Journal of the Brazilian Chemical Societyhttps://www.scielo.br/feed/jbchs/2003.v14n2/2024-02-23T20:03:52.855000ZVol. 14 No. 2 - 2003WerkzeugUnknow title10.1590/S0103-505320030002000012024-02-23T20:03:52.855000Z2020-08-09T06:48:42.529000ZCollins, Carol H.Cadore, Solange
<em>Collins, Carol H.</em>;
<em>Cadore, Solange</em>;
<br/><br/>
The development of Analytical Chemistry in Brazil: retrospective and expectations10.1590/S0103-505320030002000022024-02-23T20:03:52.855000Z2020-08-09T06:48:42.529000ZZagatto, Elias A. G.Sá, Sandra M. O.
<em>Zagatto, Elias A. G.</em>;
<em>Sá, Sandra M. O.</em>;
<br/><br/>
The development of Analytical Chemistry in Brazil in the last century is critically evaluated in relation to international achievements. Tendencies for the next century are foreseen, especially in relation to the presently observed shifts in paradigm.Electrochemical sensors: a powerful tool in analytical chemistry10.1590/S0103-505320030002000032024-02-23T20:03:52.855000Z2020-08-09T06:48:42.529000ZStradiotto, Nelson R.Yamanaka, HidekoZanoni, Maria Valnice B.
<em>Stradiotto, Nelson R.</em>;
<em>Yamanaka, Hideko</em>;
<em>Zanoni, Maria Valnice B.</em>;
<br/><br/>
Potentiometric, amperometric and conductometric electrochemical sensors have found a number of interesting applications in the areas of environmental, industrial, and clinical analyses. This review presents a general overview of the three main types of electrochemical sensors, describing fundamental aspects, developments and their contribution to the area of analytical chemistry, relating relevant aspects of the development of electrochemical sensors in Brazil.Sample preparation for atomic spectroscopy: evolution and future trends10.1590/S0103-505320030002000042024-02-23T20:03:52.855000Z2020-08-09T06:48:42.529000ZOliveira, Elisabeth de
<em>Oliveira, Elisabeth De</em>;
<br/><br/>
Sample preparation is the critical step of any analytical protocol, and involves steps from simple dilution to partial or total dissolution. The methods include dry or wet decomposition of the samples in open or closed systems, using thermal, ultrasonic or radiant (infrared, ultraviolet and microwaves) energy. This review emphasizes sample preparation for atomic spectroscopy. The present and future tendencies for sample preparation also involve on-line dissolution, extraction of the analytes, speciation, solid sample and slurry analysis, in situ and in vivo procedures, etc. Nowadays the goals are the best result, in the shortest time, with minimum contamination, using the smallest quantities of reagents and samples, and having low residue and waste generation, as well as maintaining the integrity of the sample and the traceability of the results, to have quality and confidence in the measurements as the primordial attributes required by the community and by the users.The role of the separation sciences in the 21th century10.1590/S0103-505320030002000052024-02-23T20:03:52.855000Z2020-08-09T06:48:42.529000ZLanças, Fernando M.
<em>Lanças, Fernando M.</em>;
<br/><br/>
This review examines, from a critical point-of-view, the role of the separation sciences in the new century considering the complexity of the problems to be faced. To make the exposition more dynamic the determination of a typical (hypothetical) organic analyte in a complex matrix is used to critically introduce the major separation techniques used nowadays. Techniques that promote the reduction or that fully eliminate the use of toxic solvents are stressed. After this evaluation the author discusses the future trends in this area with emphasis on the miniaturization of the instrumental techniques, the full automation of the analyses, the use of hyphenated techniques, the under-explored role of the solvents in separation techniques, the development of transition phase chromatography and unified chromatography.Near Infrared Spectroscopy: fundamentals, practical aspects and analytical applications10.1590/S0103-505320030002000062024-02-23T20:03:52.855000Z2020-08-09T06:48:42.529000ZPasquini, Celio
<em>Pasquini, Celio</em>;
<br/><br/>
This paper intends to review the basic theory of Near Infrared (NIR) Spectroscopy and its applications in the field of Analytical Science. It is addressed to the reader who does not have a profound knowledge of vibrational spectroscopy but wants to be introduced to the analytical potentialities of this fascinating technique and, at same time, be conscious of its limitations. Essential theory background, an outline of modern instrument design, practical aspects, and applications in a number of different fields are presented. This work does not intend to supply an intensive bibliography but refers to the most recent, significant and representative material found in the technical literature. Because this paper has been produced as consequence of the First Workshop on Near Infrared Spectroscopy, whose venue was Campinas - Brazil, as a pre-conference activity of the XI National Meeting on Analytical Chemistry (ENQA), it also depicts the state of the art of NIR spectroscopy in Brazil, pointing out the current achievements and the need to take the technology to a level consistent with this country's economical activities.High-resolution continuum-source atomic absorption spectrometry: what can we expect?10.1590/S0103-505320030002000072024-02-23T20:03:52.855000Z2020-08-09T06:48:42.529000ZWelz, BernhardBecker-Ross, HelmutFlorek, StefanHeitmann, UweVale, Maria Goreti R.
