• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 37
  • 33
  • 27
  • 12
  • 5
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 124
  • 33
  • 32
  • 32
  • 30
  • 26
  • 26
  • 25
  • 25
  • 23
  • 22
  • 20
  • 15
  • 14
  • 14
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Kilowatt Three-phase Rotary Transformer Design for Permanent Magnet DC Motor with On-rotor Drive System

Xu, Ye January 2016 (has links)
The aim of this thesis is to design a kilowatt three-phase step-down rotary transformer for a permanent magnet DC motor. The permanent magnet DC motor has an on-rotor drive system, and therefore requiring a power supply that can transfer power to its drive unit without mechanical contact. The rotary transformer has a detached magnetic coupling structure that qualifies it as a potential method for the wireless power transfer. This thesis studies the rotary transformer as a static device, focusing on its core loss. By using a transient finite element analysis of COMSOL Multiphysics and an iron loss prediction model, the rotary transformer was optimized in terms of efficiency and power density for the on-rotor drive system through proper material selection and geometry exploration. After this, a mechanical design, which based on a literature review of the influences of manufacturing processes on electrical steels, was proposed for realizing the core fabrication and the rotary transformer assembly. The results show that the rotary transformer can step down 400 V/50 Hz three-phase voltage to 13.15V in a Delta-wye connection and output 1.17kW power over an air-gap of 0.3mm with 95.94% overall efficiency. The proposed mechanical design enables the transformer to minimize the core loss and the manufacturing cost. Without using resonant inductive coupling, this transformer design simplifies the power supply for the motor, thereby decreasing the motor manufacturing and maintenance cost.
72

Elektroforéza v krátké kapiláře s duální detekcí. / Electrophoresis in short capillary with dual detection.

Kaliba, David January 2014 (has links)
Capillary zone electrophoresis is an analytical method frequently used in many laboratories for solving various analytical problems. This diploma thesis describes one of many applications of capillary zone electrophoresis using a unique laboratory apparatus composed of a short capillary and dual conductivity/UV detector placed in one detection point of the separation capillary. In the first part of this thesis, the laboratory apparatus was tested by the separation of small inorganic and organic ions. Sodium, potassium, tyramine and histidine ions were used to test the two parts of the dual detector. Experimentally obtained mobilities of these ions were compared with those calculated from the tabulated values. In the second part, the apparatus was used for determination of analytes in samples with more complex matrixces, pharmaceuticals Acylcoffin and B-komplex produced by Zentiva, a.s. One analyte was chosen from each pharmaceutical preparation for determination of its concentration in the preparation, caffeine from Acylcoffine and thiamine from B-komplex. The concentrations were calulated using three different calibration methods and the experimentally obtained values were compared with those specified by the pharmaceuticals producer. Key words: capillary electrophoresis; short capillary;...
73

