1)      We collected 5 products of ‘SPF 15’ and ‘SPF 30’.

2)      We produced a 10% dilution

a)     Rinsed a glass beaker using 95% alcohol and dried it.

b)     Placed the beaker on the digital scale and zeroed the scale.

c)      We added 2g of sunscreen, zeroed the scale and then added 18g of 95% alcohol.

d)     We stirred the mixture with the glass stir rods until all of the mixture was dissolved. If the sunscreen didn’t completely dissolve, the mixtures were heated on a hot plate.

3)      We produced a 1% dilution

a)     Rinsed a glass beaker using 95% alcohol and dried it.

b)     Placed the beaker on the digital scale and zeroed the scale.

c)      We added 2g of 10% dilution, zeroed the scale and then added 18g of 95% alcohol.

d)     The remaining 10% dilution was poured into labeled test tubes and saved.

4)      We produced a 0.1% dilution

a)     Rinsed a glass beaker using 95% alcohol and dried it.

b)     Placed the beaker on the digital scale and zeroed the scale.

c)      We added 2g of 1% dilution, zeroed the scale and then added 18g of 95% alcohol.

d)     The remaining 1% dilution was disposed of.

5)      We produced a 0.01% dilution

a)     Rinsed a glass beaker using 95% alcohol and dried it.

b)     Placed the beaker on the digital scale and zeroed the scale.

c)      We added 2g of 0.1% dilution, zeroed the scale and then added 18g of 95% alcohol.

d)     The remaining 0.1% dilution was poured into a labeled test tube and saved.

6)      We visited Lauri Lintott (Laboratory Instructor in the Department of Biology at the University of Regina) who programmed and set-up spectrometer for us.

7)      We prepared a blank solution of just 95% alcohol and used this to zero the spectrometer.

8)      We then filled the cuvettes up to the full line with the samples of the 0.1% dilution.

9)      Being careful not to touch the side that was read (fingerprints jeopardize the chance of accurate results), the filled cuvettes were placed in the spectrometer, and then it was closed.

10)    We began reading the samples. On the spectrometer we saw a straight line at the start that suddenly dropped off at varying nanometers (nm) depending on the sample (see picture). For our 0.1% dilution results, we recorded the single nanometer that the line began dropping at.

11)    We then, filled new cuvettes up to the full line with each samples of the 0.01% dilution.

12)    Being careful not to touch the side that was read, the filled cuvettes were placed in the spectrometer, and then it was closed.

13)    We began reading the samples. On the spectrometer we saw a line beginning somewhere less than 2 (relative absorption), this line dropped at varying rates depending on the sample (see picture). For out 0.01% dilution results, we recorded four different relative absorptions. These were found at where the line hit the graph for 310, 320, 330, and 340 nm.

14)    To finalize our results we decided it would be best to measure how much sunscreen actually dissolved in each sample. So, we got 10 pieces of filter paper and weighed each one of them using a triple-beam scale. We then poured each of the 10 original 10% dilution samples through a filter and left them overnight to dry. Once they were dry, we measured the filter papers again with a triple-beam scale and subtracted the weight of the original filter from this.