<em>Welz, Bernhard</em>;
<em>Becker-Ross, Helmut</em>;
<em>Florek, Stefan</em>;
<em>Heitmann, Uwe</em>;
<em>Vale, Maria Goreti R.</em>;
<br/><br/>
A new instrumental concept has been developed for atomic absorption spectrometry (AAS), using a high-intensity xenon short-arc lamp as continuum radiation source, a high-resolution double-echelle monochromator and a CCD array detector, providing a resolution of ~2 pm per pixel. Among the major advantages of the system are: i) an improved signal-to-noise ratio because of the high intensity of the radiation source, resulting in improved photometric precision and detection limits; ii) for the same reason, there are no more 'weak' lines, i.e. secondary lines can be used without compromises; iii) new elements might be determined, for which no radiation source has been available; iv) the entire spectral environment around the analytical line becomes 'visible', giving a lot more information than current AAS instruments; v) the CCD array detector allows a truly simultaneous background correction close to the analytical line; vi) the software is capable of storing reference spectra, e.g. of a molecular absorption with rotational fine structure, and of subtracting such spectra from the spectra recorded for a sample, using a least squares algorithm; vii) although not yet realized, the system makes possible a truly simultaneous multi-element AAS measurement when an appropriate two-dimensional detector is used, as is already common practice in optical emission spectrometry; vii) preliminary experiments have indicated that the instrumental concept could result in a more rugged analytical performance in the determination of trace elements in complex matrices.Direct electron transfer: an approach for electrochemical biosensors with higher selectivity and sensitivity10.1590/S0103-505320030002000082024-02-23T20:03:52.855000Z2020-08-09T06:48:42.529000ZFreire, Renato S.Pessoa, Christiana A.Mello, Lucilene D.Kubota, Lauro T.
<em>Freire, Renato S.</em>;
<em>Pessoa, Christiana A.</em>;
<em>Mello, Lucilene D.</em>;
<em>Kubota, Lauro T.</em>;
<br/><br/>
The most promising approach for the development of electrochemical biosensors is to establish a direct electrical communication between the biomolecules and the electrode surface. This review focuses on advances, directions and strategies in the development of third generation electrochemical biosensors. Subjects covered include a brief description of the fundamentals of the electron transfer phenomenon and amperometric biosensor development (different types and new oriented enzyme immobilization techniques). Special attention is given to different redox enzymes and proteins capable of electrocatalyzing reactions via direct electron transfer. The analytical applications and future trends for third generation biosensors are also presented and discussed.Production of organic mercury from Hg0: experiments using microcosms10.1590/S0103-505320030002000092024-02-23T20:03:52.855000Z2020-08-09T06:48:42.529000ZBisinoti, Márcia CristinaJardim, Wilson F.
