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1.
Phys Chem Chem Phys ; 22(5): 2999-3007, 2020 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-31957771

RESUMO

Infrared multiple photon dissociation (IRMPD) spectroscopy has been used to probe the structures of the three protonated base-pair mismatches containing 9-ethylguanine (9eG) in the gas phase. Computational chemistry has been used to determine the relative energies and compute the infrared spectra of these complexes. By comparing the IRMPD spectra with the computed spectra, in all cases, it was possible to deduce that what was observed experimentally were the lowest energy computed structures. The protonated complex between 9eG and 1-methylthymine (1mT) is protonated at N7 of 9eG-the most basic site of all three bases in this study-and bound in a Hoogsteen type structure with two hydrogen bonds. The experimental IRMPD spectrum for the protonated complex between 9eG and 9-methyladenine (9mA) is described as arising from a combination of the two lowest energy structures, both which are protonated at N1 of adenine and each containing two hydrogen bonds with 9eG being the acceptor of both. The protonated dimer of 9eG is protonated at N7 with an N7-H+-N7 ionic hydrogen bond. It also contains an interaction between a C-H of protonated guanine and the O6 carbonyl of neutral guanine which is manifested in a slight red shift of that carbonyl stretch. The protonated 9eG/9mA structures have been previously identified by X-ray crystallography in RNA and are contained within the protein database.


Assuntos
Gases/química , Guanina/análogos & derivados , Espectrofotometria Infravermelho , Adenina/análogos & derivados , Adenina/química , Adenina/metabolismo , Pareamento Incorreto de Bases , Cristalografia por Raios X , Guanina/química , Guanina/metabolismo , Ligações de Hidrogênio , Modelos Moleculares , Fótons , Timina/análogos & derivados , Timina/química , Timina/metabolismo
2.
J Photochem Photobiol B ; 202: 111726, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31816516

RESUMO

The objective of the study was to investigate the effects of growth-stage specific lighting for the physiological homeostasis of red leaf lettuce (Lactuca sativa L. cv. Red Cos), by measuring the productivity of photosynthesis and primary metabolism. In the experiments, the main photosynthetic photon flux consisted of red (R) and blue (B) light, supplemented with blue, green (G) or UV-A wavelengths. Decrease of fructose, accompanied by significant decrease of stomatal conductance (gs), the ratio of intracellular to ambient CO2 concentration (Ci/Ca), photosynthetic rate (Pr), light adapted actual quantum yield of PSII photochemistry (ΦPSII), biomass formation and significant increase of transpiration rate (Tr) suggest that supplemental UV-A during maturity stage, after supplemental green irradiation during seedling stage (BRG to BRUV) was the least favourable condition for red leaf lettuce. However, constant irradiation with supplemental green (BRG) or supplemental green irradiation after increased blue exposure (B↑R to BRG) resulted in significant increase of Pr, gs, Ci/Ca, and light use efficiency(LUE), and decrease of Tr and Water use efficiency (WUE). Significant increase of leaf area was observed under supplemental green in both seedlings (BR; BRG) and matured plants (B↑R to BRG). Significant increase of specific leaf area was found under supplemental green (BRG) for seedlings and under increased blue (B↑R) for matured plants. Accordingly, the most favourable growth-stage specific lighting spectrum strategy for red leaf lettuce, based on photosynthetic and primary metabolite response, is supplemental green irradiation after increased blue exposure (B↑R to BRG), whereas, the most favourable condition for seedlings is BRG. According to the PCA correlation matrix, associations among the measured data indicate that WUE negatively correlated with gs and Ci/Ca, while LUE positively correlated with gs and Pr. However, weak correlations between ФPSII, LUE and photochemical reflectance index (PRI) suggest that selected light conditions were not optimal for red leaf lettuce.


