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%.
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