Multiclass ultrasound-assisted extraction, clean-up and high performance liquid chromatography-tandem mass spectrometry quantification of steroid hormone residues in compost.

An analytical method for multiclass determination of steroid hormones in compost has been developed to fill the lack of methods for steroid residuals monitoring in this waste-derived product, increasingly produced and recycled in the circular-economy approach. The procedure simply entails an ultrasound-assisted extraction (UAE) on 300 mg compost by 3 × 2.5 mL methanol × 5 min sonication steps followed by a quick clean-up by solid-phase extraction (SPE) on the silica-based Supelclean™ LC-NH2 that avoids use of organic solvents. The clean extract is analysed by HPLC-MS/MS achieving firm identification and quantitation of the 16 steroids, i.e., glucocorticoids, progestins, androgens, oestrogens. The analytical figures of merits were assessed, viz. selectivity, sensitivity, linearity, matrix effect, trueness, precision, carry-over and robustness, in line with updated guidelines. Recovery was investigated in the concentration range 15-800 ng g-1, and at the quality control levels (15, 50, 200 and 400 ng g-1) was in the range 60-120%, with inter-day precision RSDs < 20% (n = 3). The experimental quantification limit was 15 ng g-1 for all the hormones. The method was applied to analysis of different compost samples proving to be functional to environmental monitoring.

From Rice Husk Ash to Silica-Supported Carbon Nanomaterials: Characterization and Analytical Application for Pre-Concentration of Steroid Hormones from Environmental Waters.

Rice husk (RH) in the rice industry is often air-burnt to obtain energy in the form of heat and RH ash (RHA) residue. In this work, RHA was applied as a starting material to obtain silica-supported carbon nanomaterials, resulting in a new reuse of a globally produced industrial waste product, in a circular economy approach. The preparation involves ultrasound-assisted one-pot oxidation with a sulfonitric mixture followed by wet oven treatment in a closed vessel. A study of oxidation times and RHA amount/acid volume ratio led to a solid material (nC-RHA@SiO2) and a solution containing silica-supported carbon quantum dots (CQD-RHA@SiO2). TEM analyses evidenced that nC-RHA@SiO2 consists of nanoparticle aggregates, while CQD-RHA@SiO2 are carbon-coated spherical silica nanoparticles. The presence of oxygenated carbon functional groups, highlighted by XPS analyses, makes these materials suitable for a wide range of analytical applications. As the main product, nC-RHA@SiO2 was tested for its affinity towards steroid hormones. Solid-phase extractions were carried out on environmental waters for the determination of target analytes at different concentrations (10, 50, and 200 ng L−1), achieving quantitative adsorption and recoveries (RSD < 20%, n = 3). The method was successfully employed for monitoring lake, river, and wastewater treatment plant water samples collected in Northern Italy.

Fe3O4-Halloysite Nanotube Composites as Sustainable Adsorbents: Efficiency in Ofloxacin Removal from Polluted Waters and Ecotoxicity.

The present work aimed at decorating halloysite nanotubes (HNT) with magnetic Fe3O4 nanoparticles through different synthetic routes (co-precipitation, hydrothermal, and sol-gel) to test the efficiency of three magnetic composites (HNT/Fe3O4) to remove the antibiotic ofloxacin (OFL) from waters. The chemical-physical features of the obtained materials were characterized through the application of diverse techniques (XRPD, FT-IR spectroscopy, SEM, EDS, and TEM microscopy, thermogravimetric analysis, and magnetization measurements), while ecotoxicity was assessed through a standard test on the freshwater organism Daphnia magna. Independently of the synthesis procedure, the magnetic composites were successfully obtained. The Fe3O4 is nanometric (about 10 nm) and the weight percentage is sample-dependent. It decorates the HNT's surface and also forms aggregates linking the nanotubes in Fe3O4-rich samples. Thermodynamic and kinetic experiments showed different adsorption capacities of OFL, ranging from 23 to 45 mg g-1. The kinetic process occurred within a few minutes, independently of the composite. The capability of the three HNT/Fe3O4 in removing the OFL was confirmed under realistic conditions, when OFL was added to tap, river, and effluent waters at µg L-1 concentration. No acute toxicity of the composites was observed on freshwater organisms. Despite the good results obtained for all the composites, the sample by co-precipitation is the most performant as it: (i) is easily magnetically separated from the media after the use; (ii) does not undergo any degradation after three adsorption cycles; (iii) is synthetized through a low-cost procedure. These features make this material an excellent candidate for removal of OFL from water.

