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1.
Ther Apher Dial ; 2024 May 12.
Artigo em Inglês | MEDLINE | ID: mdl-38736311

RESUMO

INTRODUCTION: The Seraph 100 Microbind Affinity blood filter eliminate bacteria, viruses, fungi and toxins from blood stream. METHODS: This is a prospective multicenter observational biomarker trial in PCR-positive SARS-CoV-2 patients with acute respiratory failure. Biomarkers were sequentially tested at three time points. RESULTS: Forty-two patients with SARS-CoV-2 detected by PCR with acute respiratory failure were included. When receiving hemoperfusion treatment, 27 (64%) patients were on mechanical ventilation, 41 (98%) patients were treated in the ICU. The 3-month survival was 52%. After one hemoperfusion treatment cycle, D-dimer (p = 0.014), hemoglobin (p = 0.003) and LDH (p = 0.001) concentrations were significantly reduced 4 days after treatment. From the multiplex assay IL-1b, CXCL8/ IL-8, IL-10, IL-13, IL-15, CCL11/Eotaxin, G-CSF, and CXCL10/IP-10 were significantly reduced 1 h after treatment, however not 4 days later. CONCLUSION: Hemoperfusion with Seraph 100 Microbind Affinity Filter in patients with severe COVID-19 can transiently reduce several inflammatory biomarkers in the blood.

2.
Pneumologie ; 76(6): 404-413, 2022 Jun.
Artigo em Alemão | MEDLINE | ID: mdl-35588746

RESUMO

BACKGROUND: The number of patients with prolonged mechanical ventilation is increasing. Weaning units (WU) in the German network "WeanNet" are specialized in the treatment of patients needing prolonged weaning. In this study we present outcome data on the patients in our WU from 2011 to 2015. METHODS: A distinction is made between the 4 outcome groups: 1. Successful weaning without mechanical ventilation, 2. Successful weaning with non-invasive mechanical ventilation (NIV), 3. Weaning failure with subsequent invasive ventilation and 4. Death in the WU. RESULTS: In 272 patients, the following distribution within the 4 outcome groups was found: Group 1: 116 patients (42.6 %), Group 2: 52 patients (19.1 %), Group 3: 45 patients (16.5 %) and Group 4: 59 patients (21.7 %).The duration of treatment in the WU depended primarily on co-morbidities and the hemoglobin level.Despite successful weaning, the tracheostoma was completely closed in only 60.3 % of patients with continuous spontaneous breathing and 67.3 % of patients with NIV at the time of discharge from the clinic.After discharge from the WU, patients with weaning failure and subsequent invasive long-term ventilation, in contrast to patients with successful weaning, were rarely transferred to rehabilitation, but re-admitted more frequently to the clinic as emergency cases (29 %).The 1-year survival rate was 59 %. Half of the patients died in less than 2 years. CONCLUSION: The majority of patients with prolonged mechanical ventilation are successfully weaned from the respirator in the WU. Nevertheless, the proportion of patients with weaning failure and subsequent invasive long-term out-of-hospital ventilation as well as the mortality rate in the WU and after discharge were high. The ethical implications of these observations are discussed in the paper.


Assuntos
Respiração Artificial , Desmame do Respirador , Humanos , Alta do Paciente , Respiração , Respiração Artificial/métodos , Taxa de Sobrevida , Resultado do Tratamento , Desmame do Respirador/métodos
3.
Sci Rep ; 10(1): 5376, 2020 03 25.
Artigo em Inglês | MEDLINE | ID: mdl-32214135

