Search

Your search keyword '"Richter, Eduardo M."' showing total 539 results
Start Over Author "Richter, Eduardo M."
539 results on '"Richter, Eduardo M."'

156. Solenoid Micro‐pumps: A New Tool for Sample Introduction in Batch Injection Analysis Systems with Electrochemical Detection.

Author

Rocha, Diego P., Cardoso, Rafael M., Mendonça, Dianderson M. H., Richter, Eduardo M., da Silva, Sidnei G., Batista, Alex D., and Muñoz, Rodrigo A. A.

Subjects
ELECTROCHEMICAL electrodes, VOLTAMMETRY, MICROPUMPS, SOLUTION (Chemistry), DERIVATIZATION, ELECTROLYTES
Abstract

Abstract: This work presents the use of solenoid micro‐pumps as a new strategy for sample introduction in batch‐injection analysis (BIA). The volume of solution dispensed on each pulse of the solenoid micro‐pump (μL) is used as fixed and reproducible injection volume for BIA. In this system, the injection steps are possible in stopped flow mode resulting in low background noise levels, which would not be possible under continuous flow conditions and using solenoid micro‐pumps. As a proof‐of‐concept, amperometric and square‐wave voltammetric (SWV) determination of dopamine was demonstrated as well as anodic‐stripping voltammetry (ASV) of metals. The micro‐pump provided injections of 14 μL of solution per pulse at 512 μL s−1 over the electrode during electrochemical measurement. Moreover, fast injections of analyte or electrolyte were programmed during deposition or conditioning steps of ASV for analyte preconcentration or electrode cleaning. The proposed system improved limits of detection and sensitivity (2‐fold), precision and sample throughput in comparison with traditional BIA due to enhanced mass transfer and consequent reduced dispersion of analyte, and possible control of injections without analyst intervention. This work opens new possibilities of applications of the BIA system, including on‐line sample treatment (derivatization or dilution steps). [ABSTRACT FROM AUTHOR]

Published
2018
Full Text
View/download PDF

157. Stripping Voltammetric Determination of Mercury in Fish Oil Capsules Using a Screen‐printed Gold Electrode.

Author

Squissato, André L., Rocha, Diego P., Almeida, Eduardo S., Richter, Eduardo M., and Munoz, Rodrigo A. A.

Subjects
MERCURY electrodes, VOLTAMMETRY, FISH oils, GOLD electrodes, TEMPERATURE effect, OXIDATION
Abstract

Abstract: This work presents a simple electrochemical method for Hg determination in fish oil capsules using anodic stripping voltammetry (ASV) on a screen‐printed gold electrode (SPGE). Samples were treated in an ultrasonic bath for 15 min in the presence of a 1 : 1 (v/v) concentrated HCl/H2O2 mixture at room temperature. The limit of detection (LOD) was estimated as 0.25 μg L−1 (corresponding to 7.6 μg kg−1 of oil) with a linear range between 5 and 400 μg L−1 (90 s of deposition time). The analyzed fish oil samples presented Hg concentration below the LOD value. Recovery values for samples spiked with oil standard containing Hg ranged from 95 to 105 %. The method is precise (inter‐day and intra‐day RSD<4 % for n=3) as well as the SPGE sensors (RSD=4.3 %, n=3), which were used continuously (around 100 analyses without replacement) under such oxidation media. The proposed method is feasible to be applied for on‐site determinations due to the portability of sensing and sample treatment approaches. [ABSTRACT FROM AUTHOR]

Published
2018
Full Text
View/download PDF

159. Determinação simultânea de ácido ascórbico e ácido acetilsalicílico usando análise por injeção em fluxo com detecção amperométrica pulsada

Author

Miranda, Joyce A. T. de, Cunha, Rafael R., Gimenes, Denise T., Munoz, Rodrigo A. A., and Richter, Eduardo M.

Subjects
FIA, simultaneous determination, multiple pulse amperometry
Abstract

A simple flow system with multiple pulse amperometric detection using a single working electrode is proposed for simultaneous determination of ascorbic (AA) and acetylsalicylic (AAS) acids in pharmaceutical formulations. The procedure is based on application of two potential pulses: 0.90 V/50 ms: oxidation and determination of AA without the interference of AAS; 1.35 V/50 ms: oxidation of both compounds and quantification of AAS by current subtraction using a correction factor. Sampling rate was estimated as 125 injections per hour and the limits of detection were 0.17 and 0.16 µmol L-1 for AA and AAS, respectively. Results for commercial samples agreed with those obtained using HPLC.

