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In the domain of high-temperature semiconductor arrays for electronic noses (e-noses), Metal Oxide Sensors (MOS) have a pivotal role despite their non-linear response to chemical vapors. A prevalent approach to enhance the identification algorithm's performance involves implementing mathematical models during the MOS signal processing. However, certain models rely solely on mathematical goodness-of-fit, overlooking crucial features that render practical e-nose applications ineffective. This paper introduces a theoretical model for the qualitative analysis of MOS signals, focusing on two primary diffusion processes: analyte migration to the sensor's surface and the subsequent dispersion of some of these molecules within the MOS bulk. Additionally, this work discusses a model validation using an ad-hoc e-nose, built with SnO 2 gas sensors, and six organic chemicals, detailing main data processing steps. Finally, disclosed results showcase a high success rate for Triacetone Triperoxide (TATP) identification, one of the most significant threats among homemade explosives (HME). The presented conclusions underscore the enhanced efficacy of the proposed signal model for e-nose vapors identification and its practical utility in strengthening pre-emptive HME identification to enhance public safety. • Innovative response model for Metal Oxide Semiconductor (MOS) sensors. • Improved accuracy of vapor identification by Principal Component Analysis. • Triperoxide Triacetone (TATP), Home-Made Explosive, identified by their vapor. • Linearization of model features by MOS signal preprocessing in enoses. [ABSTRACT FROM AUTHOR]

Highlights: [•] Metal fractionation of residues from the ferrite process was investigated by n-way PCA. [•] BCR sequential extraction procedure used for metal fractionation. [•] Tucker3 algorithm originated a coherent two-term trilinear model. [•] Metal fractionation patterns correlate with magnetic character of solids. [Copyright &y& Elsevier]

Presents a new procedure for the direct determination of picomolar levels of cobalt in seawater. Cathodic stripping voltammetry (CSV); Comparison of ligands; Effects of varying the solution composition on the CSV sensitivity for cobalt using nioxime; Nioxime concentration; Effect of pH; Cyclic voltammetry.

Expanded polystyrene (EPS) and polyurethane foams (PUFs) are widely produced and used due to their properties and, recently, it has been described that polystyrene present π–π interactions. Therefore, this work proposes to use recycled EPS to modify the surface of PUFs for the retention of 12 polycyclic aromatic hydrocarbons (PAHs) in air samples. PUF cylinders were modified with recycled polystyrene and characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and affinity experiments. The proposed material is suitable for the retention-elution of PAHs from air samples, and can be incorporated to liquid chromatography generating a quantitative methodology. This methodology is efficient, fast and use lower volumes of organic solvents compared with other methodologies. Eighteen urban air samples were collected and analyzed weekly, using principal component analysis (PCA), and a relation between meteorological parameters and concentration of PAHs was observed. [ABSTRACT FROM AUTHOR]

Swine farming produces large quantities of nutrient-rich wastewater, which often contains metals such as Cu and Zn, used as feed additives for pigs. These metals must be removed from the wastewater before discharge but their retention in the biomass can limit its subsequent utilization. Photobioreactors are a very promising alternative for swine wastewater treatment, as the consortium of microalgae and bacteria growing symbiotically in these reactors allows high nutrient and metal removal efficiency at moderate costs. This work studies the mechanisms of removal of Cu(II) and Zn(II) by the two types of microorganisms growing in these photobioreactors. A microalga commonly used in wastewater treatment (Scenedesmus almeriensis) and an activated sludge were kept in contact with synthetic wastewater containing 100 mg/L of Cu and Zn. After 72 h, Scenedesmus almeriensis removed 43% of Cu and 45% of Zn, while activated sludge removed 78% of Cu and 96% of Zn. Single and sequential extractions of the biomasses using different extracting reagents revealed that biosorption on protonable groups is the dominant removal mechanisms. Mild reagents solubilized 69% of Cu and 94% of Zn from the microalgae and 76% of Cu and 93% of Zn from the activated sludge. Low metal concentrations in the oxidizable and residual fractions evidenced minimal bioaccumulation inside the cells. FTIR and ESEM-EDX analysis confirmed biosorption by ion exchange and complexation as the main metal remediation mechanisms. The weak bonds of the biosorbed Cu and Zn ions are beneficial for the valorization of biomass and the obtaining of safe bioproducts. [Display omitted] • Sewage sludge more effective than microalga S. almeriensis to remove Cu and Zn from wastewater. • Cu is more strongly biosorbed than Zn by both sewage sludge and microalgae. • Metal biosorption on protonable electron donor groups is the main bioremoval mechanism. • Cu and Zn are biosorbed on groups –COOH, –OH, –NH contained in proteins and carbohydrates of the cell membrane. • Most metal accumulated by the biomasses is acid soluble/exchangeable and readily available. [ABSTRACT FROM AUTHOR]