RESUMO

The catalytic behavior of iron phthalocyanine (FePc)-sensitized magnetic nanocatalysts was evaluated for their application in the oxidative treatment of Bisphenol A (BPA) under mild environmental conditions. Two types of FePc (Fe(II)Pc and Fe(III)Pc), which are highly photosensitive compounds, were immobilized on the surface of functionalized magnetite. The nanomaterials were characterized by high resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analyses (TGA). The generation of singlet oxygen by nanomaterials was also investigated. In the presence of UVA light exposure (365 nm) and 15 mM H2O2, the M@Fe(III)Pc photocatalyst gave the best results; for a catalyst concentration of 2.0 g L - 1, around 60% BPA was removed after 120 min of reaction. These experimental conditions were further tested under natural solar light exposure, for which also M@Fe(III)Pc exhibited enhanced oxidative catalytic activity, being able to remove 83% of BPA in solution. The water samples were less cytotoxic after treatment, this being confirmed by the MCF-7 cell viability assay.


Assuntos
Compostos Benzidrílicos/química , Compostos Ferrosos/química , Indóis/química , Fenóis/química , Fotólise/efeitos dos fármacos , Catálise , Óxido Ferroso-Férrico/química , Peróxido de Hidrogênio/química , Magnetismo , Microscopia Eletrônica de Transmissão/métodos , Oxirredução , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Poluentes Químicos da Água/química , Difração de Raios X/métodos
4.
Appl Spectrosc ; 73(12): 1409-1419, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31271293

RESUMO

Spatial heterodyne spectroscopy (SHS) is used for quantitative analysis and classification of liquid samples. SHS is a version of a Michelson interferometer with no moving parts and with diffraction gratings in place of mirrors. The instrument converts frequency-resolved information into a spatially resolved one and records it in the form of interferograms. The back-extraction of spectral information is done by the fast Fourier transform. A SHS instrument is constructed with the resolving power 5000 and spectral range 522-593 nm. Two original technical solutions are used as compared to previous SHS instruments: the use of a high-frequency diode-pumped solid-state laser for excitation of Raman spectra and a microscope-based collection system. Raman spectra are excited at 532 nm at the repetition rate 80 kHz. Raman shifts between 330 cm-1 and 1600 cm-1 are measured. A new application of SHS is demonstrated: for the first time, it is used for quantitative Raman analysis to determine concentrations of cyclohexane in isopropanol and glycerol in water. Two calibration strategies are employed: univariate based on the construction of a calibration plot and multivariate based on partial least squares regression. The detection limits for both cyclohexane in isopropanol and glycerol in water are at a 0.5 mass% level. In addition to the Raman-SHS chemical analysis, classification of industrial oils (biodiesel, poly(1-decene), gasoline, heavy oil IFO380, polybutenes, and lubricant) is performed using the Raman-fluorescence spectra of the oils and principal component analysis. The oils are easily discriminated showing distinct non-overlapping patterns in the principal component space.

5.
Beilstein J Org Chem ; 15: 1141-1148, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31164950

RESUMO

The transformation of a base-catalyzed, mechano-assisted Knoevenagel condensation of mono-fluorinated benzaldehyde derivatives (p-, m-, o-benzaldehyde) with malonodinitrile was investigated in situ and in real time. Upon milling, the para-substituted product was found to crystallize initially into two different polymorphic forms, depending on the quantity of catalyst used. For low catalyst concentrations, a mechanically metastable phase (monoclinic) was initially formed, converting to the mechanically stable phase (triclinic) upon further grinding. Instead, higher catalyst concentrations crystallize directly as the triclinic product. Inclusion of catalyst in the final product, as evidenced by mass spectrometric analysis, suggests this complex polymorphic pathway may be due to seeding effects. Multivariate analysis for the in situ Raman spectra supports this complex formation pathway, and offers a new approach to monitoring multi-phase reactions during ball milling.

