Evaluation of polar phenolic compounds in water samples close to shale exploitation area: a case study

Abstract

Polar phenolic compounds of anthropogenic sources are widely studied by the scientific community since their effects are considered harmful to aquatic biota. From an environmental point of view, information regarding the presence of these contaminants allows promoting broader studies of environmental assessment. An evaluation of the presence of phenol, o-cresol, m-cresol, p-cresol, and 2,4-dimethylphenol in aqueous samples was carried out, to investigate the possibility of contamination owing to the shale mining activities in the most important Brazilian oil shale reserve, in the region of Sao Mateus do Sul, Parana State, Brazil. Ten water samples were collected near this region and the five mentioned phenolic compounds were preconcentrated using a previously validated liquid-phase microextraction procedure. Their quantitation was realized by liquid chromatography coupled with diode array detector. The presence of phenol was estimated in some samples below 3.3 µg L−1 and 2,4-dimethylphenol was determined (4.7 µg L−1) in one sample, whereas the cresols were not found in any sample. To confirm the presence or the absence of the analytes, the samples were spiked with the phenolic compounds, and satisfactory recovery values between 52.2 and 120.5% and relative standard deviations less than 17.2% for triplicate samples of these compounds were observed, suggesting that this chromatographic/extraction method was adequate for quantitation of these compounds in environmental samples and wastewater from shale mining area. The results suggested no contribution of the phenolic compounds as pollutants of the rivers and streams for the studied area owing to the shale activities.