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The Independent Variables were the 10 different brands of sunscreen and the two different SPF’s that we tested, which were 15 and 30. Also, we used 4 different wavelengths that we chose to measure the 0.01% dilution at. These consisted of 310nm, 320nm, 330nm, and 340nm. And last but not least, the concentrations of dilutions that we tested (10%, 1%, 0.1%, 0.01%).
We concluded to having 3 Dependent Variables. The first one was from the 10% dilution; this consisted of the weight (g) of the sunscreen in the solution that did not dissolve. Another Dependent Variable was the single wavelength recorded from the 0.1% dilution. The third Dependent Variable was the relative absorbency’s from the 0.01% dilutions at the wavelengths.
We treated all of the samples the same by using the same amount of sunscreen, amount of alcohol and we rinsed all the beakers prior to use with alcohol.
The same scale was used in measuring each sample while making dilutions
as was the same scale used in measuring the filter papers. |
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We made absolute sure not to touch the sides to be tested of the cuvettes, and just to know, we touched on purpose one cuvette and it was very obvious that ifwe had touched one, it would have been very easy to tell (the reading was very different). While reading the results off of the spectrometer, we were very careful to line up a piece of paper with the line to get a very accurate reading. When we filtered the 10% dilution, we were careful to start all samples at the same time and leave them to dry for exactly the same amount of time. Once we were done running the 0.1% dilutions through the spectrometer, we recalibrated the machine and did them again to make sure our tests were good, they were perfect the second time around.
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