Sunscreen is considered as one of the most important products when protecting ourselves against solar radiation. We practically cannot imagine a hot summer day spent on a beach, without a sunscreen on.
However, do we actually know what hides inside this widely used cosmetic product?
That was the main purpose of my thesis, to partially analyze the composition of protective creams or better said qualitatively analyze the crystalline phases with the analytical technique of so-called X-ray powder diffraction.
The principle of the X-ray powder analysis is the irradiation of a sample with the X-ray of a specific wave length. When X-rays reach the sample, their diffraction and interference will occur. The intensity of the diffracted X-rays and their angles are recorder by the detector. The result of X-ray powder diffraction is a diffraction pattern, which is considered as the fingerprint of each substance. This allows us to identify each sample accordingly.
Using the X’pert HighScore Plus programe, I displayed the diffraction patterns, read it and established groups according to the matched individual peaks in their diffraction patterns.
I carried out the identification by comparing the diffraction patterns with the standards, contained in the Crystallographica Search-Match program database PDF-2. This was the procedure I took when analyzing the qualitative phase of twentyseven samples of sunscreen. If the CSM analysis did not give me a satisfactory result, I obtained the diffraction pattern indirectly through the ConQuest and the Mercury programs, which is sometimes a possible alternative for organic compounds.
With the diffraction patterns analysis, I found that the sunscreen contained both active ingredients, which are UV filters that are either chemical or mineral, as inactive ingredients, which include mica or talc, that I identified. The most frequent mineral UV filters were zinc oxide and titanium dioxide. Identification of chemical filters performed by CSM program was not possible, since these are organic substances, which are not well covered in the PDF-2 database. However, a promising result was obtained by looking for diffraction patterns through the aforementioned programs. I managed to obtain a diffractogram of a chemical UV filter with a trivial name of ‘bisoctrizole’, which suited a group of samples with previously unidentified composition.