We have three different brands of hand sanitizers that promise to kill 99.9% of bacteria, which are:
-Virus Buster gel disinfettante (as used by school)
-Purell instant hand sanitizer
-Carex hand gel
Ingredients
Virus Buster-
Purell- water, isopropyl alcohol, glycerin, carbomer, aminomethyl propanol, fragrance, propylene glycol, isopropyl myristate, aloe barbadensis leaf juice, tocopheryl acetate, FD&C yellow no. 5 (tartrazine), FD&C blue no. 1
Carex- Alcohol Denat., Aqua, Glycerin, Aloe Barbadensis Leaf Extract, Carbomer, Parfum, Citric Acid, Potassium Sorbate, Aminomethyl Propanol, Benzophenone-1, Limonene, Linalool, Hexyl Cinnamal, Butylphenyl Methylpropional, Geraniol, Citronellol, CI 19140, CI 42090
Day One - Monday 17th May 2010
We took a swab of bacteria from the school computer keyboards and wiped 12 agar jelly dishes with the bacteria swabs.
Using a pipette/syringe to measure out the same amount of hand sanitizer, we soaked a small square of blotting paper with it.
We then placed the blotting paper in the centre of the agar dish and sealed it with with cello tape.
At 11:07 am we placed the agar dishes in an incubator for roughly 48 hours.
We will see which sanitizer has the largest kill-zone and is therefore the most effective
To measure kill-zones we used a OHT sheet and grid paper it to see how much area is bacteria-free.
We also wanted to look at the ingredients of each sanitizer to see what makes it more or less effective.
Variables and measurements:
-Temperature is kept the same as the agar dishes are kept in the incubator.
-We have three dishes for each sanitizer.
-One control dish with bacteria but no sanitizer
-One control dish with (theoretically) no bacteria
-First we took swabs of bacteria from the school computer keyboards in the same computer room.
-One fault in the experiment is that there might be more or less bacteria on the keyboards.
-We then measured 0.5cm cubed of the sanitizer to soak the small squares of blotting paper.
-We used a 0.5mL sample of sanitizer on each square of paper. It could be possible that was too much and it may just kill all the bacteria and therefore we may have no results.
Here's the URL for the video for Day One: http://www.youtube.com/watch?v=vuINEKzkUIE
Day Two - Wednesday 19th May 2010
We observed how much bacteria had grown and measured it in centimetres cubed.
We learned our method was slightly flawed and changed it. We acquired some more agar dishes and applied our improved method.
What we changed:
-Small round sections of blotting paper the exact size of a 1 cent coin
-Less sanitizer applied
-Finding the exact centre of the dish to place the circle
Day Three - Thursday 20th May 2010
Today we started making the poster, looking up the ingredients of the different sanitizers, editing the videos, recording the results of our improved method from Day Two and graphing the data using computers.
Day Four - Friday 21st May 2010
Today involved printing out graphs and pictures, cutting and sticking onto the poster and setting up our poster. We had some trouble finding some good colour prints, but eventually found a solution in the staff room!