<em>Bisinoti, Márcia Cristina</em>;
<em>Jardim, Wilson F.</em>;
<br/><br/>
Transformation of inorganic to organic mercury is a process known to occur in the water column as well as in sediment. However, little is known about the fate of metallic mercury in tropical environments. In this work the production of organic mercury in water and sediment under aerobic and anaerobic conditions was demonstrated in a microcosm setup using a 6:1 water: dry sediment ratio, after a spike of 0.1% (w/w) of Hg0. The rate of production of organic mercury in sediment was higher under anaerobic conditions (617 mg kg-1 day-1) than that obtained under aerobic conditions (280 mg kg-1 day-1). An attempt to evaluate the production of organic mercury in abiotic conditions was not possible due to drastic changes in the microcosm during sterilization when compared to the experimental conditions maintained under biotic conditions. It was concluded that metallic mercury, which enters the environment mainly due to gold-mining activities, undergoes a reactive dissolution in the aquatic medium, thus becoming a suitable substrate for the production of organic mercury in tropical environments.An automatic flow-batch standard-addition method for sodium determination in alcohol fuel by flame photometry10.1590/S0103-505320030002000102024-02-23T20:03:52.855000Z2020-08-09T06:48:42.529000ZAlmeida, Luciano F. deMartins, Valdomiro L.Silva, Edvan C. daMoreira, Pablo N. T.Araujo, Mario Cesar U.
<em>Almeida, Luciano F. De</em>;
<em>Martins, Valdomiro L.</em>;
<em>Silva, Edvan C. Da</em>;
<em>Moreira, Pablo N. T.</em>;
<em>Araujo, Mario Cesar U.</em>;
<br/><br/>
The Brazilian Regulatory Agency for fuel production and commercialization requires that the sodium concentration in alcohol fuel should be determined by flame photometry and that the analytical curves should be obtained with matrix-matched standards. Notwithstanding, this methodology can produce inexact results because alcohol fuel presents a significant variability in matrix composition and, consequently, in the matrix effect. This problem can be circumvented by using the standard addition method (SAM). However, this method is slow and laborious when it carried out by manual procedures. To overcome these drawbacks, an automatic flow-batch SAM for sodium determination in alcohol fuel by flame photometry is described. This system requires only one standard solution, handles about 80 - 140 samples per hour and consumes a total volume of sample and of standard solution smaller than 1.5 mL for each analysis. The results present a standard deviation usually less than 0.1 mg L-1 (n = 4).Reagent generation assisted by ultrasonic irradiation10.1590/S0103-505320030002000112024-02-23T20:03:52.855000Z2020-08-09T06:48:42.529000ZKorn, MauroAndrade, Marta V. A. S.Borges, Sivanildo S.Sousa, Clarivaldo S.Oliveira, Fábio S.
<em>Korn, Mauro</em>;
<em>Andrade, Marta V. A. S.</em>;
<em>Borges, Sivanildo S.</em>;
<em>Sousa, Clarivaldo S.</em>;
<em>Oliveira, Fábio S.</em>;
<br/><br/>
In this work, the potential of reagent generation assisted by ultrasonic irradiation was evaluated for Cr(III) oxidation and arsine formation. Free radical formation by sonolysis of aqueous solutions was evaluated. The sonication of an aqueous solution saturated with CCl4 leads to chlorine radical formation while the irradiation of water in the presence of metallic zinc leads to hydrogen production. The low relative standard deviations of the proposed procedures indicate that the method can be applied for analytical purposes.Monosegemented flow potentiometric titration for the determination of chloride in milk and wine10.1590/S0103-505320030002000122024-02-23T20:03:52.855000Z2020-08-09T06:48:42.529000ZVieira, Jonas A.Raimundo Jr., Ivo M.Reis, Boaventura F.Montenegro, M. Conceição B.S.M.Araújo, Alberto N.