Published
2012

162. Simultaneous Determination of Caffeine, Ibuprofen, and Paracetamol by Flow-injection Analysis with Multiple-pulse Amperometric Detection on Boron-doped Diamond Electrode

Author

Chaves, Sandro C., primary, Aguiar, Priscila N. C., additional, Torres, Lívia M. F. C., additional, Gil, Eric S., additional, Luz, Rita C. S., additional, Damos, Flávio S., additional, Munoz, Rodrigo A. A., additional, Richter, Eduardo M., additional, and dos Santos, Wallans T. P., additional

Published
2015
Full Text
View/download PDF

163. Simultaneous determination of caffeine, paracetamol, and ibuprofen in pharmaceutical formulations by high-performance liquid chromatography with UV detection and by capillary electrophoresis with conductivity detection

Author

Cunha, Rafael R., primary, Chaves, Sandro C., additional, Ribeiro, Michelle M. A. C., additional, Torres, Lívia M. F. C., additional, Muñoz, Rodrigo A. A., additional, Santos, Wallans T. P. Dos, additional, and Richter, Eduardo M., additional

Published
2015
Full Text
View/download PDF

166. Construção e caracterização de um detector eletroquímico para análises em fluxo

Author

Santos, Wallans Torres P. dos, Azevedo, Eduardo F., Richter, Eduardo M., and Albuquerque, Yaico D. Tanimoto de

Subjects
flow analysis, wall-jet cell, electrochemical detector
Abstract

The present work describes a low-cost electrochemical "wall-jet" detector for flow analysis. The electrolytic solution enters into the cell through a tube of stainless steel (200 to 300 µm i.d), reaching to the center of the working electrode perpendicularly and then being mixed to the remaining solution in the cell, which flows under atmospheric pressure into a waste reservoir. The proposed electrochemical detector can be used with any type of working electrode, from commercial to home-made, such as glassy carbon and metallic electrodes (modified or unmodified), which enlarge the applications of the electrochemical detector.

Published
2009

168. Uso da pressão gerada por uma coluna de água para controle da vazão em sistemas de análises em fluxo

Author

Santos, Wallans T. P. dos, Ceolin, Marselha P., Albuquerque, Yaico D. T. de, and Richter, Eduardo M.

Subjects
flow analysis, water column, flow rates control
Abstract

This work presents a new approach to control the flow rate in hydrodynamic flow experiments. The combination of air pressure generated by an aquarium air pump and the pressure generated by a water column were used for this purpose. This device supports a stable flow rate without pulsation for a long period of time. Furthermore, the flow rate can be easily controlled at various values in one or more streams. The performance of this approach was investigated using Fe(CN)6(4-) solutions in flowing systems using amperometric and voltammetric detection in wall-jet configuration. The results showed that the performance of the proposed device was better than a commercial peristaltic pump. It suggests that this approach can be used successfully in flow analysis systems.

Published
2007

169. Uso de frascos de polipropileno descartáveis no pré-tratamento de amostras de água para determinação de chumbo, cobre e mercúrio por voltametria de onda quadrada

Author

Richter, Eduardo M., Lago, Claudimir L. do, and Angnes, Lúcio

Subjects
polypropylene vials, water analysis, sample pretreatment
Abstract

In this work a simple and versatile procedure is described for treating water samples using small polypropylene (PP) vials (4 mL) for determining heavy metals by square wave voltammetry (SWV). This procedure involves treatment with nitric acid (0.2 mol L-1) and boiling in a water-bath (~ 100 ºC). This process is completed after one hour and allows the pretreatment of several samples simultaneously. The accuracy was estimated using addition/recovery studies and certified water sample analysis, yielding an agreement near to 100%.

Published
2006

170. Multímetro interfaceado de baixo custo para aquisição de dados

Author

Richter, Eduardo M., Rocha, Fábio R. P., and Angnes, Lúcio

Subjects
data acquisition, flow analysis, digital multimeter
Abstract

A digital multimeter (~U$ 240.00 on the national market) connected to a microcomputer by a RS-232 serial interface is proposed for data acquisition in equipment with analog output. Data are measured at the rate of 2 points per second and stored in text files by the software that accompanies the device, running in a Windows environment. The performance of the multimeter was verified by monitoring the transient signals generated in flow injection systems associated with fluorimetric, spectrophotometric and flame photometric detection. In addition, the performance of the proposed device was similar to that attained by employing an interface card with a 12-bit analog-to-digital converter for acquisition of the signals generated by a capillary electrophoresis equipment with oscillometric detection.

