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Electrochemical ochratoxin a immunosensors based on polyaniline nanocomposites templated with amine- and sulphate-functionalised polystyrene latex beadsMuchindu, Munkombwe January 2010 (has links)
Philosophiae Doctor - PhD / Polyaniline nanocomposites doped with poly(vinylsulphonate) (PV-SO3) and nanostructured polystyrene (PSNP) latex beads functionalized with amine (PSNP-NH2) and sulphate ((PSNP-OSO3) were prepared and characterised for use as nitrite electro-catalytic chemosensors and ochratoxin A immunosensors. The resultant polyaniline electrocatalytic chemosensors (PANI, PANI|PSNP-NH2 or PANI|PSNP-OSO3
−) were characterized by cyclic voltammetry (CV), ultraviolet-visible (UV-Vis) spectroscopy and scanning electron microscopy (SEM). Brown-Anson analysis of the multi-scan rate CV responses of the various PANI films gave surface concentrations in the order of 10−8 mol/cm. UV-vis spectra of the PANI films dissolved in dimethyl sulphoxide showed typical strong absorbance maxima at 480 and 740 nm associated with benzenoid p-p* transition and quinoid excitons of polyaniline, respectively. The SEM images of the PANI nanocomposite films showed cauliflower-like structures that were <100 nm in diameter. When applied as electrochemical nitrite sensors, sensitivity values of 60, 40 and 30 μA/mM with corresponding limits of detection of 7.4, 9.2 and 38.2 μM NO2 −, were obtained for electrodes, PANI|PSNP-NH2, PANI and PANI|PSNP-SO3
−; respectively. Immobilisation of ochratoxin A antibody onto PANI|PSNP-NH2, PANI and PANI|PSNPSO3 - resulted in the fabrication of immunosensors. / South Africa
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Oceanic Interfaces: Investigations of Biogeochemical Changes Across Nutriclines and Frontal BoundariesAdornato, Lori R 15 March 2007 (has links)
Biogeochemical changes across oceanic interfaces, and method development to study such changes, are described in this work. The interfaces studied include the Subtropical Front in the Pacific Ocean and the boundary at the base of the euphotic zone. Both interfaces are characterized by accumulations of phytoplankton, although the forcing functions that result in increased biomass are distinctly different.
The Subtropical Front, located at approximately 30°N in the Pacific Ocean, was detected during a cruise in the summer of 2002 by its diagnostic 34.8 salinity outcrop, in spite of the absence of its associated temperature signature. The front displayed elevated concentrations of large diatoms; Rhizosolenia and Hemiaulus, with concentrations penetrating deeper in the water column south of the front. Rhizosolenia species were dominant on the warmer, high salinity side of the front, while Hemiaulus prevailed on the cooler, low salinity side. While high cell counts were enumerated by net tows, the elevated biomass was not visible in satellite color imagery. Size fractionated chlorophyll data revealed > 10 um cells were found below 200 m, indicating export of large cells out of the euphotic zone. This confirms observations by other investigators that fronts represent important regions of episodic export, although such export may go undetected if the biomass is not visible in ocean color images.
Another region of interest was the narrow layer at the base of the euphotic zone. During stratified conditions, the layer was characterized by a fluorescence maximum, a primary nitrite maximum, and a nutricline. While fluorescence maxima have proven easy to detect using commercial fluorometers, nutrient distributions have proven more difficult. The Spectrophotometric Elemental Analysis System (SEAS) permitted detection of low concentrations of nitrite, nitrate, and phosphate with nanomolar sensitivity and 1 Hz or better sampling frequency. Using multiple wavelength spectroscopy, the range of nitrate concentrations from 2 nM to 20 uM have been detected. Profiles of nitrite obtained across the North Pacific Subtropical Gyre revealed the close correlation between nitrite and chlorophyll fluorescence maxima, suggesting that the nitrite maximum is formed by phytoplankton when insufficient light is available to permit reduction of nitrite to ammonia.
