Advancements in Multi-Detector GPC/SEC

Interview conducted by G.P. ThomasApr 13 2015

AZoM talks to Mark Pothecary, Product Manager for size exclusion chromatography products at Malvern Panalytical, about the new OMNISEC gel permeation/size exclusion chromatography (GPC/SEC) platform.

Could you please introduce OMNISEC and explain the separate modules of the system?

OMNISEC is our latest integrated and complete size exclusion chromatography or gel permeation chromatography system for the analysis of synthetic polymers, natural polymers, polysaccharides, and proteins.

OMNISEC is a system in two parts; two modules. With OMNISEC RESOLVE, we have separated and integrated all the chromatography equipment (the pump, degasser, autosampler, and column oven) altogether to consolidate the separation side of the process.

In the second module, OMNISEC REVEAL, all the detectors are integrated into a single unit because it brings technical benefits to the chromatography performance, and in the result quality and accuracy overall.

Within OMNISEC REVEAL are the four detectors that we typically use for what we would call advanced size exclusion chromatography. There are two concentration detectors: the refractive index detector and the UV/Vis absorbance photodiode array.

There is also a light scattering detector for the measurement of molecular weight, and an intrinsic viscosity detector or viscometer, which allows measurement of molecular density and molecular structure.

What inspired the development of OMNISEC?

We really looked at the challenges that we face making size exclusion chromatography measurements, and also those of our customers as well.

One of the key drivers for the development of OMNISEC was feedback from our customers, both in terms of the challenges they face with their own samples and also the challenges they face in terms of making size exclusion chromatography measurements.

We wanted to develop a system that was a step ahead of the current generation of units, both in terms of sensitivity and accuracy, and also in terms of usability, performance and robustness.

Could you give an example of a challenge that is often faced?

There are many polymers that have a low dn/dc or are only available in small amounts at very low concentrations. So being able to measure as small a mass as possible and at the maximum sensitivity is really important.

Likewise with proteins, many proteins have only been purified in very small amounts, and so customers are really looking for the ultimate sensitivity that they can achieve, and to use as little of their sample as possible.

How was the user experience taken into consideration?

With regards to the user experience, we've really worked in two areas. One is the usability - we've developed a whole new software platform, with a workflow based design going through system setup, data acquisition, and data analysis to give the user a more intuitive process and experience.

The other side of that is robustness. We really addressed that, particularly in the viscometer, where we've redesigned the viscometer with a self-balancing mechanism and user replaceable capillary bridge.

How is OMNISEC unique compared to other instruments in this area?

Temperature control is very important, and within OMNISEC the autosampler, column oven, and detector module are all independently temperature-controlled.

With the autosampler, for instance, this allows you to cool down protein samples to preserve them from aggregation.

In the column oven, it improves the quality of the overall chromatography, and in the detector module, the temperature control covers not just the detectors themselves, but also the inter-detector tubing to really maximize the baseline stability and the result quality.

What are the key application areas of OMNISEC?

We divide what we consider our market into about three different areas: synthetic polymers, natural polymers/polysaccharides, and proteins.

Synthetic polymers tend to come out of the more industrial space, so anything from bottles to car bumpers as well as tablet coatings. In general, any polymer that's used where the molecular weight and intrinsic viscosity or molecular structure of the molecules really affects the bulk performance of that polymer – for example, making it stronger, more flexible or degrade at a defined rate, for instance.

In terms of natural polymers and polysaccharides, these mainly come under pharmaceuticals, so skincare products, eyedrops and tablet excipients. In pharmaceuticals, it could be how quickly a drug is released in the stomach, for instance, or at what point through the digestive tract it is released. Polysaccharides are also widely used in the food industry as thickening agents and gelling agents.

The protein field comes into either university research, where people are trying to investigate novel proteins as they purify, or in the biopharmaceutical world, where people are using monoclonal antibodies as anti-cancer and other drugs. Here, people are interested in the molecular weight - they want to see that they've got the right protein and it has the right oligomeric state. People are also interested in studying and, indeed, eliminating aggregates from their samples.

What are the main benefits of OMNISEC in these key areas?

OMNISEC will have benefits for a whole range of customers and markets. That starts for us in universities, where different departments (including chemistry, polymer chemistry, materials characterization, biology, and biochemistry) will all see improvements in sensitivity and usability, improving their research and their output.

Within industry, it will be used in research departments where people are developing novel polymers or even just characterizing their current products to a higher level. This allows them to push their product further, create better products or reduce quality issues that they might be suffering from.

Within the pharmaceutical industry, that also includes the biopharmaceutical side where protein drugs are being produced and also need higher and higher levels of characterization to meet their standards. Again, this information is being used to help product higher quality products or understand and reduce the numbers of quality issues they face.

In terms of parameters, first and foremost, our customers are getting the most accurate molecular weight and molecular weight distributions that you can achieve with size exclusion chromatography.

Beyond that, the addition of a viscometer gives us this value of intrinsic viscosity, which is a measure of molecular density, and the combination of this with the molecular weight results from the light scattering detector gives us molecular structure, and allows us to characterize molecules such as branch polymers.

The use of two concentration detectors, including the RI detector and the photodiode array, allows you to get compositional information for samples as well. That's particularly useful in applications such as coat polymers or conjugated proteins.

Where can people find more information about OMNISEC?

Further information about the system, along with relevant application notes, can be found on our website: http://www.malvern.com/en/products/product-range/omnisec/default.aspx

Information regarding the live launch can be found at the following link: http://www.malvern.com/en/support/events-and-training/webinars/W150127-omnisec-launch.aspx  

About Mark Pothecary

Mark studied biochemistry while an undergraduate at the University of Bath before moving to London to obtain his Masters and PhD at the academic lab in the William Harvey Research Institute, part of the Queen Mary University between 2002-2006. There he studied the biochemical effects of red wine polyphenols on the production of nitric oxide in blood vessels and the subsequent control of blood pressure.

Following this he continued for another year in the same lab using chromatography to study the uptake of these same compounds into the blood, by extracting and measuring them.

Mark joined Malvern Panalytical in 2008 as a product technical specialist for the Zetasizer Nano and Viscotek products concentrating on bioscience SEC applications. In 2010, he took the role of Product Manager for Zetasizer and Viscotek products where he acts as the 'Voice of the Customer' for new products and on quality issues and recently moved to our Houston office to engage more closely with product developments there.