A Practical Example on Uncertainty Evaluation: Spectrophotometric Determination of pKa

A practical example, focused on the evaluation of uncertainty and its propagation in spectrophotometric determination of ionization constants, is proposed in this work. The Hildebrand - Reilley method has been used in order to calculate the acetaminofen pKa value. After applying this method a linear...

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Autores: Díaz Montaña, Enrique Jacobo, Alcázar Rueda, Ángela, Jurado Jurado, José Marcos, Pablos Pons, Fernando de
Tipo de recurso: artículo
Estado:Versión publicada
Fecha de publicación:2018
País:España
Institución:Universidad de Sevilla (US)
Repositorio:idUS. Depósito de Investigación de la Universidad de Sevilla
OAI Identifier:oai:idus.us.es:11441/134688
Acceso en línea:https://hdl.handle.net/11441/134688
https://doi.org/10.20431/2349-0403.0501004
Access Level:acceso abierto
Palabra clave:Uncertainty evaluation
Weighted least squares
Spectrophotometric determination of pKa
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spelling A Practical Example on Uncertainty Evaluation: Spectrophotometric Determination of pKaDíaz Montaña, Enrique JacoboAlcázar Rueda, ÁngelaJurado Jurado, José MarcosPablos Pons, Fernando deUncertainty evaluationWeighted least squaresSpectrophotometric determination of pKaA practical example, focused on the evaluation of uncertainty and its propagation in spectrophotometric determination of ionization constants, is proposed in this work. The Hildebrand - Reilley method has been used in order to calculate the acetaminofen pKa value. After applying this method a linear relationship between pH and a logarithmic term depending on absorbances, was established. The value of pKa is obtained as the intercept of this straight-line and its error is evaluated from least squares calculations. As errors in both variables have to be considered, weighted least squares (WLS) must be used. The evaluation of uncertainty in pH measurements was carried out according to IUPAC recommendations in the case of glass electrode with two calibration standards. The uncertainty contributions of absorbance and work standard concentration, evaluated according to GUM, have been propagated to Hildebrand – Reilley expression in order to obtain the errors to be used in WLS calculations. Due to the different topics included in this tutorial, it can be considered as a useful tool for training people learning about the evaluation of uncertainty in measurements and its propagation.ARC JournalsQuímica AnalíticaAGR104: Proyecto Sexia2018info:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionapplication/pdfapplication/pdfhttps://hdl.handle.net/11441/134688https://doi.org/10.20431/2349-0403.0501004reponame:idUS. Depósito de Investigación de la Universidad de Sevillainstname:Universidad de Sevilla (US)InglésInternational Journal of Advanced Research in Chemical Science, 5 (1), 20-28.https://www.arcjournals.org/international-journal-of-advanced-research-in-chemical-science/volume-5-issue-1/info:eu-repo/semantics/openAccessoai:idus.us.es:11441/1346882026-06-17T12:51:07Z
dc.title.none.fl_str_mv A Practical Example on Uncertainty Evaluation: Spectrophotometric Determination of pKa
title A Practical Example on Uncertainty Evaluation: Spectrophotometric Determination of pKa
spellingShingle A Practical Example on Uncertainty Evaluation: Spectrophotometric Determination of pKa
Díaz Montaña, Enrique Jacobo
Uncertainty evaluation
Weighted least squares
Spectrophotometric determination of pKa
title_short A Practical Example on Uncertainty Evaluation: Spectrophotometric Determination of pKa
title_full A Practical Example on Uncertainty Evaluation: Spectrophotometric Determination of pKa
title_fullStr A Practical Example on Uncertainty Evaluation: Spectrophotometric Determination of pKa
title_full_unstemmed A Practical Example on Uncertainty Evaluation: Spectrophotometric Determination of pKa
title_sort A Practical Example on Uncertainty Evaluation: Spectrophotometric Determination of pKa
dc.creator.none.fl_str_mv Díaz Montaña, Enrique Jacobo
Alcázar Rueda, Ángela
Jurado Jurado, José Marcos
Pablos Pons, Fernando de
author Díaz Montaña, Enrique Jacobo
author_facet Díaz Montaña, Enrique Jacobo
Alcázar Rueda, Ángela
Jurado Jurado, José Marcos
Pablos Pons, Fernando de
author_role author
author2 Alcázar Rueda, Ángela
Jurado Jurado, José Marcos
Pablos Pons, Fernando de
author2_role author
author
author
dc.contributor.none.fl_str_mv Química Analítica
AGR104: Proyecto Sexia
dc.subject.none.fl_str_mv Uncertainty evaluation
Weighted least squares
Spectrophotometric determination of pKa
topic Uncertainty evaluation
Weighted least squares
Spectrophotometric determination of pKa
description A practical example, focused on the evaluation of uncertainty and its propagation in spectrophotometric determination of ionization constants, is proposed in this work. The Hildebrand - Reilley method has been used in order to calculate the acetaminofen pKa value. After applying this method a linear relationship between pH and a logarithmic term depending on absorbances, was established. The value of pKa is obtained as the intercept of this straight-line and its error is evaluated from least squares calculations. As errors in both variables have to be considered, weighted least squares (WLS) must be used. The evaluation of uncertainty in pH measurements was carried out according to IUPAC recommendations in the case of glass electrode with two calibration standards. The uncertainty contributions of absorbance and work standard concentration, evaluated according to GUM, have been propagated to Hildebrand – Reilley expression in order to obtain the errors to be used in WLS calculations. Due to the different topics included in this tutorial, it can be considered as a useful tool for training people learning about the evaluation of uncertainty in measurements and its propagation.
publishDate 2018
dc.date.none.fl_str_mv 2018
dc.type.none.fl_str_mv info:eu-repo/semantics/article
info:eu-repo/semantics/publishedVersion
format article
status_str publishedVersion
dc.identifier.none.fl_str_mv https://hdl.handle.net/11441/134688
https://doi.org/10.20431/2349-0403.0501004
url https://hdl.handle.net/11441/134688
https://doi.org/10.20431/2349-0403.0501004
dc.language.none.fl_str_mv Inglés
language_invalid_str_mv Inglés
dc.relation.none.fl_str_mv International Journal of Advanced Research in Chemical Science, 5 (1), 20-28.
https://www.arcjournals.org/international-journal-of-advanced-research-in-chemical-science/volume-5-issue-1/
dc.rights.none.fl_str_mv info:eu-repo/semantics/openAccess
eu_rights_str_mv openAccess
dc.format.none.fl_str_mv application/pdf
application/pdf
dc.publisher.none.fl_str_mv ARC Journals
publisher.none.fl_str_mv ARC Journals
dc.source.none.fl_str_mv reponame:idUS. Depósito de Investigación de la Universidad de Sevilla
instname:Universidad de Sevilla (US)
instname_str Universidad de Sevilla (US)
reponame_str idUS. Depósito de Investigación de la Universidad de Sevilla
collection idUS. Depósito de Investigación de la Universidad de Sevilla
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