Uv Spectrum of SPF

According to absorbance @ 312 nm vs. log₁₀ (SPF), Coppertone SPF 30 represented a greater light absorbance at 1.826 nm when compared to non-brand SPF 30 (0.834 nm). Coppertone SPF 70 also had a greater light absorbance at 0.945 nm when compared to non-brand SPF 70 (0.891). The other compounds couldn’t be compared in this case because one was SPF 15 and the other was SPF 50. When molar extinction coefficients of the compound were compared, the active ingredient appeared to be 2-Ethylhexyl salicylate with a concentration molarity of 4 x 10^-5 mol/L and a molar extinction coefficient of 7.96 x 10⁴. 2-Ethylhexyl-p-cinnamate had a concentration molarity of 3.448 x 10^-5 mol/L and a molar extinction coefficient of 4.17 x 10⁴. When plotted, log₁₀ SPF vs. absorbance @ 312 nm does not have much of a linear relationship; however, Coppertone increases from 15 to 30 SPF and non-brand increases from 30 to 50 SPF. This increase represents somewhat of a linear relationship—as SPF increases, absorbance increases—for the smaller SPF’s of each brand. The relationship between UV and molecular structure is explanatory by the concept of conjugation—alternating double and single bonds resulting in π bonds that are delocalized. Structures that include more conjugation absorb UV radiation of lower energy and longer wavelength. If a compound with a double bond absorbs UV energy, an electron in a Pi bonding orbital is promoted to a higher energy orbital—anti-bonding orbital. The conjugation of one double bond with another double bond increases the number of orbitals in the system and reduces the energy difference between the occupied and unoccupied orbitals. Therefore, upon conjugation, the amount of UV energy needed to move the electron decreases and the wavelength of the UV radiation increases. According to UV data, Coppertone is more effective in SPF 15 and 30. Coppertone SPF 70 is similar to all the non-brand SPFs. Coppertone SPF 15 and 30 absorb the largest amount of light—1.476 and 1.826, respectively.

Conclusion: After UV analysis, Coppertone SPF 15 and 30 absorbed the most light significantly (as represented on attached graph). The 3 non-brand SPFs were oddly similar, and Coppertone 70 had an absorbance similar to the non-brand SPFs. When molar extinction coefficients were compared, 2-ethylhexyl salicylate appeared to have a greater molar extinction coefficient (7.96 x 10⁴) and a greater concentration (4.0 x 10^-5 mol/L) than 2-ethylhexyl-p-cinnamate—molar extinction coefficient: 4.17 x 10⁴, and concentration (3.448 x 10^-5 mol/L).