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Producing solar fuels through semiconductor‐based photocatalytic water splitting is one of the main options for worldwide employment of non‐fossil energy sources. Nonetheless, the relatively low efficiency of the known photocatalysts, the high prices of composing elements, and the costly preparation methods render expensive devices that would not be economically competitive with fossil energy sources. Herein, we present a facile method for the preparation of both round hematite (Fe2O3) nanoparticles, with average diameter of (56±7) nm, and of niobium‐doped hematite nanoparticles with similar size and morphology. Thin films of these nanoparticles were assembled through electrophoretic deposition, resulting in homogeneous photoanodes with nanometer thickness that can split water, under simulated solar irradiation, to produce oxygen in a photoelectrochemical cell. The optimization of the film composition and thickness resulted in the improvement of the photocurrent from 352.3 to 1,342.5 μA cm−2 at 1.23 V vs RHE for the pristine hematite and Nb‐doped hematite, respectively, both with thickness of (499±63) nm. This enhancement in the oxidation reaction yield is a clear consequence of the improvement of charge carriers transport along the nanoparticle structure due to niobium doping and adequate light absorption/charge transfer balance of the photoelectrode under operation. [ABSTRACT FROM AUTHOR]

In this work, a separation/preconcentration method is proposed for the determination of Cd(II) and Pb(II) in swimming pool waters, using ammonium pyrrolidine dithiocarbamate (APDC) as a complexing agent and unloaded polyurethane foam (PUF) as a sorbent. The proposed method was optimized, and the defined optimal conditions were a pH of 7, 30 min of shaking time, 400 mg of PUF, and 0.5% (m/v) of the APDC solution. The release of Cd(II) and Pb(II) from the solid phase was achieved through the total digestion of PUF using a microwave-assisted acid approach with a 10.5 mol·L−1 HNO3 solution. The methodology was applied to four samples of swimming pool water for the determination of Cd(II) and Pb(II) using graphite furnace atomic absorption spectrometry (GF AAS). The limits of detection and quantification obtained were 0.02 and 0.06 μg·L−1 for Cd(II) and 0.5 e 1.8 μg·L−1 for Pb(II), respectively. We analyzed four samples of swimming pool waters, finding Cd concentrations between 0.22 and 1.37 μg·L−1. On the other hand, only one sample presented Pb concentration above the limit of quantification (11.4 μg·L−1). Recovery tests were performed by spiking the samples with known concentrations of the analytes, and recovery percentages between 82% and 105% were obtained. [ABSTRACT FROM AUTHOR]

A composite electrode based on acrylonitrile‐butadiene‐styrene and graphite chemically modified with a bismuth film (AGCE‐BiF) was applied for the simultaneous determination of Cd2+ and Pb2+ in gasoline samples. Extraction induced by microemulsion breaking (EIMB) was used for the first time in the preparation of the samples for electroanalysis. AGCE‐BiF was characterized by SEM, AFM, CV, and SWASV. The sensor showed an increase in sensitivity via in situ modification with bismuth film. The LOD was 4 μg L−1 for Cd2+ and 2 μg L−1 for Pb2+. The results showed satisfactory recoveries and precision, being statistically compatible to those obtained with FAAS. [ABSTRACT FROM AUTHOR]

The present work proposes a simple method for direct determination of Cu and Mn in commercial fruit juices and nectars by graphite furnace atomic absorption spectrometry (GF AAS). We analyzed samples of different flavors (orange, mango, passion fruit, peach, and grape) and brands of Brazilian commercial fruit juices and nectars. We also carried out a study to define a suitable temperature program and to optimize the calibration conditions. It was possible to determine Cu and Mn in the samples just after a simple dilution of samples with a 0.70 mol L−1 HNO3 solution, except in the case of grape juice. We compared the results obtained with the proposed method to those obtained after a traditional treatment based on acid digestion in a microwave oven, and no significant differences were observed (except for grape juice). The accuracy of the method was assessed through a recovery test, which provided recovery percentages in the range of 81–117%. Precision was always better than 8%, and the limits of quantification for Cu and Mn were 6 μg L−1 and 9 μg L−1, respectively. We analyzed twenty-two samples, and the concentrations of Cu and Mn were in the range of 24.1–321 μg L−1 and 116–3296 μg L−1, respectively. Statistical analysis using a two-way analysis of variance (ANOVA) at 95% confidence level showed that flavor and brand impacted on the concentration of the analytes in the samples. Among the samples analyzed, the grape juice presented the highest concentrations of both Cu and Mn. [ABSTRACT FROM AUTHOR]

This work reports the development and optimization of a flow injection analysis system with fluorescence detection (FIA-FLUO) for gatifloxacin (GFX) determination in organized medium. The analytical system was based on the enhanced fluorescence of gatifloxacin in micellar medium containing sodium dodecyl sulfate (SDS) at pH 6.0. The influence of physical (carrier flow rate, sample volume and volume of reaction coil) and chemical (pH, concentration of buffer and concentration of SDS) parameters that could affect the performance of the FIA system was evaluated in order to reach optimum conditions in terms of sensitivity and analytical throughput. Under optimized conditions, the FIA-FLUO system allowed the injection of 40 samples per hour with a limit of quantification of 72 µg/L and a RSD of 3.5% at 0.20 mg/L. Real samples of commercial pharmaceutical formulations containing GFX were analyzed, and no statistical difference was observed between the results obtained using the developed system and those obtained using the reference method based on high-performance liquid chromatography with UV detection. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

ABSTRACT The fluorescence characteristics of sitagliptin phosphate were used to develop a methodology that allowed its determination in pharmaceutical formulations and urine samples; under the studied conditions, limits of determination and quantification of 0.25 and, respectively, 0.85 mg/L were achieved. Linear correlation between fluorescence analytical signal and sitagliptin concentration was achieved up to 10.0 mg/L. The method was considered selective for sitagliptin determination in pharmaceutical formulations because no interferences due to excipients present in considered matrix were observed (as demonstrated by recovery tests comparing analytical and addition curves). When the method was applied to urine samples, Interferences related to the matrix were observed, which made a solid-phase extraction system necessary. The use of calibration was possible only by applying the standard addition method. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]