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Investigation of modification and degradation pathway of the chlorhexidine in chlorinated medium and evaluation of its by-products

Grant number: 16/16646-5
Support type:Scholarships in Brazil - Scientific Initiation
Effective date (Start): November 01, 2016
Effective date (End): October 31, 2018
Field of knowledge:Engineering - Sanitary Engineering - Water Supply and Wastewater Treatment
Principal researcher:Renata Colombo
Grantee:Viviane da Silva Carvalho
Home Institution: Escola de Artes, Ciências e Humanidades (EACH). Universidade de São Paulo (USP). São Paulo , SP, Brazil


Chlorhexidine has been used for many years in several countries, as disinfectant in mouthwash, as active ingredient in human and veterinary pharmaceuticals, as well as disinfectant of materials and environments. Due to its continued use and disposal into the environment it has been detected in several samples of water, included drinking. Although the chlorhexidine is considered practically non-toxic and non-polluting it is classified as hazardous to the aquatic environment and studies have shown its ecotoxicity and resistance in bacteria. In environments slightly acidic and chlorinated this molecule becomes reactive and, despite the water supply being subject to these conditions, there are very few studies published in the literature regarding the behavior of this molecule in recreation and water supply. Thus, this project proposes an investigation into the transformation and degradation of chlorhexidine in chlorinated water and the evaluation of its byproducts. The studies will be conducted within the parameters of pH, light, temperature and concentration of chlorine (free or residual) provided in legislation and applied to water supply (during the disinfection and distribution process). The behavior of this substance in isolated form (for determination of byproducts) and in the presence of other organic substances will be evaluated. The by-products formed will have their structures elucidated by liquid chromatography coupled to mass spectrometry (LC-MS). The concentration and time of water exposure to chlorine, ideal for the chlorhexidine is completely degraded during the water treatment process will also be defined. At the end of the project aims to map the degradation and transformation pathway of chlorhexidine in chlorinated water, identifying the plausible by-products being formed.

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