6.
Anal Bioanal Chem ; 411(14): 3037-3046, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30903225

RESUMO

Modular plants using intensified continuous processes represent an appealing concept for the production of pharmaceuticals. It can improve quality, safety, sustainability, and profitability compared to batch processes; besides, it enables plug-and-produce reconfiguration for fast product changes. To facilitate this flexibility by real-time quality control, we developed a solution that can be adapted quickly to new processes and is based on a compact nuclear magnetic resonance (NMR) spectrometer. The NMR sensor is a benchtop device enhanced to the requirements of automated chemical production including robust evaluation of sensor data. Beyond monitoring the product quality, online NMR data was used in a new iterative optimization approach to maximize the plant profit and served as a reliable reference for the calibration of a near-infrared (NIR) spectrometer. The overall approach was demonstrated on a commercial-scale pilot plant using a metal-organic reaction with pharmaceutical relevance. Graphical abstract.


Assuntos
Espectroscopia de Ressonância Magnética/métodos , Preparações Farmacêuticas/síntese química , Automação , Calibragem , Desenho de Equipamento , Análise Multivariada , Projetos Piloto , Controle de Qualidade , Espectroscopia de Luz Próxima ao Infravermelho/métodos
7.
J Chem Ecol ; 45(2): 199-203, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30167919

RESUMO

Several species of the flea beetles genus Longitarsus sequester pyrrolizidine alkaloids (PAs) from their host plants. Previous data demonstrated that PAs may be transferred from root-feeding larvae into the adult beetles. Here we compared the patterns and concentrations found in larvae and pupae of L. anchusae and L. echii with those of the roots of their respective hosts, Symphytum officinale and Echium vulgare (Boraginaceae). PA patterns and concentrations in the roots were complex and variable, whereas those in the larvae and pupae were simpler and more constant. In L. anchusae, intermedine and lycopsamine were the dominant PAs even if they could not be detected in the roots. In L. echii simpler, hydrolized PAs prevailed. Overall, the concentrations of total PAs of larvae and pupae were significantly higher than those of the roots the larvae had been feeding on. Larvae and pupae of both species also had considerably higher PA concentrations than determined previously for field collected beetles. Possibly the rather immobile juvenile stages enjoy a better protection by higher PA concentrations. On the other hand, we could not detect PAs in eggs of either species, indicating that transmission of appreciable amounts of PAs from mother to offspring does not occur.


Assuntos
Besouros/química , Alcaloides de Pirrolizidina/química , Animais , Boraginaceae/química , Boraginaceae/metabolismo , Besouros/crescimento & desenvolvimento , Besouros/metabolismo , Cromatografia Gasosa-Espectrometria de Massas , Larva/química , Larva/metabolismo , Raízes de Plantas/química , Raízes de Plantas/metabolismo , Pupa/química , Pupa/metabolismo , Alcaloides de Pirrolizidina/análise , Alcaloides de Pirrolizidina/metabolismo
8.
Environ Sci Pollut Res Int ; 26(8): 7364-7374, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-29754299

RESUMO

The increasing pollution of terrestrial and aquatic ecosystems with plastic debris leads to the accumulation of microscopic plastic particles of still unknown amount. To monitor the degree of contamination, analytical methods are urgently needed, which help to quantify microplastics (MP). Currently, time-costly purified materials enriched on filters are investigated both by micro-infrared spectroscopy and/or micro-Raman. Although yielding precise results, these techniques are time consuming, and are restricted to the analysis of a small part of the sample in the order of few micrograms. To overcome these problems, we tested a macroscopic dimensioned near-infrared (NIR) process-spectroscopic method in combination with chemometrics. For calibration, artificial MP/ soil mixtures containing defined ratios of polyethylene, polyethylene terephthalate, polypropylene, and polystyrene with diameters < 125 µm were prepared and measured by a process FT-NIR spectrometer equipped with a fiber-optic reflection probe. The resulting spectra were processed by chemometric models including support vector machine regression (SVR), and partial least squares discriminant analysis (PLS-DA). Validation of models by MP mixtures, MP-free soils, and real-world samples, e.g., fermenter residue, suggests a reliable detection and a possible classification of MP at levels above 0.5 to 1.0 mass% depending on the polymer. The benefit of the combined NIRS chemometric approach lies in the rapid assessment whether soil contains MP, without any chemical pretreatment. The method can be used with larger sample volumes and even allows for an online prediction and thus meets the demand of a high-throughput method.


