Artículo
A Practical Example on Uncertainty Evaluation: Spectrophotometric Determination of pKa
Autor/es | Díaz Montaña, Enrique Jacobo
Alcázar Rueda, Ángela Jurado Jurado, José Marcos Pablos Pons, Fernando de |
Departamento | Universidad de Sevilla. Departamento de Química Analítica |
Fecha de publicación | 2018 |
Fecha de depósito | 2022-06-27 |
Publicado en |
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Resumen | 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 ... 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. |
Cita | Díaz Montaña, E.J., Alcázar Rueda, Á., Jurado Jurado, J.M. y Pablos Pons, F.d. (2018). A Practical Example on Uncertainty Evaluation: Spectrophotometric Determination of pKa. International Journal of Advanced Research in Chemical Science, 5 (1), 20-28. |
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