Green and Efficient Determination of Fluoroquinolone Residues in Edible Green Fruits and Leafy Vegetables by Ultrasound-Assisted Extraction Followed by HPLC-MS/MS.

In 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 × 2 min) in an alkaline (2% v/v NH3) aqueous solution containing Mg2+ ions (3 × 6 mL), with no need for organic solvents. The extract is submitted to cleanup on the HLB™ 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.

Combined Layer-by-Layer/Hydrothermal Synthesis of Fe3O4@MIL-100(Fe) for Ofloxacin Adsorption from Environmental Waters.

A simple not solvent and time consuming Fe3O4@MIL-100(Fe), synthesized in the presence of a small amount of magnetite (Fe3O4) nanoparticles (27.3 wt%), is here presented and discussed. Layer-by-layer alone (20 shell), and combined layer-by-layer (5 shell)/reflux or /hydrothermal synthetic procedures were compared. The last approach (Fe3O4@MIL-100_H sample) is suitable (i) to obtain rounded-shaped nanoparticles (200-400 nm diameter) of magnetite core and MIL-100(Fe) shell; (ii) to reduce the solvent and time consumption (the layer-by-layer procedure is applied only 5 times); (iii) to give the highest MIL-100(Fe) amount in the composite (72.7 vs. 18.5 wt% in the layer-by-layer alone); (iv) to obtain a high surface area of 3546 m2 g-1. The MIL-100(Fe) sample was also synthesized and both materials were tested for the absorption of Ofloxacin antibiotic (OFL). Langmuir model well describes OFL adsorption on Fe3O4@MIL-100_H, indicating an even higher adsorption capacity (218 ± 7 mg g-1) with respect to MIL-100 (123 ± 5 mg g-1). Chemisorption regulates the kinetic process on both the composite materials. Fe3O4@MIL-100_H performance was then verified for OFL removal at µg per liter in tap and river waters, and compared with MIL-100. Its relevant and higher adsorption efficiency and the magnetic behavior make it an excellent candidate for environmental depollution.

Magnetic Micro-Solid-Phase Extraction Using a Novel Carbon-Based Composite Coupled with HPLC-MS/MS for Steroid Multiclass Determination in Human Plasma.

A micron-sized sorbent, Magn-Humic, has been prepared by humic acids pyrolysis onto silica-coated magnetite. The material was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), thermogravimetric analysis (TGA), and Brunauer, Emmett, and Teller (BET) surface area measurements and applied for simultaneous magnetic solid-phase extraction (MSPE) of glucocorticoids, estrogens, progestogens, and androgens at ng mL-1 levels from human plasma followed by high-performance liquid chromatography coupled with mass spectrometry (HPLC-MS/MS). Due to the low affinity for proteins, steroids extraction was done with no need for proteins precipitation/centrifugation. As highlighted by a design of experiments, MSPE was performed on 250 µL plasma (after 1:4 dilution) by 50 mg Magn-Humic (reusable for eight extractions) achieving quantitative recovery and satisfying clean-up. This was improved by washing (2 mL 2% v/v formic acid) prior to analytes elution by 0.5 mL 1:1 v/v methanol-acetonitrile followed by 0.5 mL methanol; eluate reduction to 0.25 mL compensated the initial sample dilution. The accuracy was assessed in certified blank fetal bovine serum and in human plasma, gaining satisfactory recovery in the range 65-122%, detection limits in the range 0.02-0.3 ng mL-1 (0.8 ng mL-1 for 17-ß-estradiol) and suitable inter-day precision (relative standard deviation (RSD) <14%, n = 3). The method was evaluated in terms of selectivity, sensitivity, matrix-effect, instrumental carry-over, and it was applied to human plasma samples.

Zinc Based Metal-Organic Frameworks as Ofloxacin Adsorbents in Polluted Waters: ZIF-8 vs. Zn3(BTC)2.

