In summer, you must take sun protection measures when traveling. Strong ultraviolet rays can cause certain damage to the skin. Sunscreen can reduce the damage of ultraviolet rays to the skin. Sun Protection Factor (SPF) of current sunscreen cosmetics is mainly tested by human body under ultraviolet exposure after applying cosmetics. Although the results of this test are more accurate, it also causes certain damage to the skin of the test participants. We can also use a spectrometer to test the anti-ultraviolet ability of sunscreen.
The human eye is sensitive to light from the red end (about 780nm) to the violet end (about 380nm) of the spectrum. Therefore, sunlight with shorter wavelengths is considered to be beyond the ultraviolet range and is called "ultraviolet" (UV). Ultraviolet rays are divided into the UVA band (down to about 320nm), the higher energy and more dangerous UVB light (between 320nm and 280nm), and the high-energy UVC band (shorter wavelength). UVC is completely absorbed by the ozone layer, while UVB can make people's skin red. Ultraviolet rays in the UVA region can cause damage to human skin tissue. We can determine the anti-ultraviolet ability of sunscreen by testing the absorbance of ultraviolet rays through the UVA and UVB regions of the sunscreen sample.
There are three methods for measuring samples. The first is the solution method, which is to dissolve the active ingredients of the sunscreen in a suitable solvent, pour the solution from the solid, and measure the transmittance with a cuvette with standard absorbance, but this method ignores the effect of the solid component. The second is to evenly apply the sunscreen on a shallowly concave transparent support, so that the film transmittance can be measured, but this method is difficult to ensure the consistency of the film. The third is to apply the sunscreen on surgical tape attached to a microscope slide. The evenly distributed pores on the surgical tape allow the sunscreen to be evenly and reproducibly applied to the sample holder, and the coverage of the sunscreen on the surgical tape is about 1-2 mg per square centimeter, which is similar to the amount recommended by doctors to protect the skin.
As shown in the figure, build the projection system. First, turn on the UV light source, select the appropriate distance, and make the beam incident vertically. In order to ensure the illumination of the UV fiber light source, preheat for 30 minutes. After the light source reaches a certain intensity, adjust the fiber spectrometer and select the appropriate integration time to ensure the spectral intensity. Measure the UV transmittance of the empty slide with surgical tape, and save the white background after there is no obvious fluctuation.
Apply a thin layer of sunscreen on the sample holder, scrape it into a thin and uniform layer with a clean microscope slide, and then weigh the sample slide again and dry it for 60 minutes. After drying for a period of time, set the transmittance of the scattering reference slide to 100% reference again. Finally, measure the transmittance of the actual sample coated with sunscreen.
This method can be used to obtain the UV resistance of sunscreen. After certain standard discussions, the test of UV resistance in the future can be separated from human experiments and confirmed by spectra to ensure the personal safety of the subjects. The spectrometer used in this experiment comes from JINSP. If you need it, you can click the link below to contact us.
LINK: Fiber Optic Spectrometers - JINSP Company Limited (jinsptech.com)
Post time: Aug-08-2024