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Electrochemical ochratoxin a immunosensors based on polyaniline nanocomposites templated with amine- and sulphate-functionalised polystyrene latex beadsMuchindu, Munkombwe January 2010 (has links)
<p>Polyaniline nanocomposites doped with poly(vinylsulphonate) (PV-SO3 &minus / ) and nanostructured polystyrene (PSNP) latex beads functionalized with amine (PSNP-NH2) and sulphate (PSNP-OSO3 &minus / ) were prepared and characterised for use as nitrite electro-catalytic chemosensors and ochratoxin A immunosensors. The resultant polyaniline electrocatalytic chemosensors (PANI, PANI|PSNP-NH2 or PANI|PSNP-OSO3 &minus / ) were characterized by cyclic voltammetry (CV), ultraviolet-visible (UV-Vis) spectroscopy and scanning electron microscopy (SEM). Brown-Anson analysis of the multi-scan rate CV responses of the various PANI films gave surface concentrations in the order of 10&minus / 8 mol/cm. UV-vis spectra of the PANI films dissolved in dimethyl sulphoxide showed typical strong absorbance maxima at 480 and 740 nm associated with benzenoid p-p* transition and quinoid excitons of polyaniline, respectively. The SEM images of the PANI nanocomposite films showed cauliflower-like structures that were < / 100 nm in diameter. When applied as electrochemical nitrite sensors, sensitivity values of 60, 40 and 30 &mu / A/mM with corresponding limits of detection of 7.4, 9.2 and 38.2 &mu / M NO2 &minus / , were obtained for electrodes, PANI|PSNP-NH2, PANI and PANI|PSNP-SO3 &minus / , respectively. Immobilisation of ochratoxin A antibody onto PANI|PSNP-NH2, PANI and PANI|PSNPSO3 - resulted in the fabrication of immunosensors.</p>
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Nitric Oxide Exchange in Central and Peripheral Airways : Determinants in Health and Respiratory DiseaseMalinovschi, Andrei January 2008 (has links)
<b>Background: </b>Exhaled nitric oxide (NO) is a marker of eosinophilic steroid-sensitive inflammation in the airways of patients with respiratory disease. Moreover, information about the localization of inflammation in the respiratory tree is obtained by estimates of bronchial and alveolar contributions to exhaled NO. <b>Aims: </b>The main aim of this thesis was to identify the determinants of exhaled NO, as well as determinants of bronchial and alveolar contributions to exhaled NO in health and disease. Smoking history, degree of IgE sensitization and effects of modulating the pharyngo-oral tract production of NO were specifically studied in this context. Other specific aims were to determine the association of exhaled NO with the presence of asthma and pulmonary hypertension (PH). <b>Methods: </b>Both population-based studies and experimental studies have been performed within the frame of the thesis. The population-based studies are based on data from the European Community Respiratory Health Survey II. NO measurements at several exhalation flow rates were performed in order to estimate alveolar and bronchial contributions to exhaled NO. <b>Results: </b>Both current and previous smoking were associated with decreased exhaled NO and bronchial NO flux levels. Alveolar NO concentrations were decreased in current smokers. The degree of IgE sensitization was positively related to the levels of exhaled NO and its bronchial contribution. Exhaled NO appeared to be a more specific marker of allergic inflammation than of rhinitis or asthma. Both allergic and non-allergic asthma were associated with increased exhaled NO levels, but only in never-smoking persons. The estimated alveolar NO increased after ingestion of nitrate in individuals with high nitrate turnover in the pharyngo-oral tract. Pulmonary arterial hypertension, but not other forms of PH, was associated with decreased bronchial NO flux, whereas PH of all etiologies was related to increased alveolar NO concentrations. <b>Conclusion: </b>Smoking history and IgE sensitization, that are known determinants of exhaled NO, affected the bronchial and alveolar contributions to exhaled NO differently. The limitations of the simple NO pulmonary exchange models were highlighted by the paradoxical effects on estimated alveolar NO when modulating the NO production proximally, in the pharyngo-oral tract. Predominance of non-eosinophilic inflammation in ever-smoking patients with asthma could explain the poor association between the presence of asthma and exhaled NO in these patients. Different pathophysiological changes in terms of bronchial NO production and exchange were related to the etiology of pulmonary hypertension.