Assuntos
Alface/efeitos da radiação , Luz , Clorofila/química , Análise por Conglomerados , Gases/química , Gases/metabolismo , Alface/crescimento & desenvolvimento , Fotossíntese/efeitos da radiação , Folhas de Planta/química , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/efeitos da radiação , Análise de Componente Principal , Teoria Quântica , Raios Ultravioleta
3.
Top Curr Chem (Cham) ; 378(1): 4, 2019 Dec 02.
Artigo em Inglês | MEDLINE | ID: mdl-31788736

RESUMO

Interpenetration in metal-organic frameworks (MOFs) can have significant impacts on the structure, porous nature, and functional applications of MOFs. Considered to be disadvantageous in the initial phases leading to a decrease in surface area, interpenetration has proved to be highly useful for modulation of pore size and selective separation of gases. The importance of interpenetration has been realized over the last decade, and numerous approaches to graft interpenetration and utilize it for improved functions and applications have been achieved. Several factors such as temperature, solvent system, time duration and steric aspects of the ligands have been utilized to regulate the degree of interpenetration (DOI). In this review, we summarize recent advances in regulating the DOI in MOFs and its impact on the resulting properties.


Assuntos
Estruturas Metalorgânicas/química , Adsorção , Gases/química , Ligantes , Porosidade , Solventes/química , Temperatura Ambiente
4.
Chem Commun (Camb) ; 55(100): 15117-15120, 2019 Dec 28.
Artigo em Inglês | MEDLINE | ID: mdl-31782438

RESUMO

A nitrogen doped bio-carbon catalyst with high specific surface area and a hierarchical interconnected porous structure was fabricated by an in situ gas-foaming strategy from sodium alginate and ammonium chloride. The optimized catalyst displays a fabulous ORR activity, providing a facile approach for the mass production of metal-free bio-carbon catalysts in fuel cells and metal-air batteries.


Assuntos
Carbono/química , Fontes de Energia Elétrica , Gases/química , Nitrogênio/química , Ar , Alginatos/química , Cloreto de Amônio/química , Catálise , Porosidade , Zinco/química
5.
J Chem Phys ; 151(14): 144504, 2019 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-31615223

RESUMO

In this work, a R1SM approach was applied for the calculation of ideal-gas thermodynamic properties of five amino acids with aliphatic side chains: glycine, alanine, valine, leucine, and isoleucine. The first step of the calculation was an extensive conformational analysis that located several conformers not reported previously. A new systematic and user-friendly nomenclature of the conformers was introduced, and the stable conformers were clearly assigned with the previously used labeling where possible. Stability and calculated relative energies of the conformers were compared between various levels of theory and with several experimental studies, demonstrating a good performance of the selected B3LYP-D3/6-311+G(2df,p) level of theory. As a second step, the theoretically calculated vibrational frequencies were compared to the previously reported experimental spectra to verify the performance of the applied double-linear scaling factor. Finally, ideal-gas heat capacities, enthalpies, and absolute entropies were calculated, accounting for all stable conformers using the R1SM model. The resulting thermodynamic data are presented for the first time, since they cannot be determined experimentally and their rigorous calculation requires a complex thermodynamic model.


Assuntos
Aminoácidos/química , Termodinâmica , Teoria da Densidade Funcional , Gases/química , Modelos Químicos , Conformação Molecular , Estatística como Assunto
6.
Chem Commun (Camb) ; 55(91): 13753-13756, 2019 Nov 12.
Artigo em Inglês | MEDLINE | ID: mdl-31663548

RESUMO

A chemosensor containing an o-hydroxyaniline unit as the reaction site was developed for colorimetric and fluorimetric detection of phosgene, which showed fast response (15 s), high specificity, and an extremely low detection limit. The chemosensor was incorporated into paper strips for visual detection of phosgene vapor.


Assuntos
Papel , Fosgênio/análise , Espectrometria de Fluorescência/métodos , Corantes Fluorescentes/química , Gases/química , Limite de Detecção
7.
Phys Chem Chem Phys ; 21(41): 22782-22793, 2019 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-31595896

RESUMO

The theoretical assignment of electronic spectra of polyatomic molecules is a challenging problem that requires the specification of the character of a large number of electronic states. We propose a procedure for automatically determining the character of electronic transitions and apply it to the study of UV spectra of DNA bases in the gas phase and in the aqueous environment. The procedure is based on the computation of electronic wave function overlaps and accounts for an extensive sampling of nuclear geometries. Novelties of this work are the theoretical assignment of the electronic spectra of DNA bases up to 190 nm and a state specific analysis of solvation effects. By accounting for different effects contributing to the total solvent shift we obtained a good agreement between the computed and experimental spectra. Effects of vibrational averaging, temperature and solvent-induced structural changes shift excitation energies to lower values. Solvent-solute electrostatic interactions are state specific and strongly destabilize nRyd states, and to lesser extent nπ* and πRyd states. Altogether, this results in the stabilization of ππ* states and destabilization of nπ*, πRyd and nRyd states in solution.