Two different zinc-based metal-organic frameworks (MOFs) were investigated to remove one of the most used fluoroquinolone antibiotic, Ofloxacin (OFL), from polluted water. The most common zeolitic imidazolate framework-8 (ZIF-8) and the green Zn(II) and benzene-1,3,5-tri-carboxylate (Zn3(BTC)2) were prepared through a facile synthetic route and characterized by means of Fourier-Transform Infrared (FT-IR) Spectroscopy, X-ray Powder Diffraction (XRPD), and Scanning Electron Microscopy (SEM) analyses. The two MOFs were compared in terms of both adsorption and kinetic aspects under real conditions (tap water, natural pH). Results showed that OFL was adsorbed in remarkable amounts, 95 ± 10 and 25.3 ± 0.8 mg g-1 on ZIF-8 and Zn3(BTC)2, respectively, following different mechanisms. Specifically, a Langmuir model well described the ZIF-8 profile, while for Zn3(BTC)2, cooperative adsorption occurred. Moreover the kinetic results were quite different, pseudo-second-order and sigmoidal, respectively. The suitability of ZIF-8 and Zn3(BTC)2 as adsorbent phases for water depollution was tested on tap water samples spiked with OFL 10 µg L-1. The obtained removal efficiencies, of 88% for ZIF-8 and 72% for Zn3(BTC)2, make these materials promising candidates for removing fluoroquinolone antibiotics (FQs) from polluted waters, notwithstanding their limited reusability in tap water, as demonstrated by in-depth characterization of the two MOFs after usage.

Trace elements fingerprint of feathers differs between breeding and non-breeding areas in an Afro-Palearctic migratory bird, the barn swallow (Hirundo rustica).

Trace elements are widespread contaminants that can potentially threaten ecosystems and human health. Considering their distribution and toxicity, monitoring their presence in animals represents a priority in environmental risk assessment. Migratory birds have been suggested to be useful biomonitors for trace elements because they can provide information on contaminants even from remote areas that they may exploit during their life cycle. The aim of this study was to analyse the contamination fingerprint of trace elements of African non-breeding staging grounds and European breeding areas in a long-distance migratory passerine bird, the barn swallow (Hirundo rustica). We collected feathers grown in the African non-breeding grounds and those grown in the breeding areas of Northern Italy and measured the levels of 12 trace elements (Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se and Zn) by DRC-ICP-MS. Multivariate analysis showed that elemental profiles of feathers grown in African non-breeding areas and in the Italian breeding ones clearly differed, with feathers grown in Africa showing higher concentrations of Al, Cu, Fe, Mn and Ni, but lower concentrations of As, Se and Zn, compared to those grown in Italy. In addition, levels of trace elements were age-dependent, with higher levels in older individuals than in younger ones. Our results add to the growing evidence that feathers of long-distance migratory birds are useful tools to monitor trace elements contamination profiles across continents.

HA-C@silica sorbent for simultaneous extraction and clean-up of steroids in human plasma followed by HPLC-MS/MS multiclass determination.

Aim 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.

Glucocorticoids in Freshwaters: Degradation by Solar Light and Environmental Toxicity of the Photoproducts.

The photodegradation process of seven glucocorticoids (GCs), cortisone (CORT), hydrocortisone (HCORT), betamethasone (BETA), dexamethasone (DEXA), prednisone (PRED), prednisolone (PREDLO) and triamcinolone (TRIAM) was studied in tap and river water at a concentration close to the environmental ones. All drugs underwent sunlight degradation according to a pseudo-first-order decay. The kinetic constants ranged from 0.00082 min-1 for CORT to 0.024 min-1 for PRED and PREDLO. The photo-generated products were identified by high-pressure liquid chromatography coupled to electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS). The main steps of the degradation pathways were the oxidative cleavage of the chain 17 for CORT, HCORT and the rearrangement of the cyclohexadiene moiety for the other GCs. The acute and chronic toxicity of GCs and of their photoproducts was assessed by the V. fischeri and P.subcapitata inhibition assays. The bioassays revealed no significant differences in toxicity between the parent compounds and their photoproducts, but the two organisms showed different responses. All samples produced a moderate acute toxic effect on V. fisheri and no one in the chronic tests. On the contrary, evident hormesis or eutrophic effect was produced on the algae, especially for long-term contact.

Evidence of Low-Habitat Contamination Using Feathers of Three Heron Species as a Biomonitor of Inorganic Elemental Pollution.

