Sunscreens: Evaluation and Regulatory Aspects - Assignment Example

Experiment 1: SUNSCREENS Student Name: Date: Experiment 1: SUNSCREENS OBJECTIVE The main objective of this lab experiment was to identify the effect of organic and inorganic components of a sunscreen on its absorbance properties and also to identify the effect of concentration and the size of particles on absorbance properties of a sunscreen using the UV-VIS. Introduction Sunscreens are chemical tropical products that reflects or absorbs some of the UV radiation from the sun, and thus, helps to protect the skin against sunburn. Exposure to UV radiation has been linked to problems such as skin cancer, immune suppression and premature aging of the skin (Slevin). These problems are on the rise, especially in Australia, as the ozone layer that acts as a UV filter continues to be depleted, rendering the atmospheric UV infiltration capability inferior. Based on the wavelength and concomitant effects, the UV radiation penetrating the ozone is classified into two components; long wave UVA radiation (320 - 400 nm) and short wave UVB (290 - 320 nm). Short wave UVB is responsible for delayed sunburn, cancer and premature aging. The performance of sunscreens is described using the sun protection factor (SPF), which is a rating system for UVB radiation. It is defined by the ratio: ……………….. Where: MED – minimal erythema dose, is the minimal energy requirement for production of delayed sunburn on the skin. The SPF is a measure of the fraction of UV rays causing sunburn when they reach the skin. SPF can also be related to absorbance: Where: T – transmittance I – the intensity of light penetrating the sunscreen – intensity of the incident radiation Equation 2 above can also be written in terms of absorbance as: Where: – molar absorptivity b – path length c – concentration of the absorbing species There are two ways in which sunscreens are made to achieve the desired SPF. The first way is through use of photon absorbing species. These species become excited after absorbing the UV radiation and loose the energy through vibrational energy, hence returning to ground state to allow absorption of another photon. This protects the skin from radiation. The second way is involves the use of compounds such as titanium oxide or zinc oxide. When these compounds are used in a sunscreen, it becomes opaque and therefore, reflects or scatters the incoming sun radiation. Both titanium oxide and zinc oxide nanoparticles absorb well in the UVB region with very little absorbance in the visible region, making these compounds suitable for production of sunscreens (Reyes and Rodríguez). EXPERIMENTAL PROCEDURE Refer to the manual “Experiment 1: SUNSCREENS”. Below are pictures of the sunscreens that were used in this experiment. Figure 1: A picture showing different HAMILTON sunscreen lotions Figure 2: A picture showing different Le Tan sunscreen lotions Preparation of Standard Solutions 50 mg of sunscreen diluted with 50 mL of water: Volume needed for solution 1 (0.1g/L) = Volume needed for solution 2 (0.05g/L) = Volume needed for solution 3 (0.025g/L) = ANALYSIS OF RESULTS Results: Figure 1: UV spectrum for titanium oxide. From figure 1, the peak absorbance for titanium oxide occurs at a wavelength of 284 nm. This value of wavelength is close to the UVB region (290-320 nm) and therefore, TiO2 can be used to reduce the UV radiation penetrating the skin. Figure 2: UV spectra for the organic standard solutions The peak absorbance for the three standard solutions occur at different wavelength. Since the solutions were prepared with the same concentration, it means that the organic components present in the solutions have an influence in absorbance. Each organic compound has a unique absorbance capability at a unique wavelength. Peak absorbance occurs at 300-400 nm, which closely agrees with the UVA range. Figure 3: UV spectra for different concentrations of the sunscreen As seen in figure 3 above, different concentrations of the sunscreen have different levels of absorbance. As the concentration of the sunscreen increases, the capacity of the sunscreen to absorb UV light increases. Figure 4: UV spectra for three Le Tan sunscreens with different SPFs The results in figure 4 show that the SPF of the sunscreen has an influence on absorbance. A sunscreen with a higher SPF can effectively absorb UV light than a sunscreen with a lower SPF. The SPF in a particular sunscreen depends on the concentration of UV absorbing species or the absorbing characteristics of the compounds used in the sunscreen. High concentration of the UV absorbing species and use of compounds with high absorbing characteristics increases the SPF value, whereas low concentration of UV absorbing species and use of compounds with poor absorbing characteristics lowers the SPF of the sunscreen. Figure 5: Spectra for sunscreen and Le Tan both with SPF 15 In figure 5, the absorbance of two sunscreens (Hamilton and Le Tan) with SPF 15 have been compared. Le Tan is observed to have a more effective UV light absorbance than Hamilton. This difference in UV absorbance for sunscreens with the same SPF is due to the type of ingredients, and their concentration levels in the sunscreens. Figure 6: UV spectra for three sunscreens with the same concentration (0.2g/L) and SPF (50) Even though all the three sunscreens have the same concentration and SPF, they have different absorbance. This is due to the effect of ingredients used in the sunscreens and their concentration. The ingredients have different absorbance characteristics. Figure 7: UV spectra for different SPFs. Generally, as the SPF increases, absorbance increases. The SPF in a given sunscreen is achieved by varying the concentrations