Assuntos
Técnicas de Química Analítica/métodos , DNA/química , Solventes/química , Análise Espectral , Gases/química , Eletricidade Estática , Raios Ultravioleta
8.
Phys Chem Chem Phys ; 21(41): 22700-22703, 2019 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-31579899

RESUMO

We use cold ion spectroscopy and quantum-chemical computations to solve the structures of opioid peptides enkephalins in the gas phase. The derived structural parameters clearly correlate with the known pharmacological efficiency of the studied drugs, suggesting that gas-phase methods, perhaps, can be used for predicting the relative potency of ligand drugs that target the hydrophobic pockets of receptors.


Assuntos
Encefalinas/química , Gases/química , Modelos Moleculares , Análise Espectral , Encefalinas/farmacologia , Humanos , Interações Hidrofóbicas e Hidrofílicas , Neurotransmissores/química , Neurotransmissores/farmacologia , Relação Estrutura-Atividade
9.
J Chem Theory Comput ; 15(11): 5894-5907, 2019 Nov 12.
Artigo em Inglês | MEDLINE | ID: mdl-31538779

RESUMO

A nonempirical quantum mechanical method for the efficient and accurate quantification and analysis of intermolecular interactions is presented and tested on existing benchmark sets. The leading idea here is to focus on the intermolecular part of the correlation energy that contains the all-important London dispersion (LD) interaction. To keep the cost of the method low, essentially at the level of a Hartree-Fock (HF) calculation, the intramolecular part of the correlation energy is neglected. We also neglect the nondispersive parts of the intermolecular correlation energy. This scheme that we denote as Hartree-Fock plus London dispersion (HFLD) can be readily realized on the basis of the recently reported multilevel implementation of the domain-based local pair natural orbital coupled-cluster (DLPNO-CC) theory in conjunction with the well-established local energy decomposition (LED) analysis. The accuracy and efficiency of the HFLD method are evaluated on rare gas dimers, on the S66 and L7 benchmark sets of noncovalent interactions, and on an additional set (LP14) consisting of bulky Lewis pairs held together by intermolecular interactions of various strengths, with interaction energies ranging from -8 to -107 kcal/mol. It is first shown that the LD energy calculated with this approach is essentially identical to that obtained from the full DLPNO-CCSD(T)/LED calculation, with a mean absolute error of 0.2 kcal/mol on the S66 benchmark set. Moreover, in terms of the overall interaction energies, the HFLD method shows an efficiency that is comparable to that of the HF method, while retaining an accuracy between that of the DLPNO-CCSD and DLPNO-CCSD(T) schemes. Since the underlying DLPNO-CCSD method is linear scaling with respect to the system size, the HFLD approach also does not lead to new bottlenecks for large systems. As an illustrative example of its efficiency, the HFLD scheme was applied to the interaction between the substrate and the residues in the active site of the cyclohexanone monooxygenase enzyme. The excellent cost/performance ratio indicates that the HFLD method opens new avenues for the accurate calculation and analysis of noncovalent interaction energies in large molecular systems.


Assuntos
Modelos Moleculares , Teoria Quântica , Domínio Catalítico , Dimerização , Gases/química , Oxigenases/química , Oxigenases/metabolismo , Especificidade por Substrato , Termodinâmica
10.
Sensors (Basel) ; 19(18)2019 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-31500124

