Abstract: Effect of number of EO adducted into palm oil ethoxylate (NOE-P_n) (n=3,6,9,12 or 14) with a mass concentration of 50 mg/L on bactericidal activity of the composite cationic disinfectant that consists of didecyldimethylammonium formate (DDAF),dialkyldimethylammonium chloride (carbon chain length 8-10,D8-10),poly hexamethylene bis-guanidine hydrochloride salt (IB),didecylmethylhydroxyethylammonium chloride (DEQ) and lauryldimethylbenzylammonium chloride (1227),with a composite mass ratio of DDAF/D8-10/IB/DEQ/1227 of 3/2/3/3/3 and an overall mass concentration of 140 mg/L was examined.Results show that the influence on composite cationic disinfectant caused by NOE-P_n occurs at n=9 (i.e.,NOE-P₉) with a treatment time period of 20 min is at the minimum,which is basically same as that of fatty alcohol polyoxyethylene (9) ether (AEO₉).Furthermore,introduction of either nonionic surfactant NOE-P₉,AEO₉,alkyl polyglycoside (APG0810) or anionic-nonionic surfactant fatty alcohol polyoxyethylene (9) ether carboxylic acid (AE₉C) will result in significant impact on bactericidal activity of composite cationic disinfectant with respect to Candida albicans (ATCC10231).Comparison between effects of increase of mass concentration to 180 mg/L and extension of treatment time period up to 1 h was made and results show that the increase of mass concentration can slightly improve the bactericidal performance,while the extension of treatment time period can conspicuously raise the bactericidal efficacy especially for Staphylococcus aureus (ATCC6538) and Escherichia coli (ATCC8099),both the value of KL is higher than 6.

Key words: nonionic surfactant, palm oil ethoxylate, composite cationic disinfectant, bactericidal performance