1,720,997 research outputs found
Neonicotinoids: An overview of the newest sample preparation procedures of environmental, biological and food matrices
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Sample treatment for the determination of steroid hormone contaminants in water samples: Analytical greenness assessment
No full textHPLC-MS/MS multiclass determination of steroid hormones in environmental waters after preconcentration on the carbonaceous sorbent HA-C@silica
No full textIn this study, a sensitive and multiclass method has been developed for analysis of three families of steroid hormones, i.e. progestins, oestrogens, androgens, by SPE-HPLC-ESI-MS/MS. The extraction efficiency of thermally condensed humic acids onto silica sorbent (HA-C@silica), here for the first time studied for multiclass enrichment of these sex hormones, was tested in different environmental waters (tap and river water, urban wastewater treatment plant effluent) spiked at the nanograms per litre levels (5–1000 ng L−1). Quantitative adsorption was achieved using 200 mg sorbent for preconcentration of 250–1000 mL sample, at the native pH (pH = 6.5–7.7). Elution was performed by two sequential fractions (methanol followed by acetonitrile), obtaining in all the matrices investigated satisfactory recoveries (71% to 124% for river waters and 71–113% for urban wastewater treatment plant effluent) and RSDs below 15% (n = 3). The high enrichment factors (up to 4000) coupled with high-performance liquid chromatography tandem mass spectrometry quantification (MRM mode) provided low limits of detection and quantification (a few ng L−1), that are suitable for environmental monitoring. Most of the analytes were detected in river water and in wastewater effluent samples (in the ng L−1 concentration range), attesting their environmental diffusion. The proposed method was extended to a fourth class, Glucocorticoids, achieving good results in river samples, by the same SPE cartridge and chromatographic run
Green and Efficient Determination of Fluoroquinolone Residues in Edible Green Fruits and Leafy Vegetables by Ultrasound-Assisted Extraction Followed by HPLC-MS/MS
No full textIn this work, a simple, quick and efficient analytical method for determination of human and veterinary fluoroquinolone antimicrobial residues in lettuce, cucumber and spinach is developed. The procedure entails a 6 min ultrasound-assisted extraction (UAE, 3 x 2 min) in an alkaline (2% v/v NH3) aqueous solution containing Mg2+ ions (3 x 6 mL), with no need for organic solvents. The extract is submitted to cleanup on the HLB (TM) cartridge and the fluoroquinolones are separated and quantified by HPLC-MS/MS in a 10 min chromatographic run, using a small amount of acetonitrile in the mobile phase. The method, entirely developed in real matrices, is validated according to the updated analytical guidelines and provided suitable recoveries in the range of 67-116% and precision (RSD <= 20%, n = 3) at different concentrations (15, 70 and 150 ng g(-1)), with method quantification limits of 2-10 ng g(-1). Fluoroquinolones were detected and quantified at concentrations from few to hundreds of nanograms per gram in vegetables from supermarkets, demonstrating the applicability of the method for monitoring residues of these pharmaceuticals
Carbon nitride-perovskite composites: Evaluation and optimization of photocatalytic hydrogen evolution in saccharides aqueous solution
No full textThe application of hybrid photocatalysts made of carbon nitride and lead-free perovskites, namely DMASnBr3/g-C3N4 and PEA2SnBr4 /g-C3N4, for the H2 evolution from saccharides aqueous solution is described. The novel composites were tested and compared in terms of hydrogen evolution rate (HER) under simulated solar light, using Pt as a reference co-catalyst, and glucose as a representative sacrificial biomass. The conditions were optimized to maximize H2 generation by a design of experiments involving catalyst amount, glucose concentration and Pt loading. For both materials, such parameters affected significantly H2 photogeneration, with the best performance observed using 0.5 g L−1 catalyst, 0.2 M glucose and 0.5 wt% Pt. Under optimized conditions, DMASnBr3/g-C3N4 showed a 5-fold higher HER compared to PEA2SnBr4/g-C3N4, i.e., 925 μmoles g−1 h−1 and 190 μmoles g−1 h−1, respectively (RSD ≤ 11%, n = 4). The former composite, which affords an HER 15-fold higher in aqueous glucose than in neat water, provided H2 also with no metal co-catalyst (around 140 μmoles g−1 h−1), and it was reusable for at least three photoreactions. Encouraging results were also collected by explorative tests on raw starch solution (around 150 μmoles g−1 h−1)
A simple and fast multiclass method for determination of steroid hormones in berry fruits, root and leafy vegetables
