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Ionic mobility of the solvated proton and acid-base titration in a four-compartment capillary electrophoresis system

SAITO, Renata Mayumi; BRITO-NETO, Jose Geraldo Alves; LOPES, Fernando Silva; BLANES, Lucas; COSTA, Eric Tavares da; VIDAL, Denis Tadeu Rajh; HOTTA, Guilherme Minoru; LAGO, Claudimir Lucio do
Fonte: ROYAL SOC CHEMISTRY Publicador: ROYAL SOC CHEMISTRY
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.01%
Although H(+) and OH(-) are the most common ions in aqueous media, they are not usually observable in capillary electrophoresis (CE) experiments, because of the extensive use of buffer solutions as the background electrolyte. In the present work, we introduce CE equipment designed to allow the determination of such ions in a similar fashion as any other ion. Basically, it consists of a four-compartment piece of equipment for electrolysis-separated experiments (D. P. de Jesus et at, Anal. Chem., 2005, 77, 607). In such a system, the ends of the capillary are placed in two reservoirs, which are connected to two other reservoirs through electrolyte-filled tubes. The electrodes of the high-voltage power source are positioned in these reservoirs. Thus, the electrolysis products are kept away from the inputs of the capillary. The detection was provided by two capacitively coupled contactless conductivity detectors (CD), each one positioned about 11 cm from the end of the capillary. Two applications were demonstrated: titration-like procedures for nanolitre samples and mobility measurements. Strong and weak acids (pK(a) < 5), pure or mixtures, could be titrated. The analytical curve is linear from 50 mu M up to 10 mM of total dissociable hydrogen (r = 0.99899 for n =10) in 10-nL samples. By including D(2)O in the running electrolyte...

Cloud point extraction to avoid interferences by structured background on nickel determination in plant materials by FAAS

SILVA, Sidnei G.; OLIVEIRA, Pedro V.; NOBREGA, Joaquim A.; ROCHA, Fabio R. P.
Fonte: ROYAL SOC CHEMISTRY Publicador: ROYAL SOC CHEMISTRY
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.01%
An analytical procedure based on microwave-assisted digestion with diluted acid and a double cloud point extraction is proposed for nickel determination in plant materials by flame atomic absorption spectrometry. Extraction in micellar medium was successfully applied for sample clean up, aiming to remove organic species containing phosphorous that caused spectral interferences by structured background attributed to the formation of PO species in the flame. Cloud point extraction of nickel complexes formed with 1,2-thiazolylazo-2-naphthol was explored for pre-concentration, with enrichment factor estimated as 30, detection limit of 5 mu g L(-1) (99.7% confidence level) and linear response up to 80 mu g L(-1). The accuracy of the procedure was evaluated by nickel determinations in reference materials and the results agreed with the certified values at the 95% confidence level.; Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq); Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)

Simultaneous determination of Cr, Fe, Ni and V in crude oil by emulsion sampling graphite furnace atomic absorption spectrometry

LUZ, Maciel Santos; OLIVEIRA, Pedro Vitoriano
Fonte: ROYAL SOC CHEMISTRY Publicador: ROYAL SOC CHEMISTRY
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.08%
In this work a simple and reliable method for the simultaneous determination of Cr, Fe, Ni and V in crude oil, using emulsion sampling graphite furnace atomic absorption spectrometry is proposed. Under the best conditions, sample masses around 50 mg were weighed in polypropylene tubes and emulsified in a mixture of 0.5% (v v(-1)) hexane + 6% (m v(-1)) Triton X-100 (R). Considering the compromised conditions, the pyrolysis an atomization temperatures for the simultaneous determination of Cr, Fe, Ni and V were 1400 degrees C and 2500 degrees C, respectively. Aliquots of 20 mu L of reference solution and sample emulsion were co-injected into the graphite tube with 10 mu L of 1.0 g L(-1) Mg(NO(3))(2) as chemical modifier. The detection limits (n = 10, 3 sigma) and characteristic masses were, respectively: 0.07 mu g g(-1) and 19 pg for Cr; 2.15 mu g g(-1) and 31 pg for Fe; 1.25 mu g g(-1) and 44 pg for Ni; and 1.15 mu g g(-1) and 149 pg for V. The reliability of the proposed method was checked by fuel oil Standard Reference Material (SRMTriton X-100 (R) 1634c - NIST) analysis. The concentrations found presented no statistical differences compared to the certified values at 95% confidence level.; National Institute of Advanced Analytical Science and Technology (INCTAA)[573894/2008-6]; National Institute of Advanced Analytical Science and Technology (INCTAA)[2008/57808-1]; Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP); Conselho Nacional de Desenvolvimento Cientifico c Tecnologico (CNPq); Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)