Assuntos
Monitoramento Ambiental/métodos , Poluição Ambiental/análise , Plásticos/análise , Solo/química , Reatores Biológicos , Calibragem , Análise Discriminante , Análise dos Mínimos Quadrados , Polietileno/análise , Polietilenotereftalatos/análise , Polipropilenos/análise , Poliestirenos/análise , Espectroscopia de Luz Próxima ao Infravermelho/métodos , Máquina de Vetores de Suporte
9.
Biotechnol Prog ; 34(6): 1533-1542, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-29882305

RESUMO

The application of Raman spectroscopy as a monitoring technique for bioprocesses is severely limited by a large background signal originating from fluorescing compounds in the culture media. Here, we compare time-gated Raman (TG-Raman)-, continuous wave NIR-process Raman (NIR-Raman), and continuous wave micro-Raman (micro-Raman) approaches in combination with surface enhanced Raman spectroscopy (SERS) for their potential to overcome this limit. For that purpose, we monitored metabolite concentrations of Escherichia coli bioreactor cultivations in cell-free supernatant samples. We investigated concentration transients of glucose, acetate, AMP, and cAMP at alternating substrate availability, from deficiency to excess. Raman and SERS signals were compared to off-line metabolite analysis of carbohydrates, carboxylic acids, and nucleotides. Results demonstrate that SERS, in almost all cases, led to a higher number of identifiable signals and better resolved spectra. Spectra derived from the TG-Raman were comparable to those of micro-Raman resulting in well-discernable Raman peaks, which allowed for the identification of a higher number of compounds. In contrast, NIR-Raman provided a superior performance for the quantitative evaluation of analytes, both with and without SERS nanoparticles when using multivariate data analysis. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:1533-1542, 2018.


Assuntos
Escherichia coli/metabolismo , Análise Espectral Raman/métodos , Análise Multivariada
10.
Anal Bioanal Chem ; 410(14): 3349-3360, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29616294

RESUMO

Monitoring specific chemical properties is the key to chemical process control. Today, mainly optical online methods are applied, which require time- and cost-intensive calibration effort. NMR spectroscopy, with its advantage being a direct comparison method without need for calibration, has a high potential for enabling closed-loop process control while exhibiting short set-up times. Compact NMR instruments make NMR spectroscopy accessible in industrial and rough environments for process monitoring and advanced process control strategies. We present a fully automated data analysis approach which is completely based on physically motivated spectral models as first principles information (indirect hard modeling-IHM) and applied it to a given pharmaceutical lithiation reaction in the framework of the European Union's Horizon 2020 project CONSENS. Online low-field NMR (LF NMR) data was analyzed by IHM with low calibration effort, compared to a multivariate PLS-R (partial least squares regression) approach, and both validated using online high-field NMR (HF NMR) spectroscopy. Graphical abstract NMR sensor module for monitoring of the aromatic coupling of 1-fluoro-2-nitrobenzene (FNB) with aniline to 2-nitrodiphenylamine (NDPA) using lithium-bis(trimethylsilyl) amide (Li-HMDS) in continuous operation. Online 43.5 MHz low-field NMR (LF) was compared to 500 MHz high-field NMR spectroscopy (HF) as reference method.

