Science Buddies: "Ask an Expert"

I am trying to test the effect of retinyl palmitate in the sunscreens on the bioluminescence of dinoflagellates.
When I conduct the experiment, do you think I can use the dietary retinyl palmitate powders that are on sale online to get an accurate result?
If not, is there a better way to get the sunscreen chemicals for my experiment? (oxybenzone, octinoxate, rentinyl palmitate,...etc)

Thank you!