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Titulação em fluxo monossegmentado

Emerson Vidal de Aquino
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 03/12/2004 PT
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Este trabalho teve como objetivos a construção de um titulador automático que utiliza o Sistema de Análise em Fluxo Monossegmentado e a sua adaptação para operar com técnicas titulométricas tradicionais, visando assim melhorar o desempenho em relação à reprodutibilidade, repetibilidade, velocidade de análise e consumo de amostras e reagentes. Nesse tipo de sistema, a amostra é inserida em forma de um monossegmento impulsionado até o detector através de um líquido carregador apropriado ou através de um gás. Esse monossegmento pode ser considerado como um volume isolado, fixo e reprodutível da amostra a ser titulada. A adição de reagentes foi realizada de forma volumétrica ou por geração coulométrica. Algoritmos matemáticos foram desenvolvidos e empregados para a localização do ponto final da titulação. O rastreamento através de um algoritmo de busca binária permite que o ponto final seja alcançado sem a necessidade de uma curva completa de titulação. A amostra não é descartada e retoma para que outra adição de titulante, de volume determinado pelo algoritmo, seja feita. Outro algoritmo avaliado é baseado no método de Gran, que permite, a partir de poucos incrementos de titulante, encontrar o ponto final. Foram avaliadas as detecções espectrofotométrica...

Complexometric titration with potenciometric indicator to determination of calcium and magnesium in soil extracts¹

Pereira,Claudia Mara; Neiverth,Cristhiane Anete; Maeda,Shizuo; Guiotoku,Marcela; Franciscon,Luziane
Fonte: Sociedade Brasileira de Ciência do Solo Publicador: Sociedade Brasileira de Ciência do Solo
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2011 EN
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This study proposes a method of direct and simultaneous determination of the amount of Ca2+ and Mg2+ present in soil extracts using a Calcium Ion-Selective Electrode and by Complexometric Titration (ISE-CT). The results were compared to those obtained by conventional analytical techniques of Complexometric Titration (CT) and Flame Atomic Absorption Spectrometry (FAAS). There were no significant differences in the determination of Ca2+ and Mg2+ in comparison with CT and FAAS, at a 95 % confidence level. Additionally, results of this method were more precise and accurate than of the Interlaboratorial Control (IC).

Comprehensive one-day renal function testing in man

Györy, A. Z.; Edwards, K. D. G.; Stewart, J. H.; Whyte, H. M.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /05/1974 EN
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A comprehensive one-day renal function test consisting of a single outpatient visit lasting nine hours, with a minimum of time off work or away from home, is described in detail. Although a large number of laboratory tests are performed in one day, patients usually appreciate thoroughness, and the cost is more than offset by the saving in occupancy of hospital beds and by the early and precise diagnosis of reversible aspects of renal disease. Some aspects of improved methodology, such as the sequential determination of minimum urinary pH, bicarbonate, titratable acid, ammonium, and total acid on a single sample using an automatic titrator, are given in detail. Clinical application of the comprehensive nine-hour renal function testing system is illustrated by the result sheet of a patient with analgesic nephropathy, who was shown in one day to have secondary severe renal failure (glomerular filtration rate 20% of normal for age and surface area), renal tubular acidosis of the distal gradient type (minimum urinary pH 6·20), increased urinary white cell excretion rate, hyaline casts, and absence of red cell casts, consistent with a diagnosis of analgesic nephropathy and urinary tract inflammation. Normal values with 95% range for this laboratory are also given. This testing system has been found to be very useful in investigating patients with analgesic nephropathy...