238U is a radionuclide present in the earth's crust that provides 65.9% of annual average radiation dose and represents 99.27% of total uranium. 238U has been determined in samples from undisturbed topsoil in the Zacatecas State, Mexico, using several analytical techniques. ICP-MS and α-spectrometry produced the most reliable results. Uranium concentrations found in topsoil samples (0.4-3.7 mg kg−1) were similar to its average crustal abundance (2.8 mg kg−1) and indicate high homogeneity without evidence of enrichment. The average concentration of 2.1 mg kg−1 can be established as uranium background level in the topsoil of Zacatecas (Mexico). [ABSTRACT FROM AUTHOR]

This work represents a comparative uptake study of the toxic elements arsenic, boron, copper, manganese and zinc in monometallic and multimetallic solutions by four green microalgae species ( Chlamydomonas reinhardtii , Chlorella vulgaris , Scenedesmus almeriensis and an indigenous Chlorophyceae spp.), evaluating the effect of pH and contact time. Maximum removal efficiencies for each toxic element were 99.4% for Mn ( C. vulgaris , pH 7.0, 3 h), 91.9% for Zn ( Chlorophyceae spp., pH 5.5, 3 h), 88% for Cu ( Chlorophyceae spp., pH 7.0, 10 min), 40.7% for As ( S. almeriensis , pH 9.5, 3 h) and 38.6% for B ( S. almeriensis , pH 5.5, 10 min). B removal efficiencies decreased remarkably in multimetallic solutions (down to 0.2% in C. reinhardtii ), except for Chlorophyceae spp., the only species isolated from a polluted environment. FTIR spectra shown the highest interactions for As (1150–1300 cm −1 ) and Cu (3300, 1741, 1535, 1350–1400 cm −1 ). Results confirm microalgae biomass as a potential biosorbent for toxic elements. [ABSTRACT FROM AUTHOR]

Abstract: Temporal and spatial patterns of water quality of an important artificial water reservoir located in the semiarid Midwest of Argentina were investigated using chemometric techniques. Surface water samples were collected at 38 points of the water reservoir during eleven sampling campaigns between October 1998 and June 2000, covering the warm wet season and the cold dry season, and analyzed for dissolved oxygen (DO), conductivity, pH, ammonium, nitrate, nitrite, total dissolved solids (TDS), alkalinity, hardness, bicarbonate, chloride, sulfate, calcium, magnesium, fluoride, sodium, potassium, iron, aluminum, silica, phosphate, sulfide, arsenic, chromium, lead, cadmium, chemical oxygen demand (COD), biochemical oxygen demand (BOD), viable aerobic bacteria (VAB) and total coliform bacteria (TC). Concentrations of lead, ammonium, nitrite and coliforms were higher than the maximum allowable limits for drinking water in a large proportion of the water samples. To obtain a general representation of the spatial and temporal trends of the water quality parameters at the reservoir, the three-dimensional dataset (sampling sites×parameters×sampling campaigns) has been analyzed by matrix augmentation principal component analysis (MA-PCA) and N-way principal component analysis (N-PCA) using Tucker3 and PARAFAC (Parallel Factor Analysis) models. MA-PCA produced a component accounting for the general behavior of parameters associated with organic pollution. The Tucker3 models were not appropriate for modelling the water quality dataset. The two-factor PARAFAC model provided the best picture to understand the spatial and temporal variation of the water quality parameters of the reservoir. The first PARAFAC factor contains useful information regarding the relation of organic pollution with seasonality, whereas the second factor also encloses information concerning lead pollution. The most polluted areas in the reservoir and the polluting sources were identified by plotting PARAFAC loadings as a function of the UTM (Universal Transverse Mercator) coordinates. [Copyright &y& Elsevier]