La RFID et le droit / RFID and law

Goulvestre, Ann-maël 05 July 2013 (has links)
L'acronyme anglais RFID « Radio Frequency Identification » désigne en français l'identification par radiofréquence, une technologie qui permet d'identifier et de localiser sans contact des objets ou des personnes grâce à une micro-puce qui dialogue par ondes radio avec un lecteur, sur des distances allant de quelques centimètres à une dizaine de mètres. Déjà présente dans notre quotidien, via les cartes d'accès à certains bâtiments notamment, la RFID est appelée à se développer de manière exponentielle dans les années à venir pour concrétiser à terme le futur Internet des objets.À l'instar de toute innovation technologique, la RFID nécessite un environnement juridique pour pouvoir s'épanouir à la fois économiquement et socialement. C'est pourquoi la présente étude se propose d'exposer les diverses problématiques juridiques afférentes à la RFID. Pour assurer le succès d'une technologie émergente, il est nécessaire que les individus aient confiance en elle, sans quoi le marché ne pourra pas démarrer. Afin de générer cette confiance, la sécurité est primordiale, avant tout d'un point de vue technique mais également sur le plan juridique.L'objectif de cette thèse sera d'étudier le cadre juridique applicable à la technologie RFID, à la fois du point de vue de son contenant, le système, et de son contenu, les données. Quels sont les défis juridiques soulevés par cette technologie ? Existe-t-il des textes applicables à la RFID, et quels sont-ils ? Comment le juriste intègre-t-il cette technologie émergente au cadre juridique existant ? La réflexion est menée afin d'apprécier la nature des rapports entretenus entre la RFID et le droit, et leur éventuelle perfectibilité. / The acronym RFID stands for Radio Frequency Identification, a wireless technology that provides the ability to automatically identify and locate tags attached to objects, as well as the person who is actually carrying them. The technology relies on storing and retrieving data, through radio waves by using devices called RFID tags. Those tags are already prevalent in our everyday lives to grant building access control for example. And this is only the beginning, as RFID technology is expected to be one of the main brick of the Internet of things. Like any other new technology, RFID needs a suitable legal framework to get benefits to both consumers and businesses. This work is thus intended to bring up RFID from a legal perspective. Indeed, one of the new technology key successes lies on the way the consumers will grasp it. When looking for economic profits, it is then essential to focus on public perception and consumer confidence related to this technology. And this would not come along without security concern which represents actually the main challenge to face, most of all from a technical perspective, but also from a legal one.For this reason, the proposed work aims at exposing the legal framework which could be applied both to its container (the RFID system) and its content (the RFID data). It is worth analysing the way the legal practitioner can deal with this technology and all its related issues. Are there any specifics legislations on this subject? And if so, what are they? A critical assessment is undertaken to appreciate the substance of the relationships existing between RFID and law, and potential improvement that come along.
74

Elaboração de um sistema de controle externo do fluxo eletrosmótico para eletroforese capilar com detecção condutométrica sem contato / Development of an external electroosmotic flow control system for capillary electrophoresis with contactless conductivity detection

Vidal, Denis Tadeu Rajh 19 June 2008 (has links)
A presente dissertação trata da implementação, em um equipamento de eletroforese capilar (CE) com detecção condutométrica sem contato (C4D), de um sistema de controle externo do fluxo eletrosmótico (EOF) via tensão radial externa (Vrad). Através do potencial externo, aplicado diretamente ao capilar, é possível ter o controle do fluxo eletrosmótico de CE, pois, de forma simplificada, esta prática acopla vetorialmente um potencial externo aplicado com o potencial através da solução tampão dentro do capilar. O emprego da técnica possibilitou o aumento de resolução de 2 aminoácidos - Leucina e Isoleucina, cujas mobilidades diferem apenas de 0,12 cm2.V-1.s-1 entre si, em ácido acético 500 mmol.L-1 com pH = 2,55. A estratégia empregada aqui foi a que denominamos de \"coluna capilar infinita\", na qual, com as sucessivas inversões na direção do EOF, conseguimos aprisionar, dentro da coluna capilar, espécies com mobilidade eletroforética menor que a mobilidade do EOF. A literatura descreve que a inversão do EOF se torna mais difícil com o aumento do pH. Foram realizados testes em eletrólitos contendo agentes inversores de fluxo como o CTAB, o CaCl2 e o BaCl2. Ambos os aditivos foram usados em concentrações muito baixas, nas quais foi mantida a direção normal do EOF, sendo que a utilizaçãode tais agentes teve a finalidade apenas de reduzir os grupos silanolatos em soluções de pH acima de 6,0. Tal estratégia proporcionou a reversão do EOF no sistema tampão MES/HIS, cujo pH estava em torno de 6,1. Por fim, a pesquisa gerou uma perspectiva interessante que é a possibilidade de se encontrar combinações de eletrólitos de corrida e surfactantes com o intuito de se estender a faixa de alcance do Vrad para valores altos de pH. / This work presents the implementation, in an equipment for capillary electrophoresis (CE) with contactless conductivity detection (C4D), of a system for external control of the electroosmotic flow (EOF) via external radial voltage (Vrad). Through external potential, directly applied to the capillary, the electroosmotic flow can be controlled, because this practice couples the applied external potential to the zeta potential through the buffer solution within the capillary. The use of the technique allowed the baseline resolution of two amino acids (Leucine and Isoleucine), whose mobilities differ only by 0,12 cm2.V-1.s-1, using acetic acid 500 mmol.L-1 at pH = 2,55 as the running electrolyte. The approach, called \"infinite capillary column\", consists in successive reversals in the direction of the EOF, trapping species within the capillary column with electrophoretic mobility smaller than the EOF mobility. Thus, the two amino acids were retained by a period of approximately 120 minutes in the capillary that was enough to promote the baseline resolution. Previous works describe that the reversion of the EOF becoming more difficult as pH increases. In order to achieve a more effective control of EOF at high pH values (limiting the technique to a narrow performance band), tests were carried out in electrolytes containing flow reversing agents such as CTAB, CaCI2 and BaCI2. These additives were used at very low concentrations, which kept the normal direction of EOF, and the use of such agents had only the purpuse of reducing the density of silanolate groups in solutions of pH above 6,0. This approach allowed the reversion of the EOF using MES/HIS buffer, which pH was 6,1. Finally, this research has generated an interesting perspective about the possibility of finding combinations of electrolytes and surfactants aiming the Vrad range´s extension at high pH values.
75