The concentration of 12 elements (As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, and Zn) has been investigated in the feathers of three species of Ardeidae, namely the Grey Heron Ardea cinerea, the Little Egret Egretta garzetta, and the Cattle Egret Bubulcus ibis, all breeding at a colony located in the southern Padana Plain (NW Italy). This study is a first step for an evaluation of possible direct effects of these elements on chicks' survival and growth rate. Fe, Zn, Cu, and Mn were in the range 7-69 mg Kg-1, while lower levels of Pb, Ni, As, and Se (0.27-1.45 mg Kg-1) were measured. Co, Cd, and Cr were close to the method detection limits (MDLs) in all the species. The measured concentrations of the most abundant trace elements, such as Zn and Cu, seem to reflect the geochemical pattern of the background (running water and soil), while Hg concentration is lower and it appears to be biomagnified, particularly in Grey Heron feathers. Its concentration is higher in adults than in chicks, and it differs among the three species, as it is closely related to the fish-based dietary pattern. The measured trace elements' concentrations are below the threshold levels in all the heron species, and consequently, harmful and acute effects on the local population are unlikely; the conservation status of herons populations in northern Italy is probably more affected by other factors, such as climate changes, altered aquatic environment, and, consequently, food quality.

Simultaneous Pre-Concentration and HPLC-MS/MS Quantification of Phycotoxins and Cyanotoxins in Inland and Coastal Waters.

The purpose of this study was to set up a sensitive method for the simultaneous determination of phycotoxins and cyanotoxins-Emerging pollutants with different structures and harmful properties (hepatotoxicity, neurotoxicity and cytotoxicity)-In environmental waters. Due to the low concentrations detected in these samples, a pre-concentration step is required and here it was performed in a single step with a commercial cartridge (Strata™-X), achieving enrichment factors up to 200 and satisfactory recovery (R = 70-118%) in different aqueous matrices. After solid-phase extraction (SPE), toxins were separated and quantified by High Performance Liquid Chromatography- Heated ElectroSpray Ionisation Tandem Mass Spectrometry (HPLC-HESI-MS/MS) in Multiple Reaction Monitoring (MRM) mode. An analytical evaluation of the proposed method was done based on the analytical figures of merit, such as precision and trueness, linearity, selectivity, and sensitivity, and it turned out to be a robust tool for the quantification of ng L-1 levels, phycotoxins and cyanotoxins in both freshwater and saltwater samples.

TiO2 and N-TiO2 Sepiolite and Zeolite Composites for Photocatalytic Removal of Ofloxacin from Polluted Water.

TiO2 sepiolite and zeolite composites, as well the corresponding N-doped composites, synthesized through a sol-gel method, were tested for the photocatalytic degradation of a widespread fluoroquinolone antibiotic (ofloxacin) under environmental conditions. The catalysts were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), and diffuse reflectance spectroscopy (DRS) analyses. A complete drug degradation occurred in 10-15 min in the presence of both TiO2 sepiolite and zeolite catalysts, and in 20-30 min with the N-doped ones. Sepiolite proved to be a better TiO2 support compared to the most common zeolite both in terms of adsorption capacity and photocatalytic efficiency in pollutants degradation. The influence of nitrogen doping (red shift from 3.2 to 3.0 eV) was also investigated. Although it was blurred by a marked increase of the particle dimension and thus a decrease of the specific surface area of the doped catalysts, it allowed a faster drug removal than direct photolysis. The photochemical paths and photoproducts were investigated, too.

Silica-supported pyrolyzed lignin for solid-phase extraction of rare earth elements from fresh and sea waters followed by ICP-MS detection.

Silica-supported pyrolyzed lignin (pLG@silica) was investigated as a solid sorbent for the pre-concentration of rare earth elements (REE) from natural waters followed by inductively coupled plasma mass spectrometry (ICP-MS) analysis. The carbon-based material was easily prepared by pyrolytic treatment of lignin at 600 °C after its adsorption onto silica micro-particles. pLG@silica was characterized by scanning electron microscopy (SEM), surface area measurements (BET method), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), point of zero charge measurement, and X-ray photoelectron spectroscopy (XPS). The as-prepared material (50 mg) was tested as fixed-bed sorbent for the solid-phase extraction (SPE) of tap, river, and sea water samples spiked with REE in the 10-150 ng L-1 range, followed by ICP-MS analysis. A quantitative adsorption was observed for all REE with recoveries in the range of 72-118%. A suitable inter-day precision (RSDs 5-12%, n = 3) was obtained. Sample volumes up to 250 mL provided enrichment factors up to 100. The method detection and quantification limits (MDLs and MQLs) were in the range of 0.4-0.6 ng L-1 and 1-2 ng L-1, respectively. The batch-to-batch reproducibility was verified on four pLG@silica independent preparations. As remarkable advantages, pLG@silica proved to be of easy preparation using a waste material, inexpensive, and reusable for at least 20 SPE cycles.

