Optimizacija HPLC metode za določanje antioksidantov v polimerih

Lanišek, Neža (author), Kralj Cigić, Irena (mentor)

Antioksidanti so spojine, ki se tekom proizvodnje dodajajo polimerom za zaščito le-teh pred oksidacijo in posledično razgradnjo. V diplomskem delu sem optimizirala HPLC metodo za določanje dveh antioksidantov, ki sta lahko prisotna v polivinilkloridu (PVC); oktadecil 3-(3,5-diterc-butil-4-hidroksifenil)propionat (AO 1) in 3,9-bis(oktadeciloksi)-2,4,8,10-tetraoksa-3,9-difosfaspiro[5.5]undekan (AO 2). Najprej sem poiskala ustrezno topilo, v katerem sta se raztopila oba antioksidanta. Ugotovila sem, da je to aceton. Nato sem poiskala najbolj optimalne HPLC pogoje za separacijo obravnavanih antioksidantov. Uporabila sem reverznofazno kolono C18, za gradientno elucijo sem uporabljala dve mobilni fazi – acetonitril in MQ vodo, volumen injiciranja je znašal 30 μL, pretok pa sem ohranjala konstanten pri 1 mL/min. Na detektorju je bila nastavljena valovna dolžina 192 nm. Z injiciranjem mešanih standardnih raztopin različnih koncentracij določevanih antioksidantov sem izrisala umeritveni premici. Ugotovila sem, da je za AO 1 metoda linearna pri nižjih koncentracijah tega antioksidanta, poleg tega pa sta tudi meja zaznave in posledično meja določitve bistveno nižji kot za AO 2. Preverila sem še, če lahko s to metodo učinkovito določimo obravnavana antioksidanta v primeru, da vzorec PVC-ja vsebuje mehčala. To sem napravila z injiciranjem mešane standardne raztopine, ki je vsebovala oba antioksidanta in bis(2-etilheksil) ftalat (DEHP), ki je v PVC-ju lahko prisoten kot mehčalo. Ugotovila sem, da DEHP ne moti določitve obravnavanih antioksidantov. Nazadnje sem na dveh realnih vzorcih PVC-ja preizkusila metodo in ugotovila, da lahko s to metodo kvalitativno in kvantitativno določim le AO 1, saj za AO 2 ni bilo ustreznega kromatografskega vrha.

• Language: Slovenian
• Keywords: antioksidanti, polimeri, HPLC, optimizacija
• Work type: Bachelor thesis/paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2022
• PID: 20.500.12556/RUL-134444
• COBISS.SI-ID: 95195651
• Publication date in RUL: 14.01.2022

Secondary language

• Language: English
• Title: Optimization of HPLC method for determination of antioxidants in polymers

Abstract

Antioxidants are compounds that are added to polymers during production to protect them from oxidation and consequent degradation. In this diploma thesis, I optimized the HPLC method for the determination of two antioxidants that may be present in polyvinyl chloride (PVC); octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (AO 1) and 3,9-bis(octadecyloxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane (AO 2). First, a suitable solvent for both antioxidants was discovered. It proved to be acetone. Then the most optimal HPLC conditions for the separation of antioxidants were sought using a C18 reverse phase column and two mobile phases for gradient elution – acetonitrile and MQ water. The injection volume was 30 μL and the flow was kept constant at 1 mL/min. A wavelength of 192 nm was set on the detector. Mixed standard solutions of different concentrations of antioxidants were injected and the calibration lines were drawn. For AO 1 the method was linear at lower concentrations of this antioxidant, in addition, the limit of detection and consequently the limit of determination were significantly lower than for AO 2. Effectiveness of determination of the antioxidants in the case that the PVC contains plasticizers was discovered. This was achieved with an injection of a mixed standard solution containing both antioxidants and bis(2-ethylhexyl) phthalate (DEHP), which may be included in PVC as a plasticizer. DEHP did not interfere with the determination of the antioxidants. Finally, the method on two PVC samples was tested. Only AO 1 could be qualitatively and quantitatively determined by this method, as there was no corresponding chromatographic peak for AO 2.

• Keywords: antioxidants, polymers, HPLC, optimization