Eletroforese com dupla detecção condutométrica sem contato e espectrometrica de massas / Electrophoresis with dual contactless conductometric detection and mass spectrometry

Francisco, Kelliton José Mendonça 03 October 2017 (has links)
A presente tese descreve o aprimoramento do acoplamento de eletroforese capilar/espectrometria de massas com ionização por electrospray (CE-ESI-MS) (1) pelo desenvolvimento de estratégias de controle de temperatura e posicionamento e (2) pela inclusão de dois detectores condutométricos sem contato (C4Ds) ao capilar de separação eletroforética de modo a se obter informações complementares àquelas fornecidas pelo MS. Os primeiros aprimoramentos consistiram na introdução de uma plataforma móvel para o CE e um módulo de refrigeração da porção externa do capilar. Com estes aprimoramentos, foi possível realizar estudo de cinética de hidrólise de monoetilcarbonato (MEC) por CE-ESI-MS, obtendo-se, pela primeira vez, o valor da energia de ativação de 99 ± 8 kJ mol-1. Posteriormente, foi desenvolvida uma série de protótipos de cartuchos impressos 3D em ABS, permitindo a introdução de até dois C4Ds. Além da inclusão dos detectores, a versão aprimorada do cartucho permitiu um bom comportamento térmico da coluna, permitindo que, tal como em sistemas CE-DAD, correntes eletroforéticas alcancem valores da ordem de 100 µA sem efeitos térmicos indesejados (o que não ocorre ao se utilizar o cartucho original para CE-MS). As possibilidades do arranjo CE-(C4D)2-ESI-MS foram demonstradas pelo desenvolvimento de métodos analíticos de separação para: (1) açúcares a pH 11,2; (2) aminas biogênicas a pH 2,0 e (3) ácidos carboxílicos a pH 7,5. A compatibilização dos eletroferogramas dos C4Ds ao longo do capilar e do ESI-MS no final do capilar foi conseguida pela correção da escala de tempo. Assim, as informações obtidas com os vários detectores podiam ser facilmente complementadas. Devido à baixa seletividade intrínseca do C4D, este se mostra amplamente complementar ao ESI-MS, que é o sistema mais seletivo para CE disponível na atualidade. Embora este último também seja altamente sensível, o C4D se mostrou comparável ou até mais apropriado em alguns casos. Assim, esta combinação única apresenta um grande potencial como ferramenta analítica. / The capillary electrophoresis/mass spectrometry with electrospray source (CE-ESI-MS) was improved by (1) the development of new temperature control and positioning systems and (2) the inclusion of two capacitively coupled contactless conductivity detectors (C4Ds) to the electrophoretic separation capillary allowing to obtain complimentary information to the MS. The initial improvements were the introduction of a sliding platform for the CE equipment and a thermostatic module for the portion of the capillary outside the CE environment. These improvements allowed obtaining, for the first time, the activation energy of hydrolysis reaction of monoethyl carbonate: 99 ± 8 kJ mol-1. However, the most important improvement was the development of 3D-printed cartridge allowing the inclusion of up to two C4Ds along the capillary. This cartridge also allowed a significant improvement of the thermal control over the capillary. No significant difference of the original CE-DAD was observed for electrophoretic currents up to 100 µA. The original CE-MS has similar behavior only until 60 µA. New possibilities of the CE-(C4D)2-ESI-MS setup were demonstrated by the development of analytical methods for separation of: (1) sugars at pH 11.2, (2) biogenic amines at pH 2.0, and (3) carboxylic acids at pH 7.5. The electropherograms of the three detectors were made compatible by correcting the time scales. Therefore, the information obtained from the three detectors may be easily complemented. Thanks to the intrinsic low-selectivity of the C4D, that is complementary to the MS, which is the most selective detector for CE today. Although MS is also highly sensitive, C4D had similar or even better performance in some cases. Therefore, this unique combination is powerful analytical tool
76

