A Study of Bactericidal Effect of Sodium Chlorite Preparation

Abstract

The bactericidal effect of a sodium chlorite preparation recently developed in the USA was examined with several test methods (available chlorine germicidal equivalent concentration method in A. O. A. C., phenol coefficient method and phenol coefficient method under dirty conditions). The changes with the lapse of time of available chlorine and bactericidal effect were also examined. The base NaClO2 solution exhibited no bactericidal effect, but when lactic acid was added as the activator, it became effective.Base concentration of NaClO2 (%) and available chlorine concentration (ppm) with the activator allowing growth at 5min but not 10min of E. coli, P. aeruginosa, S. aureus and B. subtilis spores were 0.029 (500), 0.014 (250), 0.058 (1000) and 0.23% (4000ppm), respectively. On the other hand, the corresponding values of sodium hypochlorite were 0.015 (150) of E. coli and P. aeruginosa and 0.025% (250ppm) of S. aureus and B. subtilis spores.These results indicated that equivalent bactericidal effects at almost the same concentration of both NaClO2 and NaClO could be expected of P. aeruginosa, but the base concentration of the NaClO2 preparation needed to be several times as high as that of NaClO in order to obtain equivalent bactericidal effects of the other 3 species. Bactericidal effect of E. coli under dirty conditions was one-half of that in clean conditions for NaClO2 and from one-third to one-fifth for NaClO. The degree of decrease suggested less influence of dirty conditions for NaClO2.Available chlorine immediately after preparing the use dilution was decreased to one-half, one-fourth…one-fortieth with the lapse of preservation time. However, the bactericidal effect was enhanced from 1 day after the preparation, continued to increase or remained constant up to 7 days and was lower after 10 days.