Flow injection analysis of paracetamol using a biomimetic sensor as a sensitive and selective amperometric detector

OLIVEIRA, Mariana C. Q.; LANZA, Marcos R. V.; TANAKA, Auro A.; SOTOMAYOR, Maria D. P. T.
Fonte: ROYAL SOC CHEMISTRY Publicador: ROYAL SOC CHEMISTRY
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.01%
This work describes the coupling of a biomimetic sensor to a flow injection system for the sensitive determination of paracetamol. The sensor was prepared as previously described in the literature (M. D. P. T. Sotomayor, A. Sigoli, M. R. V. Lanza, A. A. Tanaka and L. T. Kubota, J. Braz. Chem. Soc., 2008, 19, 734) by modifying a glassy carbon electrode surface with a Nafion (R) membrane doped with iron tetrapyridinoporphyrazine (FeTPyPz), a biomimetic catalyst of the P450 enzyme. The performance of the sensor for paracetamol detection was investigated and optimized in a flow injection system (FIA) using a wall jet electrochemical cell. Under optimized conditions a wide linear response range (1.0 x 10(-5) to 5.0 x 10(-2) mol L(-1)) was obtained, with a sensitivity of 2579 (+/- 129) mu A L mu mol(-1). The detection and quantification limits of the sensor for paracetamol in the FIA system were 1.0 and 3.5 mu mol L(-1), respectively. The analytical frequency was 51 samples h(-1), and over a period of five days (320 determinations) the biosensor maintained practically the same response. The system was successfully applied to paracetamol quantification in seven pharmaceutical formulations and in water samples from six rivers in Sao Paulo State...

Simultaneous determination of chromium and manganese in alumina by slurry sampling graphite furnace atomic absorption spectrometry using NbC and NaF as modifiers

SOUZA, Alexandre Luiz; OLIVEIRA, Pedro Vitoriano
Fonte: ROYAL SOC CHEMISTRY Publicador: ROYAL SOC CHEMISTRY
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.01%
This paper reports a method for the direct and simultaneous determination of Cr and Mn in alumina by slurry sampling graphite furnace atomic absorption spectrometry (SiS-SIMAAS) using niobium carbide (NbC) as a graphite platform modifier and sodium fluoride (NaF) as a matrix modifier. 350 mu g of Nb were thermally deposited on the platform surface allowing the formation of NbC (mp 3500 degrees C) to minimize the reaction between aluminium and carbon of the pyrolytic platform, improving the graphite tube lifetime up to 150 heating cycles. A solution of 0.2 mol L(-1) NaF was used as matrix modifier for alumina dissolution as cryolite-based melt, allowing volatilization during pyrolysis step. Masses (c.a. 50 mg) of sample were suspended in 30 ml of 2.0% (v/v) of HNO(3). Slurry was manually homogenized before sampling. Aliquots of 20 mu l of analytical solutions and slurry samples were co-injected into the graphite tube with 20 mu l of the matrix modifier. In the best conditions of the heating program, pyrolysis and atomization temperatures were 1300 degrees C and 2400 degrees C, respectively. A step of 1000 degrees C was optimized allowing the alumina dissolution to form cryolite. The accuracy of the proposed method has been evaluated by the analysis of standard reference materials. The found concentrations presented no statistical differences compared to the certified values at 95% of the confidence level. Limits of detection were 66 ng g(-1) for Cr and 102 ng g(-1) for Mn and the characteristic masses were 10 and 13 pg for Cr and Mn...

