Magnetically recoverable TiO2-WO3 photocatalyst to oxidize bisphenol A from model wastewater under simulated solar light.

A novel magnetically recoverable, visible light active TiO2-WO3 composite (Fe3O4@SiO2@TiO2-WO3) was prepared to enable the photocatalyst recovery after the degradation of bisphenol A (BPA) under simulated solar light. For comparison, the photocatalytic activity of other materials such as non-magnetic TiO2-WO3, Fe3O4@SiO2@TiO2, TiO2, and the commercial TiO2 P25 was also evaluated under the studied experimental conditions. The structure and morphology of the synthesized materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), and electron dispersion spectroscopy (EDS). Moreover, Brunauer-Emmett-Teller (BET) surface area and magnetic properties of the samples were determined. The Fe3O4@SiO2@TiO2-WO3 and TiO2-WO3 led to a BPA degradation of 17.50 and 27.92 %, respectively, after 2 h of the simulated solar light irradiation. Even though their activity was lower than that of P25, which degraded completely BPA after 1 h, our catalysts were magnetically separable for their further reuse in the treatment. Furthermore, the influence of the water matrix in the photocatalytic activity of the samples was studied in municipal wastewater. Finally, the identification of reaction intermediates was performed and a possible BPA degradation pathway was proposed to provide a better understanding of the degradation process. Graphical abstract ᅟ.

Inter-laboratory comparison of an analytical method for the determination of the feed additive semduramicin in poultry feed at authorised level by liquid chromatography single quadrupole mass spectrometry.

A collaborative study was carried out according to internationally recognised guidelines in order to establish the performance characteristics of an LC/MS method for the determination of the feed additive semduramicin (SEM) in poultry feed at the level (20-25 mg kg(-1)) authorised within the European Union. Fifteen laboratories participated in the validation study, and all reported results. The content of SEM in the tested materials, provided as blind duplicates, ranged from 11.5 mg kg(-1), which corresponds to half the mean authorised level, to 45.0 mg kg(-1), which corresponds to twice the mean authorised level. All the materials were analysed by the participating laboratories using two different quantification approaches: standard addition and external standard calibration. The relative standard deviation of reproducibility (RSD(R)) for both quantification approaches varied from 8% to 18%, corresponding to HORRAT values ranging from 0.8 to 1.5, which were therefore in all cases below the critical value of 2.0. Consequently, the proposed analytical method and both quantification approaches can be considered to be fully validated and transferable to the control laboratories and applied for the determination of SEM in poultry compound feed at authorised level within the frame of official control. Further steps in the administrative procedure aiming to adopt the method as part of an ISO/CEN standard are currently ongoing.

Analysis of macrolide antibiotics by liquid chromatography.

A compilation of the most representative single and multianalyte HPLC methods for the analysis of macrolide antibiotics published during the last two decades is presented in this paper. Its scope is the coverage of two main areas which require the determination of macrolide antibiotics at a low concentration level, i.e. pharmacokinetic studies and residue analysis. Both of these areas involve the treatment of biological and foodstuff matrices, respectively. A detailed explanation of the different sample preparation procedures as well as the experimental conditions and the main analytical features are provided for each referred method in order to allow the reader to select the most suitable conditions for their particular purpose.

Determination of linuron in soil by stripping voltammetry with a carbon fiber microelectrode.

A carbon fiber microelectrode was used for the electroanalytical determination of Linuron (LIN) in soil extracts. The microelectrode was subjected to an electrochemical pretreatment in order to improve the herbicide adsorption on the electrode surface. With this preconcentration step, detection limits of 80 ng ml(-1) and determination limits of 260 ng ml(-1) were reached. Optimal conditions with respect to accumulation time and potential, scan rate and pH were established. The LIN was determined in a soil sample with the method proposed and the results found were comparable to those obtained by HPLC.

Determination of carbendazim in soil samples by anodic stripping voltammetry using a carbon fiber ultramicroelectrode.

A method for the determination of carbendazim (MBC) by anodic stripping voltammetry using a carbon fiber ultramicroelectrode was developed. The ultramicroelectrode was made in our laboratory and its electrochemical behavior was characterized by measuring the electrochemical response with a solution of potassium ferricyanide. The optimum parameters used for the determination of MBC are the following: 0.05 M phosphate buffer at pH 2.0 as supporting electrolyte; a scan rate of v = 10.00 V s(-1) and an accumulation potential of Eac = 0.00 V. The MBC was determined in a soil sample with the method proposed and the results found were comparable to those obtained by HPLC.

Rapid identification of carbendazim and linuron by adsorptive stripping on a carbon fiber ultramicroelectrode.

A method is described for the identification of a mixture of carbendazim and linuron. It is based on adsorptive stripping voltammetry at a carbon fiber ultramicroelectrode. Conditions for the determination of carbendazim in a mixture were optimized and the method was applied to soil samples. It was compared to HPLC with spectrophotometric detection, where similar results were obtained.