An inorganic biocide using a novel presentation of silver

Synopsis A silver-based preservative system has been developed which overcomes difficulties often associated with metals, namely solubility, dispersion and toxicity. It comprises a silver chloride titanium dioxide composite which allows the controlled release of silver ions. Microbiological data has shown the composite to be active at concentrations less than 25 ppm against a wide range of micro-organisms, including Gram-negative non-fermentative bacteria, yeasts and moulds. The composite has satisfactory preservative activity against bacteria and fungi at application concentrations of between 50 ppm and 500 ppm, depending on the formulation. At high concentrations (>300 ppm) there may be some grey discoloration of the product, but the composite remains effective. To overcome this problem, a system of enhancing antimicrobial activity was devised, based on a sulphosuccinate salt dispersing agent. This allows lower concentrations of composite to be used whilst maintaining equivalent antimicrobial activity.