Simultaneous determination of dissolved phenanthrene and its metabolites by derivative synchronous fluorescence spectrometry with double scans method in aqueous solution

Various non-destructive SFS techniques for simultaneous recognition and monitoring of 1-amino pyrene and 1-napthyl amine in the mixture

The sensitive, non-destructive constant wavelength (CW) and constant energy (CE) SFS techniques have been used for the simultaneous determination of 1-amino pyrene (AP) and 1-napthyl amine (NA) in their mixtures without prior separation via optimization of different experimental conditions (ΔλCW 70.0 nm, ΔνCE 4000.0 cm-1, scan rate 240.0 nm/min, 25.0 °C, methanol). Amplitude-concentration plots have been linear for 1-amino pyrene, AP (0.01-0.1 mg/L) and 1-napthyl amine, NA (0.1-1.0 mg/L). In aqueous methanolic binary mixtures, the mean recoveries (RSD, LOD and LOQ) of AP were found to be 100.09% (0.053, 0.008 mg/L and 0.034 mg/L) for emission, 100.11% (0.141, 0.008 mg/L, 0.034 mg/L) for CWSFS, 100.05% (0.109, 0.007 mg/L and 0.032 mg/L) for first derivative CWSFS, 100.00% (0.148, 0.007 mg/L and 0.031 mg/L) for CESFS, 99.99% (0.109, 0.008 mg/L and 0.035 mg/L) for first derivative CESFS modes respectively. Additionally, for NA the mean recoveries (RSD, LOD and LOQ) were 100.29% (0.360, 0.046 mg/L and 0.204 mg/L) for emission, 100.06% (0.089, 0.098 mg/L, 0.436 mg/L) for CWSFS, 100.09% (0.144, 0.065 mg/L and 0.288 mg/L) for first derivative CWSFS, 100.05% (0.178, 0.077 mg/L and 0.339 mg/L) for CESFS, 100.03% (0.181, 0.082 mg/L and 0.364 mg/L) for first derivative CESFS modes respectively. Considering their safety and greenness, these methods might be considered as green tools using analytical eco-scale approaches (eco-scale score 88.0).

Constant-wavelength synchronous fluorescence spectrometry for simultaneous and rapid determination of five polycyclic aromatic hydrocarbon residues in dairy products

A new method for simultaneously determining five polycyclic aromatic hydrocarbons (PAHs) (fluorene, benzofluorene, pyrene, benzo(a)pyrene, and perylene) in dairy products using constant-wavelength synchronous fluorescence spectrometry (CWSFS) was established in this study. Acetonitrile was chosen as the extraction solvent to extract the five PAHs from the dairy products, and an ultrasound extraction method was adopted. The supernatants were filtered using a 0.45-μm microporous filter membrane and concentrated to dryness with a nitrogen dryer. The extracts were then re-dissolved in cyclohexane for analysis. To overcome interference from the background matrix and between PAHs, the difference in wavelength (Δλ) at 40 nm was chosen for CWSFS scanning. With only one single scan, the five PAHs in dairy products could be distinguished and determined using the standard curve method without the need for previous chromatographic separation of the analyte solution. Detection limits of fluorene, benzofluorene, pyrene, benzo(a)pyrene, and perylene were 0.0051 μg·L^-1 , 0.016 μg·L^-1 , 0.021 μg·L^-1 , 0.0056 μg·L^-1 , and 0.0062 μg·L^-1 , respectively. Recoveries were between 85.60% and 98.42%. These five PAHs in dairy products were determined with good results and therefore expected to be a routine detection method for PAHs in dairy products.

Spectroscopic and theoretical studies of fluorescence effects induced by the ESIPT process in a new derivative 2-Hydroxy-N-(2-phenylethyl)benzamide - Study on the effects of pH and medium polarity changes

The paper presents the results of studies conducted with the use of stationary and time-resolved fluorescence spectroscopy for the new derivative 2-Hydroxy-N-(2-phenylethyl)benzamide (SAL-3) in aqueous solutions with various concentrations of hydrogen ions as well as in solvent mixtures (i.e. media with changing polarity/polarizability). For the compound selected for the study placed in aqueous solutions with varying concentrations of hydrogen ions, the fluorescence emission spectra revealed a single emission band within most of the pH range, however, at low pH (pH<3) a significant broadening (noticeable effect of dual fluorescence) and shifting of the band was observed. Whereas, for water and polar (protic) solvents, we observed a very interesting phenomenon of dual fluorescence never before reported for this particular group of analogues (with the specific substituent system). Based on the results of the experiments, it was observed that the presented effects may be related both with conformational effects (related to the possible positioning of the-OH group on the side of the carbonyl system, which facilitates the possibility of proton transfer) as well as, most importantly, the effects of excited state intramolecular proton transfer (ESIPT-Excited State Intramolecular Proton Transfer) related in this case with the necessary (new/previously unobserved in published literature) presence of ionic and non-ionic forms of the compound). Both the conducted quantum-mechanical [TD]DFT-Time-Dependent Density Functional Theory) calculations and excited state dipole moment change calculations for the analyzed molecule in solvents with varying pH confirmed the association between the observed fluorescence phenomena and the two aforementioned effects.

Magnetic dispersive micro-solid phase extraction with the CuO/ZnO@Fe3O4-CNTs nanocomposite sorbent for the rapid pre-concentration of chlorogenic acid in the medical extract of plants, food, and water samples

CuO/ZnO@Fe₃O₄-CNTs-NC was synthesized and used as a sorbent in a MDMSPE method for the determination of chlorogenic acid in the medical extract of plants, food, and water samples.