How to Create Working Solution of TRICLOSAN.

[dancers104]

Hi,

The title of my science fair project is "Do Different Dilutions of Disinfectants Affect the Development of Resistance of Bacteria?". I think I understand the guidelines of my project. I create a solution of triclosan, and then I dilute it into three different concentrations of 50%, 25%, and 12.5%. Four filter disks are used for each dilution and placed on the agar plates after swabbing the plates with E. coli. I then measure the zone of inhibition, and I select the bacteria with the most resistance to start another round. I repeat these steps four more times. My main problem is creating the solution of triclosan. Sciencebuddies recommended creating a solution of 17.5% ethanol and 82.5% distilled water with 500 micrograms/mL of triclosan. I have carried this suggestion out, but the results still leave me with several questions. The result was a milky white solution. Is this correct? Another problem is that after only one day the solution would completely separate. I understand that it is necessary to dissolve the triclosan into the ethanol before adding the water, but it still doesn't seem correct. My teacher helped me with the molarity equations, and we calculated 175 mL of ethanol, 825 mL of water, and .5 grams of triclosan powder. Is this mixture correct? Thank you.

[deleted-71417]

Hi,

I am unsure how to answer you. I agree your master solution should not be milky or separate into two phases on standing. My suspicion is that your alcohol has more water in it than the directions anticipated.. If this is true, then the solution would be to add ethanol or reduce the water in the mix until you get a clear solution. You can then adjust your dilutions as needed to achieve the desired concentrations in your experimental disks.

I hope this helps. Good luck!

Best regards,

Barrett L. Tomlinson