Abstract: A magnetic solid phase extraction method coupled to capillary electrophoresis is proposed for the determination of tetracycline, oxytetracycline, chlortetracycline and doxycycline in milk samples. Five different magnetic phenyl silica adsorbents covered with magnetite were synthesized by varying the molar ratio of phenyltrimethylsilane and tetramethylorthosilicate; these adsorbents were evaluated in terms of their pH and degree of hydrophobicity for tetracycline retention. The optimal, selected combination of conditions was a pH of 10.0 and a magnetic sorbent ratio of 4:1; under these conditions, the retention capacity ranged from 99.7% to 101.2% for the four tetracyclines analyzed. The elution conditions and initial sample volume of the proposed extraction method were also optimized, and the best results were obtained with 1×10−3 M acetic acid in methanol as eluent and a 200ml of sample volume. Under optimal conditions, average recoveries ranged from 94.2% to 99.8% and the limits of detection ranged from 2 to 9μgl−1 for the four tetracyclines. After the proposed method was optimized and validated, 25 milk samples of different brands were analyzed, oxytetracycline residues were detected in five samples, in concentrations ranging from 98 to 213μgl−1. Subsequent analysis of positive samples by SPE–CE and magnetic solid phase extraction–HPLC revealed than no significant differences were found from results obtained by the proposed methodology. Thus, the developed magnetic extraction is a robust pre-concentration technique that can be coupled to other analytical methods for the quantitative determination of tetracyclines. [Copyright &y& Elsevier]

• Cell wall of pure microalgae was less resistant than microalgae-bacteria consortium. • High degradation of components solubilized from pure microalgae. • Proteases solubilized high amount of xylose, but with high degradation. • Alcalase provided the highest protein solubilization and recovery from both biomasses. • The largest peptide sizes were obtained by Protamex hydrolysis. Photobioreactors for wastewater treatment coupled with nutrient recovery from the biomass is a promising biorefinery platform but requires working with microalgae-bacteria consortia. This work compares the effect that hydrolysis time and different enzymes have on the solubilization and recovery of components from microalgae-bacteria grown in piggery wastewater and microalgae grown in synthetic media by enzymatic hydrolysis. Higher carbohydrate solubilizations were obtained from microalgae-bacteria than from pure microalgae (38.5% vs. 27% Celluclast, 5 h), as expected from the SEM images. Proteases solubilized xylose remarkably well, but xylose recovery was negligible in all experiments. Alcalase hydrolysis (5 h) provided the highest peptide recovery from both biomasses (≈34%), but the peptide sizes were lower than 10 kDa. Low peptide recoveries (<20%) but larger peptide sizes (up to 135 kDa) were obtained with Protamex. Pure microalgae resulted in remarkably higher losses, but similar amino acid profiles and peptide sizes were obtained from both biomasses. [ABSTRACT FROM AUTHOR]

The accumulation of Cd(II), Cu(II), Pb(II) and Zn(II) at mg L-1 concentration levels by inactive freeze-dried biomass of Pseudomonas Putida has been investigated. These metals could be efficiently removed from diluted aqueous solutions. A contact time of 10 min was sufficient to reach equilibrium. The pH has a strong effect on metal biosorption and the optimal pH values were 6.0, 5.0–6.0, 6.0–6.5 and 7.0–7.5 for Cd(II), Cu(II), Pb(II) and Zn(II) respectively. Under these conditions there was 80% removal for all metals studied. The process of biosorption can be described by a Langmuir-type adsorption model. This model accounts for 98% of the data variance. The KA and qmax parameters for each metal are strongly correlated (at confidence levels greater than 98%) with the metal acidity, quantified by the constant of the corresponding M(OH)+ complex, thus confirming previous assertions by other authors. [ABSTRACT FROM AUTHOR]

