Nou analitzador on-line de residus contaminants en biogas

Investigadors del Grup de Tractament de Residus Gasosos del Departament d'Enginyeria Química de la UAB han desenvolupat un analitzador per a la detecció d'ió sulfur en líquid i sulfur d'hidrogen en gas, especialment dissenyat per ser utilitzat en el control de biofiltres per al tractament de biogas amb alta càrrega de sulfur d'hidrogen.Investigadores del Grupo de tratamiento de resíduos gaseosos del Departamento de Ingeniería Química de la UAB han desarrollado un analizador para la detección de ion sulfuro en líquido y sulfuro de hidrógeno en gas, especialmente diseñado para ser utilizado en el control de biofiltros para el tratamiento de biogás con alta carga de sulfuro de hidrógeno.Researchers of the Group of Waste Gas Treatment at the Department of Chemical Engineering of the UAB have developed an analyser for the detection of sulfide ion in liquid and hydrogen sulfide in gas samples, especially designed to be used in the control of biofílters for the treatment of biogas with high loads of hydrogen sulfide

Enantioseparations with polysaccharide-based chiral stationary phases in HPLC. Application to the enantioselective evaluation of the biodegradability of chiral drugs in activated sludge from a Valencian waste water treatment plant

The chiral nature of living systems has obvious implications for the biologically active compounds that interact with them. At the molecular level, chirality represents an intrinsic property of the essential building blocks of life, such as amino acids and sugars, and therefore, of peptides, proteins, enzymes, carbohydrates, nucleosides and a number of alkaloids and hormones. As a consequence, processes mediated by biological systems are stereochemistry-sensitive, and a pair of enantiomers can have different effects on living organisms. The scientific community has been studying the implications of chirality for life for more than a century. Today, it is still a topic of active research and debate due to the large number of chiral molecules that are part of living organisms and of our everyday life. In this context, analytical methods for the separation of the enantiomers of chiral molecules play a crucial role. Undoubtedly, the use of chiral stationary phases (CSPs) in high performance liquid chromatography (HPLC) is the preferred choice for enantioseparations. This is evidenced by the huge number of CSPs available on the market. This fact, together with the trial-and-error methods commonly used to select the most suitable chromatographic system (CSP/mobile phase combination) for a given enantioseparation, results in enormous cost and experimental effort. This makes it necessary to develop strategies to simplify this important task. This Doctoral Thesis has two clearly differentiated main objectives: (i) To contribute to the knowledge of chiral HPLC with polysaccharide-based CSPs (the most popular commercial ones: three amylose and five cellulose derivatives), and hydro-organic mobile phases (comprising acetonitrile (ACN) and methanol (MeOH) aqueous solutions compatible with aqueous matrices and mass spectrometry (MS) detection). To this end, the following specific objectives were set: (a) to contribute to a rational selection of the chromatographic system to separate the enantiomers of a given compound. To this end, the retention and enantioresolution of a large dataset of structurally unrelated chiral compounds (approximately 60 basic and neutral drugs and pesticides) in the chromatographic systems above-indicated is compared. Moreover, quantitative structure-property relationships (QSPRs) for enantioresolution related data obtained in some of the chromatographic systems studied are developed. (b) To explore the use of deconvolution of overlapping peaks to achieve the mathematical resolution when the baseline resolution cannot be achieved experimentally. To illustrate the potential of this peak model strategy, the enantioseparation of eight chiral drugs in five polysaccharide-based CSPs and ACN or MeOH hydro-organic mobile phases at different separation temperatures is considered. (ii) To contribute to the advancement of knowledge of the risks and hazards of chiral pollutants. To this end, OECD (Organisation for Economic Co-operation and Development) biodegradability tests using activated sludge from a Valencian waste water treatment plant (Quart Benàger) are performed for some common chiral pharmaceutical pollutants: trimeprazine, ibuprofen, ketoprofen, bupivacaine, mepivacaine, prilocaine and propanocaine. Next, the separation and determination of the enantiomers of the intact compound is performed using chiral HPLC methods (with amylose- or cellulose-based CSPs and ACN or MeOH hydro-organic mobile phases compatible with aqueous matrices and MS detection) developed for that purpose

Carbon-paste nanocomposites as unconventional gate electrodes for electrolyte-gated organic field-effect transistors: electrical modulation and bio-sensing

