Carrageenans are important naturally occurring polysaccharides used predominantly in the food industry – in the European Union they are designated as E 407. Several types are known, the most important being kappa, iota, and lambda carrageenan (κ, ι, and λ). They differ in their basic sugar units and in the number of sulfate ester groups that replace hydroxyl groups. The addition of carrageenans thickens food and also serves as an emulsifier. Native carrageenans are generally not problematic for human health; however, the same cannot be said for their degradation products, known as poligeenans. For this reason, an effective method for determining the molar mass of carrageenans is very important.
In this thesis, I set out to develop and optimize a size exclusion chromatography method for the determination of different types of carrageenans. The first step involved selecting suitable solvents for carrageenan standards, which would later serve as mobile phases. Solubility was tested in Milli-Q water and 0.1 M solutions of NaNO₃ and LiCl at different temperatures. All three solvents proved suitable, and the solutions were heated at 80 °C for one hour prior to injection.
I then proceeded to test the following three columns: TSKgel G3000SWXL, Bio SEC-3, and AdvanceBio SEC. Due to numerous issues encountered on the first column, Milli-Q water was excluded as a potential mobile phase, and further work was carried out only with the salt solutions. While working with the first column, I determined the appropriate concentration of carrageenan solutions and optimized separation conditions, such as flow rate, autosampler temperature, column temperature, and injection volume.
The best combination proved to be the second column tested, Bio SEC-3, with 0.1 M NaNO₃ as the mobile phase. On the selected column, I evaluated the separation using pullulan standards of different molar masses. I also calculated the specific refractive index increments (the dn/dc factors), which play a key role in determining molar mass.
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