Diagnostics for the Developing World: Microfluidic Paper-Based Analytical Devices

MARTINEZ, Andres W.; PHILLIPS, Scott T.; WHITESIDES, George M.; CARRILHO, Emanuel
Fonte: AMER CHEMICAL SOC Publicador: AMER CHEMICAL SOC
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.12%
Microfluidic paper-based analytical devices (mu PADs) are a new class of point-of-care diagnostic devices that are inexpensive, easy to use, and designed specifically for use in developing countries. (To listen to a podcast about this feature, please go to the Analytical Chemistry multimedia page at pubs.acs.org/page/ancham/audio/index.html.); Bill & Melinda Gates Foundation; Bill & Melinda Gates Foundation[51308]; N/MEMS S&T Fundamentals MF3 Center (DARPA); N/MEMS S&T Fundamentals MF3 Center (DARPA); Damon Runyon Cancer Research Foundation; Damon Runyon Cancer Research Foundation[DRG-1805-04]; National Institutes of Health (NIH); National Institute of Health (NIH); Fundacao de Amparo a Pesquisa do Estado de Sao Paulo-FAPESP; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Essential steps to providing reliable results using the Analytical Quality Assurance Cycle

Olivares, Igor Renato Bertoni; Lopes, Fernando Antunes
Fonte: ELSEVIER SCI LTD; OXFORD Publicador: ELSEVIER SCI LTD; OXFORD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.21%
Considering how demand for quality assurance (QA) has grown in analytical laboratories, we show the trends in analytical science, illustrated through international standard ISO/IEC 17025, validation, measurements of uncertainty, and quality-control (QC) measures. A detailed review of the history of analytical chemistry indicates that these concepts are consistently used in laboratories to demonstrate their traceabilities and competences to provide reliable results. We propose a new approach for laboratory QA, which also develops a diagram to support routine laboratories (which generally apply a quality system, such as ISO/IEC 17025) or research laboratories (that have some difficult applying this international standard). This approach, called the Analytical Quality Assurance Cycle (AQAC), presents the major QA concepts and the relationships between these concepts in order to provide traceability and reliable results. The AQAC is a practical tool to support the trend towards QA in analytical laboratories. (C) 2012 Elsevier Ltd. All rights reserved.

Evaluation of the detection and quantification limits in electroanalysis using two popular methods: application in the case study of paraquat determination

da Silva, Osmair Benedito; Machado, Sergio Antonio Spinola
Fonte: ROYAL SOC CHEMISTRY; CAMBRIDGE Publicador: ROYAL SOC CHEMISTRY; CAMBRIDGE
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.08%
In this work, the reduction reaction of paraquat herbicide was used to obtain analytical signals using electrochemical techniques of differential pulse voltammetry, square wave voltammetry and multiple square wave voltammetry. Analytes were prepared with laboratory purified water and natural water samples (from Mogi-Guacu River, SP). The electrochemical techniques were applied to 1.0 mol L-1 Na2SO4 solutions, at pH 5.5, and containing different concentrations of paraquat, in the range of 1 to 10 mu mol L-1, using a gold ultramicroelectrode. 5 replicate experiments were conducted and in each the mean value for peak currents obtained -0.70 V vs. Ag/AgCl yielded excellent linear relationships with pesticide concentrations. The slope values for the calibration plots (method sensitivity) were 4.06 x 10(-3), 1.07 x 10(-2) and 2.95 x 10(-2) A mol(-1) L for purified water by differential pulse voltammetry, square wave voltammetry and multiple square wave voltammetry, respectively. For river water samples, the slope values were 2.60 x 10(-3), 1.06 x 10(-2) and 3.35 x 10(-2) A mol(-1) L, respectively, showing a small interference from the natural matrix components in paraquat determinations. The detection limits for paraquat determinations were calculated by two distinct methodologies...

