Use of the ninhydrin assay to measure the release of chitosan from oral solid dosage forms.

This study evaluated and optimised the ninhydrin assay as a tool for measuring the in vitro release and dissolution of chitosan from solid dosage forms. The precision and accuracy of the assay for the type of chitosan used in the study were examined by measuring the inter- and intra-sample variation and found to be within acceptable limits. The assay was applied practically to construct a pH/solubility profile for chitosan and subsequently to measure the release and dissolution of chitosan from dosage forms in the presence and absence of a model drug, sodium salicylate. Assay performance was found to be satisfactory over a wide range of physiologically relevant pH values. It is concluded that the ninhydrin assay is an essential aid in the design and testing of solid dosage forms with different chitosan-drug release profiles.