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Hur påverkar dietärt nitrat muskelfunktionen och återhämtningen vid styrketräning? : En pilotstudie i samarbete med Karolinska Institutet och Åstrands laboratoriet.Jakobs, Kristin January 2011 (has links)
Forskning om människans fysiologi och hur den fungerar uppdateras dagligen. Inom idrottens värld testas nya som gamla, naturliga som onaturliga preparat och träningsmetoder kontinuerligt, allt för att optimera en idrottares prestation. Ett ämne som det forskas mycket om idag är kvävemonoxid och dess påverkan i kroppen. Från att ha tolkats som ett skadligt ämne i kroppen har det gått till att möjligen kunna hjälpa hjärtsjuka patienter och även optimera idrottsutövande. Kvävemonoxid bildas i kroppen naturligt med hjälp av syre, men det kan även bildas utan syre genom intag av nitrat som hittas i många grönsaker. Studier om nitrat inom idrottsområdet har koncentrerats till dess påverkan vid uthållighetsidrott och effekten har visat på ökad verkningsgrad och blodflöde till muskulaturen. Senare fann forskarna även hur dietärt nitrat sänkte ens syreupptagningsförmåga (Vo2max) tillsammans med en ökad uthållighet. Detta är en intressant upptäckt då sänkt Vo2max ofta leder till en försämrad arbetsprestation. Dessa studier ger en bild av hur nitrat fungerar vid aerobt arbete, det vill säga med syre. Det som forskningen inte tagit upp ännu är hur nitrat påverkar anaerobt arbete och maximala prestationer som förekommer vid styrketräning. Syftet med denna studie var därför att undersöka hur nitrat påverkar muskelfunktion och uthållighet vid styrketräning. I en randomiserad, dubbelblind, korsande studie, konsumerade åtta män (ålder 19-26, 23 (±2, 3)) nitrat eller placebo (0,1 mmol/kg kroppsvikt/dag) under tre dagar. Under fjärde dagen testades männens prestation i fyra olika styrketest. Laktat och glukosvärden mättes för att se hur den laktacida systemet påverkades. Studien gav inget stöd till att dietärt nitrat påverkar styrketräning. Resultaten från tillfället med nitrat respektive placebo förblev i stort sett oförändrade. Slutsatsen blev att ett intag av nitrat inte har någon större betydelse för denna modell av styrketräning. Den främsta förklaringen till detta kan tänkas vara att nitratet ger störst inverkan vid långvariga arbetsdurationer och främst under aerobt arbete. I detta fall används mestadels lagrad energi i kroppen, och energisystemen där syre krävdes är troligen inte av större betydelse. / Research on human physiology and how it is working is updated daily. In the world of sports they are testing new as old, natural as unnatural preparations and different training methods continuously in order to optimize athletic performance. A substance that´s been research on, up till today is nitric oxide and its influence in the body. From being interpreted as a harmful substance in the body, it went to possibly help heart disease patients, and also optimize the physic in sport performance. Nitric oxide is formed in the body naturally by oxygen, but it can also be formed without oxygen through the ingestion of nitrates found in many vegetables. Studies on nitrate in the sport field have concentrated on the effect on endurance sports and the effect has been shown to increase the efficiency and the blood flow to the muscles. Later on they also found that nitrate supplementation seems to give a lower Vo2max together with an increased time to exhaustion. These findings are really interesting because normally a reduction in Vo2max leads us to a decrease in workability. All these studies give an idea on how nitrate works aerobic, that is with oxygen. The research has not yet an explanation on how nitrate affect anaerobic work and maximum performance that occurs in weight training. The purpose of this study was to investigate how nitrate affects muscle function and endurance in strength training. In a randomized, double-blind, crossover trial, eight men (age 19-26, 23 (±2, 3)) consumed nitrate or a placebo (0.1 mmol/kg bodyweight/day) for three days. During the fourth day the test persons were tested in four different strength tests to see how they performed. Lactate and glucose concentrations were measured to see how the laktacid system was influenced. The study gave no support that dietary nitrate affects weight training. The results from the occasion with nitrate respectively placebo remained essentially unchanged. It was concluded that an intake of nitrate not will give any significant effects on the model of strength training. The main reason for this may be that nitrate provides the greatest impact on long-term work-duration and mainly during aerobic work. In this case the main use is mostly stored energy in the body, and the energy systems in which oxygen is required will probably not be of major importance. / Pilotstudie i samarbete med Åstrands laboratoriet och Karolinska Institutet