11.
Magn Reson Chem ; 54(6): 513-20, 2016 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-25854892

RESUMO

Medium-resolution nuclear magnetic resonance spectroscopy (MR-NMR) currently develops to an important analytical tool for both quality control and process monitoring. In contrast to high-resolution online NMR (HR-NMR), MR-NMR can be operated under rough environmental conditions. A continuous re-circulating stream of reaction mixture from the reaction vessel to the NMR spectrometer enables a non-invasive, volume integrating online analysis of reactants and products. Here, we investigate the esterification of 2,2,2-trifluoroethanol with acetic acid to 2,2,2-trifluoroethyl acetate both by (1) H HR-NMR (500 MHz) and (1) H and (19) F MR-NMR (43 MHz) as a model system. The parallel online measurement is realised by splitting the flow, which allows the adjustment of quantitative and independent flow rates, both in the HR-NMR probe as well as in the MR-NMR probe, in addition to a fast bypass line back to the reactor. One of the fundamental acceptance criteria for online MR-MNR spectroscopy is a robust data treatment and evaluation strategy with the potential for automation. The MR-NMR spectra are treated by an automated baseline and phase correction using the minimum entropy method. The evaluation strategies comprise (i) direct integration, (ii) automated line fitting, (iii) indirect hard modelling (IHM) and (iv) partial least squares regression (PLS-R). To assess the potential of these evaluation strategies for MR-NMR, prediction results are compared with the line fitting data derived from the quantitative HR-NMR spectroscopy. Although, superior results are obtained from both IHM and PLS-R for (1) H MR-NMR, especially the latter demands for elaborate data pretreatment, whereas IHM models needed no previous alignment. Copyright © 2015 John Wiley & Sons, Ltd.

12.
Child Welfare ; 92(2): 161-78, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24199328

RESUMO

Because of the complexity and depth of problems facing children and families today, child protection can be best accomplished through a community effort--not simply through the efforts of the traditional child welfare system and other child- and family-serving agencies. Community-based initiatives supporting families and individuals are promising mechanisms through which to efficiently reach a wide range of community members consistent with a public health model. This conceptual paper describes the principles of community-based approaches for the prevention of child maltreatment and briefly describes four initiatives that are providing comprehensive, community-based prevention.


Assuntos
Maus-Tratos Infantis/prevenção & controle , Redes Comunitárias , Criança , Proteção da Criança , Humanos , Estudos de Casos Organizacionais , Estados Unidos
13.
Bioresour Technol ; 150: 98-105, 2013 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-24157681

RESUMO

Hydrothermal carbonization (HTC) can be used for converting the biomass into a carbon-rich material, whose application as a fuel requires higher heating value, whereas soil amendment needs stable carbon. This work was focused on the characterization of hydrochars derived from microcrystalline cellulose. The chars were investigated using elemental analysis, Brunauer-Emmett-Teller technique, nuclear magnetic resonance spectroscopy, Raman, Fourier transform infrared, and electron spin resonance spectroscopy. Severity in temperature between 230 and 270°C with reaction times between 2 and 10 h only affect the carbon content moderately. The results show that aromatization of HTC chars correlates well with temperature, which was further supported by the increase of organic radicals with decreasing g values at higher temperatures. Based on these results, the energetic use of chars favors mild HTC (T<230°C and t≤6 h), while the soil amendement favors serve conditions (T≥230°C, and t>6 h).


Assuntos
Celulose/química , Carvão Vegetal/química , Análise Espectral Raman , Adsorção , Ácidos Carboxílicos/química , Cromatografia Líquida de Alta Pressão , Espectroscopia de Ressonância de Spin Eletrônica , Concentração de Íons de Hidrogênio , Espectroscopia de Ressonância Magnética , Porosidade , Temperatura , Fatores de Tempo , Vibração
14.
Anal Bioanal Chem ; 402(4): 1443-50, 2012 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-21845528

RESUMO

The authenticity of objects and artifacts is often the focus of forensic analytic chemistry. In document fraud cases, the most important objective is to determine the origin of a particular ink. Here, we introduce a new approach which utilizes the combination of two analytical methods, namely Raman spectroscopy and laser-induced breakdown spectroscopy (LIBS). The methods provide complementary information on both molecular and elemental composition of samples. The potential of this hyphenation of spectroscopic methods is demonstrated for ten blue and black ink samples on white paper. LIBS and Raman spectra from different inks were fused into a single data matrix, and the number of different groups of inks was determined through multivariate analysis, i.e., principal component analysis, soft independent modelling of class analogy, partial least-squares discriminant analysis, and support vector machine. In all cases, the results obtained with the combined LIBS and Raman spectra were found to be superior to those obtained with the individual Raman or LIBS data sets.

