Question

The presence (+) or absence (-) of growth of a specific organism after exposure to the shown dilutions of phenol and disinfectant A for 5, 10, or 15 minutes is shown in the table below. Calculate the phenol coefficient for this disinfectant. 5 minutes 10 minutes 15 minutes 1 + + + Phenol Dilution 1:50 1:60 1:70 1:80 1:90 Disinfectant A Dilution 1:90 1:100 1:150 1:200 1:250 5 minutes 10 minutes 15 minutes + + Describe the phenol coefficient and what it is used for. What does a higher phenol coefficient mean? (5)

Answer 1

Phenol coefficient is a measure to determine the effectiveness of any disinfectant in comparison with phenol under given conditions. Here the highest dilution of disinfectant A which prevents growth after 10 minutes but doesn't prevent at 5 minutes is 1:90.Highest dilution of phenol which prevents growth after 10 minutes but doesn't prevent at 5 minutes is 1:60.

Hence phenol coefficient for disinfectant A= 90/60=1.5.

This implies disinfectant A is more effective than phenol.

Phenol coefficient u's calculated to determine the effectiveness of a test disinfectant en comparison with phenol lie. whether it us more effective or less effective than phenol under given conditions. It is calculated as Phenol coefficient Highest dilution of disinfectant of a disinfectant killing microorganisms in 10minutes but not in 5 minutes Highest dilution of disinfectan H Phenol) killing microorganisms in 10 minutes but not in 5 minutes As given, Highest dilution of disinfectant A at which no growth occurs after 10 minutes, but there is growth at 5 minutes is 1:90 Highest dilution of phenol at which no growth occurs after 10 minutes, but there is growth at 5 minutes is 1:60 Hence phenol coefficient 90 - 105 for disintectant A - Go Value of 105 shows that disintectant A is more effective than phenol. of value >1 > Disinfectant is more effective than phenol Higher the phenol value (phenol coefficient value), more effective the disinfectant under consideration is.