The efficiency of the ‘ferrite process’ for the purification of wastewater heavily contaminated with nickel is evaluated, and the solid residues formed are characterised. The efficiency of the purification process is always above 99.9% for Fe2+/Ni2+ ratios greater than 3. The tested Fe2+/Ni2+ molar ratios (15/1, 7/1 and 3/1) yielded three different nickel ferrites. Inductively-coupled plasma atomic emission spectroscopy (ICP-AES), potentiometric titration, X-ray fluorescence (XRF), X-ray diffractometry (XRD) and differential scanning calorimetry (DSC) yielded NixFe1−xIIFe2IIIO4 (x=0.18, 0.40 and 0.65, respectively) as the most probable stoichiometry, and inverse spinel as the most probable structure. Heating at 600 °C causes the transformation of the solids into a mixture of NiFe2O4, α-Fe2O3 and NiO. Electrochemical analysis of the solid nickel ferrites was performed using carbon paste electrodes (CPEs) in HClO4 and HCl media. In each case, the first cyclic voltammogram showed the participation of solid species in the electrochemical transformation process, since the shape of the redox peaks could be related to the structure and stoichiometry of the ferrites. In second and successive scans, the voltammograms indicated the redox couples Feads3++1e−&iff;Feads2+ (0.525 V vs. Ag/AgCl) and Niads2++2e−&iff;Ni(s) (−0.470 V) in HClO4, and FeCl2,ads++1e−&iff;FeClads++Cl− (0.475 V) and NiClx,ads(x−2)−+2e−&iff;Ni(s)+xCl− (−0.550 V) in HCl. [Copyright &y& Elsevier]

Thorium is a radionuclide highly widespread in the earth's crust with a relevant contribution to the exposure to radiation of living organisms. Natural concentrations of thorium in the soil can be altered due to human activities such as mining, agriculture, and cattle industry. Mining and related industry have been operating for centuries in Zacatecas State, Mexico, leaving mining waste dumps that can release trace elements to the topsoil. There are not enough previous studies of thorium concentration in this area. Thirty-three soil samples from different locations from Zacatecas State were analyzed, using alpha-spectrometry and ICP-MS, to estimate the reference value for thorium in surface soil in order to provide regulatory agencies with a tool to verify possible disturbances due to anthropogenic activities. Geoaccumulation indexes and enrichment factors did not reveal significant alterations in topsoil thorium concentration. The average concentration was 13.6 ± 7.6 mg kg−1, which is consistent with the estimated average concentration in the earth crust and is then proposed as average basal concentration for this region. A slight disequilibrium has been found between the natural isotopes of thorium due to the semi-arid nature of the areas and climatic factors. • Thorium baseline concentration of 13.6 ± 7.6 mg⋅kg−1 in topsoil of Zacatecas, Mexico. • Geological enrichment indexes do not reveal significant Th accumulation in topsoil. • Natural Th isotopes are a valuable tool for geological exploration and research. • Slight disequilibrium of Th isotopes can be related to semiarid climate of Zacatecas. [ABSTRACT FROM AUTHOR]

Terconazole belongs to synthetic triazole antifungal agents, inhibiting biosynthesis of ergosterol or other sterols and thus disrupting cell wall synthesis in fungi. In this study, electrochemical behavior of terconazole was studied for the first time using cyclic voltammetry and differential pulse voltammetry on boron doped diamond electrode (BDD) with different surface treatments leading to O-terminated, H-terminated and polished surfaces, as well as on glassy carbon (GCE) and basal-plane pyrolytic graphite electrodes (PGE). Terconazole is not reducible within the potential window on these electrode materials. It is oxidizable in aqueous solutions in pH range from 2.0 to 12.0 in two steps due to the presence of piperazine ring in its molecule, possessing two redox centers at the tertiary nitrogen atoms, by an ECE mechanism. Optimal conditions were found for determination of terconazole in 0.1 mol L−1 phosphate buffer pH 7.2. Using differential pulse voltammetry, the lowest detection limit of 0.40 μmol L−1 and excellent repeatability (RSD 1.1%) were achieved on O-terminated BDD when in-situ anodic activation was used prior to each scan. This is beneficial in comparison with GCE and PGE; their necessity of ex-situ polishing worsens the signal repeatability (RSD ~ 4%) and detection limits reaching 0.50 μmol L−1 and 1.23 μmol L−1, respectively. Unlabelled Image • The first electrochemical study of terconazole using voltammetric techniques is described. • Glassy carbon, pyrolytic graphite and oxygen-, hydrogen- and polished boron doped diamond (BDD) electrodes were employed • Terconazole gives pH-dependent peaks in cyclic voltammetry at ca +0.5 – 0.8 V due to oxidation of piperazine moiety • Terconazole is not reducible within the potential window of tested electrode materials • The lowest detection limit of 0.40 μmol L−1 was achieved on O-terminated BDD using in-situ anodic activation [ABSTRACT FROM AUTHOR]