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Factors influencing natural attenuation of dinitrotoluenes in surface soils: Badger Army Ammunition Plant a case studyTulsiani, Urvi Kotak 18 July 2005 (has links)
Factors influencing natural attenuation of dinitrotoluenes (DNT) in surface soils and the application of monitored natural attenuation (MNA) as a remediation strategy were examined using contaminated soils from Badger Army Ammunition Plant (BAAP). Based on the previous research involving contaminated media obtained from locations at BAAP, and the fact that groundwater at the site is not contaminated, it seemed likely that aerobic biodegradation of DNT is active without intervention, and that natural attenuation may be an effective strategy for managing the contamination that exists at BAAP. Microcosms showed that microbes indigenous to soils are capable of 2,4-DNT mineralization and that DNT will adsorb reversibly and become bioavailable. In column studies 2,4-DNT biodegradation was observed and the nitrite evolved during DNT degradation was presumably removed due to oxidation by nitrite oxidizers. The use of simulated rainwater as influent with no nutrient amendments suggests that nutrients do not limit the biodegradation of low concentrations of DNT in the soil tested. In the chemostat study carried out to study effect lowering of temperature (22㬠15㬠10㬠7.5㠡nd 4㩠on biodegradation of DNT at hydraulic retention time of 2.5 days, no sustained change in the DNT substrate removal was observed with change in temperature, but it had a large effect on the nitrite oxidizers. This suggests that the seasonal fluctuations in temperature will have minimal effect on the DNT removal via biodegradation at temperatures above 0㮠Nitrite oxidizers were active at 22㬠their activity decreased at 15㠡nd ceased at temperatures 10㠡nd lower. Nitrite is generally taken as a line of evidence for biodegradation of DNT. The results from the soil column study and chemostat showed that nitrite measurement should not be always taken as a conclusive indicator of DNT degradation. It should be taken into consideration that absence of nitrite does not necessarily mean absence of DNT biodegradation (probably at high temperatures).
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Electrochemical ochratoxin a immunosensors based on polyaniline nanocomposites templated with amine- and sulphate-functionalised polystyrene latex beadsMuchindu, Munkombwe January 2010 (has links)
<p>Polyaniline nanocomposites doped with poly(vinylsulphonate) (PV-SO3 &minus / ) and nanostructured polystyrene (PSNP) latex beads functionalized with amine (PSNP-NH2) and sulphate (PSNP-OSO3 &minus / ) were prepared and characterised for use as nitrite electro-catalytic chemosensors and ochratoxin A immunosensors. The resultant polyaniline electrocatalytic chemosensors (PANI, PANI|PSNP-NH2 or PANI|PSNP-OSO3 &minus / ) were characterized by cyclic voltammetry (CV), ultraviolet-visible (UV-Vis) spectroscopy and scanning electron microscopy (SEM). Brown-Anson analysis of the multi-scan rate CV responses of the various PANI films gave surface concentrations in the order of 10&minus / 8 mol/cm. UV-vis spectra of the PANI films dissolved in dimethyl sulphoxide showed typical strong absorbance maxima at 480 and 740 nm associated with benzenoid p-p* transition and quinoid excitons of polyaniline, respectively. The SEM images of the PANI nanocomposite films showed cauliflower-like structures that were < / 100 nm in diameter. When applied as electrochemical nitrite sensors, sensitivity values of 60, 40 and 30 &mu / A/mM with corresponding limits of detection of 7.4, 9.2 and 38.2 &mu / M NO2 &minus / , were obtained for electrodes, PANI|PSNP-NH2, PANI and PANI|PSNP-SO3 &minus / , respectively. Immobilisation of ochratoxin A antibody onto PANI|PSNP-NH2, PANI and PANI|PSNPSO3 - resulted in the fabrication of immunosensors.</p>
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Estudo de inibidores de corros?o em concreto armado, visando a melhoria na sua durabilidadeSilva, Djalma Ribeiro da 01 March 2007 (has links)