An environmentally friendly analytical procedure for nickel determination by atomic and molecular spectrometry after cloud point extraction in different samples

Garcia, Samara; Galbeiro, Rafaela; Silva, Sidnei Gonçalves da; Nomura, Cassiana Seimi; Rocha, Fabio Rodrigo Piovezani; Gaubeur, Ivanise
Fonte: ROYAL SOC CHEMISTRY; CAMBRIDGE Publicador: ROYAL SOC CHEMISTRY; CAMBRIDGE
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.01%
Cloud point extraction (CPE) was employed for separation and preconcentration prior to the determination of nickel by graphite furnace atomic absorption spectrometry (GFAAS), flame atomic absorption spectrometry (FAAS) or UV-Vis spectrophotometry. Di-2-pyridyl ketone salicyloylhydrazone (DPKSH) was used for the first time as a complexing agent in CPE. The nickel complex was extracted from the aqueous phase using the Triton X-114 surfactant. Under optimized conditions, limits of detection obtained with GFAAS, FAAS and UV-Vis spectrophotometry were 0.14, 0.76 and 1.5 mu g L-1, respectively. The extraction was quantitative and the enrichment factor was estimated to be 27. The method was applied to natural waters, hemodialysis concentrates, urine and honey samples. Accuracy was evaluated by analysis of the NIST 1643e Water standard reference material.; Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES); Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES); Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq); Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq); Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP); Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) [2011/19730-3]

A estrutura e organização da ciência química na visão de estudantes de graduação: uma aplicação da técnica de mapeamento conceitual; The structure and organization of Chemistry concerned by undergraduate students: an application of conceptual mapping

Oliveira, Iara Terra de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 05/05/2011 PT
Relevância na Pesquisa
46.08%
Este trabalho analisa algumas das atividades desenvolvidas no âmbito da disciplina Química Integrada III, oferecida no segundo semestre de 2008 a alunos que então cursavam o sexto semestre dos cursos do IQ-USP do período noturno. As atividades desenvolvidas na disciplina tiveram como finalidade promover a reflexão dos alunos a respeito de suas concepções sobre a natureza e a organização da Química como ciência, e da natureza das relações existentes entre os conceitos (conteúdos) aprendidos nas diferentes disciplinas do curso de graduação. Com o intuito de promover tal reflexão, a disciplina em questão utilizou como ferramenta a elaboração em grupos de dois mapas conceituais. O primeiro mapa conceitual tinha como objetivo que os alunos mostrassem explicitamente as principais relações existentes entre os conceitos estudados em seu curso. Já o segundo mapa conceitual tinha como objetivo representar a visão dos estudantes a respeito da organização estrutural da Química. A análise dos conceitos utilizados e da relação expressa entre os mesmos permitiu observar que as disciplinas do curso e as cinco áreas tradicionais da Química estão presentes como elementos estruturantes da mesma. São também consideradas estruturantes as áreas de atuação profissional destes alunos (Química Ambiental e Ensino de Química). A Bioquímica é geralmente vista como dependente de outras áreas. A Química Analítica é considerada como uma "ferramenta" a serviço das demais. O mesmo ocorre com outras áreas do conhecimento (Matemática e Física).; This work analyzes some of the activities developed within the subject of Integrated Chemical III...

DDesenvolvimento de eletrodos modificados e métodos analíticos; Development of modified electrodes and analytical methods

Azevedo, Carla Maria Nunes
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 16/04/1999 PT
Relevância na Pesquisa
46.15%
Neste trabalho foram desenvolvidos eletrodos modificados e procedimentos para a sua utilização na determinação de diversas espécies químicas de interesse analítico, dentre as quais sulfito, ácido ascórbico, nitrito, dopamina, NADH e peróxido de hidrogênio. Foram realizados estudos envolvendo eletrodos de carbono vítreo modificados com filmes contendo uma única metaloporfirina tetrarrutenada (catiônica) e aplicações analíticas destes sensores associando-os à análise por injeção em fluxo (FIA). Estes eletrodos apresentaram efeitos catalíticos sobre a oxidação de vários analitos, intensificando o sinal de corrente e deslocando seus picos de oxidação para a região de oxidação dos átomos de Ru(II) à Ru(III), sítios ativos das porfirinas. Contudo, para a obtenção de sensores estáveis, foi necessária a utilização de uma elevada concentração do contra-íon trifluorometanossulfonato em solução, prevenindo a gradual solubilização do filme modificador. Tal dificuldade foi contornada recobrindo-se os eletrodos com filmes laminares contendo simultaneamente pares de porfirinas catiônicas e aniônicas. Estes sensores apresentaram ação catalítica igual aos eletrodos recobertos por uma única porfirina...

