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Analiza krem za sončenje z rentgensko praškovno difrakcijo
Vrščaj, Teja (Author), Meden, Anton (Mentor) More about this mentor... This link opens in a new window

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Abstract
Krema za sončenje velja kot ena izmed ključnih sredstev za zaščito pred sončnim sevanjem. Praktično si brez nje ne moremo predstavljati poletnega dne, prebitega na plaži. Pa vendarle vemo kaj se skriva v tem široko uporabnem kozmetičnem izdelku? Prav to je bil glavni namen mojega diplomskega dela, delno določiti sestavo zaščitnih krem oz. kvalitativno analizirati kristalinične faze z analitsko tehniko rentgenske praškovne difrakcije. Princip rentgenske praškovne analize je obsevanje vzorca z rentgensko svetlobo specifične valovne dolžine. Ko rentgenski žarki dosežejo vzorec, pride do njihovega uklanjanja in interferiranja. Intenziteto uklonjenih žarkov in njihove kote zabeleži detektor. Rezultat rentgenske praškovne difrakcije je difraktogram, ki velja kot prstni odtis vsake snovi. Ravno to pa nam omogoči identifikacijo vzorca. S pomočjo programa Xˈpert HighScore Plus sem difraktogram lahko prikazala, ga prebrala in osnovala skupine glede na ujemanje posameznih difraktogramov. Indentifikacijo sem izvedla s primerjavo difraktogramov s standardi, ki se nahajajo v zbirki podatkov PDF-2 v okviru programa Crystallographica Search-Match. Na tak način sem izvedla kvalitativno fazno analizo sedemindvajsetih vzorcev sončnih krem. V primeru, da mi analiza s programom CSM ni dala zadovoljivih rezultatov, sem difraktogram pridobila posredno preko programa ConQuest in programa Mercury, kar je za organske spojine včasih možna alternativa. Z analizo difraktogramov sem ugotovila, da kreme za sončenje vsebujejo tako aktivne sestavine-UV filtre, ki so bodisi kemični ali pa mineralni, kot neaktivne sestavine, kamor spadata identificirana sljuda ali talk. Najpogosteje obravnavana mineralna filtra sta bila cinkov oksid in titanov dioksid. Identifikacija kemičnih filtrov, s programom CSM ni bila mogoča, saj so to organske snovi, ki jih uporabljena zbirka PDF-2 slabo pokriva. Tu je dalo obetaven rezultat posredno iskanje difraktograma preko že prej omenjenih programov, saj mi je uspelo pridobiti difraktogram kemičnega UV filtra s trivialnim imenom ‘bizoktrizol’, ki je ustrezal skupini vzorcev s prej neidentificirano sestavo.

Language:Slovenian
Keywords:krema za sončenje, rentgenska praškovna difrakcija, difraktogram, difraktometer, kvalitativna fazna analiza
Work type:Bachelor thesis/paper (mb11)
Tipology:2.11 - Undergraduate Thesis
Organization:FKKT - Faculty of Chemistry and Chemical Technology
Year:2019
COBISS.SI-ID:1538436803 This link opens in a new window
Views:498
Downloads:256
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Secondary language

Language:English
Title:Characterization of particles in sunscreen using X-ray powder diffraction
Abstract:
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.

Keywords:sunscreen, X-ray powder diffraction, diffraction pattern, diffractometer, qualitative phase analysis

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