RESUMO

This study explores the use of a butyrylcholinesterase (BChE)-based, reversible reaction biosensor using screen-printed electrodes (SPEs) having a smaller working surface area than the single-use electrodes previously studied. Previous research demonstrated the prospective application of a single-use biosensor fabricated with an acetylcholinesterase (AChE) enzyme encapsulated in peptide nanotubes (PNTs) and enhanced with horseradish peroxidase (HRP) to detect organophosphorus compounds (OPCs) in aqueous and gas phases. In the current study, potential improvements to the biosensor are investigated. BChE-based biosensors were fabricated using PNTs, HRP, and Nafion in combination to increase the reactive surface area, enhance sensitivity, and maintain enzyme stability. Cyclic voltammetry (CV) was used along with the new modified sensor to measure malathion concentration in the gas phase. The results show that a BChE-based biosensor could reliably measure gas phase malathion concentrations between 6-25 ppbv by CV with the extent of inhibition linearly proportional to the malathion concentration (R2 = 0.941). This research demonstrated that fabricated BChE-based biosensors could be stored without cold storage requirement for up to six weeks with minimal performance degradation. Moreover, the sensor electrodes were each reused several times, and were still useable at the conclusion of the research. This research demonstrates the potential of fabricating a reusable, inexpensive biosensor that is capable of OPC detection with high sensitivity and a low detection limit without a long-term cold storage requirement.


Assuntos
Técnicas Biossensoriais , Gases/isolamento & purificação , Malation/isolamento & purificação , Nanotubos de Peptídeos/química , Acetilcolinesterase , Butirilcolinesterase/química , Enzimas Imobilizadas/química , Gases/química , Ouro/química , Peroxidase do Rábano Silvestre/química , Limite de Detecção , Malation/química , Nanotubos de Carbono/química , Compostos Organofosforados/química , Compostos Organofosforados/isolamento & purificação , Água/química
11.
Biosens Bioelectron ; 143: 111628, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31476599

RESUMO

A combined calorimetric gas- and spore-based biosensor array is presented in this work to monitor and evaluate the sterilization efficacy of gaseous hydrogen peroxide in aseptic filling machines. H2O2 has been successfully measured under industrial conditions. Furthermore, the effect of H2O2 on three different spore strains , namely Bacillus atrophaeus, Bacillus subtilis and Geobacillus stearothermophilus, has been investigated by means of SEM, AFM and impedimetric measurements. In addition, the sterilization efficacy of a spore-based biosensor and the functioning principle are addressed and discussed: the sensor array is convenient to be used in aseptic food industry to guarantee sterile packages.


Assuntos
Técnicas Biossensoriais , Calorimetria , Peróxido de Hidrogênio/isolamento & purificação , Esporos Bacterianos/efeitos dos fármacos , Bacillus/efeitos dos fármacos , Bacillus/crescimento & desenvolvimento , Bacillus subtilis/efeitos dos fármacos , Bacillus subtilis/crescimento & desenvolvimento , Desinfetantes/química , Desinfetantes/isolamento & purificação , Gases/química , Gases/isolamento & purificação , Geobacillus stearothermophilus/efeitos dos fármacos , Geobacillus stearothermophilus/crescimento & desenvolvimento , Humanos , Peróxido de Hidrogênio/farmacologia , Infertilidade , Esporos Bacterianos/crescimento & desenvolvimento , Esterilização
12.
Environ Sci Pollut Res Int ; 26(29): 29660-29668, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31402436

RESUMO

Alkali metal chlorides emitted from sintering flue gas are easily adsorbed on the surface of activated carbon (AC) in the purification process. In this paper, NaCl particles adsorbing onto AC were simulated by impregnation method, and the size and morphology of NaCl particles were similar to those of NaCl-PM10 emitted from sintering flue gas. With the adsorption of NaCl particles, 2-10-µm pores of AC were filled, and the specific surface area of AC decreased. But NaCl led to the increase of acidic functional groups on the surface of AC. When 0.75 wt% NaCl was adsorbed, it was beneficial for AC catalytic denitration (de-NOx), because the chemical reaction was strengthened by acidic functional groups, so it showed a certain promotion of de-NOx efficiency. As 1.5 wt% NaCl and 3 wt% NaCl were adsorbed, NaCl had an inhibitory effect on AC de-NOx, which was because the specific surface area of AC decreased, and the prevention of physical adsorption played a major role. As a result, the de-NOx efficiency of AC adsorbed with 3 wt% NaCl decreased from 40.59 to 23.02% at 150 °C. Therefore, the absorption of NaCl fine particles on AC should not exceed 0.75 wt%.