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Previous issue date: 2007-03-01 / Petr?leo Brasileiro SA - PETROBRAS / This thesis has as objective presents a methodology to evaluate the behavior of the corrosion inhibitors sodium nitrite, sodium dichromate and sodium molybdate, as well as your mixture, the corrosion process for the built-in steel in the reinforced concrete, through different techniques electrochemical, as well as the mechanical properties of that concrete non conventional. The addition of the inhibitors was studied in the concrete in the proportions from 0.5 to 3.5 % regarding the cement mass, isolated or in the mixture, with concrete mixture proportions of 1.0:1.5:2.5 (cement, fine aggregate and coarse aggregate), superplasticizers 2.0 % and 0.40 water/cement ratio. In the modified concrete resistance rehearsals they were accomplished to the compression, consistence and the absorption of water, while to analyze the built-in steel in the concrete the rehearsals of polarization curves they were made. They were also execute, rehearsals of corrosion potential and polarization resistance with intention of diagnose the beginning of the corrosion of the armors inserted in body-of-proof submitted to an accelerated exhibition in immersion cycle and drying to the air. It was concluded, that among the studied inhibitors sodium nitrite , in the proportion of 2.0 % in relation to the mass of the cement, presented the best capacity of protection of the steel through all the studied techniques and that the methodology and the monitoring techniques used in this work, they were shown appropriate to evaluate the behavior and the efficiency of the inhibitors / Esta tese tem como objetivo apresentar uma metodologia para avaliar o comportamento dos inibidores de corros?o nitrito de s?dio, molibdato de s?dio, dicromato de s?dio, bem como a suas misturas, no processo de corros?o para o a?o embutido no concreto armado, atrav?s de diferentes t?cnicas eletroqu?micas, bem como as propriedades mec?nicas desse concreto n?o convencional. Estudou-se a adi??o dos inibidores no concreto nas propor??es de 0,5 a 3,5 % em rela??o ? massa do cimento, isolados e em mistura, num tra?o 1,0:1,5:2,5 (cimento, areia e brita), superplastificante 2,0 % e rela??o ?gua/cimento 0,40. No concreto modificado foram realizados ensaios de resist?ncia ? compress?o, consist?ncia e a absor??o de ?gua, enquanto que para analisar o a?o embutido no concreto foram efetuados ensaios de curvas de polariza??o. Foram executados tamb?m ensaios de potencial de corros?o e resist?ncia de polariza??o com intuito de diagnosticar o in?cio da corros?o das armaduras inseridas em corpos-de-prova submetidos a uma exposi??o acelerada em ciclo de imers?o e secagem ao ar. Concluiu-se que, dentre os inibidores estudados, o nitrito de s?dio, na propor??o de 2,0 % em rela??o ? massa do cimento, apresentou a melhor capacidade de prote??o do a?o atrav?s de todas as t?cnicas estudadas e que a metodologia e as t?cnicas de monitoramento utilizadas neste trabalho mostraram-se adequadas para avaliar o comportamento e a efici?ncia dos inibidores
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Cavity enhanced spectroscopies for small volume liquid analysisJames, Dean January 2017 (has links)
Cavity enhanced spectroscopies (CES) are currently amongst the most sensitive spectroscopic techniques available for probing gas-phase samples, however their application to the liquid-phase has been more limited. Sensitive analysis of submicrolitre liquid samples is highly desirable, as miniaturisation allows for the reaction and analysis of scarce or expensive reagents, produces less waste, and can increase the speed of separations and reactions, whilst having a small footprint and high throughput. Absorption spectroscopy is a particularly desirable technique due to its universal, label-free nature, however its application to small volume liquid samples is hampered by the associated short absorption pathlengths, which limit sensitivity. CES improve sensitivity by trapping light within a confined region, increasing the effective pathlength through the sample. Three distinct types of optical cavity were constructed and evaluated for the purposes of making optical absorption measurements on liquid samples. The first incorporated a high optical quality flow cell into a "macrocavity" formed from two dielectric mirrors separated by 51.3 cm. Cavity losses were minimised by positioning the flow cell at Brewster's angle to the optical axis, and the setup was used to perform a single-wavelength