Development of instrumentation for coulometric titrations

D 2019

Development of instrumentation for coulometric titrations

KUČERA, Matěj, Jiří VOLÁNEK, Pavel KRÁSENSKÝ, Přemysl LUBAL, Zdeněk FARKA et. al.

Basic information

Original name

Development of instrumentation for coulometric titrations

Authors

KUČERA, Matěj, Jiří VOLÁNEK, Pavel KRÁSENSKÝ, Přemysl LUBAL, Zdeněk FARKA and Marta FARKOVÁ

Edition

1st edition. Brno, XIX. Workshop of Biophysical Chemists and Electrochemists, p. 48-49, 2 pp. 2019

Publisher

Masaryk University Press

Other information

Language

English

Type of outcome

Stať ve sborníku

Field of Study

10406 Analytical chemistry

Country of publisher

Czech Republic

Confidentiality degree

není předmětem státního či obchodního tajemství

Publication form

storage medium (CD, DVD, flash disk)

References:

URL

Organization unit

Faculty of Science

ISBN

978-80-210-9309-6

Keywords in English

electrochemistry; coulometry; titration; iodometry

Změněno: 25/4/2024 10:18, Mgr. Marie Šípková, DiS.

Abstract

V originále

This contribution is focused on the development and testing of coulometric analyzer, which was employed for in situ generation of analytical agent. The goal of the project was construction of a new coulometer, which ensures the exact and precise automatic coulometric titration. Coulometry is one of the basic electroanalytical methods. Two main approaches are direct and indirect coulometry, based on monitoring of the current required to convert the substance of interest into a precisely defined product (direct), and/or the amount of current required to produce an equivalent amount of reagent which takes place in the reaction with selected analyte (indirect). The main advantage of indirect coulometry is the possibility of in situ generation of reactive unstable ions that may serve as titration agents. The newly constructed device is based on an integrated circuit with a connected screen and electrode connection inputs. The measurement set-up consists of a beaker in which the coulometric titration takes place, and a pair of generator Pt electrodes connected to a controllable DC source for coulometric analyzer. Reference and Pt indicator electrodes are utilized for potentiometric detection of equivalence point. The titrations in this work are based on oxidization of analyte by iodine, which was coulometrically generated from alkaline potassium iodide. Other additives in solution were oxalic acid, which ensures the stability of analyzed ascorbic acid, and starch, which serves as an indicator forming blue-colored inclusive compounds with iodine. Firstly, the sample solution of ascorbic acid was titrated and its oxidation over time was recorded. Oxidation of ascorbic acid occurs due to oxygen in the air, even in solution, where metal ions have the same effect. All titrations of ascorbic acid for different concentrations were evaluated by observing the blue color of starch-iodine inclusion complex. However, the color of titration solution is very weak at the equivalence point, and thus the end of titration is subjective. Secondly, the purity of sodium thiosulphate was checked using two ways of equivalence point estimation – (i) again using visual detection with starch, and (ii) by potentiometric indication using the second-derivative curve, which allowed to achieve significantly improved results under the optimized experimental conditions.

Links

LQ1601, research and development project

Name: CEITEC 2020 (Acronym: CEITEC2020)

Investor: Ministry of Education, Youth and Sports of the CR

MUNI/A/1359/2018, interní kód MU

Name: Vývoj metod a instrumentace pro analýzu biologicky významných látek 2019

Investor: Masaryk University, Category A

Citovat

KUČERA, Matěj, Jiří VOLÁNEK, Pavel KRÁSENSKÝ, Přemysl LUBAL, Zdeněk FARKA and Marta FARKOVÁ. Development of instrumentation for coulometric titrations. In Libuše Trnková. XIX. Workshop of Biophysical Chemists and Electrochemists. 1st edition. Brno: Masaryk University Press, 2019, p. 48-49. ISBN 978-80-210-9309-6.

@inproceedings{1547157,
   author = {Kučera, Matěj and Volánek, Jiří and Krásenský, Pavel and Lubal, Přemysl and Farka, Zdeněk and Farková, Marta},
   address = {Brno},
   booktitle = {XIX. Workshop of Biophysical Chemists and Electrochemists},
   edition = {1st edition},
   editor = {Libuše Trnková},
   keywords = {electrochemistry; coulometry; titration; iodometry},
   howpublished = {paměťový nosič},
   language = {eng},
   location = {Brno},
   isbn = {978-80-210-9309-6},
   pages = {48-49},
   publisher = {Masaryk University Press},
   title = {Development of instrumentation for coulometric titrations},
   url = {https://www1.sci.muni.cz/~labifel/files/soubory/sborn%C3%ADk_2019.pdf},
   year = {2019}
}

TY  - JOUR
ID  - 1547157
AU  - Kučera, Matěj - Volánek, Jiří - Krásenský, Pavel - Lubal, Přemysl - Farka, Zdeněk - Farková, Marta
PY  - 2019
TI  - Development of instrumentation for coulometric titrations
PB  - Masaryk University Press
CY  - Brno
SN  - 9788021093096
KW  - electrochemistry
KW  - coulometry
KW  - titration
KW  - iodometry
UR  - https://www1.sci.muni.cz/~labifel/files/soubory/sborn%C3%ADk_2019.pdf
N2  - This contribution is focused on the development and testing of coulometric analyzer, which was employed for in situ generation of analytical agent. The goal of the project was construction of a new coulometer, which ensures the exact and precise automatic coulometric titration. Coulometry is one of the basic electroanalytical methods. Two main approaches are direct and indirect coulometry, based on monitoring of the current required to convert the substance of interest into a precisely defined product (direct), and/or the amount of current required to produce an equivalent amount of reagent which takes place in the reaction with selected analyte (indirect). The main advantage of indirect coulometry is the possibility of in situ generation of reactive unstable ions that may serve as titration agents. The newly constructed device is based on an integrated circuit with a connected screen and electrode connection inputs. The measurement set-up consists of a beaker in which the coulometric titration takes place, and a pair of generator Pt electrodes connected to a controllable DC source for coulometric analyzer. Reference and Pt indicator electrodes are utilized for potentiometric detection of equivalence point. The titrations in this work are based on oxidization of analyte by iodine, which was coulometrically generated from alkaline potassium iodide. Other additives in solution were oxalic acid, which ensures the stability of analyzed ascorbic acid, and starch, which serves as an indicator forming blue-colored inclusive compounds with iodine. Firstly, the sample solution of ascorbic acid was titrated and its oxidation over time was recorded. Oxidation of ascorbic acid occurs due to oxygen in the air, even in solution, where metal ions have the same effect. All titrations of ascorbic acid for different concentrations were evaluated by observing the blue color of starch-iodine inclusion complex. However, the color of titration solution is very weak at the equivalence point, and thus the end of titration is subjective. Secondly, the purity of sodium thiosulphate was checked using two ways of equivalence point estimation – (i) again using visual detection with starch, and (ii) by potentiometric indication using the second-derivative curve, which allowed to achieve significantly improved results under the optimized experimental conditions.
ER  -

KUČERA, Matěj, Jiří VOLÁNEK, Pavel KRÁSENSKÝ, Přemysl LUBAL, Zdeněk FARKA and Marta FARKOVÁ. Development of instrumentation for coulometric titrations. In Libuše Trnková. \textit{XIX. Workshop of Biophysical Chemists and Electrochemists}. 1st edition. Brno: Masaryk University Press, 2019, p.~48-49. ISBN~978-80-210-9309-6.

Detailed Information on Publication Record