Assuntos
Poluentes Atmosféricos/química , Carvão Vegetal/química , Gases/química , Cloreto de Sódio/química , Adsorção , Poluentes Atmosféricos/isolamento & purificação , Catálise , Resíduos Industriais , Óxido Nítrico/química , Espectroscopia de Infravermelho com Transformada de Fourier , Difração de Raios X
13.
J Appl Microbiol ; 127(5): 1403-1420, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31410952

RESUMO

Medical devices are an important and growing aspect of healthcare provision and are increasing in complexity to meet established and emerging patient needs. Terminal sterilization plays a vital role in the provision of safe medical devices. While terminal sterilization technologies for medical devices include multiple radiation options, ethylene oxide remains the predominant nonthermal gaseous option, sterilizing c. 50% of all manufactured devices. Vaporized hydrogen peroxide (abbreviated VH2O2 by the International Organization for Standardization) is currently deployed for clinical sterilization applications, where its performance characteristics appear aligned to requirements, constituting a viable alternative low-temperature process for terminal processing of medical devices. However, VH2O2 has operational limitations that create technical challenges for industrial-scale adoption. This timely review provides a succinct overview of VH2O2 in gaseous sterilization and addresses its applicability for terminal sterilization of medical devices. It also describes underappreciated factors such as the occurrence of nonlinear microbial inactivation kinetic plots that may dictate a need to develop a new standard approach to validate VH2O2 for terminal sterilization of medical devices.


Assuntos
Contaminação de Equipamentos/prevenção & controle , Peróxido de Hidrogênio/química , Esterilização/métodos , Bactérias/efeitos dos fármacos , Equipamentos e Provisões Hospitalares/microbiologia , Equipamentos e Provisões Hospitalares/estatística & dados numéricos , Óxido de Etileno/química , Óxido de Etileno/farmacologia , Gases/química , Peróxido de Hidrogênio/farmacologia , Esterilização/instrumentação
14.
Sensors (Basel) ; 19(17)2019 Aug 25.
Artigo em Inglês | MEDLINE | ID: mdl-31450646

RESUMO

The qualitative and quantitative analysis to trace gas in exhaled human breath has become a promising technique in biomedical applications such as disease diagnosis and health status monitoring. This paper describes an application of a high spectral resolution optical feedback cavity enhanced absorption spectroscopy (OF-CEAS) for ammonia detection in exhaled human breath, and the main interference of gases such as CO2 and H2O are approximately eliminated at the same time. With appropriate optical feedback, a fibered distributed feedback (DFB) diode laser emitting at 1531.6 nm is locked to the resonance of a V-shaped cavity with a free spectral range (FSR) of 300 MHz and a finesse of 14,610. A minimum detectable absorption coefficient of αmin = 2.3 × 10-9 cm-1 is achieved in a single scan within 5 s, yielding a detection limit of 17 ppb for NH3 in breath gas at low pressure, and this stable system allows the detection limit down to 4.5 ppb when the spectra to be averaged over 16 laser scans. Different from typical CEAS with a static cavity, which is limited by the FSR in frequency space, the attainable spectral resolution of our experimental setup can be up to 0.002 cm-1 owing to the simultaneous laser frequency tuning and cavity dither. Hence, the absorption line profile is more accurate, which is most suitable for low-pressure trace gas detection. This work has great potential for accurate selectivity and high sensitivity applications in human breath analysis and atmosphere sciences.


Assuntos
Amônia/isolamento & purificação , Técnicas Biossensoriais , Gases/isolamento & purificação , Amônia/química , Testes Respiratórios/métodos , Expiração , Gases/química , Humanos , Limite de Detecção , Espectroscopia de Luz Próxima ao Infravermelho
15.
Analyst ; 144(19): 5738-5747, 2019 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-31453603

