This may be the result of degradation due to base peeling or due to some hydrolysis during the short dialysis step in the purification. However, the molecular weight is still in an acceptable range, thus, the modified samples are suitable to evaluate the influence of -units on IRI activity. The sulfate content as well as the type and content of cations were analyzed by ICP-OES (Tab. 3). The results confirm that the cations in the carrageenans were successfully exchanged. The potassium and sodium forms of the carrageenans almost exclusively contain this cation and only trace amounts of the respective other cations. For the calcium forms of carrageenans containing a comparably high portion of κ-units, small amounts of potassium can be detected in addition to calcium. This is most likely caused by the strong affinity of κ-units to this cation.