<em>Vieira, Jonas A.</em>;
<em>Raimundo Jr., Ivo M.</em>;
<em>Reis, Boaventura F.</em>;
<em>Montenegro, M. Conceição B.s.m.</em>;
<em>Araújo, Alberto N.</em>;
<br/><br/>
An automated flow potentiometric titration procedure for the determination of chloride in milk and wine exploiting the monosegmented flow approach is described. The flow network was designed based on a six-way solenoid valve, controlled by a microcomputer running software written in VisualBasic 3.0, allowing selection of the titration conditions. An Ag2S tubular electrode selective for Cl- and a conventional Ag/AgCl electrode were employed as indicator and reference, respectively. An algorithm based on the potential difference between two subsequent titrant additions was developed, allowing to reach the end point in less than 10 attempts, with a precision better than 1.0%. The proposed system was evaluated by determining chloride in milk and wine, using a standard AgNO3 solution as titrant. Accuracy was ascertained by comparing the results with those obtained using the AOAC procedure. No significant difference at a 95% confidence level was observed.Improved separation of IA and IIA metal cations in matrices with high sodium concentration by capillary electrophoresis with contactless conductometric detection10.1590/S0103-505320030002000132024-02-23T20:03:52.855000Z2020-08-09T06:48:42.529000ZSilva, José A. Fracassi daRicelli, Nara L.Carvalho, Alexandre Z.Lago, Claudimir L. do
<em>Silva, José A. Fracassi Da</em>;
<em>Ricelli, Nara L.</em>;
<em>Carvalho, Alexandre Z.</em>;
<em>Lago, Claudimir L. Do</em>;
<br/><br/>
One of the most common uses of capillary electrophoresis with conductometric detection is the analysis of different samples containing alkaline and alkaline earth metals. However, the high sodium content, which is a very common occurrence, may cause loss of resolution of some peaks. In this work, the conditions and a running buffer suitable for serum and hemodialysis fluid analyses are presented. The approach basically consists in the reduction of mobilities of Ca2+ and Mg2+ by addition of methanol and lactate in the running buffer. Limits of detection in the range from 0.5 to 1.0 mmol L-1 with molar Na+/Ca2+ ratios as high as 1000 were obtained, which are conditions that exceed the requirements of the proposed determination.Boron isotope dilution in cellular fractions of coffee leaves Evaluated by Inductively Coupled Plasma Mass Spectrometry with direct injection nebulization (DIN-ICP-MS)10.1590/S0103-505320030002000142024-02-23T20:03:52.855000Z2020-08-09T06:48:42.529000ZBellato, Ana Cláudia S.Menegário, Amauri A.Giné, Maria Fernanda
<em>Bellato, Ana Cláudia S.</em>;
<em>Menegário, Amauri A.</em>;
<em>Giné, Maria Fernanda</em>;
<br/><br/>
Enriched 10B (94.14 atom %) was supplied to coffee plantlets for three months. Then boron isotope ratios were determined in the leaf cell compartments, cell wall, nuclei and chloroplast, after a sub-cellular fractionation procedure. The isotopic measurements were performed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) provided with a direct injection nebulizer (DIN), introducing a sample volume of 50 mL. Isotopic ratios from 1.002 to 1.326 were determined with precision characterized by RSD lower than 1.5% for the enriched cell fractions with B concentrations ranging from 3.3 to 10.8 mg g-1. The detection limit (3s) was 0.5 ng B mL-1. The average enrichments in 10B atom % found in the cell walls, nuclei and chloroplasts were 46.7, 44.5 and 48.8, respectively.Determination of ranitidine in drugs using a mercury coated platinum ultramicroelectrode and hanging mercury dropping electrode10.1590/S0103-505320030002000152024-02-23T20:03:52.855000Z2020-08-09T06:48:42.529000ZMalagutti, Andréa R.Mazo, Luiz H.
<em>Malagutti, Andréa R.</em>;
<em>Mazo, Luiz H.</em>;
<br/><br/>
The voltammetric behavior of ranitidine has been studied in aqueous media with a mercury coated platinum ultramicroelectrode (Hg-UME) and by HMDE. The LSV curves for the electroreduction of ranitidine showed that the compound presents two reduction waves in pH < 4.0 and only one in pH > 4.0, the observed waves being attributed to the reduction of the nitro group to hydroxylamine. A linear relation between the current peak or limiting current and the ranitidine concentration using HMDE or Hg-UME was observed, demonstrating that these ultramicroelectrodes can be used in the analytical determination of ranitidine. An alternative and more sensitive methodology for the analytical determination of ranitidine by SWV was also developed, with a detection limit of 3.5 x 10-8 mol L-1 (or 11 mg L-1). The apparent recovery (AR) studies proved the accuracy and precision of the assay developed. The excipients found in comercial Antak tablets (Glaxo Wellcome) and the generic from EMSâ do not interfere in the determination.Applications of capillary electrophoresis to the analysis of compounds of clinical, forensic, cosmetological, environmental, nutritional and pharmaceutical importance10.1590/S0103-505320030002000162024-02-23T20:03:52.855000Z2020-08-09T06:48:42.529000ZTavares, Marina F. M.Jager, Alessandra V.Silva, Clóvis L. daMoraes, Edgar P.Pereira, Elisabete A.Lima, Elizabete C. deFonseca, Fabiana N.Tonin, Fernando G.Micke, Gustavo A.Santos, Márcia R.Oliveira, Marcone A. L. deMoraes, Maria de Lourdes L. deKampen, Maria Helena vanFujiya, Neide M.