RESUMO

Ion mobility spectrometry (IMS) is of significant interest as a platform for glycoanalysis. While much attention has been focused on the resolution of isomeric carbohydrates and glycoconjugates, another appealing aspect of IMS is the ability to sort different classes of biomolecules into distinct regions of mass vs. mobility space. This capability has potential to greatly simplify glycoproteomic analyses, as glycosylated and non-glycosylated peptides can be rapidly partitioned in the gas phase. Nevertheless, the physical and chemical characteristics of glycopeptides that dictate their mass vs. mobility loci have yet to be systematically investigated. This report presents an IMS study of model protonated glycopeptide ions with systematically varied oligosaccharide topologies, polypeptide sequences, and charge states. In all, over 110 ion-neutral collision cross sections (CCSs) were measured and analyzed in the context of the physicochemical characteristics of the analytes. Glycan size and composition emerged as a decisive factor in dictating the CCS space occupied by the glycopeptides and exerted this influence in a charge state dependent fashion. Furthermore, elongation of the glycan group was found to either increase or decrease glycopeptide CCSs depending on the ion charge state and the size of the glycan. Molecular dynamics (MD) simulations of the gas phase structures and CCSs of selected glycopeptides revealed that the experimental observations were consistent with a glycan size and charge state dependent interplay between destabilizing coulombic repulsion effects (tending to result in more extended structures) and stabilizing charge solvation effects in which the glycan plays a major role (tending to result in more compact structures). Taken together, these IMS and MD findings suggest the possibility of predicting and delineating glycopeptide-enriched regions of mass vs. mobility space for applications in glycoproteomics.


Assuntos
Carboidratos/química , Glicopeptídeos/química , Sequência de Aminoácidos , Gases/química , Glicosilação , Espectrometria de Mobilidade Iônica/métodos , Isomerismo , Espectrometria de Massas , Simulação de Dinâmica Molecular , Conformação Proteica , Solventes/química
16.
Sensors (Basel) ; 19(15)2019 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-31382683

RESUMO

Soil organic matter (SOM) is a major indicator of soil fertility and nutrients. In this study, a soil organic matter measuring method based on an artificial olfactory system (AOS) was designed. An array composed of 10 identical gas sensors controlled at different temperatures was used to collect soil gases. From the response curve of each sensor, four features were extracted (maximum value, mean differential coefficient value, response area value, and the transient value at the 20th second). Then, soil organic matter regression prediction models were built based on back-propagation neural network (BPNN), support vector regression (SVR), and partial least squares regression (PLSR). The prediction performance of each model was evaluated using the coefficient of determination (R2), root-mean-square error (RMSE), and the ratio of performance to deviation (RPD). It was found that the R2 values between prediction (from BPNN, SVR, and PLSR) and observation were 0.880, 0.895, and 0.808. RMSEs were 14.916, 14.094, and 18.890, and RPDs were 2.837, 3.003, and 2.240, respectively. SVR had higher prediction ability than BPNN and PLSR and can be used to accurately predict organic matter contents. Thus, our findings offer brand new methods for predicting SOM.


Assuntos
Nariz Eletrônico , Solo/química , Calibragem , Gases/química , Análise dos Mínimos Quadrados , Máquina de Vetores de Suporte/normas , Compostos Orgânicos Voláteis/análise , Compostos Orgânicos Voláteis/normas
17.
Sensors (Basel) ; 19(17)2019 Aug 22.
Artigo em Inglês | MEDLINE | ID: mdl-31443499

RESUMO

Biologically inspired to mammalian olfactory system, electronic noses became popular during the last three decades. In literature, as well as in daily practice, a wide range of applications are reported. Nevertheless, the most pioneering one has been (and still is) the assessment of the human breath composition. In this study, we used a prototype of electronic nose, called Wize Sniffer (WS) and based it on an array of semiconductor gas sensor, to detect ammonia in the breath of patients suffering from severe liver impairment. In the setting of severely impaired liver, toxic substances, such as ammonia, accumulate in the systemic circulation and in the brain. This may result in Hepatic Encephalopathy (HE), a spectrum of neuro-psychiatric abnormalities which include changes in cognitive functions, consciousness, and behaviour. HE can be detected only by specific but time-consuming and burdensome examinations, such as blood ammonia levels assessment and neuro-psychological tests. In the presented proof-of-concept study, we aimed at investigating the possibility of discriminating the severity degree of liver impairment on the basis of the detected breath ammonia, in view of the detection of HE at its early stage.