Nanocomposite carbon-paste electrodes (NC-CPEs) have been investigated for the first time in electrolytegated organic field-e¿ect transistors (EGOFETs) as a replacement of conventional metal gate electrodes, using carbon nanotubes (CNTs) as a model carbon filler. Interestingly, the electrical properties of the resulting devices have been modulated by changing the loading percentage of CNTs within the insulating polymeric matrix. The potential of using such non-conventional gate electrodes for sensing purposes has also been evaluated by investigating, as a proof of concept, the formation of a supramolecular complex between a functionalized CNT-based NC-CPE containing ß-cyclodextrin (ß-CD) as a bio-recognition element and tryptophan (TRP). This approach, in synergism with the amplification function of an EGOFET, a¿ords a shift in the threshold voltage (VTH) of the transistor, giving promising analytical results with detection limits at picomolar levels (1.0 ± 0.1 pM) as well as a linear response from 10-12 to 10-9 M. Accordingly, NC-CPEs have been demonstrated to be a potential alternative to metal gate electrodes for the development of a new generation of highly sensitive carbon-based EGOFET bio-sensorsPostprint (published version

Composite Electrodes Based on Carbon Materials Decorated with Hg Nanoparticles for the Simultaneous Detection of Cd(II), Pb(II) and Cu(II)

Monitoring water quality has become a goal to prevent issues related to human health and environmental conditions. In this sense, the concentration of metal ions in water sources is screened, as these are considered persistent contaminants. In this work, we describe the implementation of customized graphite electrodes decorated with two types of Hg nanoparticles (Hg-NPs), optimized toward the electrochemical detection of Cd, Pb and Cu. Here, we combine Hg, a well-known property to form alloys with other metals, with the nanoscale features of Hg-NPs, resulting in improved electrochemical sensors towards these analytes with a substantial reduction in the used Hg amount. Hg-NPs were synthesized using poly(diallyldimethylammonium) chloride (PDDA) in a combined role as a reducing and stabilizing agent, and then appropriately characterized by means of Transmission Electron Microscopy (TEM) and Zeta Potential. The surface of composite electrodes with optimized graphite content was modified by the drop-casting of the prepared Hg-NPs. The obtained nanocomposite electrodes were morphologically characterized by Scanning Electron Microscopy (SEM), and electrochemically by Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS). The results show that the Hg-NP-modified electrodes present better responses towards Cd(II), Pb(II) and Cu(II) detection in comparison with the bare graphite electrode. Analytical performance of sensors was evaluated by square-wave anodic stripping voltammetry (SWASV), obtaining a linear range of 0.005-0.5 mg·L−1 for Cd2+, of 0.028-0.37 mg·L−1 for Pb2+ and of 0.057-1.1 mg·L−1 for Cu2+. Real samples were analyzed using SWASV, showing good agreement with the recovery values of inductively coupled plasma-mass spectrometry (ICP-MS) measurement

Customized in situ functionalization of nanodiamonds with nanoparticles for composite carbon-paste electrodes

The incorporation of nanomaterials on (bio)sensors based on composite materials has led to important advances in the analytical chemistry field due to the extraordinary properties that these materials offer. Nanodiamonds (NDs) are a novel type of material that has raised much attention, as they have the possibility of being produced on a large scale by relatively inexpensive synthetic methodologies. Moreover, NDs can present some other interesting features, such as fluorescence, due to surface functionalization and proved biocompatibility, which makes them suitable for biomedical applications. In addition, NDs can be customized with metallic nanoparticles (NPs), such as silver or gold, in order to combine the features of both. Raw NDs were used as modifiers of sensors due to the electrocatalytic effect of the sp2 and oxygenated species present on their surface. The aim of this research work is evaluating the applicability of NDs modified with silver (Ag@NDs) and gold (Au@NDs) nanoparticles for the development of a suitable (bio)sensing platform. A complete morphological and electrochemical characterization as a function of the prepared nanocomposite composition was performed in order to improve the electroanalytical properties of the developed (bio)sensors. In the present work, the optimal composition for Au@NDs present on the nanocomposite matrix is 3.5% and the one for Ag@NDs is 1%. Good results were obtained in the evaluation of the optimal composition towards hydrogen peroxide and glucose as a model analyte using a (bio)sensor based on graphite-epoxy-Ag@NDs (17:82:1)

Integration of a sensitive carbon nanotube composite electrode in a ceramic microanalyzer for the amperometric determination of free chlorine

