Automatic potentiometric titration in monosegmented flow system exploiting binary search

Martelli, Patrícia Benedini; Reis, Boaventura F.; Korn, Mauro; Lima, José L.F.C.

doi:10.1016/s0003-2670(99)00092-6

Cited by 45 publications

(32 citation statements)

References 20 publications

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“…A review about analytical applications of conducting polymers in potentiometric sensors has been published by Kubota and co-workers. 17 The construction of a hydrogen ion-selective potentiometric electrode based on a tridodecylamine ionophore dispersed in a poly(vinylchloride) (PVC) membrane, 18,19 or poly(1-aminoanthracene) films 20 has been described. In addition, Rodwedder et al 21 and Fatibello and co-workers [22][23][24][25] have shown the use of coated graphite epoxy ion selective electrodes for determinaton of cations using ion-pair formation with tricaprylylmethylammonium cation in a PVC matrix.…”

Section: Potentiometric Sensorsmentioning

confidence: 99%

Electrochemical sensors: a powerful tool in analytical chemistry

Stradiotto¹,

Yamanaka²,

Zanoni³

2003

J. Braz. Chem. Soc.

335

154

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Sensores potenciométricos, amperométricos e condutométricos são sensores eletroquímicos com imensa aplicação nas áreas de meio ambiente, indústria e análises clínicas. O presente trabalho apresenta uma revisão generalizada dos aspectos fundamentais, os desenvolvimento e a contribuição destes sensores na área de química analítica, e reporta alguns aspectos relevantes dos avanços na área de sensores eletroquímicos no Brasil.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.

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Section: Potentiometric Sensorsmentioning

confidence: 99%

Electrochemical sensors: a powerful tool in analytical chemistry

Stradiotto¹,

Yamanaka²,

Zanoni³

2003

J. Braz. Chem. Soc.

335

154

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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%

“…Although a titration curve with a shape similar to that of manual titration is obtained, several injections of sample and titrant must be made in order to obtain the curve; the concentration of the analyte can be straightforwardly determined by knowing the volumes of the injected solutions. The binary search concept 14 has been utilised by Martelli et al 25 to perform acid-base potentiometric titration. In this system, the volume of sample is maintained constant, while the volumes of titrant and an inert diluent solution are varied in order to keep the monosegment volume also constant.…”

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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“…11 Tanaka et al 12,13 proposed a feedback-based flow ratiometry, a new concept for continuous titration. In their approach, the titrant flow rate is linearly varied while the total (titrant + titrand) flow rate (FT) is held constant.…”

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confidence: 99%

High-Throughput Photometric Titrimetry Based on a Feedback-based and Subsequent Fixed Triangular Wave-controlled Flow Ratiometry

Tanaka

Baba

2005

ANAL. SCI.

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Titrimetry is a classical analytical method that is still widely in use. It is adopted, for example, as a method for the quantitative analysis of nearly 60% of drugs listed in Part 1 of the Japanese Parmacopoeia. 1 According to a book by Szabadváry, 2 the origin of titrimetry can be traced back to 1729 when Geoffroy analyzed vinegar samples with K2CO3. However, conventional manual titration using glassware, such as a burette, is tedious and time-consuming. Various flow titration techniques have therefore been developed, as recently reviewed by Tanaka and Nakano. 3These include flow injection titration, 4 sequential injection titration, 5 triangle programmed coulometric titration, 6-8 flow ratiometric titration 9,10 and monosegmented flow titration. 11 Tanaka et al. 12,13 proposed a feedback-based flow ratiometry, a new concept for continuous titration. In their approach, the titrant flow rate is linearly varied while the total (titrant + titrand) flow rate (FT) is held constant. The scan direction of the titrant flow rate is reversed from upward to downward, and vice versa, whenever the equivalence point EP is detected. Thus, the scan range is limited to the range around EP. A high throughput was attained for photometric 12 and potentiometric 13 titrtions (6 and 5 titrations per minute, respectively). Jo and Dasgupta 14 applied this method to cheletometric titrations.Very recently, we introduced a new strategy to feedback-based flow ratiometry. 15 After feedback-based operation, fixed triangular waves were used to control the titrant flow rate in order to further limit the scan to the range of interest. The developed method realized potentiometric titrations having an extremely high throughput rate at reasonable precision (maximally 17.6 titrations per minute at RSD = 0.35%). In the present study, we extended the principle of the method to photometric titrimetry, because the photo-sensor is one of the most popular detectors in flow analyses, and is expected to have a quicker response than an electrode. ExperimentalFlow system Figure 1 shows the flow system of the present study. The principle of flow ratiometry for high-throughput titration, which we recently proposed for potentiometric titration, was extended to photometric titration. The flow rate (FB) of a base solution containing an acid-base indicator was linearly varied in response to a control voltage (Vc) generated from a computer. With the total (acid + base) flow rate (FT) being kept constant, the base solution was merged with an acid solution, which was aspirated to the confluence point at a flow rate of FT -FB. Downstream, the relative transmittance of the mixed solution was measured at the maximum absorption wavelength of the base form of the indicator. Initially, a feedback-based control was applied, where the scan direction of Vc was reversed from upward to downward, and vice versa, whenever the transition of the indicator at the equivalence point (EP) was sensed. Next, the scan range of Vc was further limited to the range just around EP by using f...

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Automatic potentiometric titration in monosegmented flow system exploiting binary search

Cited by 45 publications

References 20 publications

Electrochemical sensors: a powerful tool in analytical chemistry

Electrochemical sensors: a powerful tool in analytical chemistry

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

High-Throughput Photometric Titrimetry Based on a Feedback-based and Subsequent Fixed Triangular Wave-controlled Flow Ratiometry

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