Authors: Anne Cornish Frazer Josephine N Smyth Vishvesh K Bhupathiraju
Publish Date: 2013/03/27
Volume: 40, Issue: 6, Pages: 601-611
Abstract
pHadjusted bleach was one of the agents used to disinfect contaminated public buildings in the USA following the 2001 bioterrorist attack with Bacillus anthracis spores A USEPA fact sheet describes the preparation of pHadjusted bleach by combining diluted sodium hypochlorite NaOCl with a controlled amount of 5 acetic acid This paper reports a modification of this procedure to qualify the use of pHadjusted bleach for routine disinfection of cleanroom surfaces in pharmaceutical manufacturing facilities whenever a short contact time is desirable or there is a need for enhanced germicidal or sporicidal activity Adjustment of pH was obtained reproducibly with either acetic acid or HCl confirming the feasibility of developing standard procedures for the controlled addition of acid to diluted NaOCl solutions without compromising operator safety and convenience Efficacy testing using spores from an inhouse isolate of Bacillus pumilus confirmed that NaOCl solutions in the pH 5–8 range have much greater sporicidal activity on surfaces than do unadjusted alkaline solutions pH 11 With a contact time of 05 min the log10 reduction in spore viable counts was 54 for the five representative surfaces tested relative to untreated controls Solutions of pHadjusted NaOCl are known to be less stable than unadjusted alkaline solutions Stability studies were performed by monitoring sporicidal efficacy level of free available chlorine FAC and pH Testing included several NaOCl concentrations and adjustment to different starting pHs The efficacy of pHadjusted solutions persisted in open containers for at least 12 h even though some FAC degradation occurred In addition solutions of 029 or 050 NaOCl stored at room temperature protected from light retained efficacy for at least 4 weeks indicating that shortterm storage of solutions is possible following pH adjustment The inorganic chemical degradation of pHadjusted NaOCl solutions generates chlorate ion an undesirable byproduct A comparison of chemical stability for 012 025 and 050 NaOCl solutions adjusted to different initial pHs indicated that the least chlorate formation occurred with 012 NaOClThe authors are indebted to John Matsubara and Sol Nho for excellent technical assistance Cristina Vigano for recommending the methodology of European Standard EN 13697 Wayne Yamamoto for helpful discussions and John D Coates for his sustained interest
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