次亜塩素酸ナトリウム液の有効利用に関する検討

Sodium hypochlorite solution is cheap and powerful disinfectant widely used in hospitals and food industries. The bactericidal activity of chlorine solution is considered to depend on the amount of dissociated hypochlorite (HClO) in the solutions. The most important factor affecting the amount of HClO in the chroline solution is pH, and the decrease in pH increases the concentration of dissociated HClO. Alkaline solutions of both sodium and calcium hypochlorite contain only small amount (about 10% of free available chroline in these solution) of HClO. Recently, there are several reports showing the effectiveness of “acidic hypochlorite solution”, which is adjusted pH with hydrochloric acid (HCl) to 5.0, as a powerful disinfectant. However, special attention must be paid to handling and storage of HCl, and the increase of chlorine content in the solution by the addition of HCl might possibly induce toxic chlorine gas production. In this study, the bactericidal activity of acidic hypochlorite solutions, which have been adjusted to pH 5.0 with hydrochloric acid, acetic acid, citrate, lactate, formate, phosphate or sulphate, was investigated using various bacterial strains. The acidic hypochlorite solution prepared with acetic acid showed the equivalent bactericidal activity to that with hydrochloric acid and killed all of the Bacillus subtilis spores within 10 min. In addition, the acidic hypochlorite solution with acetic acid killed all of bacterial cells of Escherichia coli O157 : H 7, Legionella pneumophila, Pseudomonas aeruginosa, Salmonella Typhimurium and methicillin-resistant Staphylococcus aureus within 30 sec. On the other hand, the solutions prepared with citrate and lactate showed no bactericidal activity against any bacterial strains tested in this study despite of low pH. We proposed that acetic acid is a desirable acid to safely and easily prepare the acidic hypochlorite solution with the equivalent bactericidal activity to the solution prepared by HCl.