In this paper we report a green tape ceramic microfluidic analyzer that integrates a complete amperometric detection system based on a highly sensitive carbon nanotube composite electrode. As a proof of the integration concept, reference and counter electrodes were embedded into the microanalyzer body during the fabrication process.In order to increase the system functionality, and taking advantage of the surface renewability associated to composite electrodes, the working electrode was integrated in an exchangeable configuration. The microanalyzer was automated by means of the multicommutation technique, which allowed its autocalibration by the on-line preparation of standard solutions from a unique stock solution. The system was applied to the analysis of free chlorine in water samples. A noticeable low detection limit (0.05 mg L-1) and a high-term stability were observed. To demonstrate the potentiality of thisapproach, in terms of analytical performance, it was also applied to the analysis of real samples obtained from a public swimming pool. The system characteristics make it ideal for unattended applications where the minimum user interaction and the maximum analyzer autonomy are required.This work was partly supported by the Spanish MICINN project CTQ2009-13873 (BQU subprogram). R. Olivé-Monllau thanks Universitat Autònoma de Barcelona (UAB) for the award of PIF studentship

Role of physical activity and health- related fitness on self-confidence and interpersonal relations in 14-year-old adolescents from secondary school settings: DADOS study

Background: The effect of physical activity (PA) and physical fitness (PF) on self-confidence and interpersonal relations in adolescents is uncertain. Aim: To analyzed the associations of PA and PF with self-confidence and interpersonal relations in adolescents. Sample: A total of 268 (138 boys) adolescents (13.9 ± 0.3 years) from the DADOS study were included in the analysis. Methods: PA was evaluated using GENEActiv accelerometers and the health-related PF components by the ALPHA health-related fitness test battery. The levels of self-confidence and interpersonal relations were determined by the Behavior Assessment System for Children Level 3. Results: The associations of PA levels and PF components with self-confidence reported positive associations of moderate-vigorous PA (MVPA), standing long jump, and 20-m shuttle run (shuttle run test) tests (all p < 0.05), and negative association of 4 × 10-m shuttle run test (4 × 10-m test), but only the 4 × 10-m test remained significant in the adjusted model for the whole sample and only in boys (p ≤ 0.01) when analyzed by sex. Regarding interpersonal relations, positive associations of standing long jump and shuttle run test (all p < 0.05), and negative association of 4 × 10-m test were found in all the adolescents. The shuttle run test was associated with interpersonal relations in boys independently of confounders. PA levels were not associated with interpersonal relations. Conclusion: A higher level of lower-limb muscle strength, speed-agility, and cardiorespiratory fitness might improve self-confidence and interpersonal relations in adolescents, but these relationships seem to be influenced by sex, body mass index, and pubertal status. Speed-agility and cardiorespiratory fitness seem to have a stronger impact on boys. MVPA may improve self-confidence in adolescents

An inkjet-printed amperometric H2S sensor for environmental applications

Peer ReviewedPostprint (published version

Simultaneous methylmercaptan and hydrogen sulfide removal in the desulfurization of biogas in aerobic and anoxic biotrickling filters

Hydrogen sulfide (H2S) and methylmercaptan (CH3SH) are the most common sulfur compounds found in biogas. The simultaneous removal of H2S and CH3SH was tested at neutral pH in two biotrickling filters, one operated under aerobic conditions and the other one under anoxic conditions. Both reactors were run for several months treating a H2S concentration of around 2000 ppmv. Then, the effect of CH3SH loading rate (LR) on H2S and CH3SH removal was investigated in both reactors maintaining a constant H2S LR of 53–63 gS-H2S m−3 h−1, depending on the reactor. Initially, CH3SH concentration was stepwise increased from 0 to 75–90 ppmv. Maximum elimination capacities (ECs) of around 1.8 gS-CH3SH m−3 h−1 were found. After that, the CH3SH LR was increased by testing different empty bed residence times (EBRTs) between 180 and 30 s. Significantly lower ECs were found at short EBRTs, indicating that the systems were mostly mass transfer limited. Finally, EBRT was stepwise reduced from 180 to 30 s at variable CH3SH and H2S loads. Maximum H2S ECs found for both reactors were between 100 and 140 gS-H2S m−3 h−1. A negative influence was found in the ECs of CH3SH by the presence of high H2S LR in both biotrickling filters. However, sulfur mass balances in both reactors and batch tests under aerobic and anoxic conditions showed that CH3SH chemically reacts with elemental sulfur at neutral pH, enhancing the overall reactors performance by reducing the impact of sulfur accumulation. Also, both reactors were able to treat CH3SH without prior inoculation because of the already existing sulfide-oxidizing microorganisms grown in the reactors during H2S treatment. Co-treatment of H2S and CH3SH under aerobic and anoxic conditions was considered as a feasible operation for concentrations commonly found in biogas (2000 ppmv of H2S and below 20 ppmv of CH3SH)