<em>Tavares, Marina F. M.</em>;
<em>Jager, Alessandra V.</em>;
<em>Silva, Clóvis L. Da</em>;
<em>Moraes, Edgar P.</em>;
<em>Pereira, Elisabete A.</em>;
<em>Lima, Elizabete C. De</em>;
<em>Fonseca, Fabiana N.</em>;
<em>Tonin, Fernando G.</em>;
<em>Micke, Gustavo A.</em>;
<em>Santos, Márcia R.</em>;
<em>Oliveira, Marcone A. L. De</em>;
<em>Moraes, Maria De Lourdes L. De</em>;
<em>Kampen, Maria Helena Van</em>;
<em>Fujiya, Neide M.</em>;
<br/><br/>
Since its inception in the 80's, capillary electrophoresis has matured into a well-established separation technique, actually encompassing a family of electrodriven techniques with distinct separation mechanisms and selectivity, performed in a single capillary column. In this work, the versatility of capillary electrophoresis in handling materials from a diversity of chemical classes and complex sample matrices is illustrated by representative applications in the clinical, forensic, cosmetological, environmental, nutritional and pharmaceutical areas, grouping together our own research interests and results.Determination of cadmium in sediments and in sewage sludge by slurry sampling electrothermal atomic absorption spectrometry using iridium as permanent modifier10.1590/S0103-505320030002000172024-02-23T20:03:52.855000Z2020-08-09T06:48:42.529000ZBorges, Daniel L. G.Dias, Lúcia F.Veiga, Márcia A. M. S. daCurtius, Adilson J.
<em>Borges, Daniel L. G.</em>;
<em>Dias, Lúcia F.</em>;
<em>Veiga, Márcia A. M. S. Da</em>;
<em>Curtius, Adilson J.</em>;
<br/><br/>
A procedure for the determination of Cd in sediment and sewage sludge as slurries by electrothermal atomic absorption spectrometry is proposed. The slurry, 1 mg mL-1, was prepared by mixing sample ground to a particle size £ 50 mm with 5% v/v nitric acid in an ultrasonic bath. The homogeneity of the slurries was assured by passing a constant flow of argon into the autosampler cup, just before transferring an aliquot to the graphite furnace. Two permanent modifiers deposited on the platform were tested: Ru and Ir. Modifiers in solution were also tested: Pd plus Mg and phosphate alone or plus Mg. The Ir-treated tube was adopted due to its good performance as modifier and also for practical reasons. About 80% of Cd is extracted to the water phase of the slurry. To test the accuracy of the method, three certified materials were analyzed: a marine sediment, a river sediment and a domestic sewage sludge. The concentrations obtained, using calibration against aqueous standards prepared in the same medium as the slurries, are in agreement with the certified values, at a confidence level of 95%, according to the Student-t test. The limit of detection (3s) was 43 ng g-1 in the solid sample and the relative standard deviation for the sediment MESS-2 was 2.3% (n = 10).Determination of catecholamines in pharmaceutical formulations using a biosensor modified with a crude extract of fungi laccase (Pleurotus ostreatus)10.1590/S0103-505320030002000182024-02-23T20:03:52.855000Z2020-08-09T06:48:42.529000ZLeite, Oldair D.Fatibello-Filho, OrlandoBarbosa, Aneli de M.
