Abstract:
Linear oligosacchardies of 1,4 linked β-D-glucopyranose are commonly
referred to as cellodextrins (CD) or cellooligosaccharides (CO). They are of interest
to those working in disciplines involving cellulose chemistry because they are often
used as model substrates for cellulose itself. They are of interest to food scientists
and nutritionists because they are easily incorporated into foods as non-digestible
oligosaccharides, a category of food ingredients that is thought to be beneficial lo
human health. The intent of the research presented in this thesis was to evaluate the
potential of using cellulose supports for the chromatographic separation of soluble
CDs differing in their degree of polymerization (DP; a numerical value indicating
the number of glucose substituents per molecule). Soluble CDs range in DP from 2
to 8. Thin layer chromatography (TLC), using cellulose-coated TLC plates, was
used as a model chromatographic system.
Mixed CD preparations, containing CDs ranging in DP from 2 to 8 were
prepared by incomplete acid-catalyzed hydrolysis of cellulose. The DP profiles of
the different CD preparations were qualitatively demonstrated by TLC using silica-coated
plates, an organic solvent-based mobile phase, and a standard carbohydrate
visualizing reagent (p-anisaldehye in sulfuric acid). CD-preparations were then
chromatographed on cellulose-coated TLC plates. Visualization of the
chromatographed CDs was accomplished using a silver nitrate-sodium hydroxide
reagent system, a reducing-sugar visualizing reagent. The silver nitrate-sodium
hydroxide system was found to be the most appropriate, based on detection limits,
simplicity and safety, of the several visualization reagents tested.
Eight different mobile phases, all aqueous-based, were tested as potential
solvents for the resolution of CDs, differing in DP, on cellulose-coated tlc plates at
room temperature. The optimum solvent was found to be 60% ethanol/40% water.
This solvent clearly resolved CDs of DP 3, 4 and 5. CD preparations
chromatographed with the same mobile phase, but with silica-coated TLC plates,
were not resolved. These combined results suggest that the TLC system with the
cellulose stationary phase behaves similar to an affinity system, since silica and
cellulose are both relatively hydrophilic stationary phases (i.e. both systems are
typically considered examples of normal phase adsorption chromatography). The
results further illustrate that cellulose supports have potential for use in the
preparation of CDs of defined DP.
