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An Eu(III) β-diketonate complex was produced and employed as a photoluminescent probe to determine methylmercury (CH 3 Hg + ). To establish its molecular structure, the Eu(III) complex was characterized by elemental (CHNS) and thermogravimetric analyses and infrared spectroscopy. After establishing robust conditions to use the Eu(III) complex as an analytical probe, it was employed for the analysis of produced water (PW) samples with the analytical response based on the luminescence suppression proportional to the concentration of CH 3 Hg + (a linear model after normalization of the response within the concentration range from 0.2 μg L -1 up to 2.0 μg L -1 ). Selectivity was guaranteed by a simple liquid-liquid extraction of the analyte in dichloromethane, which also allowed a 50 times pre-concentration factor. The instrumental limit of quantification of 0.2 μg L -1 is equal to the limit established in Brazilian resolution for total mercury content in waters, but pre-concentration (50 times factor) improved the overall method limit of quantification down to 4 ng L -1 . Recovery results agreed with the ones achieved using cold vapor atomic absorption spectrometry., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Mercury speciation was achieved using a nanocomposite, consisting of graphene quantum dots (GQDs) and TiO 2 nanoparticles, to mediate photo-degradation of mercurial species into the Hg cold vapor detected by atomic spectrometry. Sample solution (containing Hg 2+ , CH 3 CH 2 Hg, and CH 3 Hg at hundreds of ng L -1 ) was placed in quartz tube containing formic acid solution (2% v/v) and microliter aliquot of GQDs/TiO 2 nanocomposite dispersion (0.6 mg of nanocomposite). The tube was placed inside a photochemical reactor then, adapted to the mercury-dedicated spectrometer. Quantitative speciation was achieved taking advantage of the differences in UV photodegradation kinetics: Hg 2+ (5 min), CH 3 CH 2 Hg (9 min) and CH 3 Hg (13 min). Gas-chromatography cold vapor atomic fluorescence spectrometry was used to confirm the evolution of the reactions over time during photo-reaction. The limits of detection were 10 ng L -1 for CH 3 CH 2 Hg and 7 ng L -1 for Hg 2+ and CH 3 Hg., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Thiomersal is an organomercury derivative that degrades producing thiosalicylic acid, dithiobenzoic acid and ethylmercury. It is widely used in topical pharmaceutical preparations and as preservative in vaccines and cosmetics. In this work, an electro-analytical method for thiomersal was developed using graphene quantum dots (GQDs) as a surface modifier of a glassy carbon electrode. The method rely on using square-wave voltammetry and exploring the synergistic effect between GQDs, visible radiation and the applied potential in producing very intense Hg oxidation peak during the anodic scan. A linear voltammetric response was obtained for the analyte in the concentration range from 3.0 μmol L -1 (1.2 μg mL -1 ) to 32 μmol L -1 (12 μg mL -1 ), with a detection limit of 0.9 μmol L -1 (0.34 μg mL -1 ). The proposed method was successfully applied for thiomersal determination in influenza vaccine., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

We study the potentialities of a two-color Surface Plasmon Resonance (SPR) spectroscopy nanosizer by monitoring the assembling of a colloidal dispersion of citrate stabilized gold nanoparticles (AuNPs) on SiO 2 surface. When the AuNPs/water composite's optical density layer is negligible and the electron mean-free path limitation is taken into account in the AuNPs' dielectric constant;s formulation, the surface density σ of the nanoparticle array and the statistical mean size of the nanoparticles can be straightly determined by using two-color SPR spectroscopy in the context of Maxwell's Garnett theory. The optical method, demonstrated experimentally for AuNPs with a nominal mean diameter of 15 nm, can, theoretically, be extended to bigger nanoparticles, based on a simple scaling relation between the extinction cross section of the single nanoparticle σ ext and the surface density σ. The experimental results, comparable to those obtained by AFM, transmission electron microscopy and dynamic light scattering technique, establish a novel insight on the SPR spectroscopy's potential to accurately characterize nanomaterials.

