Characterising polysaccharides by triple detection

Edited by the Laboratorytalk editorial team Jul 23, 2007

Viscotek has produced a series of new application notes demonstrating how precise and comprehensive characterisation of different polysaccharides can be achieved with its triple detection GPC system

Chitosans are a focus of interest for various applications.

They can be used in a range of medical applications as they are biocompatible, hypoallergenic, biodegradable and bioabsorbable.

Triple detection application note 7 examines how physical processing of chitosan samples can directly affect characteristic properties, such as molecular weight distribution, size and conformation.

The application note demonstrates how by using the triple detector approach, changes in molecular structure and molecular chain length can be simultaneously and independently monitored.

Many hydrocolloids such as agar, pectin, gelatine and carrageenan find application as thickening, gelling and stabilising agents in products such as frozen desserts, chocolate milk, yoghurt and toothpaste.

In the application note 'Structural distribution of carrageenan samples', a Viscotek triple detection GPC system and Omnisec software is used to fully characterise three carrageenan samples at elevated temperature to ensure complete dissolution.

Data is provided demonstrating how the tripe detection technique provides valuable information on chain conformation as well as the structural distribution of the kappa, iota and lambda forms of this complex naturally occurring polymer in a single experiment.

Maltodextrins are produced from the degradation of starch, often by the use of enzymes.

The products are widely used as ingredients in food and pharmaceutical products.

Because maltodextrins are derived from starch they are a mixture of both linear and branched molecules.

This can lead to large errors if they are characterised by conventional GPC.

The application note 'Analysis of maltodextrins' shows how the use of Triple Detection GPC can clearly measure the differences in both structure and molecular weight for three maltodextrins with similar bulk viscosities but very different end-use properties.

Triple detection sets the standard for GPC/SEC technology and is the preferred method for even complex polysaccharides.

The Viscotek triple detector system (TDA) employs a concentration detector, viscometer and low angle light scattering (Lals) detector acting in concert, with each detector providing complimentary but different information.

Using Lals to measure molecular weights is extremely important when studying large biomolecules such as polysaccharides.

Other extrapolation based light scattering techniques, such as those using multi angle detectors, cannot be used because the large molecule sizes result in large data fitting errors.

By comparison the Viscotek Lals detector measures scattered light at 7 deg, close enough to zero that the measurement is direct with no need to extrapolate or calculate to get accurate molecular weight and structure data.

The application notes demonstrate however that it is the combination of the three detectors acting in concert that allows the Viscotek TDA system to unlock molecular weight distribution, viscosity, molecular size, conformation and branching frequency data from the polysaccharide samples.