A Computational Framework for Control of Machining System Capability : From Formulation to Implementation

Archenti, Andreas January 2011 (has links)
Comprehensive knowledge and information about the static and dynamic behaviour of machine tools, cutting processes and their interaction is essential for machining system design, simulation, control and robust operation in safe conditions. The very complex system of a machine tool, fixture and cutting tools during the machining of a part is almost impossible to model analytically with sufficient accuracy. In combination with increasing demands for precision and efficiency in machining call for new control strategies for machining systems. These strategies need to be based on the identification of the static and dynamic stability under both the operational and off-operational conditions. To achieve this it is necessary to monitor and analyze the real system at the factory floor in full production. Design information and operational data can then be linked together to make a realistic digital model of a given machining system. Information from such a model can then be used as input in machining simulation software to find the root causes of instability. The work presented in this thesis deals with the static and dynamic capability of machining systems. The main focus is on the operational stability of the machining system and structural behaviour of only the machine tool, as well. When the accuracy of a machining system is measured by traditional techniques, effects from neither the static stiffness nor the cutting process are taken into account. This limits the applicability of these techniques for realistic evaluation of a machining system’s accuracy. The research presented in this thesis takes a different approach by introducing the concept of operational dynamic parameters. The concept of operational dynamic parameters entails an interaction between the structural elements of the machining systems and the process parameters. According to this concept, the absolute criterion of damping is used to evaluate the dynamic behaviour of a machining system. In contrast to the traditional theory, this methodology allows to determine the machining system's dynamic stability, in real time under operating conditions. This framework also includes an evaluation of the static deformations of a machine tool.  In this context, a novel concept of elastically linked system is introduced to account for the representation of the cutting force trough an elastic link that closes the force loop. In addition to the elastic link which behaves as a static element, a dynamic non-contact link has been introduced. The purpose is to study the non-linear effects introduced by variations of contact conditions in joints due to rotational speed. / QC 20111123
77

Contactless detection of cardiopulmonary activity for a person in different scenarios / Détection sans contact de l'activité cardio-pulmonaire d'une personne dans différents scenarios