16.
Environ Sci Technol ; 43(10): 3639-45, 2009 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-19544866

RESUMO

Arsenic is a redox-active metalloid whose toxicity and mobility strongly depends on its oxidation state, with arsenite (As(III)) being more toxic and mobile than arsenate (As(V)). Humic substances (HS) are also redox-active and can potentially react with arsenic and change its redox state. In this study we show that semiquinone radicals produced during microbial or chemical reduction of a HS model quinone (AQDS, 9,10-anthraquinone-2,6-disulfonic acid) are strong oxidants. They oxidize arsenite to arsenate, thus decreasing As toxicity and mobility. This reaction depends strongly on pH with more arsenite (up to 67.3%) being oxidized at pH 11 compared to pH 7 (12.6% oxidation) and pH 3 (0.5% oxidation). In addition to As(III) oxidation by semiquinone radicals, hydroquinones that were also produced during quinone reduction reduced As(V) to As(III) at neutral and acidic pH values (less than 12%) but not at alkaline pH. In order to understand redox reactions between arsenite/arsenate and reduced/oxidized HS, we quantified the radical content in reduced quinone solutions and constructed Eh-pH diagrams that explain the observed redox reactions. The results from this study can be used to better predict the fate of arsenic in the environment and potentially explain the occurrence of oxidized As(V) in anoxic environments.


Assuntos
Arsênio/química , Bactérias/metabolismo , Benzoquinonas/química , Substâncias Húmicas/microbiologia , Hidroquinonas/química , Modelos Químicos , Quinonas/química , Biodegradação Ambiental , Espectroscopia de Ressonância de Spin Eletrônica , Meio Ambiente , Concentração de Íons de Hidrogênio , Oxirredução , Soluções , Termodinâmica
17.
Aquat Toxicol ; 83(2): 93-103, 2007 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-17475348

RESUMO

Humic substances (HS) account for 50-80% of the dissolved organic matter in non-eutrophicated freshwater ecosystems. HS are not inert, but are taken up by and may interact with aquatic organisms. However, at present no information is available on the interaction of HS with fungi, for instance, the fish-pathogenous species Saprolegnia parasitica. To fill this gap, we tested effects of HS on S. parasitica growth in-vitro using 25-500mgL(-1) carbon of HS on GY-agar. We investigated 20 HS including natural organic matter (NOM) samples, two lignite derived HS, and one synthetic HS. The aim was (1) to find out, if there are inhibiting effects and (2) if potential effects can be explained by humic matter properties by structure activity relationships. The growth of S. parasitica was related to the growth on HS-free agar controls. Characterization of HS and NOMs included elemental analysis, high-pressure size exclusion chromatography (HPSEC), UV/VIS, FTIR-, and EPR-spectroscopy in order to obtain information on elemental and structural composition including various metals, molecular weights of the HS fraction, aromaticity, free organic radicals, and functional groups. NOMs with high moieties of high-molecular carbohydrates supported the growth of S. parasitica, all other HS and NOMs reduced it. However, no inhibition of the development of the sporangia and primary zoospores was found. Therefore, the impact of the HS on S. parasitica has to be classified as fungistatic, rather than fungicidal. Synthetic and lignite-derived HS were among the most efficient HS sources. Growth inhibition was correlated (p<0.05) with the molecular weights of the HS-fraction, sUVa, COOH groups, C and H. Our results suggest that especially HS with higher molecular weights and aromaticity which contain a high number of organic radicals are the most efficient in reducing fungal growth. Furthermore, highly functionalized HS seem to be important for the observed effect. The development of internal oxidative stress could be a mechanism explaining the observed growth inhibition of S. parasitica.