<em>Leite, Oldair D.</em>;
<em>Fatibello-Filho, Orlando</em>;
<em>Barbosa, Aneli De M.</em>;
<br/><br/>
A carbon paste biosensor modified with a crude enzymatic extract of the Pleurotus ostreatus fungi as a laccase source is proposed for catecholamine determination in pharmaceutical formulations. This enzyme catalyzes the oxidation of adrenaline or dopamine in the corresponding quinones and the current obtained in the electrochemical reduction of each of the products is related to the concentration of these catecholamines in the sample solution. The effect of the laccase concentration from 0.29 to 1.8 U/mg of carbon paste, pH from 3.0 to 8.0, scan rate from 10 to 40 mV s-1 and potential pulse amplitude from 10 to 60 mV on the differential pulse voltammetric response was investigated. The relative standard deviation was smaller than 1.8% for a 2.8 x 10-4 mol L-1 hydroquinone solution at pH 7.0 (n=10). Recoveries varied from 97.3 to 101% for adrenaline and from 95.8 to 102% for dopamine. The analytical curves were rectilinear in the adrenaline concentration range from 6.0 x 10-5 to 7.0 x 10-4 mol L-1 and 7.0 x 10-5 to 4.0 x 10-4 mol L-1 for dopamine, with detection limits of 7.9 x 10-6 mol L-1 and 9.8 x 10-6 mol L-1, respectively. This biosensor was used for adrenaline and dopamine determinations in pharmaceutical formulations. The results obtained using the proposed biosensor are in close agreement with those obtained using an American Pharmacopoeia procedure at a 95% confidence level.Analysis of pesticide residues in Brazilian medicinal plants: matrix solid phase dispersion versus conventional (European Pharmacopoeia) methods10.1590/S0103-505320030002000192024-02-23T20:03:52.855000Z2020-08-09T06:48:42.529000ZZuin, Vânia G.Yariwake, Janete H.Lanças, Fernando M.
<em>Zuin, Vânia G.</em>;
<em>Yariwake, Janete H.</em>;
<em>Lanças, Fernando M.</em>;
<br/><br/>
This paper proposes a method based on matrix solid phase dispersion (MSPD) to determine the presence of organochlorine (OC) and organophosphorus (OP) pesticide residues in species of Passiflora L. (passion fruit) leaves by gas chromatography, using an electron capture detector (HRGC-ECD). A comparison with conventional methods, mainly the European Pharmacopoeia method (EP), showed MSPD to be efficient, fast, simple and easy to perform. To date, there are no official methods or limits that take into account Brazil's "real life" conditions in the analysis of pesticides in medicinal plants and phytomedicines, and the MSPD method described herein has proved to be a feasible one for the analysis of Passiflora L-based phytomedicines.Analytical performance of an inductively coupled plasma optical emission spectrometry with Dual View configuration10.1590/S0103-505320030002000202024-02-23T20:03:52.855000Z2020-08-09T06:48:42.529000ZSilva, Júlio C. J.Baccan, NivaldoNóbrega, Joaquim A.
<em>Silva, Júlio C. J.</em>;
<em>Baccan, Nivaldo</em>;
<em>Nóbrega, Joaquim A.</em>;
<br/><br/>
The analytical performance of axially and radially viewed inductively coupled plasma optical emission spectrometers (AX-ICP OES and RD-ICP OES, respectively) were evaluated in terms of the Mg II/Mg I ratio, matrix effects, and detection limits (LOD). All solutions were made in either 1% v v-1 nitric acid or in a 10% v v-1 water-soluble tertiary amine solution (CFA-C) adjusted to pH 8. Using a nebulization gas flow-rate of 0.5 L min-1 and applied power of 1.3 kW, Mg II/Mg I ratio was at least 15 in any medium for both configurations. Under robust conditions, plasma processes were practically not affected by the presence of 0.1% m v-1 of Ca, K, or Na in both configurations. However, interference effects were observed with non-robust conditions, mainly with AX-ICP OES in both media. The best detection limits were obtained using AX-ICP OES under robust conditions, with solutions prepared in the amine medium.Determination of vitamin B6 (pyridoxine) in pharmaceutical preparations by cyclic voltammetry at a copper(II) hexacyanoferrate(III) modified carbon paste electrode10.1590/S0103-505320030002000212024-02-23T20:03:52.855000Z2020-08-09T06:48:42.529000ZTeixeira, Marcos F. S.Segnini, AlineMoraes, Fernando C.Marcolino-Júnior, Luiz H.Fatibello-Filho, OrlandoCavalheiro, Éder T. G.
