Navegando por Assunto "Espectrofotometria"

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Acesso aberto (Open Access)
Caracterização físico-química e análises por espectrofotometria e cromatografia de Peperomia pellucida L. (H. B. K.)
(2013) SILVA, Rosali Maria Ferreira da; RIBEIRO, Jeane Francisca Alves; FREITAS, Manolo Cleiton Costa de; ARRUDA, Mara Silvia Pinheiro; NASCIMENTO, M.N.; BARBOSA, Wagner Luiz Ramos; ROLIM NETO, Pedro José
The aim of this study was the physical chemical characterization of the powder and the tincture, and the chromatographic and spectrophotometric analysis of the Peperomiapellucida L. (H. B. K.) dry extract. The methodology followed the Farmacopeia Brasileira IV ed., except for the chemical prospection, the chromatographic profile obtained and the spectrophotometry of the dry extract, and determination of dried residues. The chemical prospection revealed the presence of foaming saponins; reducing sugars; proteins and amino acids; phenols; tannins; flavonoids; steroids and triterpenoids; depsideos and depsidones. The best profile from TLC for flavonoidic fraction was obtained with methanol/formic acid (90:10 v/v). HPLC confirmed the presence of 3 ‘,4’,7-tri-methoxyflavone in the dry extract of the plant material. The results obtained in this work should contribute for the determination of specifications for a future monograph on Peperomia pellucida L. (H.B.K.)
Acesso aberto (Open Access)
Determinação espectrofotométrica do arsênio em cabelo usando o método do dietilditiocarbamato de prata (SDDC) e trietanolamina/CHCl3 como solvente
(2002) PEREIRA, Simone de Fátima Pinheiro; FERREIRA, Sérgio Luis Costa; COSTA, Antonio Celso Spínola; SARAIVA, Augusto Cesar Fonseca; SILVA, Antonia Kelen Frota
The silver diethyldithiocarbamate (SDDC) method, has been employed for the determination of arsenic in different materials. The disagreeable odor of the pyridine, the lower stability and reproducibility of the complex are justifications for many works related to the alternatives of the method. The SDDC/pyridine system was substituted for system using triethanolamine 5% v/v in chloroform with many advantages. The method was used for arsenic determination in hair samples with good recovery. Many kinds of digestions was studied.
Acesso aberto (Open Access)
Estudo da utilização do extrato aquoso de barbatimão (Stryphnodendron barbatimão, M.) no ensino de química
(1999) PINHEIRO, Marta Helena Tavares; LIMA, Waterloo Napoleão de
In the present work, the pH dependent colour change of the crude vegetal extracts is suggested in teaching chemical or acid-base equilibria, visual indicators and some aspects of spectrophotometric concepts its applications. The extraction methodology proposed is inexpensive and easy to perform in secondary schools and in general chemistry or instrumental undergraduate courses.
Acesso aberto (Open Access)
Simultaneous spectrometric determination of Cu2+, Mn2+ and Zn2+ in polivitaminic/polimineral drug using SPA and GA algorithms for variable selection
(2005-02) DANTAS FILHO, Heronides Adonias; SOUZA, Ênio Sartre Oliveira Nunes de; VISANI, Valeria; BARROS, Sara Regina Ribeiro Carneiro de; SALDANHA, Teresa Cristina Bezerra; ARAÚJO, Mário César Ugulino de; GALVÃO, Roberto Kawakami Harrop
The application of the method for the simultaneous spectrophotometric determination of the divalent ions of copper, manganese and zinc for analysis of a pharmaceutical formulation of polivitaminic/polimineral is reported. This method uses 4-(2-pyridylazo) resorcinol (PAR) and multivariate calibration and was optimized using the successive projections algorithm (SPA) and a genetic algorithm (GA) for choosing the best series of wavelengths for analysis. Thus the construction of calibration models based on multiple linear regression (MLR-SPA and MLR-GA respectively) was made possible. The results obtained were compared with models based on latent variables, principal component regression (PCR) and partial least square regression (PLS) through the criterion of the root mean square error of prediction (RMSEP). All the methods presented even performance but the RLM methods are simpler since they require a smaller number of wavelengths and are easier to interpret than those based on latent variables.
Acesso aberto (Open Access)
Spectrophotometric determination of arsenic in soil samples using 2-(5-bromo-2-pyridylazo)-5-di-ethylaminophenol (Br-PADAP)
(2008) PEREIRA, Simone de Fátima Pinheiro; FERREIRA, Sérgio Luis Costa; OLIVEIRA, Geiso Rafael Fonseca; PALHETA, Dulcidéia da Conceição; BARROS, Bruno de Cássio Veloso de
In this paper, a new, simple and sensitive method for arsenic determination in soil is proposed. This is based on the reduction of silver (I) and iron (III) ions by arsine followed by a complexation reaction of iron (II) with the spectrophotometric reagent Br-PADAP 2-(5-bromo-2-pyridylazo)-5-di-ethylaminophenol. Arsenic determination with a Sandell's sensitivity of 3.1 10-4 cm-2, linear range from 0.1 µg ml-1 to 2.0 µg ml-1 (r560 = 0.9995), molar absorptivity of 2.45 105 l mol-1 cm-1 and a concentration detection limit of 1.4 ng ml-1 (3s) were obtained using a 10 ml sample volume. Selectivity was increased with the use of EDTA as a masking agent. The proposed method was applied for arsenic determination in the presence of several ions amounts in digested soil samples. The results revealed that antimony (III), mercury (II), germanium (IV), platinum (IV) interferes at all analyzed proportions. The interferences can be easily removed by the use of EDTA. Precision and accuracy obtained were satisfactory with a R.S.D. < 5 %. Recovery of arsenic in soil samples varied from 95.55 to 102.70 % with a mean of 99.63 %. These results demonstrated that the proposed method is applicable for arsenic analysis in different soil samples.
Acesso aberto (Open Access)
Staining of esthetic brackets by plaque disclosing solutions
(2014-06) ISMAEL, Luiza Novelino Acatauassú; NUNES, Mauro de Amorim Acatauassú; NUNES, Ana Maria Novelino Acatauassú; MOTTA, Rogério Heládio Lopes; DEMASI, Ana Paula Dias; FLÓRIO, Flávia Martão
AIM: To evaluate the staining of esthetic orthodontic brackets by plaque disclosing solutions. METHODS: Two types of brackets manufactured by GAC/DENTSPLY(r) were evaluated: ceramic (n=30) and polycarbonate (n=30). The brackets were divided into 6 groups. Two control groups (n=6) were immersed in absolute ethanol: GI - ceramic brackets and GII - polycarbonate brackets. Four experimental groups (n=12) were immersed in different plaque disclosing solutions: GIII (ceramic brackets) and GIV (polycarbonate brackets) were immersed in Replak(r); GV (ceramic brackets) and GVI (polycarbonate brackets) were immersed in Replasul "S"(r). Relative quantitative analysis of the influence of plaque disclosing tablets on bracket staining was performed using reflectance spectrophotometry of stain deposition. Exploratory analysis of the data was performed using Analysis of Variance (ANOVA) in a 2x2 factorial setup (bracket x immersion) with additional treatments (controls). RESULTS: The results demonstrated that the ceramic brackets presented the highest amount of staining when Replasul "S"(r) was used (pd"0.05). However, when Replak(r) was used, no statistically significant difference was found in comparison with the control group (p>0.05). For polycarbonate brackets, staining was detected for both disclosing solutions (p>0.05). CONCLUSIONS: The disclosing solutions caused stain formation on polycarbonate brackets and, under the tested conditions, use of Replak(r) on ceramic brackets did not cause staining.