Using Escherichia coli as test organism, three quaternary detergent-sanitizers and their constituent QACs were evaluated by modified glass slide and Weber and Black methods at 5°, 20°, and 45°C in artificial hard and distilled waters. QAC activity was reduced by low temperature and water hardness, the latter exerting the greater effect. Each detergent product was more effective than its constituent QAC component alone. Reasons for the earlier endpoints obtained with glass slide method are discussed.

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Author notes

T. W. Humphreys graduated from the Ontario Agricultural College, in 1949 with a B.S.A. in bacteriology, and subsequently joined the staff of the University of Manitoba as lecturer in bacteriology. In 1950 he joined the food microbiology section of the Division of Bacteriology and Dairy Research at Ottawa. He received his M.S.A. degree from the University of Toronto in 1952 and has been carrying out investigations in the fields of disinfection and food microbiology.