cavity ringdown spectroscopy experiment to detect and quantify nitrite within aqueous samples. The detection limit was determined to be 8.83 nM nitrite in an illuminated volume of only 74.6 nL. Scattering and reflective losses from the flow cell surfaces were found to be the largest barrier to increased sensitivity, leading us to focus on the integration of cavity mirrors within a microfluidic flow system in the work that followed. In the second set of experiments, cavity enhanced absorption spectroscopy (CEAS) measurements were performed on Thymol Blue using custom-made microfluidic chips with integrated cavity mirrors. Unfortunately, due to the plane-parallel configuration of the mirrors and the corresponding difficulty in sustaining stable cavity modes, the results were underwhelming, with a maximum cavity enhancement factor (CEF) of only 2.68. At this point, attention was focussed toward a more well-defined cavity geometry: open-access plano-concave microcavities. The microcavities consist of an array of micron-scale concave mirrors opposed by a planar mirror, with a pathlength that is tunable to sub-nanometer precision using piezoelectric actuators. In contrast to the other experimental setups described, themicrocavities allow for optical measurements to be performed in which we monitor the change of wavelength and/or amplitude of a single well-defined cavity mode in response to a liquid sample introduced between the mirrors. In the first microcavity experiment, we used 10 μm diameter mirrors with cavity lengths from 2.238 μm to 10.318 μm to demonstrate refractive index sensing in glucose solutions with a limit of detection of 3.5 x 10<sup>-4</sup> RIU. The total volume of detection in our setup was 54 fL. Thus, at the limit of detection, the setup can detect the change of refractive index that results from the introduction of 900 zeptomoles (500,000 molecules) of glucose into the device. The microcavity sensor was then adapted to enable broadband absorption measurements of methylene blue via CEAS. By recording data simultaneously from multiple cavities of differing lengths, absorption data is obtained at a number of wavelengths. Using 10 μm diameter mirrors with cavity pathlengths from 476 nm to 728 nm, a limit of detection, expressed as minimum detectable absorption per unit pathlength, of 1.71 cm<sup>-1</sup> was achieved within a volume of 580 attolitres, corresponding to less than 2000 molecules within the mode volume of the cavity. Finally, a new prototype was developed with improved cavity finesse, a much more intense and stable light source, and improved flow design. Using a single plano-concave microcavity within the array with a cavity pathlength of 839.7 nm, and 4 μm radius of curvature mirror, absorption measurements were performed on Methylene Blue. Analysis of this data indicated a CEF of around 9270, and a limit of detection based on the measured signal-to-noise ratio of 0.0146 cm<sup>-1</sup>. This corresponds to a minimum detectable concentration of 104 nM Methylene Blue, which given the mode volume of 219 aL, suggests a theoretical minimum detectable number of molecules of 14.
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Desenvolvimento de procedimentos e sistemas automatizados para controle de qualidade de carnes e produtos cárneosLopes, Mariângela Vieira January 2005 (has links)
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Tese Mariangela V Lopes.pdf: 3032469 bytes, checksum: 36404d46d79768ab384fb49c544f496e (MD5) / Neste trabalho, foram desenvolvidos procedimentos e sistemas automatizados para
o controle de qualidade de carnes e produtos cárneos quanto à presença de aditivos
(NO2- e NO3-), degradação (evolução de H2S), presença de adulterante (SO3-) e
riscos de contaminação pela capacidade sortiva de metais. O desenvolvimento
destes procedimentos vem contrapor as metodologias clássicas recomendadas
pelos órgãos oficiais brasileiros. Os métodos e procedimentos aqui desenvolvidos
obedecem às recomendações da Química Analítica moderna, as quais priorizam
precisão, exatidão, sensibilidade, custos operacionais, versatilidade, robustez,
rastreabilidade, minimização de resíduos e produtividade analítica. O sistema de
analise por injeção em fluxo (FIA), para análise seletora e discriminatória de H2S
evoluído pela carne, foi desenvolvido baseado no método do azul de metileno. O
emprego da multicomutação, associado à câmara de pervaporação, conferiu
versatilidade ao sistema com produtividade analítica de 30 determinações h-1.