Thermally condensed humic acids onto silica as SPE for effective enrichment of glucocorticoids from environmental waters followed by HPLC-HESI-MS/MS.

Pristine humic acids (HAs) were thermally condensed onto silica microparticles by a one-pot, inexpensive and green preparation route obtaining a mixed-mode sorbent (HA-C@silica) with good sorption affinity for glucocorticoids (GCs). The carbon-based material, characterized by various techniques, was indeed applied as the sorbent for fixed-bed solid-phase extraction of eight GCs from river water and wastewater treatment plant effluent, spiked at different concentration levels in the range 1-400 ng L-1. After sample extraction, the target analytes were simultaneously and quantitatively eluted in a single fraction of methanol, achieving enrichment factor 4000 and 1000 in river water and wastewater effluent, respectively. Full recovery for all compounds, was gained in the real matrices studied (80-125% in river water, 79-126% in wastewater effluent), with inter-day precision showing relative standard deviations (RSD) below 15% and 18% (n = 3), for river and wastewater effluent, correspondingly. The high enrichment factors coupled with high-performance liquid chromatography tandem mass spectrometry quantification (MRM mode) provided method quantification limits of 0.009-0.48 ng L-1 in river water and 0.06-3 ng L-1 in wastewater effluent and, at the same time, secure identification of the selected drugs. As also evidenced by comparison with literature, HA-C@silica proved to be a valid alternative to the current commercial sorbents, in terms of extraction capability, enrichment factor, ease of preparation and cost. The batch-to-batch reproducibility was assessed by recovery tests on three independently prepared HA-C@silica powders (RSD lower than 7%).

Dispersive multi-walled carbon nanotubes extraction of benzenesulfonamides, benzotriazoles, and benzothiazoles from environmental waters followed by microwave desorption and HPLC-HESI-MS/MS.

This work shows a novel analytical method for the simultaneous extraction of environmental emerging contaminants as benzenesulfonamides (BSAs), benzotriazoles (BTRs), and benzothiazoles (BTs) from water samples. Pristine multi-walled carbon nanotubes (MWCNTs), not yet tested for such analytes, are here employed as the sorbent phase for dispersive solid-phase extraction (d-SPE) followed by high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC-HESI-MS/MS). Quantitative sorption is gained by treating 50 mL sample with 100 mg MWCNTs (2 g L-1) in 10 min contact, both in tap and raw river water. After sorption, the analytes are quantitatively desorbed by microwaves (20 min, 160 °C, 250 W) by using 5 mL methanol-ethylacetate-acetic acid (10:70:20, v/v), according to the indications obtained by a chemometric study. The extract is reduced to small volume before analysis, thus reaching overall enrichment factors up to 400. Recovery of the entire procedure, evaluated on tap and surface water samples spiked with 0.1/0.5-50 µg L-1 of each analyte, was in the range 70-116%, with excellent inter-day precision (RSD < 7%). Selectivity and firm analyte identification were assured by MRM detection, and suitable sensitivity was obtained for determination of these pollutants in actual matrices (experimental MDLs 30-170 ng L-1). The proposed analytical method was applied to the analysis of surface water samples, containing concentrations of these contaminants ranging from 100 ng L-1 to 2 µg L-1. Pristine MWCNTs proved to be a valid alternative to other commercial sorbents, both in terms of cost and sorption capacity. Graphical abstract Determination of benzenesulfonamides, benzotriazoles, and benzothiazoles in environmental waters by dispersive multi-walled carbon nanotube extraction prior HPLC-MS.

Newest applications of molecularly imprinted polymers for extraction of contaminants from environmental and food matrices: A review.

