diplomsko delo
Matevž Polak (Avtor), Helena Prosen (Mentor)

Povzetek

Alkilfenoli so obstojni razgradni produkti alkilfenol etoksilatov. Slednji so, zaradi zelo dobrih površinsko aktivnih lastnosti, pogosto prisotni v številnih komercialnih in industrijskih čistilih ter ostalih izdelkih. Skozi zadnja desetletja so številne raziskave potrdile izrazito endokrino ter kancerogeno aktivnost alkilfenolov, skupaj s precejšnjo akutno toksičnostjo za morske organizme in nezanemarljivim biokoncentracijskim faktorjem pri določenih izomerih. Ker pa njihov vpliv na okolje in organizme še ni popolnoma razjasnjen, jih uvrščamo v skupino novih oziroma emergentnih onesnaževal – CEC. Alkifenoli v naravi sami po sebi niso prisotni, ampak so prisotni le kot posledica antropogenih emisij. Največ v obliki odpadnih vod in odplak. Posledično so lahko kot onesnaževala v relativno nizkih koncentracijah prisotni tako v pitni kot tudi površinskih vodah. Kljub nizkim koncentracijam, so dolgoročni učinki zelo zaskrbljujoči, zato se je do sedaj na to temo odvilo že mnogo raziskav in razvilo veliko metod, ki nam pomagajo razumeti njihov učinek na ekosisteme in določati njihovo prisotnost. S podobnim namenom je nastalo tudi moje diplomsko delo. Cilj je bila optimizacija ekstrakcijske metode za tri alkilfenole, prisotne v vodnih vzorcih. Preizkušal sem številne ekstrakcijske parametre (sorbenti, elucijska topila, volumni elucijskega topila, prebojni volumen,…) in lastnosti vzorca (pH ter ionska moč), vse z namenom po čim višjih izkoristkih. Koncentracije analitov sem določal z metodo visoko ločljivostne tekočinske kromatografije – HPLC, ki je bila že predhodno optimizirana. Kot zadnji korak sem vse optimalne parametre združil v končni postopek in metodi določil še ponovljivost. Za ekstrakcijo alkilfenolov je bila, na podlagi hidrofobnosti, najprimernejša ekstrakcijska kolona C8 (Supelco). Volumen nanosa je znašal 20 mL, najboljšo elucijo sorbiranih analitov pa je dosegel metanol z volumnom 2 mL. Sprememba volumna vmesnega spiranja z 10 % metanolom v MQ vodi ni pokazala bistvenih razlik v izkoristkih. Dodatek soli (NaCl) do 2 % masnega deleža in nakisanje vzorca do pH = 3 pa je izrazito povečalo izkoristke pri večini analitov (za skoraj 20%). Prebojni volumen za 4-nonilfenol znaša okoli 100 mL, za 4-t-oktilfenol in 4-oktilfenol pa ta ni bil določen, vendar je nad 250 mL. Pri končni metodi, z vsemi optimalnimi parametri, so bili izkoristki bistveno nižji od pričakovanih. Za 4-t-oktilfenol je bil izkoristek 91,3 %, kar je 5 % nižje od večine prejšnjih določitev. Za 4-oktilfenol in 4-nonilfenol pa sta izkoristka znašala 44,4 % in 42,1 %, kar je 20 % nižje od predhodnih določitev. Ponovljivost ekstrakcije je bila pri 4-t-OF razmeroma dobra (CV=2,55 %), pri ostalih dveh analitih pa slabša. CV za 4-oktilfenol je bil 9,44 %, za 4-nonilfenol pa 7,42 %.

Ključne besede

emergentna onesnaževala;alkilfenoli;ekstrakcija na trdno fazo;SPE;optimizacija ekstrakcije;optimizacijski parametri;tekočinska kromatografija visoke ločljivosti;HPLC;diplomska dela;

Podatki

Jezik: Slovenski jezik
Leto izida:
Tipologija: 2.11 - Diplomsko delo
Organizacija: UL FKKT - Fakulteta za kemijo in kemijsko tehnologijo
Založnik: [M. Polak]
UDK: 542.61:543.544.5HPLC(043.2)
COBISS: 165422595 Povezava se bo odprla v novem oknu
Št. ogledov: 54
Št. prenosov: 9
Ocena: 0 (0 glasov)
Metapodatki: JSON JSON-RDF JSON-LD TURTLE N-TRIPLES XML RDFA MICRODATA DC-XML DC-RDF RDF

Ostali podatki

Sekundarni jezik: Angleški jezik
Sekundarni naslov: Optimization of extraction for alkylphenols from water samples
Sekundarni povzetek: Alkylphenols are stable degradation products of alkylphenol ethoxylates. The latter are, due to their excellent surfactant properties, commonly found in numerous commercial and industrial cleaners and other products. Over the past decades, numerous studies have confirmed the pronounced endocrine and carcinogenic activity of alkylphenols, along with significant acute toxicity to marine organisms and notable bioconcentration factors of some isomers. However, their impact on the environment and organisms is not yet fully understood, which classifies them as new contaminants or so-called contaminants of emerging concern (CECs). Alkylphenols are not naturally present in the environment but are there because of anthropogenic emissions, primarily from numerous forms of wastewater and effluents. As a result, they can be present as pollutants in relatively low concentrations in both drinking and surface waters. Despite the low concentrations, their long-term effects are highly concerning, leading to numerous research efforts and the development of various methods to understand their effects on ecosystems and detect their presence. With a similar objective, my thesis was developed. The aim was to optimize a solid phase extraction method for three alkylphenols present in water samples. I tested several extraction parameters (sorbents, elution solvents, elution solvent volumes, breakthrough volumes, etc.) and sample properties (pH and ionic strength) to achieve maximum recoveries. The analyte concentrations were determined using a high-performance liquid chromatography (HPLC) method that was previously optimized. In the final step, all the optimal parameters were combined into a complete procedure, and the method's reproducibility was determined. For the extraction of alkylphenols, the most suitable extraction column, based on hydrophobicity, was C8 (Supelco). The sample loading volume was 20 mL and the best elution of sorbed analytes was achieved using 2 mL of methanol. Changing the volume of intermediate rinsing with 10 % methanol in MQ water did not show significant differences in recoveries. Adding salt (NaCl) up to 2 % and adjusting the sample to a pH of 3 significantly increased recoveries for most analytes (by almost 20%). The breakthrough volume for 4-nonylphenol was around 100 mL, while it was not determined for 4-tert-octylphenol and 4-octylphenol, but was at least 250 mL. In the final method with all the optimal parameters, the yields were lower than expected. The yield for 4-tert-octylphenol was 91.3%, which is 5% lower than in most previous determinations. For 4-octylphenol and 4-nonylphenol, the yields were 44.4% and 42.1%, which is nearly 20% lower than in previous determinations. The reproducibility of the extraction was good for 4-tert-octylphenol (CV=2.55%), but worse for the other two analytes. The CV for 4-octylphenol was 9.44%, and for 4-nonylphenol, it was 7.42%.
Sekundarne ključne besede: water pollution;alkylphenols;solid phase extraction;high-performance liquid chromatography;Onesnaževanje vode;Ekstrakcija (kemija);Univerzitetna in visokošolska dela;
Vrsta dela (COBISS): Diplomsko delo/naloga
Študijski program: 1000373
Konec prepovedi (OpenAIRE): 1970-01-01
Komentar na gradivo: Univ. v Ljubljani, Fak. za kemijo in kemijsko tehnologijo, UNI Kemija
Strani: 28 str.
ID: 19888197