Paralelo a isto, foi realizada uma avaliação da degradação de carnes empregando a
espectroscopia no infravermelho próximo (NIR) para averiguação das condições de
conservação de carnes. Os resultados foram concordantes para as duas
metodologias (NIR e FIA), sendo possível detectar indícios de deterioração após 30
min de exposição da carne à atmosfera em temperatura ambiente. O
desenvolvimento de sistema em fluxo para análise seqüencial de NO2- e NO3-, em
produtos cárneos, utilizando câmara de tubos concêntricos (CTC) foi baseado no
método de Greiss. A CTC proporcionou a divisão da zona da amostra, facilitando as
determinações seqüenciais de NO2- e NO3-. A subzona da amostra que passava pelo
tubo central da CTC resultava apenas na determinação do NO2-. A amostra que
passava pelo tubo externo (coroa) da CTC, percolava grãos de cádmio coperizado,
resultando na redução do NO3- existente à NO2-. Este sistema ofereceu boa
sensibilidade para a quantificação dos analitos, apresentando limites de detecção de
0,018 e 0,036 mg L-1 para NO2- e NO3-, respectivamente. O procedimento proposto
atingiu produtividade analítica de 120 determinações h-1. O desenvolvimento de
sistema automatizado em fluxo para análise discriminatória de sulfito em carnes foi
baseado no método da p-rosanilina. Foi empregado câmara de permeação gasosa,
onde o SO3- presente na amostra, permeava através de membrana de PTFE para a
reação com o reagente cromogênico. O sistema foi satisfatório para screening
analysis, com produtividade analítica de 12 determinações h-1. A capacidade sortiva
de metais pela carne bovina foi também avaliada. Foi avaliado o contato estático da
carne com soluções de referência de Cd e Pb, preparadas com água de torneira, a
pH 6. Foi empregada válvula multiportas, com oito canais para execução dos
experimentos, enquanto que metais foram determinados por ICP OES. Os
resultados indicaram um elevado poder sortivo, cerca de 80% para ambos os metais,
evidenciando risco potencial de contaminação para as carnes submetidas a práticas
inadequadas de abate e comercialização / In the present work automated systems and procedures to control the quality of
meats and meat products had been developed, in concern to the additive presence
(NO2- and NO3-), degradation (H2S evolution) and presence of adulterating species
(SO32-). Also the metal sorption capacity on meat was evaluated. The development of
these methods comes to oppose classical methods recommended by brazilian official
agencies. The developed procedures follow the recommendations of the modern
Analytical Chemical, which prioritizes the precision, exactness, sensitivity,
traceability, robustness, reduced operational costs, lesser production of residue and
raised analytical productivity. The flow analysis (FIA) procedure to discriminate H2S
in meat sample was developed based on methylene blue method. Multicommutation,
associated to gas permeation conferred versatility to the system with analytical
throughput of 30 determinations h-1. Parallel to this, the spectroscopy in the near
infrared region (NIR) was carried out to evaluate meat degradation. A flow system for
sequential NO2- and NO3- analysis in meat products, using concentric tubes chamber
(CTC) was based on the Greiss method. The CTC provides the division of sample
zone, permitting the sequential analysis. The sample sub zone that passed for the
central pipe of the CTC resulted in the determination of the NO2-. The sample that
passed through external CCP pipe, percolated the cadmium column, allowing the
reduction of the NO3- to NO2-. This system offers sensitivity in the quantification of
anilities with detection limits of 0.036 for NO3- and 0.018 mg L-1 for NO2-, reaching
120 determinations h-1. The flow system for the screening analysis of SO32- in meat
sample was based on p-rosanilne method. Chamber for gas permeation was
employed. The system revealed efficient for screening analysis with analytical
throughput of 12 determination h-1. The metal sorption capacity on meat was
evaluated. The investigated species comprised Cd and Pb from solutions prepared
with tap water at pH 6. In the experimental set, it was employed an eight channels
multiport valve in order to prepare part of the samples, while the metal determinations
was carried out by using ICP OES technique. The results obtained demonstrated an
expressive retention capacity of meat for Cd2+ and Pb2+ ions with percentages ca.
80% (m/m) for both metals, indicating the potential risks related to the consumption of
meat submitted to inappropriate conditions of abattoir, handling, storage and
commercialization.
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