Optimizacija ekstrakcije policikličnih aromatskih ogljikovodikov iz tal

Česnik, Maša (author), Prosen, Helena (mentor)

Policiklični aromatski ogljikovodiki (PAH) so skupina organskih spojin, ki v veliki večini prehaja v okolje zaradi človeške dejavnosti. Uvrščamo jih med obstojna organska onesnaževala, nekateri izmed njih pa so tudi rakotvorni in mutageni. V tleh lahko dosežejo koncentracijo, ki pomeni tveganje za človekovo zdravje, zato je nujno spremljati onesnaženost tal. V magistrski nalogi sem za namen čiščenja ekstraktov najprej optimizirala ekstrakcijo na trdno fazo (SPE) za ekstrakcijo PAH iz vode. Preizkusila sem več SPE kolon, izmed katerih sem najboljše rezultate dobila s Supelco LC-18 kolono. Ovrednotila sem vpliv pretoka, odparevanja, dodatka NaCl in acetona na učinkovitost SPE. Koncentriranje ekstrakta z odparevanjem topila je vodilo do pomembnih izgub naftalena, acenaftena in fluorena, vendar manj, ko sem odparevala pri sobni temperaturi. Prisotnost acetona v raztopini PAH je poslabšala izkoristke SPE, prisotnost NaCl pa ni imela pomembnega vpliva. Določila sem tudi ponovljivost SPE metode, pri čemer so bili relativni standardni odmiki 4,3–8,7 %. Ekstrakcijo iz tal sem optimizirala z umetno kontaminiranimi tlemi (z 10 µg PAH/g tal), ki sem jih čez noč pustila (za prib. 20 h) , da je izhlapelo topilo. Pri tem so bili izkoristki ultrazvočne ekstrakcije (UE) 3,1–81,2 %, ko pa sem ekstrakt čistila s SPE, so bili še nižji. Tak način priprave kontaminiranih tal vodi do izgub bolj hlapnih PAH (naftalena, acenaftena in fluorena) zaradi izhlapevanja. Boljše rezultate sem dobila pri tleh, ki sem jim tik pred UE dodala PAH (74,8–90,4 %). Tudi v tem primeru sem dobila bistveno slabše izkoristke, če sem uporabila SPE. Ko sem ekstrakte tal očistila s SPE brez odparevanja topila v eluatu, so izkoristki padli pod 20 % za vse PAH. Ponovljivost ultrazvočne ekstrakcije sem določila s tlemi s svežim dodatkom 2 µg PAH/g tal, pri čemer so izkoristki znašali 76,1–90,1 %. Podobno primerljive izkoristke sem dobila tudi pri tleh z 1 µg PAH/g tal.

• Language: Slovenian
• Keywords: policiklični aromatski ogljikovodiki, tla, ekstrakcija na trdno fazo, ultrazvočna ekstrakcija, plinska kromatografija z masno spektrometrijo (GC-MS)
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2021
• PID: 20.500.12556/RUL-127285
• COBISS.SI-ID: 66412035
• Publication date in RUL: 02.06.2021

Secondary language

• Language: English
• Title: Optimization of polycyclic aromatic hydrocarbons extraction from soil

Abstract

Polycyclic aromatic hydrocarbons are a group of organic compounds that are mainly released to the environment due to anthropogenic sources of pollution. They are classified as persistent organic pollutants, some of them are cancerogenic and mutagenic. PAH accumulate in the soil, where they can reach concentrations dangerous to human health. For this reason, it has become essential to monitor concentrations of PAH in the soil. In order to develop an extract clean-up method, I optimized solid phase extraction of PAH from water. Several different SPE cartridges were tested, of which Supelco LC-18 cartridge gave the best results. I evaluated the effect of sample flow, evaporation, and the addition of NaCl and acetone on the efficiency of SPE. Evaporation of solvent led to significant losses of naphthalene, acenaphthene and fluorene, which were even higher when evaporation at higher temperatures was used. Acetone in PAH solution lowered the extraction efficiency, meanwhile, the addition of NaCl didn’t affect it significantly. Repeatability of SPE was also evaluated and relative standard deviations were in the range of 4.3-8.7 %. Extraction from soil was optimized by using artificially spiked soil (10 µg PAH/g soil), that was left in a fume hood overnight (approximately 20 h) to evaporate the solvent. The efficiency of ultrasonic extraction from this soil was in the range 3.1-81.2 % and was even lower when SPE clean-up was used. The method mentioned above for soil spiking is not appropriate for more volatile PAH (naphthalene, acenaphthene and fluorene), due to their evaporation. Better efficiency of ultrasonic extraction was obtained with the use of freshly spiked soil (74.8-90.4 %). Also, in this case, SPE clean-up led to low extraction efficiency (under 20 % for all PAH). Repeatability of ultrasonic extraction of PAH from freshly spiked soil was tested with soil with 2 µg PAH/g soil. Extraction efficiencies were within 76.1-90.1 %. Similar results were obtained with the freshly spiked soil that contained 1 µg PAH/g soil.

• Keywords: polycyclic aromatic hydrocarbons, soil, solid phase extraction, ultrasonic extraction, gas chromatography-mass spectrometry (GC-MS)