A Study On Germicidal Efficacy Of A Solid Chlorine Dioxide

Chlorine dioxide(ClO₂) is a broad-spectrum disinfectant. With high efficient and low toxicity characteristic, it has been widely used in disinfection for surface of goods and environment, equipments for food processing, sets of dinner or drinking and water. In recent years, the numbers of factories which producing ClO2 disinfectant are increased greatly in Chongqing. In these factories, the products of ClO2 disinfectant have different types. But there isn't uniform product standard. Their product quality is variant. When identifying these germicidal products with national criteria in our actual work, we found that the germicidal efficacy was the only index to evaluate the disinfectant. This method could not describe all characters of ClO₂ disinfectant. It's also hard to give us the information which as scientific evidence helps us to monitor the quality of disinfectant and instruct application. So, it is necessary for us to make system analysis of germicidal efficacy of ClO₂ disinfectant. In this study, the assays of measuring of content of ClO₂, the germicidal efficacy in suspending solution or in (simulative) locale, the determining about affecting factors of germicidal efficacy, the measuring about accelerated stability, the capacity consume of disinfectant and the detecting of byproducts from ClO2 by vapor phase chromatography instrument had been used to observe the characters and the germicidal efficacy rules of Kangbaojie solid ClO₂, the impact factors to germicidal efficacy and additional potential indexes to evaluate this kind of disinfectants. Our research work provided an experimental basis for system evaluation of the quality of ClO₂ disinfectants. The results are as follows: 1 The Kangbaojie solid ClO₂ consisted of two components, A and B. The A reagent is white powder containing more than 82% sodium chlorite. Used as activator, the B reagent is white small granule containing citric acid. Blending the reagents A and B, added some water, and hold the reaction (activation reaction of disinfection) for some time. The free ClO₂ would release from the mixture. The release concentration of free ClO₂ was decreased with the increasing of added water volume. During 4 hours, the free ClO₂ was increased with time of activation. 4 hours later, the concentration decreased gradually. Blending 1.0g reagent A and 1.0g reagent B in 5.0 ml water, hold the activation reaction for 4 hours, the released ClO2 was about 90.79 mg ClO2/g. This was the highest level of ClO2 released from mixture. 2 The Kangbaojie ClO2 is a disinfection with good stability,it has high-efficient and fast germicidal characters. At the treatment condition of killing B.niger with 225mg/L for 2 min(or 150 mg/L for 15 min), killing P.aeruginosa with 5mg/L for 1 min, killing S.aureus with 7.5mg/L for 1 min (or 5mg/L for 3 min), killing E.coli with 7.5 mg/L for 3 min and killing C.albicans with 7.5 mg/L for 3 min (or 5mg/L for 7 min ), all of the test bacteria could be reduced over 5 log(4 log for C.albicans) . 3 According to capacity test, the solution of Kangbaojie ClO2 could be used to disinfect objects time after time. The reference dosage was about 10mg/L; According to the (simulative) locale application test,The natural bacteria on the surface of object could be reduced at the level of disinfection with 5mg/L for 5 min; The test bacteria on the surface of sets of dinner, vegetables(or fruits)could be disinfected with 7.5mg/L for 7 min, 10mg/L for 5 min respectively; At the condition of 5℃-30℃, chroma less than 15, pH 5.5-8.5, the E.coli in water could be reduced to 0/100ml with 0.5mg/L for 30min. 4 The organic substance could affect the germicidal efficacy. The organic substance at the concentration of 50% and 40% could reduce the germicidal efficacy at a middle and low level respectively. The organic substance at the concentration of less than 30% had no effect of reducing the kill rate.15℃-35℃and pH less than 7 were the optimal germicidal condition. 5 Disinfecting the water to the same source, the chloroform could not be detected after using with Kangbaojie ClO2. Other while, instead with Sodium dichloroisocyanurate, the concentration of chloroform could be detected with the doses of 55.51μg/L-233.46μg/L. Also the same, the concentration of carbon tetrachloride in water, the level treated by ClO2 was lower than that Sodium dichloroisocyanurate treated. Research characteristic: 1 First time, we chosed the optimal condition of solid ClO2 activation reaction: Blending 1.0g reagent A and 1.0g reagent B in 5ml water for 4 hours. Under this condition, the maximum concentration ClO2 (90.79mg/g) could be released. This result could help toincrease the disinfection efficacy and reduce the cost of disinfectant. 2 Comparing with Sodium dichloroisocyanurate, we validated that lesser organic product could be get after disinfecting with high-quality ClO2.So high-quality ClO2 was useful to environment protection. According to this result, we suggested that the item of detection of organic product such as halogenated hydrocarbon should be added into the industry criterion of ClO2, into technological specification of disinfection issued by the National Ministry of Health. This could make up the deficiency of detection of effective component of ClO2 only to control the quality of ClO2.