Induced and spontaneous movements of potassium ions into mitochondria

Harris, E. J.; Cockrell, R.; Pressman, B. C.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /04/1966 EN
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1. Net movements of K+ into metabolizing liver mitochondria before and after the addition of valinomycin have been measured by using selective glass electrodes. The advantage of using an automatic titrator to hold the K+ concentration constant is demonstrated. 2. According to the energy source provided the induced movement after the addition of valinomycin can be either in or out. 3. Uptakes and rates of movement are higher in media containing acetate (20mm) than in media containing chloride (20mm). In each mixture comparisons were made at three pH values; at pH6·36 the induced rates are less than at pH7·0 or 7·8 but the final uptakes attained are increased. 4. The rate of uptake is increased by inorganic phosphate. 5. The presence of Mg2+ slightly decreases the induced uptake and rate of movement; Ca2+ can cause the induced movement of K+ to be outward. 6. The rate of induced K+ movement is related to the rate of extra oxygen consumption but with different factors in acetate (24 K+ ions/oxygen molecule) and chloride media (10 K+ ions/oxygen molecule). 7. The amount of K+ gained is proportional to the loss of fluorescence of the suspension. 8. When K+ moves there is a contrary movement of H+ but the ratio depends on the conditions. At pH6·36 in chloride media the K+/H+ ratio exceeded 10:1 and in no case did it fall to unity. 9. When K+ is taken up there is a proportional diminution of light-scattering; it is inferred that swelling takes place along with K+ accumulation. 10. It is shown by the use of tracer 42K+ that turnover of the ion in mitochondria is increased by valinomycin. 11. It is concluded that valinomycin both increases the permeability to K+ and also...

Role of nitric oxide in regulation of gastric acid secretion in rats: effects of NO donors and NO synthase inhibitor

Kato, Shinichi; Kitamura, Motohiro; Korolkiewicz, Roman P; Takeuchi, Koji
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /03/1998 EN
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The role of nitric oxide (NO) in the regulation of acid secretion was examined in the anaesthetized rat.A rat stomach was mounted in an ex vivo chamber, instilled with 2 ml of saline every 15 min, and the recovered sample was titrated at pH 7.0 against 0.1 N NaOH by use of an automatic titrator for acid secretion. Gastric mucosal blood flow (GMBF) was measured simultaneously by laser Doppler flowmeter.Intragastric application of NO donors such as FK409 (3 and 6 mg ml−1) and sodium nitroprusside (SNP; 6 and 12 mg  ml−1) as well as i.p. administration of cimetidine (60 mg kg−1), a histamine H2-receptor antagonist, significantly inhibited the increase in acid secretion in response to pentagastrin (60 μg kg−1 h−1, i.v.), in doses that increased gastric mucosal blood flow (GMBF).Intragastric application of FK409 (6 mg ml−1) increased both basal and stimulated acid secretion induced by YM-14673 (0.3 mg kg−1, i.v.), an analogue of thyrotropin-releasing hormone (TRH), but had no effect on the acid secretory response induced by histamine (4 mg kg−1 h−1, i.v.).Pretreatment with NG-nitro-L-arginine methyl ester (L-NAME; 10 mg kg−1, i.v.) did not affect basal acid secretion, but significantly potentiated the increase in acid secretion induced by YM-14673 and slightly augmented the acid secretory response to pentagastrin.Both pentagastrin and YM-14673 increased the release of nitrite plus nitrate (NOx)...

Design of an automatic titrator

Migneault, D.; Forcé, R. K.
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
Publicado em //1987 EN
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Pop-Cola Acids and Tooth Erosion: An In Vitro, In Vivo, Electron-Microscopic, and Clinical Report

Borjian, Amirfirooz; Ferrari, Claudia C. F.; Anouf, Antoni; Touyz, Louis Z. G.
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
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Introduction. Manufactured Colas are consumed universally as soft drinks. Evidence about the acid contents of Cola-beverages and its effects on teeth is rare. Aim. To assess (i) cola acidity and buffering capacity in vitro, (ii) tooth erosion after swishing with colas in vivo (iii) scanning electron microscopic effects on teeth of colas, and tooth-brush abrasion, and (iv) report a clinical case of erosion from cola consumption. Materials and Methods. (i) We measured six commercially available pop “Cola beverages”, pH, and buffering capacities using a pH-Mettler Automatic Titrator, with weak solution of Sodium Hydroxide (ii) two cohorts, one with teeth, the second without teeth rinsed with aliquots of Cola for 60 seconds. Swished cola samples tested for calcium and phosphorus contents using standardized chemical analytical methods (iii) enamel, dentine, and the enamel-cemental junction from unerupted extracted wisdom teeth were examined with a scanning electron microscope after exposure to colas, and tested for tooth-brush abrasion; (iv) a clinical case of pop cola erosion presentation, are all described. Results. Comparisons among pop colas tested in vitro reveal high acidity with very low pH. Buffering capacities in millilitres of 0.5 M NaOH needed to increase one pH unit...