Samad, Sarah 24 May 2017 (has links)
De nos jours, les mesures sans contact du signal cardiaque du patient en utilisant le radar Doppler a suscité un intérêt considérable chez les chercheurs, surtout que les électrocardiographes traditionnels avec des électrodes fixes ne sont pas pratiques dans certains cas comme les nourrissons ou les victimes de brûlure. En raison de la sensibilité des micro­ondes à de petits mouvements, le radar a été utilisé comme système de surveillance de l'activité cardio-pulmonaire humaine. Selon l'effet Doppler, un signal de fréquence constante est transmis vers la cible ayant un déplacement variable puis réfléchi. Le signal réfléchit possède une variation de phase par rapport au temps. Dans notre cas, la cible est la poitrine du patient; Le signal réfléchi de la poitrine de la personne contient le signal cardiorespiratoire. Le système est basé sur un analyseur de réseau vectoriel et deux antennes cornet. Le S21 est calculé en utilisant un analyseur de réseau. La variation de phase de S21 contient des informations de l'activité cardio-pulmonaire. Des techniques de traitement sont utilisées pour extraire le signal cardiaque de la variation de la phase de S21 . Cette thèse présente une étude comparative dans la détection des signaux de battements cardiaques au niveau de la puissance rayonnée et de la fréquence opérationnelle. Les puissances rayonnées sont comprises entre 3 et -17 dBm et les fréquences opérationnelles utilisées sont 2.4, 5.8, 1 0 et 20 GHz. Cela permet de spécifier la fréquence opérationnelle optimale, qui donne un compromis entre la puissance minimale émise ainsi que la complexité du système de mesure. De plus, une étude comparative entre plusieurs méthodes de traitement de signal est proposée pour extraire la meilleure méthode qui permet de mesurer le signal cardiaque et par suite extraire ses paramètres. Des techniques de traitement basées sur des transformées en ondelettes ou le filtrage classique sont présentées et utilisées afin de faire une comparaison entre elles. Le paramètre extrait dans cette thèse est le taux des battements cardiaques. Les mesures ont été effectuées simultanément avec un électrocardiographe afin de valider les mesures du signal cardiaque. Puisque la personne peut se déplacer d'une pièce à une autre à l'intérieur de son domicile, des mesures des quatre côtés de la personne et derrière un mur sont réalisées. Ajoutons une approche de modélisation fondée sur la mesure cardio-respiratoire pour une personne qui exerce une marche en avant. De plus, une comparaison entre un système à micro-ondes à simple et deux antennes pour une personne qui prend son souffle est effectuée afin de tester la précision du système à antenne unique par rapport au a la deuxième. Par suite, des mesures sont effectuées pour une personne qui respire en utilisant un système à une seule antenne. / Nowadays, contact-less monitoring patient's heartbeat using Doppler radar has attracted considerable interest of researchers, especially when the traditional electrocardiogram (ECG) measurements with fixed electrodes is not practical in some cases like infants at risk or sudden infant syndrome or burn victims. Due to the microwave sensitivity toward tiny movements, radar has been employed as a noninvasive monitoring system of human cardiopulmonary activity. According to Doppler effect, a constant frequency signal reflected off an object having a varying displacement will result in a reflected signal, but with a time varying phase. In our case, the object is the patient's chest; the reflected signal of the person's chest contains information about the heartbeat and respiration. The system is based on a vector network analyzer and 2 horn antennas. The S21 is computed using a vector network analyzer. The phase variation of S21 contains information about cardiopulmonary activity. Processing techniques are used to extract the heartbeat signal from the S21 phase. This thesis presents a comparative study in heartbeat detection, considering different radiated powers and frequencies. The radiated powers used are between 3 and -17 dBm and the operational frequencies used are 2.4, 5.8, 10 and 20 GHz. This helps to make a compromise between the minimum power emitted and the complexity of the measurement system. In addition, a comparative study of several signal processing methods is proposed to extract the best technique for heartbeat measurement and thus to extract its parameters. Processing techniques are based on wavelet transforms and conventional filtering in order to make a comparison between them. The parameter extracted in this thesis is the heartbeat rate HR. Measurements were performed simultaneously with a PC-based electrocardiograph to validate the heartbeat rate measurement. Since the person can move from a room to another inside his home, measurements from the four sides of the person and behind a wall are performed. In addition, a modeling approach based on cardio-respiratory measurement for a person who is walking forward is presented. Furthermore, a comparison between single and two-antenna microwave systems for a non-breathing person is carried out to test the accuracy of the single-antenna system relative to the two ­antenna microwave system. After that, measurements are performed using one antenna microwave system for a person who breathes normally.
78

Inovace v obchodě / Innovation in commerce

MARTÍŠEK, Petr January 2015 (has links)
The diploma thesis "Innovation in Commerce" provides an analysis of the development and usage of up-to-day innovative technologies in trade sphere both in our country and abroad. It maps their forms and scope of usage in selected trade units, primarily focusing on modern payment instruments and self-service cash desks and, further on, also from the point of view of their development and usage in the nearest future. The thesis gives an independent solution of using up-to-date payment instruments and self-service cash desks depending on the customer´s age as well as payment forms (cash, non-cash) from z point of view of differences between "rural" and urban population. The thesis includes a proposal for the implementation of two arising up-to-date technologies - self-scanning and iBeacon technology in the Terno Supermarket in České Budějovce.
79

