Titulador potenciométrico automatizado baseado em sistema de fluxo monossegmentado

Ganzarolli, Edgard Moreira; Lehmkuhl, Arilson; Queiróz, Roldão Rosevelt R. de; Souza, Ivan Gonçalves de

doi:10.1590/s0100-40421999000100011

Cited by 8 publications

(5 citation statements)

References 4 publications

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“…The analytical performance of the proposed system is comparable to monosegmented titrators described in the literature, 22,23,[25][26][27] presenting an advantage when compared with ordinary sequential injection analysis titration systems, 15-17 since it does not need a calibration step with standard solutions. Table 2.…”

Section: Resultsmentioning

confidence: 77%

“…The precision for determination of the end point (stop condition) was set in 1.0%, providing sample throughputs of eight and ten samples hour -1 for milk and wine, respectively. The lower analytical frequency for milk is due to coagulation, which takes place when the nitric acid is added, requiring a longer reaction coil to provide a proper mixing of sample and titrant.The analytical performance of the proposed system is comparable to monosegmented titrators described in the literature, 22,23,[25][26][27] presenting an advantage when compared with ordinary sequential injection analysis titration systems, 15-17 since it does not need a calibration step with standard solutions. Table 2.…”

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confidence: 77%

“…A potentiometric methodology based on a successive aproximation algorithm has also been proposed to carry out titration in a monosegmented flow system. 27 This work describes an automatic sequential injection flow system, which incorporates the monosegmented approach, to perform potentiometric titrations. The end point was achieved by employing a successive approximation strategy and the feasibility of the system was ascertained by determination of chloride in milk and wine, using a tubular silver sulphide indicator electrode.…”

Section: Introductionmentioning

confidence: 99%

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Monosegemented flow potentiometric titration for the determination of chloride in milk and wine

Vieira¹,

Raimundo²,

Reis³

et al. 2003

J. Braz. Chem. Soc.

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Este trabalho descreve um procedimento automático em fluxo monossegmentado para titulação potenciométrica aplicado à determinação de cloreto em leite e vinho. O sistema de fluxo foi desenvolvido com base em uma válvula solenóide de 6 vias, controlada por um microcomputador através de um programa escrito em VisualBasic 3.0. Um eletrodo indicador tubular de Ag 2 S seletivo a Cl -e um eletrodo de referência convencional de Ag/AgCl foram empregados. Um algoritmo baseado na diferença de potencial entre duas adições subsequentes de titulante foi desenvolvido, possibilitando a determinação do ponto final da titulação em, no máximo, 10 tentativas, com uma precisão melhor que 1,0%. O sistema proposto foi avaliado pela determinação de cloreto em leite e vinho, usando uma solução padrão de AgNO 3 como titulante. A exatidão foi avaliada comparando-se os resultados com aqueles obtidos pelo método da AOAC, não sendo encontradas diferenças significativas ao nível de confiança de 95%.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 Ag 2 S 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 AgNO 3 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.Keywords: potentiometric titration, monossegmented flow, multicommutation, ion selective electrode, chloride in milk, chloride in wine IntroductionThe mechanisation of the potentiometric titration procedure was first described in 1914 1 and the introduction of flow injection analysis in 1975 2 improved this mechanisation, including for potentiometric and spectrophotometric titrations. [3][4][5] Flow injection titration usually employs a calibration step, in which the peak width (instead of height) is taken as the analytical parameter. The simplest approach, which was first proposed by Ruzicka et al. 6 in 1977, employs a single line manifold and is still being employed nowadays. 7,8 Different alternatives have been proposed to determine the stoichiometric point in a flow titration procedure. Continuous flow systems based on the ratio of sample and titrant flow rates have been exploited to achieve the end point. 9,10 In order to vary the flow rates of the solutions independently, two peristaltic pumps are necessary, which 260 Vieira et al. J. Braz. Chem. Soc. represents the main drawback of these...

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Section: Resultsmentioning

confidence: 77%

mentioning

confidence: 77%

Section: Introductionmentioning

confidence: 99%

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Monosegemented flow potentiometric titration for the determination of chloride in milk and wine

Vieira¹,

Raimundo²,

Reis³

et al. 2003

J. Braz. Chem. Soc.

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“…Different approaches have been proposed to implement titration in flow analysis, based on the ratio of the flow rates of the sample and titrant, 1,2 triangleprogrammed flow, 3 dispersion of the sample in the titrant carrier fluid, 4 flow-batch 5 and monosegmented systems. [6][7][8] Although flow titration can be performed easier and faster than manual titration, it is still slow when compared with ordinary flow methodologies, because the procedures are usually based on the dispersion concept and a calibration J. Braz. Chem.…”

