Effect of Temperature and Contact Time on the Activity of Eight Disinfectants - A Classification

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Abstract
The combined influence of temperature (4, 20, 37 and 50°C) and contact time (10, 20 and 30 min) on the efficacy of eight commercial disinfectants was evaluated by the Association of Official Analytical Chemists use-dilution method. An increase of temperature greatly enhanced the activity of all tested solutions, particularly glutaraldehyde, chlorhexidine acetate and the amphoteric surfactant, whereas contact time mainly enhanced the efficacy of sodium hypochlorite, the quaternary ammonium compound and the amphoteric surfactant. Temperature and contact time influenced the activity profile of the disinfectants tested, with a maximum efficacy near the optimum growth temperature (37°C) of the test organism (Pseudomonas aeruginosa ATCC 15442). This organism was highly resistant to the amphoteric surfactant as well as to the two quaternary ammonium compounds. Classification of disinfectants is proposed on the basis of their mode of action, temperature dependence and activation energies, heat and light stability, and tolerance to organic matter.