<em>Teixeira, Marcos F. S.</em>;
<em>Segnini, Aline</em>;
<em>Moraes, Fernando C.</em>;
<em>Marcolino-Júnior, Luiz H.</em>;
<em>Fatibello-Filho, Orlando</em>;
<em>Cavalheiro, Éder T. G.</em>;
<br/><br/>
A copper(II) hexacyanoferrate(III) (CuHCF) modified carbon paste electrode was used for the electroanalytical determination of pyridoxine (vitamin B6) in pharmaceutical preparations, using cyclic voltammetry. Diverse parameters were investigated for the optimization of the sensor response, such as composition of the electrode, electrolytic solution, effect of pH, scan rate of potential and interferences. The optimum conditions were found at an electrode composition of 20% CuHCF, 55% graphite and 25% mineral oil (m/m) in an acetate buffer (pH 5.5) containing 0.05 mol L-1 of NaCl. The range of determination of pyridoxine was from 1.2 x 10-6 to 6.9 x 10-4 mol L-1. The procedure was successfully applied to the determination of vitamin B6 in formulation preparations. The CuHCF modified carbon paste electrode gave results comparable to those obtained using spectrophotometry.LC-MS-MS identification of drug metabolites obtained by metalloporphyrin mediated oxidation10.1590/S0103-505320030002000222024-02-23T20:03:52.855000Z2020-08-09T06:48:42.529000ZMaurin, Andrea J. M.Iamamoto, YassukoLopes, Norberto P.Lindsay-Smith, John R.Bonato, Pierina S.
<em>Maurin, Andrea J. M.</em>;
<em>Iamamoto, Yassuko</em>;
<em>Lopes, Norberto P.</em>;
<em>Lindsay-Smith, John R.</em>;
<em>Bonato, Pierina S.</em>;
<br/><br/>
In this paper we report the application of liquid chromatography-mass spectrometry (LC-MS-MS) to the identification of the products formed by oxidation of albendazole and disopyramide with metalloporphyrins in dichloroethane, using iodosylbenzene as an oxygen donor. Our results show that LC-MS-MS is a powerful tool to study the in vitro metabolism of drugs, allowing the identification of known and unknown metabolites. In addition, it was observed that the catalyst system used resulted in the formation of the same metabolites as obtained in vivo, although for disopyramide other products were also observed.FIA-FAAS method for tannin determination based on a precipitation reaction with hemoglobin10.1590/S0103-505320030002000232024-02-23T20:03:52.855000Z2020-08-09T06:48:42.529000ZFerreira, Edilene C.Souza, Gilberto B.Nogueira, Ana Rita A.
<em>Ferreira, Edilene C.</em>;
<em>Souza, Gilberto B.</em>;
<em>Nogueira, Ana Rita A.</em>;
<br/><br/>
A flow system, coupled with flame atomic absorption spectrometry (FIA-FAAS), was developed for tannin determination in pigeon pea samples, exploring the precipitation reaction between tannins and proteins. Sample extracts obtained by sonication with a 50% (v/v) methanol solution were introduced into the system and induced to react with a hemoglobin solution. The precipitate produced was retained on a filter located in the analytical flow. A reversed flow of 1% (w/v) sodium dodecyl sulfate solution was used for solubilization of the precipitate from the filter and to conduct the tannin-hemoglobin complex to the FAAS, to quantify the iron ions present in the hemoglobin structure. A tannic acid solution was used to prepare the analytical curve. The proposed method allowed determination of 30 samples per hour, a standard deviation of 9.7% (n=10), and a quantification limit of 0.27 mg L-1 for tannic acid.Determination of fluoride in coal using pyrohydrolysis for analyte separation10.1590/S0103-505320030002000242024-02-23T20:03:52.855000Z2020-08-09T06:48:42.529000ZDressler, Valderi L.Pozebon, DirceFlores, Éder L. M.Paniz, José N. G.Flores, Érico M. M.
<em>Dressler, Valderi L.</em>;
<em>Pozebon, Dirce</em>;
<em>Flores, Éder L. M.</em>;
<em>Paniz, José N. G.</em>;
<em>Flores, Érico M. M.</em>;
<br/><br/>
A method for the determination of fluoride in coal using pyrohydrolysis for sample decomposition is proposed. An apparatus was constructed, and the influence of vanadium pentoxide (V2O5) as a catalyst for the pyrohydrolysis reaction was investigated. It was verified that V2O5 does not influence the release of fluoride from coal. Certified and non-certified samples were analysed using an ion selective electrode (ISE) for analyte detection. Precise (RSD < 7%) and accurate (recovery in accordance with certified values) results were obtained. The limit of quantification (LOQ) of the method was 5.0 mgF/g of sample, using 20 mg of sample and a final dilution to 10 mL. The sample frequency was 5 samples h-1.