Assuntos
Substâncias Húmicas/toxicidade , Saprolegnia/crescimento & desenvolvimento , Cromatografia em Gel/métodos , Espectroscopia de Ressonância de Spin Eletrônica , Água Doce/química , Água Doce/microbiologia , Inibidores do Crescimento/análise , Inibidores do Crescimento/química , Substâncias Húmicas/análise , Hifas/ultraestrutura , Concentração Inibidora 50 , Saprolegnia/efeitos dos fármacos , Espectroscopia de Infravermelho com Transformada de Fourier , Relação Estrutura-Atividade
18.
Environ Sci Technol ; 40(19): 5897-903, 2006 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-17051776

RESUMO

Dissolved natural organic matter (NOM) plays an essential role in freshwater geochemical and biochemical processes. A major property, its redox behavior, can be attributed to the chinone building blocks, which can form stable radicals. However, electron paramagnetic resonance (EPR) data indicating free radicals on solid NOM are sparse. Here we present EPR spectra of 23 NOM from European surface waters isolated by reverse osmosis. The organic radical concentrations of NOM ranged from 5 x 10(15) to 1.84 x 10(17) spins g(-1), and g values ranged from 2.0031 to 2.0045. Number and type of organic radicals in solid NOM are significantly influenced by the pH of raw water. EPR experiments indicate the presence of semiquinone-type radicals in coexistence with carbon-centered "aromatic" radicals, with the semiquinone-type radicals dominating at alkaline pH. Basically these processes are reversible. Organic radical concentrations in NOM adjusted to pH 6.5 before freeze-drying correlate with iron and aluminum contents. UV- and VIS-irradiation of solid NOM can lead to more than a 10-fold increase of the concentration of organic radicals. These radicals were long-lived and had the same g value as the original radical. Similar effects were not observed with isolated humic and fulvic acids, demonstrating the limited reflection of environmental properties of organic carbon by the classical isolation procedure.


Assuntos
Radicais Livres/análise , Substâncias Húmicas/efeitos da radiação , Raios Ultravioleta , Benzopiranos/química , Benzopiranos/efeitos da radiação , Cromatografia em Gel , Espectroscopia de Ressonância de Spin Eletrônica , Concentração de Íons de Hidrogênio , Espectroscopia de Infravermelho com Transformada de Fourier
19.
Photochem Photobiol Sci ; 3(3): 273-80, 2004 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-14993944

RESUMO

The singlet oxygen (1(O2)) luminescence of 27 isolated humic substances (HS), natural organic matter, ultrafiltrates, and the synthetic fulvic acid HS1500 has been investigated by time-resolved spectroscopy in buffered D(2)O. The samples include both reverse osmosis isolates from lakes in Scandinavia, Canada, and Germany, and IHSS fulvic and humic acids of aquatic and terrestrial origin. The quantum yields of 1(O2) formation (PhiDelta) obtained on laser excitation at 480 nm ranged between 0.06 (HS1500) and 2.7%(fulvic acid from soil, IHSS). In our study, a general trend towards higher PhiDelta in terrestrial HS was observed. The comparison of reverse osmosis isolates from surface waters collected during fall 1999 and spring 2000 from five Scandinavian sites yielded, in all cases, higher PhiDelta for the spring samples. For the aquatic sampling sites Hietajarvi and Birkenes, PhiDelta even exceeded values of 0.6%, which were found to be typical for terrestrial or soil water material. Investigation of the excitation wavelength dependence of PhiDelta in the spectral range 355-550 nm yielded different spectral shapes for aquatic HS and "non-aquatic" HS, respectively. On the basis of these excitation spectra, 1(O2) production rates were calculated for eight representative HS.

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