A comparison of sodium hypochlorite and sodium dichloroisocyanurate products

A comparison of commercial sodium hypochlorite (NaOCl) and sodium dichloroisocyanurate (NaDCC) products was made. Solutions of NaOCl and NaDCC containing the same levels of available chlorine (av.Cl) exhibited very similar bactericidal activities, despite significant differences in pH. A level of 12.5 ppm av. Cl achieved a greater than 5 log 10 reduction of Staphylococcus aureus in 2 min. A level of 5 ppm av.Cl achieved a greater than 5 log 10 reduction of Pseudomonas aeruginosa in 2 min whilst approximately 100 ppm av.Cl achieved the same reduction in the presence of 1% horse serum, and approximately 200 ppm av.Cl in the presence of 2% horse serum, indicating inactivation levels of around 95 and 97.5% respectively. Tablets of NaDCC were stable but solutions were unstable and decomposed much faster than NaOCl solutions of the same strength. Batch-to-batch variability of different NaOCl and NaDCC products was investigated; whilst NaDCC products always contained the minimum level of av.Cl specified, concentrated NaOCl products sometimes did not due to inherent instability.