Rentgenska praškovna difrakcija pralnih praškov

Kodrič, Eva (author), Golobič, Amalija (mentor)

Rentgenska praškovna analiza je metoda, s katero lahko določujemo sestavo trdnih vzorcev in temelji na difrakciji rentgenske svetlobe na kristaliničnih snoveh. To metodo sem uporabila za identifikacijo različnih snovi oziroma kristalnih faz v enajstih vzorcih pralnih praškov za perilo, ki so na voljo v slovenskih trgovinah, saj sem želela izvedeti več o sestavi teh proizvodov, ki jih uporabljamo v običajnem gospodinjstvu. Poleg tega sem želela tudi pridobiti več teoretičnega in praktičnega znanja o rentgenski praškovni analizi. Kvalitativno praškovno analizo na osnovi praškovnih posnetih praškovnih difraktogramov sem izvedla s programom Crystallographica Search-Match (CSM) in podatkovne zbirke praškovnih difraktogramov standardov PDF-2. Ugotovila sem, da so prav vsi obravnavani pralni praški vsebovali precej poceni polnila Na2SO4, nekateri pa tudi NaCl. Ti dve snovi nista bili navedeni v nobeni deklaraciji izdelka. Vsi pralni praški so vsebovali kot graditelj s pralnim učinkom v dosti veliki količini Na2CO3 ali NaHCO3 oziroma njun kristalohidrat. Tisti praški, ki se uporabljajo za pranje belega perila, so vsebovali belilo Na2CO3(H2O2)1,5. Ob raztapljanju te trdne snovi se namreč sprošča vodikov peroksid, ki kot oksidant učinkuje kot belilo. V nekaterih praških sem identificirala zeolite, ki veljajo kot sredstva za mehčanje vode na osnovi izmenjave kationov. V posameznih primerih jih kljub temu, da so bili navedeni v deklaraciji izdelka in so kristalinične snovi, nisem identificirala v vzorcih, kar pomeni, da bodisi v prašku niso bili prisotni ali pa da so bili dodani le v zelo majhni količini. V posameznih praških pa sem kot graditelje oz. mehčala identificirala tudi različne fosfate. V vzorcih sem pojasnila vse ali večino uklonskih vrhov. Kljub temu določenih snovi, ki so bile deklarirane na embalaži proizvodov, predvsem površinsko aktivnih snovi, dišav, parfumov in encimov nisem identificirala v vzorcih. Bodisi, ker so bili v praških v zelo nizkih koncentracijah in posledično pod mejo detekcije izbrane metode, ali ker so amorfne snovi ali pa niso kot standard zastopane v podatkovni zbirki PDF-2.

• Language: Slovenian
• Keywords: rentgenska praškovna difrakcija, kvalitativna fazna analiza, pralni praški
• Work type: Bachelor thesis/paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2021
• PID: 20.500.12556/RUL-128368
• COBISS.SI-ID: 72174595
• Publication date in RUL: 09.07.2021

Secondary language

• Language: English
• Title: X-ray diffraction of washing powders

Abstract

X-ray powder analysis is a method by which the composition of solid samples can be determined and is based on the diffraction of X-rays on crystalline substances. I used this method to identify different compounds or crystalline phases in eleven samples of laundry detergents available in Slovenian stores, as I wanted to know more about the composition of these products, which are used in ordinary household. Additionally, I also wanted to gain more theoretical and practical knowledge about X-ray powder analysis. Qualitative powder analysis based on X-ray powder patterns was performed using the Crystallographica Search-Match (CSM) program and the powder diffraction file PDF-2. I found that all investigated samples of washing powders contained fairly inexpensive Na2SO4 fillers, and some also NaCl. These two substances were not mentioned in any of the product declarations. All washing powders contained a large amount of Na2CO3 or NaHCO3 being as crystal hydrate or unhydrous as a builder with a washing effect. Those powders used to wash white laundry contained the bleaching agent Na2CO3(H2O2)1.5. When this solid dissolves, hydrogen peroxide is released, which acts as an oxidative bleaching agent. In some powders, I have identified zeolites that are considered as softeners based on cation exchange. In some cases, despite being listed in the product declaration and being crystalline substances, I did not identify them in the samples. This means that they were either not present in the powder or were added only in a very small amount. In individual powders, however, I have also identified different phosphates as builders or softeners. For these, I explained all or most of the diffraction peaks. Nevertheless, certain substances declared on the packaging of products, in particular surfactants, perfumes and enzymes, were not identified in the samples. This is possible either because these were in very low concentrations and consequently below the detection limit or because they are amorphous or not included as standards in the PDF-2 database.

• Keywords: X - ray powder diffraction, qualitative phase analysis, washing powders