Flavonoids are polyphenols that help the maintenance of health, aiding the prevention of diseases. In this work, CdTe QDs coated with 3-mercaptopropionic acid (3MPA), with an average size of 2.7nm, were used as photoluminescence probe for flavonoids in different conditions. The interaction between 14 flavonoids and QDs was evaluated in aqueous dispersions in the absence and in the presence of cetyltrimethylammonium bromide (CTAB). To establish a relationship between photoluminescence quenching and the concentration of flavonoids, the Stern-Volmer model was used. In the absence of CTAB, the linear ranges for quercetin, morin and rutin were from 5.0×10 -6 molL -1 to 6.0×10 -5 molL -1 and from 1.0×10 -5 molL -1 to 6.0×10 -4 molL -1 for kaempferol. The sensibility of the Stern-Volmer curves (K s ) indicated that quercetin interacts more strongly with the probe: K s quercetin >K s kaempferol >K s rutin >K s morin . The conjugation extension in the 3 rings, and the acidic hydroxyl groups (positions 3'and 4') in the B-ring enhanced the interaction with 3MPA-CdTe QDs. The other flavonoids do not interact with the probe at 10 -5 molL -1 level. In CTAB organized dispersions, K s 3-hydroxyflavone >K s 7-hydroxyflavone >K s flavona >K s rutin in the range from 1.0×10 -6 molL -1 to 1.2×10 -5 molL -1 for flavones and of 1.0×10 -6 molL -1 to 1.0×10 -5 molL -1 for rutin. Dynamic light scattering, conductometric measurements and microenvironment polarity studies were employed to elucidate the QDs-flavonoids interaction in systems containing CTAB. The quenching can be attributed to the preferential solubility of hydrophobic flavonoid in the palisade layer of the CTAB aggregates adsorbed on the surface of the 3MPA CdTe QDs., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Colloidal suspensions of oxocarbon-encapsulated gold nanoparticles have been synthesized in a one-step procedure by pulsed-laser ablation (PLA) at 532 nm of a solid gold target placed in aqueous solution containing CO2 absorbers, but without any stabilizing agent. Multi-wavelength surface enhanced Raman spectroscopy allows the identification of adsorbed amorphous carbon and graphite, Au-carbonyl, Au coordinated CO2-derived bicarbonates/carbonates and hydroxyl groups around the AuNPs core. Scanning electron microscopy, energy dispersive x-ray analysis and high resolution transmission electron microscopy highlight the organic shell structure around the crystalline metal core. The stability of the colloidal solution of nanocomposites (NCs) seems to be driven by solvation forces and is achieved only in neutral or basic pH using monovalent hydroxide counter-ions (NaOH, KOH). The NCs are characterized by a blue shift of the localized surface plasmon resonance (LSPR) band typical of metal-ligand stabilization by terminal π-back bonding, attributed to a core charging effect caused by Au-carbonyls. Total organic carbon measurements detect the final content of organic carbon in the colloidal solution of NCs that is about six times higher than the value of the water solution used to perform PLA. The colloidal dispersions of NCs are stable for months and are applied as analytical probes in amino glycoside antibiotic LSPR based sensing.

Based on green analytical chemistry principles, an efficient approach was applied for the simultaneous determination of galantamine, a widely used cholinesterase inhibitor for the treatment of Alzheimer's disease, and its major metabolites in serum samples. After a simple serum deproteinization step, second-order data were rapidly obtained (less than 6 min) with a chromatographic system operating in the isocratic regime using ammonium acetate/acetonitrile (94:6) as mobile phase. Detection was made with a fast-scanning spectrofluorimeter, which allowed the efficient collection of data to obtain matrices of fluorescence intensity as a function of retention time and emission wavelength. Successful resolution was achieved in the presence of matrix interferences in serum samples using multivariate curve resolution-alternating least-squares (MCR-ALS). The developed approach allows the quantification of the analytes at levels found in treated patients, without the need of applying either preconcentration or extraction steps. Limits of detection in the range between 8 and 11 ng mL(-1), relative prediction errors from 7 to 12% and coefficients of variation from 4 to 7% were achieved., (Copyright © 2012 Elsevier B.V. All rights reserved.)