Section: Introductionmentioning

confidence: 99%

Gran method for end point anticipation in monosegmented flow titration

Aquino¹,

Pasquini²,

Rohwedder³

et al. 2004

J. Braz. Chem. Soc.

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Este trabalho descreve o uso do método de linearização de Gran em titulações em fluxo monossegmentado com detecção potenciométrica. O programa de controle pode estimar o ponto final após a adição de três ou quatro alíquotas de titulante. Alternativamente, o ponto final da titulação pode ser determinado pelo método da segunda derivada. Neste caso, alíquotas adicionais de titulante são adicionadas até a proximidade do ponto final e três pontos antes e após o ponto estequiométrico são usados para o cálculo de ponto final. O desempenho do sistema foi avaliado pela determinação de cloreto em soluções isotônicas e parenterais. O sistema emprega um eletrodo indicador tubular de Ag 2 S/AgCl. Uma titulação típica, realizada de acordo com a definição IUPAC, requer apenas 60 µL de amostra e aproximadamente o mesmo volume de titulante (AgNO 3). Uma titulação completa pode ser realizada entre 1 e 5 min. Foram obtidas exatidão e precisão (desvio padrão relativo de 10 replicatas) de 2% e 1% para o método de Gran e 1% e 0,5% para o método de Gran associado ao método da segunda derivada, respectivamente. O sistema proposto reduz o tempo para realizar uma titulação, com baixo consumo de amostra e reagente, além de possibilitar uma amostragem automática completa e adição de titulante sem a necessidade de uma etapa de calibração. An automatic potentiometric monosegmented flow titration procedure based on Gran linearisation approach has been developed. The controlling program can estimate the end point of the titration after the addition of three or four aliquots of titrant. Alternatively, the end point can be determined by the second derivative procedure. In this case, additional volumes of titrant are added until the vicinity of the end point and three points before and after the stoichiometric point are used for end point calculation. The performance of the system was assessed by the determination of chloride in isotonic beverages and parenteral solutions. The system employs a tubular Ag 2 S/AgCl indicator electrode. A typical titration, performed according to the IUPAC definition, requires only 60 µL of sample and about the same volume of titrant (AgNO 3) solution. A complete titration can be carried out in 1-5 min. The accuracy and precision (relative standard deviation of ten replicates) are 2% and 1% for the Gran and 1% and 0.5% for the Gran/derivative end point determination procedures, respectively. The proposed system reduces the time to perform a titration, ensuring low sample and reagent consumption, and full automatic sampling and titrant addition in a calibration-free titration protocol.

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“…While the titration was carried out, the interval of uncertainty related to the titrant volume was minimized, until a prede® ned interval was reached, indicating the titration end point. Ganzarolli et al [31] also described an automatic potentiometric titrator to determine strong and weak acids with a standard sodium hydroxide solution. The end-point was determined by injecting several mixtures of sample and titrant in diå erent volumetric ratios, de® ned according to a successive approximation algorithm.…”

Section: Introductionmentioning

confidence: 99%

Simultaneous multiple injection to perform titration and standard addition in mono-segmented flow analysis

Raimundo¹

2001

Journal of Automated Methods & Management in Chemistry

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An automated system to perform titration and standard addition in monosegemented £ow analysis by employing the simultaneous multiple injection is described. The system was controlled by a PC-AT-386 microcomputer through a home-made parallel interface, employing a diode array spectrophotometer as detector. Software was written in QuickBasic 4.5 to control the system and for data acquisition. A three-way solenoid valve was used in conjunction with a proportional injector to add the titrant solution or the standard solution to the sample, to carry out titration or standard addition, respectively. Only one standard solution was used in each procedure and di¡erent quantities of titrant or standard were added to the sample by controlling the time interval in which the solenoid valve was switched on. Titration and standard addition curves similar to those of the manual methods were obtained in both cases, since the sample dispersion was very low due to the air bubbles of the monosegment. The titration system was evaluated through the determination of Fe(II) with a KMnO 4 standard solution in pharmaceutical preparations. The standard addition process was assessed by determining Cr(VI) in natural waters and domestic wastewater using the diphenylcarbazide method. The results obtained in both methodologies did not di¡er signi¢cantly from the reference methods at a 95% con¢dence level.

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Titulador potenciométrico automatizado baseado em sistema de fluxo monossegmentado

Cited by 8 publications

References 4 publications

Monosegemented flow potentiometric titration for the determination of chloride in milk and wine

Monosegemented flow potentiometric titration for the determination of chloride in milk and wine

Gran method for end point anticipation in monosegmented flow titration

Simultaneous multiple injection to perform titration and standard addition in mono-segmented flow analysis

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