Wolfgang Radke

Reliable calibration curves in the low molar mass region can be obtained when using the elution volumes of all separated oligomers of low molar mass standards on high resolution columns. This article explains how to do this.

How to overcome calibration issues in GPC/SEC using DMF and DMAc.

How do you judge the potential success of separating two polymers using GPC/SEC?

Determining a theoretical number of plates is an effective tool to ensure that the column is still applicable for the desired separation.

Determination of molar mass distributions and the molar mass averages derived therefrom are the main objectives of gel permeation chromatography/size-exclusion chromatography (GPC/SEC) analysis. But what is the meaning of these averages and how are they influenced by the setting of baselines and integration limits? This instalment of Tips and Tricks in GPC/SEC will try to provide a better understanding.

This installment of Tips & Tricks will provide some helpful pointers to keep your GPC/SEC system in good shape.

This instalment of Tips & Tricks discusses the effect of column order on separation efficiency.

What experimental details need to be considered when analyzing PEGs?

The benefits of a molar mass distribution over molar mass averages and the differences between the different representations of molar mass distributions are discussed.

This instalment of Tips & Tricks focuses on whether a complete separation can be achieved using GPC/SEC and, if so, under what conditions.

Often incorrect conclusions on molar mass and molar mass distribution are drawn by simply looking at a chromatogram. However, certain valuable information can be obtained directly from the chromatogram. This instalment of Tips & Tricks will deal with some common misinterpretations of chromatograms.

This instalment describes the interplay between column length, pore size distribution, and particle size to optimize GPC/SEC separations.

Hydrolyzed collagens (collagen peptides) are water-soluble products obtained by hydrolysis of natural proteins and used for dietary supplements. A simple GPC/SEC method is described for molar mass determination of collagen peptides, allowing reliable molar mass determination using ultraviolet (UV) detection.

How to create a calibration curve when no chemically-matching reference materials with narrow molar mass distribution are available.

A review of alternative approaches to narrow standard calibration.

Gel permeation chromatography/size-exclusion chromatography (GPC/SEC) columns are filled with porous particles differing in particle and pore sizes. Typical particle sizes in analytical GPC/SEC range from sub-2-µm particles applied in oligomer and protein separations to approximately 20 µm for separations of ultrahigh molar mass macromolecules (1,2). While the effect of combining columns of different pore sizes has previously been discussed in GPC/SEC Tips & Tricks (3,4), the effect of combining columns of different particle sizes has not been addressed before.

While gel permeation chromatography/size-exclusion chromatography (GPC/SEC) of uncharged molecules in organic eluents in most cases is a straightforward task, aqueous GPC/SEC of polyelectrolytes usually requires more parameters to be considered and optimized. This instalment of Tips & Tricks explains more.

The intensity of the light scattering signal depends on concentration, molar mass, and the specific refractive index increment, dn/dc, of the sample. dn/dc therefore usually needs to be known to derive molar masses by gel permeation chromatography/size-exclusion chromatography-light scattering (GPC/SEC-LS). How to overcome the issue of unknown refractive index increments is outlined in this instalment of Tips & Tricks. In particular, a new approach to derive molar masses by GPC/SEC-LS that requires only the molar mass of a reference material, and not the dn/dc of the sample or of the reference material, is introduced.

Combinations of detectors are often used in gel permeation chromatography/size-exclusion chromatography (GPC/SEC) to measure absolute molar masses or chemical compositions as a function of elution volume. Such multidetector setups require the correction of the delay volume between the detectors for correct data processing. This instalment of Tips & Tricks explains more.

The vast majority of macromolecules exhibit a molar mass distribution that is often described by the polydispersity index (PDI). This Tips & Tricks instalment offers practical advice to consider when analyzing macromolecules using liquid chromatography (LC).

Branching is one of the parameters chemists can adjust to produce polymer materials with optimized physical properties. Chromatography and advanced detection can help to characterize branched molecules. This instalment of Tips & Tricks explains more.

Experienced gel permeation chromatography/size-exclusion chromatography (GPC/SEC) users know that equilibration of the columns takes much longer than the time needed by the pump to produce a constant flow. An analysis in this phase would clearly yield different results from those achieved after complete equilibration of GPC/SEC columns. Furthermore, false but constant flow rates affect the molar masses derived from a GPC/SEC calibration curve. An internal flow marker can help to increase reproducibility and accuracy of GPC/SEC results.

Tips & Tricks GPC/SEC: Answering Common Questions About GPC/SEC Columns

Calibration using broad standards in GPC/SEC is discussed.