CONICET | Buscador de Institutos y Recursos Humanos

Introduction and objectives: In the context of COVID-19, the World Health Organization has recommended the use of extemporaneously prepared bleach solutions of 1 g/L, as a conservative concentration able to inactivate SARS-CoV-2 and the vast majority of other pathogens that may be present in the healthcare setting. Consequently, there is a renewed interest in conducting stability studies of these solutions. The goal of this work was to verify the available chlorine concentration in several bleach solutions trademarks and to propose a beyond use date for 1 g/L bleach solutions, obtained after dilution with drinking water from different sources. Methods: Bleach trademarks, with nominal concentrations between 25-60 g/L, were subjected to iodometric titration to determine the available chlorine concentration. One trademark was used to prepare 1 g/L dilutions using water from different purification plants in Córdoba, Argentina. The samples were stored at room-temperature, both exposed or protected from light. The available chlorine concentration was determined by titration at preestablished time intervals. The beyond use date was reached when the available chlorine concentration dropped below 90 % of its initial.Results: The concentration of active chlorine in the different trademark bleaches was within the values established by current regulations. Diluted solutions protected from light showed a decrease of less than 10% in active chlorine concentration during the first 10 days of assay. However, one sample exceeded the acceptance limit after 14 days. In contrast, in the samples exposed to light, the concentration of active chlorine dropped to 96.4% at 24 hours and 79.3% after 48 hours. No differences related to drinking water sources were observed.Conclusions: Compliance of the nominal available chlorine concentration in trademark bleach solutions was confirmed. Regardless the water source used for dilution, 1 g/L bleach solutions were stable for 10 days when stored at room temperature and protected from light. Instead, solutions exposed to light maintain their available chlorine concentration for only 24 hours.

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