An integrated approach of analytical chemistry

Guardia,Miguel de la
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/1999 EN
Relevância na Pesquisa
46.37%
The tremendous development of physical methods of analysis offers an impressive number of tools to simultaneously determine a large number of elements and compounds at very low concentration levels. Todays Analytical Chemistry provides appropriate media to solve technical problems and to obtain correct information about chemical systems in order to take the most appropriate decisions for problem solving. In recent years the development of new strategies for sampling, sample treatment and data exploitation through the research on field sampling, microwaveassisted procedures and chemometrics, additionally the revolution of the analytical methodology provided by the development of flow analysis concepts and process analysis strategies offer a link between modern instrumentation and social or technological problems. The integrated approach of Analytical Chemistry requires correctly incorporating the developments in all of the fields of both, basic chemistry, instrumentation and information theory, in a scheme which considers all aspects of data obtention and interpretation taking also into consideration the side effects of chemical measurements. In this paper, new ideas and tools for trace analysis, speciation, surface analysis, data acquisition and data treatment...

Detection of calcium phosphate crystals in the joint fluid of patients with osteoarthritis – analytical approaches and challenges

Yavorskyy, Alexander; Hernandez-Santana, Aaron; McCarthy, Geraldine; McMahon, Gillian
Fonte: Royal Society of Chemistry Publicador: Royal Society of Chemistry
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
46.01%
The detection of basic calcium phosphate (BCP) crystals in the synovial fluid of patients with osteoarthritis is important as they represent a therapeutic target as well as a potential biomarker for the disease. This review collates the work that has been done on developing analytical assays for BCP crystals.

Development of presumptive and confirmatory analytical methods for the simultaneous detection of multiple improvised explosives

Peters, Kelley L
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
46.17%
In recent years, there has been a dramatic increase in the use of improvised explosive devices (IEDs) due to ease of synthesis and improved controls placed on commercial/military explosives. Commonly used materials for IED preparations include fertilizers and industrial chemicals containing oxidizers such as ClO3-, ClO4 -, and NO3-, as well as other less stable compounds, such as peroxides. Due to these materials having a wide range of volatility, polarity, and composition, detection can be challenging, increasing the amount of time before any analytical information on the identity of the explosive can be determined. Therefore, this research project developed two analytical methods to aid in the rapid detection of multiple explosive compounds. ^ The use of microfluidic paper-based analytical devices (μPADs) allows for the development of inexpensive paper devices utilizing colorimetric reactions, which can perform five or more simultaneous analyses in approximately five minutes. Two devices were developed: one for the detection of inorganic explosives including ClO3-, ClO4-, NH4+, NO3-, and NO 2-, and the second device detects high/organic explosives including RDX, TNT, urea nitrate, and peroxides. Limits of detection ranged from 0.4 μg – 20 μg of explosive residue with an analysis time of less than five minutes. ^ Development of a confirmatory method utilizing infusion electrochemical detection-electrospray ionization-time-of-flight mass spectrometry (EC-ESI-TOF MS) and 18-crown-6 ethers to produce guest/host complexes with inorganic ions has also been completed. Utilizing this method the inorganic ions present in many IEDs can be successfully detected as ion pairs...