No full textThis study is focused on the development of a multiclass analytical method for sensitive determination of steroid hormones (progestins, oestrogens, androgens and glucocorticoids) in fruits and vegetables. The herein considered analytes present a wide logP range, thus they tend to accumulate differently in edible parts. Therefore, a berry fruit (strawberry), a root vegetable (carrot), and a leafy vegetable (spinach) were chosen as probes to develop the extraction procedure. This, optimized by a chemometric approach (23 experimental design) on lyophilized samples (0.25 g, spike 100 ng g −1), entails a rapid ultrasonic extraction (3 × 1 min cycles) with low consumption (3 × 2 mL) of MeOH, selected as extraction solvent by a preliminary screening. The clean-up step, necessary due to the complexity of the matrices, was performed by a simple solid-phase extraction procedure on the SupelcleanTM LC-NH2 sorbent afore the selective quantification by HPLC–ESI-MS/MS (MRM mode). The final analytical method was successfully applied to multianalyte extraction at lower concentrations (10–50 ng g−1) with good recoveries and repeatability, and it was successfully extended to raspberry, radish and arugula, further supporting applicability to this kind of samples. The results from the analysis of fruits and vegetables purchased from local markets, where some steroids have been quantified at the low ng g−1 levels, are consistent with literature data about concentration of these emerging pollutants in edible plants, also according to their LogP values
Tungsten Catalysts for Visible Light Driven Ofloxacin Photocatalytic Degradation and Hydrogen Production
No full textSome tungsten catalysts of interest that are synthesized are bismuth tungstate (BT) and Tetrabutylammonium decatungstate (TBADT), using two consolidated procedures. BT is used as a photo-catalyst for the simulated solar light degradation of ofloxacin (OFL) antibiotic under relevant real conditions (μg L−1, fresh water) with the limit of 0.05 g L−1 of catalyst. A quantitative drug decomposition occurred following a bi-exponential first-order law, with an efficiency comparable with the most used P25 TiO2 catalyst. The photocatalytic profiles of OFL at μg L−1 and mg L−1 were monitored by high-pressure liquid chromatography (HPLC) coupled with fluorescence (FD) and ultraviolet (UV) detectors. Additionally, the main photoproducts were identified by high-pressure liquid chromatography coupled to electrospray ionization in tandem with mass spectrometry (HPLC-ESI-MS/MS). The catalyst Tetrabutylammonium decatungstate (TBADT) was used as a catalyst to produce hydrogen from glucose and 2-propanol in aqueous solution, providing hydrogen gas evolution up to 10 μmol g−1 h−1
Agri-food waste biochar-based green vial wall sorptive extraction: Downscaled portable device for steroids in fresh and brackish water samples
No full textHA-C@silica sorbent for simultaneous extraction and clean-up of steroids in human plasma followed by HPLC-MS/MS multiclass determination
No full textAim and novelty of this work are the development of a simple and straightforward analytical procedure for multiclass determination of steroid hormones in human plasma. The method entails a single pre-treatment step based on solid-phase extraction using a recently proposed sorbent phase (HA-C@silica). This is easily prepared with good reproducibility via pyrolysis of humic acids onto silica, and not yet tested in biological fluids. It proved to be advantageous as it showed poor affinity for the protein matrix constituents while quantitatively extracting and pre-concentrating the target analytes. Indeed, as demonstrated in bovine serum albumin solution, up to ca. 90% protein is not retained by the sorbent, similarly to the behaviour of restricted access carbon nanotubes, tested for comparison. The high albumin exclusion allowed a satisfactory clean-up avoiding protein precipitation and centrifugation before extraction. The extraction procedure, optimized by a chemometric approach (23 experimental design) in BSA solution, provided quantitative recovery (76–119%, n = 3) for all steroids working with 1:8-diluted plasma (2 mL) and 100 mg HA-C@silica. Before analytes elution by 1 mL methanol-acetonitrile (1:1, v/v), selective washings (2% v/v formic acid and 30% v/v methanol) were applied to remove the small fraction of retained proteins, thus obtaining very clean SPE extracts to be analyzed by HPLC-ESI-MS/MS. This allowed identification/quantification (MRM mode) at few ng mL−1 by a single chromatographic run. The procedure was verified in blank-certified foetal bovine serum (spikes 10–100 ng mL−1), obtaining good recovery and suitable inter-day precision (RSDs < 15%, n = 3). The analytical method, applied to real plasma samples analysis, is appealing in terms of sample throughput, extraction efficiency and clean-up
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