The present article describes the spectrofluorimetric determination of galantamine, a widely used acetylcholinesterase inhibitor, through excitation-emission fluorescence matrices and second-order calibration. With the purpose of enhancing the fluorescence intensity of this substance, the effect of different organized assemblies was evaluated. Although the interaction of galantamine with different cyclodextrins is weak, it was corroborated that the fluorescence intensity of this pharmaceutical in the presence of alpha-cyclodextrin is increased by a twofold factor. Among the studied micellar media, the anionic surfactant sodium dodecyl sulfate produced the largest signals for the compound of interest (sixfold enhancement), and was selected as auxiliary reagent for the subsequent determinations. The developed approach enabled the determination of galantamine at the ng mL(-1) level without the necessity of applying separation steps, and in the presence of uncalibrated interferences. The applied second-order chemometric tools were parallel factor analysis (PARAFAC), unfolded partial least-squares coupled to residual bilinearization (U-PLS/RBL), and multidimensional partial least-squares coupled to residual bilinearization (N-PLS/RBL). The ability of U-PLS/RBL to successfully overcome spectral interference problems is demonstrated. The quality of the proposed method was established with the determination of galantamine in both artificial and natural water samples., (Copyright 2010 Elsevier B.V. All rights reserved.)

The selective determination of norfloxacin in mixtures with other fluorquinolones was achieved by synchronous scanning solid surface room-temperature phosphorimetry (SSRTP) and Th(NO(3))(4) as selective phosphorescence inducer. The method also allowed the determination of levofloxacin in a sequential way. The optimization of experimental conditions was made through an univariate approach, in order to find the best conditions for norfloxacin phosphorescence, followed by a 2(3) factorial design in order to verify interaction among relevant variables, to check robustness for each variable and to perform final adjustment of parameters. Absolute limit of detection (ALOD) for norfloxacin was 12ng with a linear signal response extending up to 400ng. Under the same experimental conditions set for norfloxacin, the ALOD for levofloxacin was 13ng with linear signal response up to 450ng. Accuracy of the method, using Th (IV) as selective phosphorescence inducer, was evaluated through the analysis of commercial and simulated pharmaceutical formulations with recoveries between 94.4 and 101% for norfloxacin and 95.9 and 103.8% for levofloxacin. The use of Cd (II), a traditional phosphorescence inducer for fluorquinolones, did not allow selective determination of norfloxacin. Further studies indicated the potential application of the method in urine samples.

In this work, a fluorimetric approach for the determination of cyclofenil, 4-4'-(cyclohexylidenemethylene)bis(phenylacetate), is presented. The method was based on the intense fluorescence (250/410 nm) observed after a UV photochemical treatment of cyclofenil. The influence of the pH and solvent system and UV exposure time on the fluorescence magnitude was studied. Optimization of parameters was made using experimental design (factorial design and central composite design). Limit of detection (3S(b)/m) were estimated to be 1.1 x 10(-8)mol L(-1) with the linear dynamic range extending up to 8 x 10(-5)mol L(-1). This analytical approach was tested through the analysis of a commercial pharmaceutical formulation. In this case, tests enabled an average recovery of 98.3+/-3.9% (for n=9) using the analytical curve. The identification of the fluorescent derivative is proposed based on results achieved from GC-MS.

An analytical method based on solid surface room temperature phosphorescence (SSRTP) for the determination of rescinamine was developed. Signal enhancements were obtained by heavy atom effect, use of surfactant agent and use of basic medium. Alternatively, an ultraviolet treatment of the analyte was tried in order to induce a phoshor with higher phosphorescence quantum efficiency. A limit of detection of 2.70 ng and linear dynamic range of 2 orders of magnitude were achieved in paper substrate treated for background reduction. A study was performed to verify potential interferences of several pharmacological active ingredients that could be associated with rescinamine in a pharmaceutical preparation. The method was tested by analyzing rescinamine in three different laboratory-made tablets.