How Learning Styles, Chemistry Attitudes and Experiences, Confidence, and Demographics Correlate with Academic Success in First and Second Year Chemistry Courses

Ilnicki-Stone, Elizabeth
Fonte: Brock University Publicador: Brock University
Relevância na Pesquisa
46.12%
At Brock University, the Faculty of Mathematics and Science currently has one of the highest percentages of students on academic probation, with many students reporting the most difficulty with Introductory Chemistry in first year and Organic Chemistry in second year. To identify strategies to improve students' performance and reduce the number of students on academic probation, a multi-year research project was undertaken involving several chemistry courses. Students were asked to complete three questionnaires, and provide consent to obtain their final Chemistry grade from the Registrar's Office. Research began at the end of the 2007-08 academic year with CHEM IPOO, and in the 2008-09 academic year, students in the larger CHEM IF92 Introductory Chemistry course were invited to participate in this research near the beginning of the academic year. Students who went on to take second year Organic and Analytical Chemistry were asked to complete these questionnaires in each second year course. The three questionnaires included the Kolb Learning Styles Inventory (Kolb, 1984) modified to include specific reference to Chemistry in each question, Dalgety, ColI, and Jones' (2002) Chemistry Attitudes and Experiences Questionnaire (CAEQ)...

The development of an immobilized enzyme reactor containing glyceraldehyde-3-phosphate dehydrogenase from Trypanosoma cruzi: the effect of species' specific differences on the immobilization

CARDOSO, Carmen Lucia; MORAES, Marcela Cristina de; GUIDO, Rafael Victorio Carvalho; OLIVA, Glaucius; ANDRICOPULO, Adriano Defini; WAINER, Irving William; CASS, Quezia Bezerra
Fonte: ROYAL SOC CHEMISTRY Publicador: ROYAL SOC CHEMISTRY
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.01%
Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) plays an important role in the life cycle of the Trypanosoma cruzi, and an immobilized enzyme reactor (IMER) has been developed for use in the on-line screening for GAPDH inhibitors. An IMER containing human GAPDH has been previously reported; however, these conditions produced a T. cruzi GAPDH-IMER with poor activity and stability. The factors affecting the stability of the human and T. cruzi GAPDHs in the immobilization process and the influence of pH and buffer type on the stability and activity of the IMERs have been investigated. The resulting T. cruzi GAPDH-IMER was coupled to an analytical octyl column, which was used to achieve chromatographic separation of NAD+ from NADH. The production of NADH stimulated by D-glyceraldehyde-3-phosphate was used to investigate the activity and kinetic parameters of the immobilized T. cruzi GAPDH. The Michaelis-Menten constant (K-m) values determined for D-glyceraldehyde-3-phosphate and NAD(+) were K-m = 0.5 +/- 0.05 mM and 0.648 +/- 0.08 mM, respectively, which were consistent with the values obtained using the non-immobilized enzyme.

Fluorescence images combined to statistic test for fingerprinting of citrus plants after bacterial infection

PEREIRA, Fabiola Manhas Verbi; MILORI, Debora Marcondes Bastos Pereira; PEREIRA-FILHO, Edenir Rodrigues; VENANCIO, Andre Leonardo; RUSSO, Mariana de Sa Tavares; MARTINS, Polyana Kelly; FREITAS-ASTUA, Juliana
Fonte: ROYAL SOC CHEMISTRY Publicador: ROYAL SOC CHEMISTRY
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.01%
The citrus greening (or huanglongbing) disease has caused serious problems in citrus crops around the world. An early diagnostic method to detect this malady is needed due to the rapid dissemination of Candidatus Liberibacter asiaticus (CLas) in the field. This analytical study investigated the fluorescence responses of leaves from healthy citrus plants and those inoculated with CLas by images from a stereomicroscope and also evaluated their potential for the early diagnosis of the infection caused by this bacterium. The plants were measured monthly, and the evolution of the bacteria on inoculated plants was monitored by real-time quantitative polymerase chain reaction (RT-qPCR) amplification of CLas sequences. A statistical method was used to analyse the data. The selection of variables from histograms of colours (colourgrams) of the images was optimized using a paired Student's t-test. The intensity of counts for green colours from images of fluorescence had clearly minor variations for healthy plants than diseased ones. The darker green colours were the indicators of healthy plants and the light colours for the diseased. The method of fluorescence images is novel for fingerprinting healthy and diseased plants and provides an alternative to the current method represented by PCR and visual inspection. A new...

