Molecular weight distribution of carrageenans studied by a combined gel permeation/inductively coupled plasma (GPC/ICP) method

Degraded carrageenan (known as poligeenan, molecular weight: 20 kDa to 30 k Da) causes ulcerative colitis in experimental animals. In this paper, the m olecular weight distributions of 29 samples of food-grade refined carrageen ans were studied by high performance liquid gel permeation chromatography ( GPC) directly connected to vacuum-ultraviolet inductively coupled plasma-at omic emission spectrometry (ICP) (GPC/ICP) as well as GPC/refractive index (RI) detection. All samples of food-grade carrageenan had a major broad pea k of high molecular weight which eluted at around 6.5 min in both RI and IC P mode (sulphur and carbon), and each sample of them had no obvious peak of poligeenan (the detection limit was about 5%). The number average molecula r weights of these carrageenans ranged from 193 kDa to 324 kDa, and the wei ght average molecular weights ranged from 453 kDa to 652 kDa based on RI da ta. Some samples had a few minor peaks which eluted around 10-12 min. These peaks came from ionic sulphate, sucrose or glucose. It was considered that if the data-sampling programme was improved, the GPC/ICP system would beco me a more powerful technique for evaluation of carrageenan samples containi ng ionic substances and sugar.