The aim of this study was to investigate the effects of ionizing radiation on the physicochemical properties of
four excipients used in pharmaceutical technology (microcrystalline cellulose, methylcellulose, hydroxyethylcellulose and
hydroxypropyl methylcellulose) with the view of using ionizing radiation for their sterilization.
A number of analytical methods (FT-IR, XRD, TG,CPMAS NMR and measurements of pH and viscosity) were used to
determine the radiostability of cellulose derivatives to ionizing radiation.
The odour, form, microscopic presentation and water content determined by the Karl Fischer method of cellulose derivatives
did not change after irradiation up to 200 kGy. There was a small difference (+/- 0.1 to 2 °C) between irradiated and
non-irradiated samples for the decomposition temperature determined via DTG/TG method and for relaxation times determined
by the CPMAS NMR.
Significant changes were observed however in the colour and the pH of aqueous solutions (or suspensions). The viscosity
was reduced as a result of irradiation and thixotropic properties disappeared. In the FT-IR spectra, a new peak was observed
at ca 1730 cm-1 indicating the presence of either carbonyl or carboxylic groups.
It was concluded that radiosterilization method as a way of decontamination of cellulose derivatives should not be used in
doses exceeding 25 kGy because ionizing radiation may lead to changes in physicochemical properties and to the formation
of radiolysis products.