of the ingredients or by using compounds which possess different absorbing characteristics. However, there is a limit for the concentration of these ingredients as they can be toxic to the skin. Questions Question 1 Quartz is used in the spectrophotometer because it is transparent to UV light within the desired range of wavelengths. Both plastic and glass absorb UV light. Question 2 The peak absorbance of TiO2 colloid, as can be observed in figure 1, is between 230 and 260 nm. Question 3 Titanium nanoparticles block UV by reflection/ absorption of the light. It is effective in blocking UVB and short UVA (320-340 nm). Question 4 The change in pH directly affects the ligands, especially in the case of metal ion solutions. This usually results in shifting of the UV-Vis absorption. Question 5 Components of sunscreen that do not dissolve in isopropanol are mostly physical blocking agents such as ZnO. Question 6 From equation 3, we can see that transmittance and absorbance are inversely related i.e. the more a given light wavelength is absorbed by a substance, the lesser it becomes transmitted. I addition, the inverse relationship is non-linear, it is logarithmic (Gause and Chauhan). Question 7 As SPF increases, absorbance also increases (figure 4). This is because increased absorbance of UV light results in minimal energy requirement for production of delayed sunburn on the skin, thus increasing the SPF factor. Question 8 Light absorbance increases as the concentration of the sunscreen increases (refer to figure 3). Figure 4 shows the variation between SPF and absorbance. From this figure, we can see that absorbance increases as SPF increases. Therefore, we can say that as concentration of the sunscreen increases, SPF also increases. Question 9 By comparing the UV spectra of the sunscreen and that of individual constituents, it is possible to identify the components present in the sunscreen by carrying out comparison of the two spectra. Question 10 From the TiO2 spectrum in figure 1, maximum absorbance is within 230-260 nm, compared to 250-350 nm for the sunscreens. Moreover, the peak absorbance of Titanium oxide is higher (4 a.u) compared to that achieved by the sunscreens (max = 2.5 a.u – refer to figure 6). By comparing the two spectra in figure 1 and 6, none of the sunscreens contain titanium oxide. Question 11 The table below shows the active ingredients in each of the sunscreens Sunscreen Active ingredient Hamilton SPF 15 Octylmet-hoxyinnamate7.5% 4-methylbenzyliden 1.5% Butyt-methoxydibenzoylemthan 1. 5% Hamilton SPF 30 Zinc Oxide 2.9%, TiO2 4.75% Titanium dioxide 1.5% Octocrylene 4% Methoxycinnamate 7.5% Hamilton SPF 50+ (golden packaging) Octocrylene 3%
Butyl Methoxydibenzoyle- methan 2%
4-Methylbenzylidene Camphor 2% octyl Triazone 2% Hamilton SPF 50+ (Pink packing) 4-Methylbenzylidene Camphor 4% octyl Triazone 3% Butyt-methoxydibenzoylemthan 4% Octocylene 4% Le Tan SPF 4 0ctyl Methoxycinnamate 30 mg/g Le Tan SPF 15 0ctyl Methoxycinnamate
1.5%
Butyl Methoxydibenzoyle- methan 4.5%
4-Methylbenzylidene Camphor 1% Le Tan SPF 50+ Butyl Methoxydibenzoyle- methan 5%
4-Methylbenzylidene Camphor 4% Octocylene 2% Bemotrizinol 1% The active minerals in these sunscreen products are either chemical or mineral filters. Each of the ingredients uses a different mechanism to protect the skin from sunburn; either physical blocking (zinc oxide) or chemical absorbance, and maintain stability when exposed to sunlight. They have different toxicity concerns that pose hazards to human health. Question 12 Figure 6 shows a UV spectra for the three sunscreens with the same concentration (0.2g/L) and SPF (50). All the sunscreens have an SPF greater than 15, which is a requirement for a good performing sunscreen. Looking on figure 6, you can easily tell that Sensitive sunscreen has the highest UV absorbance, and therefore performs best of the three, followed by Le Tan and Everyday respectively. Sensitive sunscreen lotion contains zinc oxide as one of its active ingredients which the other two sunscreens (La Tan and Everyday) do not. Zinc oxide is highly stable under most conditions and has the broadest spectrum. It a physical blocker that works by reflecting/scattering UV light, with a broad range of effectiveness. It covers both UVB and UVA. Regular ZnO blocks visible light up to a wave length of 700 nm. This ingredient gives the sunscreen a high quality SPF and hence, its good performance compared to the Everyday and La Tan sunscreen lotions. On the other hand, La Tan sunscreen is more effective compared to Everyday sunscreen lotion. All the sunscreens have similar ingredients and may be, what is causing the difference in performance is the proportion of these ingredients in the sunscreens. Question 13 UV light absorption causes most of the sunscreen active ingredients to undergo structural changes or chemical reactions on the skin. Normally, these ingredients quickly return to their original state to absorb more UV radiation. However, these ingredients may degrade with time and lose their UV protectiveness, hence lowering the absorbance (Lowe). In certain cases, degradation of the ingredients can produce other toxic chemicals, especially if the skin absorbs the sunscreen. Apart from micronized ZnO and TiO2 and Benzophenone-4, the rest of the ingredients are expected to degrade with exposure to UV at varying rates. Conclusion The absorbance of a particular sunscreen is dependent on the type and concentration of the constituents, and the SPF of the sunscreen. The ingredients protect the skin from UV radiation by absorbing the UV light or by reflection and scattering. This experiment provides good knowledge on how sunscreens protect the skin from the UV light. References Read More

