In this master's thesis, we focused on determining benzotriazoles and alkylphenols, which are among the most prevalent emerging pollutants. These compounds are widely used in industry, agriculture, and households, primarily added to corrosion protection agents, detergents, and plastic products.
We determined benzotriazoles in model wastewater treated with the electrooxidation process and the electro-Fenton process. For the latter, we also examined how the choice of cathode affect its efficiency. Compounds were determined using liquid chromatography, and the results were used to compare the effectiveness of individual processes. The electro-Fenton process proved to be more effective than electrooxidation. One hour of treatment was sufficient to remove 96% of benzotriazole, and after two hours, the compounds were no longer detectable. In electrooxidation, approximately 40% and 10% remained after 60 and 120 min, respectively. Both processes performed better at pH 2 than at pH 4. The choice of a graphite felt cathode proved to be more effective than a stainless steel cathode. The former degraded benzotriazole below the detection limit within one hour, while 7.6% of benzotriazole remained with the latter. The electrooxidation process was also tested under alkaline conditions, where it was found that high and low pH values give similar results.
For the determination of selected alkylphenols (4-tert-octylphenol, 4-octylphenol, and 4- nonylphenol), we developed an efficient method based on solid-phase extraction for pre- concentration of analytes and gas chromatography coupled with tandem mass spectrometry. Due to their low volatility and high polarity, the compounds needed to be derivatized. In the first step, we optimized the solid-phase extraction conditions, determining the appropriate cartridge, elution solvent, and its volume. The C8 sorbent cartridge and elution with 5 mL of ethyl acetate were selected as the most suitable. We also found that acidifying the samples to pH 3 and adding 2% electrolyte improved extraction efficiency. Next, we optimized the derivatization process, examining how the choice of derivatization solvent, volume of the derivatization reagent, and reaction time affected its efficiency. BSTFA + 1% TMCS was used as the derivatization reagent. Derivatization worked best with the addition of 30 μL of solvent and 70 μL of reagent. One hour at room temperature was sufficient for complete conversion. The detection limits of the entire method were 5.19 ng/L for 4-tert-octylphenol, 6.87 ng/L for 4- octylphenol, and 6.45 ng/L for 4-nonylphenol. The recovery and repeatability of the entire process were 137.7% and 4.3% for 4-tert-octylphenol, 113.8% and 3.5% for 4- octylphenol, and 67.3% and 4.8% for 4-nonylphenol.
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