Synthèse de polymères à empreintes moléculaires d'alcaloïdes Vinca pour leur extraction sur phase solide dans des extraits de plantes ou des fluides biologiques : développement du détecteur conductimétrique sans contact à couplage capacitif et de la technique de la double injection en électrophorèse capillaire / Synthesis of molecularly imprinted polymers of Vinca alkaloids for their solid phase extraction in plants extracts or biological fluids : development of the capacitively coupled contactless conductivity detector and of the double injection in capillary electrophoresis

Lopez, Claire 09 December 2010 (has links)
Ce mémoire reporte dans une première partie les études menées sur des polymères à empreintes moléculaires (MIP) en extraction solide-liquide (SPE). La nature des interactions polymère-analyte, l’influence de la composition de la matrice de l’échantillon et la sélectivité des MIPs sont étudiés.La première application concerne l’extraction de molécules ciblées dans un extrait de plante. Deux MIPs respectivement préparés à partir de l’acide méthacrylique (MAA) et l’acide itaconique (IA) et avec respectivement la catharanthine et la vindoline comme molécule empreinte ont montré leur sélectivité sur des solutions standards puis sur un extrait de plante. Des expériences de réactivité croisée réalisées sur des molécules analogues à la molécule empreinte (alcaloïdes dimères) montrent la spécificité de reconnaissance des analytes par les MIPs. Le MIP-catharanthine est caractérisé par les isothermes de Scatchard et sa capacité est évaluée en SPE à partir de l’extrait de Catharanthus roseus. Un MIP préparé à partir de MAA avec la vinorelbine comme molécule empreinte a été appliqué à des matrices aqueuses salines pour l’extraction de la vinflunine et de son métabolite dans du plasma bovin et de l’urine. Des rendements d’extraction élevés ont été atteints grâce à une étude de l’impact des sels et au choix de solvants de lavage adaptés à la matrice. Une deuxième partie montre la simplicité d’utilisation et la sensibilité de la détection conductimétrique sans contact à couplage capacitif (C4D) lors de l’analyse du contre-ion et du principe actif dans des composés pharmaceutiques en électrophorèse capillaire (EC). La technique de la double injection a permis l’analyse simultanée des cations et des anions. La méthode EC-C4D développée est appliquée aux alcaloïdes Vinca et à différents médicaments avec des contre-ions anioniques ou cationiques. / This thesis reports in a first part results obtained with molecularly imprinted polymers (MIP) during solid liquid extraction. Polymer-analyte interactions, composition of the sample matrix and selectivity of MIPs have been studied.The first application concerned the extraction of molecules in a plant extract. Two MIPs respectively prepared from the methacrylic acid (MAA) and itaconic acid ( IA) and with respectively catharanthine and vindoline as template showed their selectivity on standard solutions then on a plant extract. Experiments of cross reactivity performed with analogue of the template (dimers alkaloids) have proved the specificity of analytes recognition by the MIPs. The MIP-catharanthine is characterized by Scatchard isotherms and its capacity was estimated from the extract of Catharanthus roseus. A MIP prepared from MAA with the vinorelbine as template was applied in salt aqueous matrices for the extraction of vinflunine and its metabolite in bovine plasma and urine. High extraction recoveries were reached with a study of the impact of salts and the choice of washing solvents adapted to the matrix. The second part showed the simplicity of use and the sensibility of capacitively coupled contactless conductivity detection (C4D) for the analysis of counter-ion and active principle in pharmaceutical compounds in capillary electrophoresis (CE). The technique of double injection allowed the simultaneous analysis of cations and anions. The developed method EC-C4D was applied to Vinca alkaloids and various medicines with anionic or cationic counter-ions.
80

Metodologia para a determinação de cátions inorgânicos em formulações minerais e fitoquímicas por eletroforese capilar com detecção condutométrica / Methodology for inorganic cations determination in mineral and fitochemical formulations through capillar eletrophoresis with conductivity detection