Figure 5: Spectra for sunscreen and Le Tan both with SPF 15 In figure 5, the absorbance of two sunscreens (Hamilton and Le Tan) with SPF 15 have been compared. Le Tan is observed to have a more effective UV light absorbance than Hamilton. This difference in UV absorbance for sunscreens with the same SPF is due to the type of ingredients, and their concentration levels in the sunscreens. Figure 6: UV spectra for three sunscreens with the same concentration (0.2g/L) and SPF (50) Even though all the three sunscreens have the same concentration and SPF, they have different absorbance.

This is due to the effect of ingredients used in the sunscreens and their concentration. The ingredients have different absorbance characteristics. Figure 7: UV spectra for different SPFs. Generally, as the SPF increases, absorbance increases. The SPF in a given sunscreen is achieved by varying the concentrations of the ingredients or by using compounds which possess different absorbing characteristics. However, there is a limit for the concentration of these ingredients as they can be toxic to the skin.

Questions Question 1 Quartz is used in the spectrophotometer because it is transparent to UV light within the desired range of wavelengths. Both plastic and glass absorb UV light. Question 2 The peak absorbance of TiO2 colloid, as can be observed in figure 1, is between 230 and 260 nm. Question 3 Titanium nanoparticles block UV by reflection/ absorption of the light. It is effective in blocking UVB and short UVA (320-340 nm). Question 4 The change in pH directly affects the ligands, especially in the case of metal ion solutions.

This usually results in shifting of the UV-Vis absorption. Question 5 Components of sunscreen that do not dissolve in isopropanol are mostly physical blocking agents such as ZnO. Question 6 From equation 3, we can see that transmittance and absorbance are inversely related i.e. the more a given light wavelength is absorbed by a substance, the lesser it becomes transmitted. I addition, the inverse relationship is non-linear, it is logarithmic (Gause and Chauhan). Question 7 As SPF increases, absorbance also increases (figure 4).

This is because increased absorbance of UV light results in minimal energy requirement for production of delayed sunburn on the skin, thus increasing the SPF factor. Question 8 Light absorbance increases as the concentration of the sunscreen increases (refer to figure 3). Figure 4 shows the variation between SPF and absorbance. From this figure, we can see that absorbance increases as SPF increases. Therefore, we can say that as concentration of the sunscreen increases, SPF also increases. Question 9 By comparing the UV spectra of the sunscreen and that of individual constituents, it is possible to identify the components present in the sunscreen by carrying out comparison of the two spectra.

Question 10 From the TiO2 spectrum in figure 1, maximum absorbance is within 230-260 nm, compared to 250-350 nm for the sunscreens. Moreover, the peak absorbance of Titanium oxide is higher (4 a.u) compared to that achieved by the sunscreens (max = 2.5 a.u – refer to figure 6). By comparing the two spectra in figure 1 and 6, none of the sunscreens contain titanium oxide. Question 11 The table below shows the active ingredients in each of the sunscreens Sunscreen Active ingredient Hamilton SPF 15 Octylmet-hoxyinnamate7.

5% 4-methylbenzyliden 1.5% Butyt-methoxydibenzoylemthan 1. 5% Hamilton SPF 30 Zinc Oxide 2.9%, TiO2 4.75% Titanium dioxide 1.5% Octocrylene 4% Methoxycinnamate 7.5% Hamilton SPF 50+ (golden packaging) Octocrylene 3%
Butyl Methoxydibenzoyle- methan 2%
4-Methylbenzylidene Camphor 2% octyl Triazone 2% Hamilton SPF 50+ (Pink packing) 4-Methylbenzylidene Camphor 4% octyl Triazone 3% Butyt-methoxydibenzoylemthan 4% Octocylene 4% Le Tan SPF 4 0ctyl Methoxycinnamate 30 mg/g Le Tan SPF 15 0ctyl Methoxycinnamate
1.

5%
Butyl Methoxydibenzoyle- methan 4.5%
4-Methylbenzylidene Camphor 1% Le Tan SPF 50+ Butyl Methoxydibenzoyle- methan 5%
4-Methylbenzylidene Camphor 4% Octocylene 2% Bemotrizinol 1% The active minerals in these sunscreen products are either chemical or mineral filters.

Read More