Assuntos
Gases/isolamento & purificação , Encefalopatia Hepática/diagnóstico , Fígado/química , Monitorização Fisiológica/métodos , Testes Respiratórios , Monóxido de Carbono/química , Monóxido de Carbono/isolamento & purificação , Nariz Eletrônico , Gases/química , Encefalopatia Hepática/patologia , Humanos , Hidrogênio/química , Hidrogênio/isolamento & purificação , Fígado/patologia
18.
J Chromatogr A ; 1608: 460406, 2019 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-31378524

RESUMO

A novel liquid chromatography (LC) detector based on continuous-flow chemical vapor generation (CVG)-coupled glow discharge (GD) atomic emission spectrometry (AES) was proposed herein for the simultaneous determination of organotins (OTs) in food samples. OTs were separated on an LC column and converted into volatile gases by the CVG technique. The GD microplasma was used to excite the Sn atoms to generate the special atomic emission lines of Sn at 317.66 nm, which were recorded by a charge-coupled device (CCD) spectrometer. For an injection volume of 1 mL, the linear correlation coefficients (R) were higher than 0.99 in the concentration range from 0.1 to 10 µg mL-1. The recoveries of OTs from spiked samples were 70-103%, and the relative standard deviations (RSD) were 0.2-8.7%. The limits of detection (LOD) for the tested OTs, i.e. trimethyltin chloride (TMT) and dimethyltin dichloride (DMTC), were determined to be 0.59 and 0.93 µg L-1, respectively. The CVG-GD-AES detector can be used to simultaneously determine TMT and DMTC with high sensitivity, in a simple and cost-effective manner.


Assuntos
Cromatografia Líquida , Análise de Alimentos/métodos , Compostos Orgânicos de Estanho/análise , Análise Espectral , Gases/química , Limite de Detecção
19.
J Chromatogr A ; 1605: 460370, 2019 Nov 08.
Artigo em Inglês | MEDLINE | ID: mdl-31337500

RESUMO

The transfer of dichlorodifluoromethane to water was utilized as model system to provide better insight on the determination of mass transport parameters across the gas-liquid interface. Weak signals by reversed-flow gas chromatography were recorded at various temperatures, from 320.7 to 344.3 K, by digitizing and smoothing the output of the flame ionization detector. A flexible uncertainty analysis distinguished the main sources of error in the determined parameters, suggesting improvements on the utilized experimental setup. Liquid diffusivities decreased with rising temperature (4.39 to 1.01 × 10-10 m2 s-1), approaching literature values at lower temperatures. The estimated liquid film thicknesses similarly decreased (1.8 to 1.0 × 10-4 m) and were one order of magnitude larger than previous findings, due to the larger extent of evaporation permitted by the current experimental setup. A mass transfer coefficient was estimated, corresponding to the endothermic contribution of the reverse (liquid-to-gas) process, whose activation energy (43.4 ±â€¯2.8 kJ mol-1) matched the vaporization enthalpy of water in the studied temperature range. Successful comparisons were made with literature distribution coefficients and Henry's law constants. The dissolution of CFC-12 in water was found to be exothermic, slightly spontaneous at lower temperatures and approaching equilibrium at higher ones (indicated by the small negative molar Gibbs free energy values), with negative entropy change values [average: -(190.7 ±â€¯6.9) J K-1 mol-1], as expected for a process of increased order.


Assuntos
Cromatografia Gasosa/métodos , Gases/química , Reologia , Difusão , Temperatura Ambiente , Incerteza , Água/química
20.
Food Chem ; 299: 125172, 2019 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-31325716

RESUMO

The composition of inorganic elements is a key factor in determining the quality of fruit wines. However, the use of direct sample injection is challenging for multi-elemental analysis of fruit wine samples. In this paper, an analytical method using inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) was established for determining multiple elements (Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Cd, Hg, and Pb) in fruit wine. The fruit wine was diluted using ultrapure water and acidified with nitric acid before injecting into the ICP-MS/MS. Spectral interferences in the complex matrix composition of different fruit wine samples, in the MS/MS mode, were eliminated using mixed reaction gases of O2/H2 and NH3/He/H2 through the mass shift and on-mass methods. The limits of detection ranged from 0.41 to 58.1 ng L-1. This study demonstrates a new approach for multi-elemental analysis in fruit wine with great convenience and high accuracy.


Assuntos
Análise de Alimentos/métodos , Espectrometria de Massas em Tandem/métodos , Oligoelementos/análise , Vinho/análise , Amônia/química , Frutas , Gases/química , Hidrogênio/química , Ácido Nítrico/química , Oxigênio/química
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