Raabe, Alice 18 November 2010 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The selective determination of inorganic cations, like alkaline, earth-alkaline, of transition and the ammonium ion (NH4 +) is considered as a difficult practice, because generally, these ions show very close apparent mobilities, by the similarities in their sizes (hydrated ionic rays) and same charges, in some cases it may make the separation not viable. This work describes the simultaneous determination of 14 analytes: ammonium (NH4 +), potassium (K+), calcium (Ca2+), sodium (Na+), magnesium (Mg2+), manganese (Mn2+), thallium (Tl+), chrome (Cr3+), lead (Pb2+), cadmium (Cd2+), zinc (Zn2+), copper (Cu2+), cobalt (Co2+) and nickel (Ni2+). The mechanism of separation used was the capillary zone electrophoresis (CZE, capillary zone electrophoresis) with capacitively coupled contactless conductivity detection (C4D, capacitively coupled contactless conductivity detection) CZE-C4D. The experimental conditions optimized to the determination of cations were: working electrolyte 30 mmol L-1 MES/His, containing 1.5 mmol L-1 18-crown-6 ether, in pH 6; followed by a second stage containing 1 mmol L-1 citric acid in its composition to the selective determination of ions K+ and Tl+. Even other operational parameters with the separation potential of -10 kV, the work temperature of 25 ±1°C, hydrodynamic injection by the samples gravity (20 cm versus 60 s), and the detector C4D operating with the frequency of 600 kHz and varying the amplitude in 2 Vpp (peak to peak). The developed methodology was evaluated for the 14 analytes, where the method was shown adequate to the determination of inorganic cations studied, showing wide linear work rates of 5.18 to 2,217.06 Umol L-1 and of 19.00 to 1,538.46 Umol L-1 for ions NH4 + and Cr3+, respectively; also showing limits of detection (LD) and of quantification (LQ) in the order of Umol L-1 for all analytes. The study also involved the analysis of the alkaloids in real samples and in distinct molds, like phytotherapyc formulations and formulations of mineral fertilizers. / A determinação seletiva de cátions inorgânicos, como metais alcalinos, alcalinos terrosos, de transição e o íon amônio (NH4 +) é considerada uma prática difícil, pois geralmente estes íons apresentam mobilidades aparentes muito próximas, pela semelhança de seus tamanhos (raios iônicos hidratados) e mesmas cargas, em alguns casos, podendo inviabilizar a separação. Este trabalho descreve a determinação simultânea de 14 analitos: amônio (NH4 +), potássio (K+), cálcio (Ca2+), sódio (Na+), magnésio (Mg2+), manganês (Mn2+), tálio (Tl+), cromo (Cr3+), chumbo (Pb2+), cádmio (Cd2+), zinco (Zn2+), cobre (Cu2+), cobalto (Co2+) e níquel (Ni2+). O mecanismo de separação utilizado foi a eletroforese capilar de zona (CZE, capillary zone eletrophoresis) com detecção condutométrica sem contato capacitivamente acoplada (C4D, capacitively coupled contactless conductivity detection) CZE-C4D. As condições experimentais otimizadas para a determinação dos cátions foram: eletrólito de trabalho MES/His 30 mmol L-1, contendo éter 18-coroa-6 1,5 mmol L-1, em pH 6; seguida de uma segunda etapa contendo ácido cítrico 1 mmol L-1 na sua composição, para a determinação seletiva dos íons K+ e Tl+. Ainda outros parâmetros operacionais como o potencial de separação de -10 kV, a temperatura de trabalho de 25 ±1°C, injeção hidrodinâmica por gravidade das amostras (20 cm versus 60 s), e o detector C4D operando com frequência de 600 kHz e variando a amplitude em 2 Vpp (pico a pico). A metodologia desenvolvida foi avaliada para os 14 analitos, onde o método mostrou-se adequado para a determinação dos cátions inorgânicos estudados apresentando amplas faixas lineares de trabalho de 5,18 a 2.217,06 Umol L-1 e de 19,00 a 1.538,46 Umol L-1 para os íons NH4 + e Cr3+, respectivamente; apresentando também limites de detecção (LD) e de quantificação (LQ) na ordem de Umol L-1 para todos os analitos. O estudo também envolveu a análise desses metais em amostras reais e de matrizes distintas, como formulações fitoterápicas e formulações de fertilizantes minerais.

Page generated in 0.0568 seconds