Published
2004

171. Multímetro interfaceado de baixo custo para aquisição de dados

Author

Richter,Eduardo M., Rocha,Fábio R. P., and Angnes,Lúcio

Subjects
data acquisition, flow analysis, digital multimeter
Abstract

A digital multimeter (~U$ 240.00 on the national market) connected to a microcomputer by a RS-232 serial interface is proposed for data acquisition in equipment with analog output. Data are measured at the rate of 2 points per second and stored in text files by the software that accompanies the device, running in a Windows environment. The performance of the multimeter was verified by monitoring the transient signals generated in flow injection systems associated with fluorimetric, spectrophotometric and flame photometric detection. In addition, the performance of the proposed device was similar to that attained by employing an interface card with a 12-bit analog-to-digital converter for acquisition of the signals generated by a capillary electrophoresis equipment with oscillometric detection.

Published
2004

183. Voltammetric Determination of Pb, Cu and Hg in Biodiesel Using Gold Screen-printed Electrode: Comparison of Batch-injection Analysis with Conventional Electrochemical Systems.

Author

Tormin, Thiago F., Oliveira, Gracy K. F., Richter, Eduardo M., and Munoz, Rodrigo A. A.

Subjects
VOLTAMMETRY, ELECTROCHEMICAL analysis, LEAD, CLASS B metals, ELECTRODES
Abstract

This article compares the use of batch-injection analysis (BIA) with a conventional batch system for the anodic stripping voltammetric (ASV) determination of Pb, Cu and Hg in biodiesel using screen-printed gold electrode (SPGE). The optimized BIA conditions were 200 µL of injection volume of the digested samples at 5 µL s−1 directly on the working electrode of the SPGE immersed in 0.1 mol L−1 HCl solution. Therefore, BIA-ASV presented the advantages of low sample consumption, which extended the SPGE lifetime to a whole working day of analyses, and potential for on-site analysis using battery-powered micropipettes and potentiostats. Although presenting lower sensitivity than conventional systems, the BIA-ASV presented detection limit values of 1.0, 0.5 and 0.7 µg L−1, respectively for Pb, Cu and Hg, a linear range between 20 and 280 µg L−1, and adequate recovery values (90-110 %) for spiked biodiesel samples. [ABSTRACT FROM AUTHOR]

Published
2016
Full Text
View/download PDF

184. Voltammetric Lead Determination in Aviation Fuel Samples Using a Screen-Printed Gold Electrode and Batch-Injection Analysis.

Author

Almeida, Eduardo S., Richter, Eduardo M., and Munoz, Rodrigo A. A.

Subjects
*AIRCRAFT fuels, *GOLD electrodes, *LEAD, *VOLTAMMETRY, *ORGANIC compounds, *MICROPIPETTES, *POTENTIOSTAT
Abstract

This work presents the lead determination in aviation (bio)fuels using disposable screen-printed gold electrodes (SPGEs) adapted on a batch-injection cell associated with a micropipette for portable analysis. The method involves injections of 200 µL of sample or standard solutions at controlled dispensing rate (4.8 µL s−1) during deposition step (−550 mV for 90 s), followed by anodic-stripping voltammetry. Either samples treated by sonication or dry-ashing can be analyzed with detection limits of 0.0071 and 0.0008 µg g−1 Pb, respectively. A single SPGE can be applied for 60 consecutive measurements (or 120 for samples dry-ashed). The ultrasound-assisted treatment is faster, safer, and easily adapted for on-site analyses, especially considering the portable characteristics of commercially-available potentiostats and batch-injection analysis cell using SPGEs. [ABSTRACT FROM AUTHOR]

Published
2016
Full Text
View/download PDF

185. Batch-injection versus Flow-injection Analysis Using Screen-printed Electrodes: Determination of Ciprofloxacin in Pharmaceutical Formulations.

Author

Stefano, Jéssica S., Cordeiro, Denise S., Marra, Mariana C., Richter, Eduardo M., and Munoz, Rodrigo A. A.

Subjects
MULTIWALLED carbon nanotubes, CIPROFLOXACIN, ANTIBIOTICS, QUINOLONE antibacterial agents, CAPILLARY electrophoresis
Abstract

This article highlights the potential use of multi-walled carbon-nanotube modified screen-printed electrodes (SPEs) for the amperometric sensing of ciprofloxacin and compares the association of batch-injection analysis (BIA) and flow-injection analysis (FIA) with amperometric detection. Both analytical systems provided precise (RSD<5 %) and sensitive determination of ciprofloxacin (LOD<0.1 μmol L−1) within wide linear range (up to 200 μmol L−1). Accuracy of both methods was attested by recovery values (93-107 %) and comparison with capillary electrophoresis. The BIA system is completely portable (especially due to association with SPEs) and provided faster analyses (130 h−1) and more sensitive detection than the FIA system due to the higher flow rates of injection. [ABSTRACT FROM AUTHOR]

Published
2016
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results