Evaluation and validation of detailed and simplified models of the uncertainty of unified pHabsH2O measurements in aqueous solutions

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http://hdl.handle.net/10138/337518

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Ricardo J.N. Bettencourt da Silva, Jaan Saame, Bárbara Anes, Agnes Heering, Ivo Leito, Teemu Näykki, Daniela Stoica, Lisa Deleebeeck, Frank Bastkowski, Alan Snedden, M. Filomena Camões. Evaluation and validation of detailed and simplified models of the uncertainty of unified pHabsH2O measurements in aqueous solutions. Analytica Chimica Acta 1182 (2021), 338923, ISSN 0003-2670. https://doi.org/10.1016/j.aca.2021.338923

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Title: Evaluation and validation of detailed and simplified models of the uncertainty of unified pHabsH2O measurements in aqueous solutions
Author: Bettencourt da Silva, Ricardo J.N; Saame, Jaan; Anes, Bárbara; Heering, Agnes; Leito, Ivo; Näykki, Teemu; Stoica, Daniela; Deleebeeck, Lisa; Bastkowski, Frank; Snedden, Alan; Camões, M. Filomena
Publisher: Elsevier
Date: 2021
Language: en
Belongs to series: Analytica Chimica Acta 1182 (2021), 338923
ISSN: 0003-2670
DOI: https://doi.org/10.1016/j.aca.2021.338923
URI: http://hdl.handle.net/10138/337518
Abstract: The use of the unified pH concept, pHabsH2O, applicable to aqueous and non-aqueous solutions, which allows interpreting and comparison of the acidity of different types of solutions, requires reliable and objective determination. The pHabsH2O can be determined by a single differential potentiometry measurement referenced to an aqueous reference buffer or by a ladder of differential potentiometric measurements that allows minimisation of inconsistencies of various determinations. This work describes and assesses bottom-up evaluations of the uncertainty of these measurements, where uncertainty components are combined by the Monte Carlo Method (MCM) or Taylor Series Approximation (TSM). The MCM allows a detailed simulation of the measurements, including an iterative process involving in minimising ladder deviations. On the other hand, the TSM requires the approximate determination of minimisation uncertainty. The uncertainty evaluation was successfully applied to measuring aqueous buffers with pH of 2.00, 4.00, 7.00, and 10.00, with a standard uncertainty of 0.01. The reference and estimated values from both approaches are metrologically compatible for a 95% confidence level even when a negligible contribution of liquid junction potential uncertainty is assumed. The MCM estimated pH values with an expanded uncertainty, for the 95% confidence level, between 0.26 and 0.51, depending on the pH value and ladder inconsistencies. The minimisation uncertainty is negligible or responsible for up to 87% of the measurement uncertainty. The TSM quantified measurement uncertainties on average only 0.05 units larger than the MCM estimated ones. Additional experimental tests should be performed to test these uncertainty models for analysis performed in other laboratories and on non-aqueous solutions.
Description: Highlights • First detailed evaluation of the uncertainty of pHabsH2O measurements. • Bottom-up uncertainty evaluations proven valid for 95% confidence. • Monte Carlo Simulation of pHabsH2O measurement ladder with least-squares minimisation. • Described simplified and detailed bottom-up uncertainty evaluations are equivalent. • Measurements from 2 to 10 pHabsH2O with a 95% expanded uncertainty of 0.26–0.51.
Subject: unified pH scale
differential potentiometry
validation
uncertainty
Monte Carlo method
aqueous solutions
chemistry
confidence leves
detailed models
evaluation
evaluation methods
measurement
measuring
measuring methods
measuring technology
metrology
modelling
models
potentiometry measurement
reliability
simplified models
spectrometers
success
unified measurement
pH
acidity
analysis
chemical analysis
Subject (ysa): arviointi
arviointimenetelmät
epävarmuus
kemia
luotettavuus
luottamustasot
mallintaminen
menestyminen
metrologia
mittaus
mittausmenetelmät
mittaustekniikka
Monte Carlo -menetelmät
simulointi
spektrometrit
tavoitteet
pH
happamuus
analyysi
kemiallinen analyysi
Rights: In Copyright 1.0
Full text embargoed until: 2022-08-10


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