Quality Assesment of Interpretative Commenting in Clinical Chemistry

Lim, Ee Mun; Sikaris, Ken; Gill, Janice; Calleja, John; Hickman, Peter; Beilby, John; Vasikaran, S
Fonte: American Association of Clinical Chemistry Publicador: American Association of Clinical Chemistry
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.03%
Background: Clinical interpretation of laboratory results is an integral part of clinical chemistry. However, the performance goals for assessing interpretative commenting in this discipline have not been as well established as for the quality of analytical requirements. Methods: We present a review of the 10 case reports circulated in the 2002 Patient Report Comments Program by the Royal College of Pathologists of Australasia (RCPA) and the Australasian Association of Clinical Biochemists Chemical Pathology Group of RCPA-Quality Assurance Programs Pty Ltd. Participants were expected to add an interpretative comment to a set of results accompanied by brief clinical details. Comments received were broken down into components that were translated into key phrases. An expert panel evaluated the appropriateness of the key phrases and proposed a suggested composite comment. A case summary/rationale was also returned to participants. Results: There was considerable diversity in the range of interpretative comments received for each case report. Although the majority of comments received were felt to be acceptable by the expert panel, some comments were felt to be inappropriate, misleading, or in a few instances, dangerous. Conclusion: The golden rule in medicine is "do no harm". Although there is no objective evidence that interpretive comments help to improve patient outcomes...

The Contributions of James Moir to Physical Chemistry

Loyson,P.
Fonte: South African Journal of Chemistry Publicador: South African Journal of Chemistry
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2014 EN
Relevância na Pesquisa
46.2%
James Moir was a pioneering chemist in the early 1900s who played a leading role in various chemical societies in South Africa. Although he was mainly an organic chemist, he was a very good all-round chemist, whose analytical and organic activities have already been covered in this j ournal. This article examines his research in physical chemistry, covering the spectral analysis of the ruby and emerald gemstones, a detailed analysis of part of the Fraunhofer lines of the solar spectrum, and an examination of the spectra of cobalt compounds, the permanganate ion, and uranium compounds. Finally, as part of his inorganic and analytical investigations, he also delved into the physical chemistry aspects of solution chemistry, particularly the hydrolysis of the cyanide ion.

Biological sulphate reduction with primary sewage sludge in an upflow anaerobic sludge bed (UASB) reactor - Part 2: Modification of simple wet chemistry analytical procedures to achieve COD and S mass balances

Poinapen,J; Ekama,GA; Wentzel,MC
Fonte: Water SA Publicador: Water SA
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/10/2009 EN
Relevância na Pesquisa
56.24%
The use of the conventional COD method to measure sulphide proved to be problematic due to the loss of hydrogen sulphide (H2S) during sample handling. For calibration of models based on mass balances, and operation of full-scale systems, it was imperative to develop simple wet chemistry analytical procedures for the accurate measurement of parameters like sulphide, COD, alkalinities and VFA in order to monitor BSR systems and achieve 100% COD and S mass balances. Three different analytical methods were investigated to minimise the loss of un-dissociated H2S. Method 1, which is the recommended Standard Methods COD test method, resulted in poor S mass balance (64-75%) due to loss of H2S during sample handling, mainly vacuum filtration. Method 2, in which 3 drops of 10 M NaOH are added immediately upon effluent sample collection to raise the pH to > 10 and converting un-dissociated H2S species into the HS- species resulted in minimal sulphide loss during sample vacuum filtration, dilution, mixing and standing. Method 3, in which a polyelectrolyte is added to the effluent sample to coagulate the organic particles with centrifugation for solid-liquid separation instead of vacuum filtration. Results from Method 3 showed an improvement in the S mass balance with respect to Method 1 - 91% against 75% without a long sample standing period and 88% against 65% with a long sample standing period. However...