Herein, we utilized carbon nanodots (R-CNDs) for the electrochemical detection of estrogens in tap, natural water samples and simulated effluents from Swedish Waste Water Treatment Plants (WWTPs). R-CNDs were prepared from 2-aminophenol by solvothermal synthesis and used as a modifier for chitosan-based selective membranes. The data obtained from atomic force microscopy and transmission electron microscopy suggest a spherical morphology of the R-CNDs with lateral size in the range of 3–8 nm and the height of 1–8 nm. In contrast to most other known carbon nanodots, R-CNDs are soluble in various organic solvents, including apolar, and less soluble in water. Small nanodots (3 nm) are more hydrophilic than large ones (6–8 nm) and can be separated from the bulk suspension of R-CNDs in heptane by their extraction into water/ethanol mixture. Suspensions of large R-CNDs in apolar solvents exhibit green photoluminescence, while small R-CNDs in polar solvents have orange. This phenomenon was attributed to a solvatochromic rather than to a quantum effect. The R-CNDs were embedded on a chitosan-modified pencil electrode and the electrode was applied for voltammetric determination of four abandoned estrogens: Estrone, Estradiol, Estriol, and Ethynyl Estradiol. The sensor demonstrates a group-selective response to the estrogens with a detection limit of 17.0 nmol·L-1. It can be applied to determine the estrogens in the range of 0.05–4.6 μmol·L−1 in the presence of typical interfering bioactive compounds, such as paracetamol, uric acid, progesterone, sulfamethoxazole, trimethoprim, ibuprofen, caffeine. The developed sensors show repeatability and reproducibility values of 1.8–3.4% and 4.3%, respectively. The efficiency of the was proved by application for tap and lake water samples, where the recovery range was found to be 93–100%. The low cost, stability and high sensitivity and selectivity of fabricated sensors, make R-CNDs a perspective modifier for electrochemical sensors for the detection of estrogen microquantities in variable water samples.
Two samples of functionalized mesoporous silica containing anchored anthrylmethylamine groups (SiO<sub>2</sub>-Ant) have been prepared by surface assembling (1) and one step silane immobilization (2). Both adsorbents can be attributed to bimodal balanced hydrophobic-hydrophilic adsorbents with loading of anthracene groups about 15-33%. The adsorbents have been used for SPE of anthracene from organic solvents (acetonitrile, acetone and heptane) and model solutions of lipids (myristic acid and vegetable oil). The obtained results were compared with commercial C18 SPE cartridge. While C18 cartridge recovers anthracene from water-containing media (acetonitrile/water, 1/1), SiO<sub>2</sub>-Ant cartridges much more efficient in extraction of anthracene from non-polar solvent (heptane). Lipids macrocomponents such as myristic acid and vegetable oil do not decrease the dynamic adsorption capacity and recovery of the model PAH on SiO<sub>2</sub>-Ant. It was demonstrated that π-π stacking interaction with the analyte determine the selectivity of SiO<sub>2</sub>-Ant towards of anthracene. This makes SiO<sub>2</sub>-Ant attractive for selective pre-concentration of PAHs from high lipid content objects, such as vegetable oils.
Two samples of functionalized mesoporous silica containing anchored anthrylmethylamine groups (SiO<sub>2</sub>-Ant) have been prepared by surface assembling (1) and one step silane immobilization (2). Both adsorbents can be attributed to bimodal balanced hydrophobic-hydrophilic adsorbents with loading of anthracene groups about 15-33%. The adsorbents have been used for SPE of anthracene from organic solvents (acetonitrile, acetone and heptane) and model solutions of lipids (myristic acid and vegetable oil). The obtained results were compared with commercial C18 SPE cartridge. While C18 cartridge recovers anthracene from water-containing media (acetonitrile/water, 1/1), SiO<sub>2</sub>-Ant cartridges much more efficient in extraction of anthracene from non-polar solvent (heptane). Lipids macrocomponents such as myristic acid and vegetable oil do not decrease the dynamic adsorption capacity and recovery of the model PAH on SiO<sub>2</sub>-Ant. It was demonstrated that π-π stacking interaction with the analyte determine the selectivity of SiO<sub>2</sub>-Ant towards of anthracene. This makes SiO<sub>2</sub>-Ant attractive for selective pre-concentration of PAHs from high lipid content objects, such as vegetable oils.
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