TEMPR Learning organized its first event - the SEC-MALS Workshop - on April 3, 2025.

More to come.

What the Jargons

Mixing things can be fun, we know that from watching kids putting play doughs of different colors together. It is a different story, however, if you ask them to separate them. You think, why would I want to do that? It turns out that the separation of matters is as important as mixing them, if not more, once you want to make the world a better place by being a scientist.

SEC, size exclusion chromatography, a.k.a. gel permeation chromatography (GPC) in the polymer field, is a method for separating matters - as its name suggests - by their sizes. To make it work, a column is packed with porous beads made of materials like crosslinked dextran, agarose, or polystyrene. These beads have pores of various sizes by design. As a sample mixtures flow through the column, matters enter or bypass the pores depending on if they fit in:

• Larger ones cannot enter any pores and therefore move faster out of the column.
• Smaller ones visit pores of various sizes. The detour makes a long stay and is, therefore, the last to emerge.
• Anything in between behaves intermediate in order.

In its a little over 50 years of history, SEC has evolved into an essential tool in biotech, pharma, nanotech, and polymer industry, shaping everyday life with new materials.

Detection Methods

Once the matter is out of the column by size, how to tell it's there?

Scientists developed all kinds of ways for this purpose: optical responses, light emission, viscosity, mass spectrometry, or even better, measuring size/mass. By interacting with particles using controlled light (laser), sizes beyond the naked eye can be visualized from light that scatters off particles from different angles. This is light scattering detection at multiple angles, or Multi-angle light scattering (MALS).

Most methods rely on reference standards to identify the unknowns by comparing them under the same conditions. Light scattering, however, determines molar mass directly from the nature of the material and how it interacts with the media and the light. This is important for materials that do not have standards to compare with. It is not a surprise that all new materials are in this arena.

With all the tools available to us, optical absorption, refractive index, fluorescence, viscosity, and light scattering, targeted information of a given material is at hand. Moving beyond academic research, industry weighs heavy in SEC-MALS for product development and R&D, in areas of molecular biology, biomedical, pharmaceuticals, and polymer chemsitry.

Takeaways from the Workshop

• We get to know this important tool for separating materials and the detection methods available for researchers in different fields - biomedical, pharmaceutical, and polymer industry.
• The conventional time method disregards material structure by comparing to standards with different conformations. Light scattering, however, takes into account the structure factors unique to each material, which offers a much more accurate picture of the substance.
• A deep dive into the mechanism behind light scattering in real industrial settings shows how molar mass, size, conformation, and branching of polymers can be determined with SEC-MALS.
• dn/dc, an important parameter in MALS, reflects how a certain material reacts to its surroundings. It considers chemical structures, dispersion media, environments, and light-matter interaction. Understanding the meaning of dn/dc and ways to measure it is a necessary task for the next generation of scientists transitioning from academia to industry.
• Software, data interpretation, and data visualization in SEC-MALS help with experimental design for proposing projects, monitoring progress, and evaluating outcomes.
• Relevant knowledgebase of practical use of SEC-MALS moves us closer to real world applications, away from the learn-for-test mindset.

About Our Guest Speaker

We thank Parker Lee from Waters | Wyatt Technology for joining us to discuss SEC-MALS. He joined Wyatt Technology in 2022 as a Field Application Scientist II and teaches customers light-scattering applications to improve and accelerate their research.  He earned his B.S. in Biological Systems Engineering from Virginia Tech and his Ph.D. in Macromolecular Science and Engineering from Case Western University.

About TEMPR Learning

TEMPR Learning is an initiative to bring together materials scientists from all sectors to share, learn, and collaborate. We want to bridge the gap between education and real life. What you learn is supposed to give you an edge to be an essential part of the world. Let's make sure there is one.

Join Us - Learn and Contribute

We organize workshops, webinars, lectures, discussions, and more. Free to everyone. Join our TEMPR Learning group for all future events, learn, share, and contribute to free learning.

References

Porath, J., & Flodin, P. (1959)."Gel filtration: a method for desalting and group separation by means of dextran gels."Nature, 183 (4676), 1657–1659.

W. W. Yau, J. J. Kirkland, D. D. Bly (1979)."Modern Size-Exclusion Liquid Chromatography: Practice of Gel Permeation and Gel Filtration Chromatography."Wiley-Interscience.

Andrews, P. (1964)."Estimation of the molecular weights of proteins by Sephadex gel-filtration."Biochemical Journal, 91 (2), 222–233.