products, polymers, pharmaceutical and medical device manufacturers. Our team of PhD analytical chemists specialize in chemical identification. One of core competencies is Extractables & Leachables testing.
We are also worldwide leaders in;
- Particulates & residue analysis
- Good-bad comparisons
- Method development/validation
- Polymer analysis
- Polymer failure
We also help companies from Fortune 500s to innovative startups with method development, preparative HPLC, training seminars, depositions and consulting. As a family company, we take pride in the production of all of our products and analytical service offerings. It is our goal to help our customers overcome their analytical challenges by providing excellent products and personal assistance from our highly-trained staff of PhD chemists.
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