Characterisation of northern Patagonian bentonites for pharmaceutical uses

This paper evaluates the suitability of some smectite-rich samples from northern Patagonia (Argentina) for pharmaceutical use. The clays must comply with some general features before considering their use in pharmacy, including high mineral and chemical purity and the absence of microbial pathogens. Specific characteristics such as sediment volume, swelling power and gel formation are also important for particular applications such as their use as suspending agent. The mineralogical and chemical compositions of the samples are typical of bentonites, mainly consisting of montmorillonite. Considering the requisites of major pharmacopoeias for the use of silicates in pharmacy and taking into account the microbiological results, we could designate a pharmaceutically acceptable denomination for all samples, although some of them might need removal of quartz. The chemical, textural and porosimetric properties showed some differences between the samples that would affect their particular technical properties as pharmaceutical excipients. The samples could be used in pharmacy for topical applications as suspending agent. Regarding their use as adsorbents, specific sorption studies could help to discriminate their usefulness, as suggested by their high CEC values.