This paper presents an overview of the recent applications of molecularly imprinted polymers (MIPs) to sample preparation. The review is thought to cover analytical procedures for extraction of contaminants (mainly illegal/noxious organic compounds) from food and environmental matrices, with a particular focus on the various pre-concentration/cleanup techniques, that is offline and online solid-phase extraction (SPE), dispersive SPE (d-SPE), magnetic SPE (MSPE), solid-phase microextraction (SPME) and stir-bar sorptive extraction (SBSE), applied before instrumental quantification. The selectivity and extraction efficiency of MIP-based sorbent phases are critically discussed, also in relation to the physical-chemical properties resulting from the synthetic procedures. A variety of molecularly imprinted sorbents is presented, including hybrid composites embedding carbon nanomaterials and ionic liquids. The analytical performance of MIP materials in sample preparation is commented as function of the complexity of the matrix, and it is compared to that exhibited by (commercial) aspecific and/or immunosorbent phases.

Facile and fast preparation of low-cost silica-supported graphitic carbon nitride for solid-phase extraction of fluoroquinolone drugs from environmental waters.

The analytical application of silica-supported graphitic carbon nitride (g-C3N4@silica) for solid-phase extraction (SPE) of fluoroquinolone (FQ) pollutants from water is presented for the first time. g-C3N4@silica was easily and quickly prepared by one-pot thermal condensation of dicyandiamide and characterized by powder X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, Fourier transform infrared spectroscopy and surface area measurements. The novel composite was applied as sorbent for SPE of FQs from water prior high-performance liquid chromatography with fluorescence detection. The extraction efficiency of g-C3N4 was tested in tap and surface waters at actual concentrations (10-100ngL-1). Quantitative adsorption was achieved using 100mg sorbent (20wt% g-C3N4) for pre-concentration of 50-500mL sample, at the native pH (∼7.5-8). Elution was performed with 25mM H3PO4 aqueous solution-acetonitrile (80:20), obtaining recoveries in the range 70-114%, enrichment factors up to 500 and inter-day RSDs≤12%. The batch-to-batch reproducibility was assessed on three independently synthesized g-C3N4@silica preparations (RSD 6-12%). g-C3N4 supported on silica microparticles proved to be of easy preparation, inexpensive, reusable for at least 4 extractions of raw surface waters, and suitable for determination in real matrices.

g-C3N4-promoted degradation of ofloxacin antibiotic in natural waters under simulated sunlight.

This is the first report on the photodegradation of ofloxacin under simulated solar light and in actual environmental matrices in the presence of a g-C3N4 suspension. The catalyst, prepared from the polymerization of dicyandiamide (650 °C, reaction yield 60%), was characterized by means of powder X-ray diffraction (PXRD), UV-vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), and BET surface area measurements. The experiments were carried out in a lab-scale batch reactor at concentrations in the range of micrograms/milligrams per liter. The course of the reaction was monitored by high-pressure liquid chromatography with UV-vis and fluorescence detectors. The g-C3N4-promoted photodegradation occurred at a rate 10 times faster than the direct photolysis and obeyed a first-order kinetics; in addition, the photodegradation kinetics of sonicated g-C3N4 resulted to be of the same order of that caused by P25 TiO2. Finally, the photochemical paths and the photoproducts have been identified and compared to those obtained by using P25 TiO2. From the results of this study, it can be concluded that g-C3N4 is a very attractive photocatalyst compared to P25 TiO2 in view of its ease of preparation, low cost, excellent oxidizing properties, large fraction of solar radiation absorbed, and intrinsically layered structure.

Haematic silicon in drowning.

The aim of this paper was to evaluate silicon (Si) concentration in human whole ventricular blood as a further potential chemical marker in the diagnosis of drowning. We employed an acidic digestion for the extraction of soluble Si, and an alkaline digestion for the determination of total Si, including particulate matter, both arising from drowning medium. 29 suspected drowning situations, 24 in fresh water (Fw) and 5 in seawater (Sw), were examined. The difference in Si concentration between the left and right ventricular blood (Si ΔL-R) was measured and alkaline Si ΔL-R seems, indeed, a potentially significant complementary tool in the diagnosis of Fw drowning, because insoluble silicon fraction does not undergo hemo-dilution or hemo-concentration, and the ΔL-R is not affected by exogenous factors. In spite of the limited number of cases investigated, a good correlation was observed between the analytical results and the macro-microscopic autoptic findings.