Evaluation and validation of detailed and simplified models of the uncertainty of unified <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"><mml:mrow><mml:mtext>p</mml:mtext><mml:msubsup><mml:mtext>H</mml:mtext><mml:mrow><mml:mtext>a</mml:mtext><mml:mtext>b</mml:mtext><mml:mtext>s</mml:mtext></mml:mrow><mml:mrow><mml:msub><mml:mtext>H</mml:mtext><mml:mn>2</mml:mn></mml:msub><mml:mtext>O</mml:mtext></mml:mrow></mml:msubsup></mml:mrow></mml:math> measurements in aqueous …

The use of the unified pH concept, abs H 2 O , applicable to aqueous and non-aqueous solutions, which allows interpreting comparison acidity different types requires reliable objective determination. can be determined by a single differential potentiometry measurement referenced an reference buffer or ladder potentiometric measurements that minimisation inconsistencies various determinations. This work describes assesses bottom-up evaluations uncertainty these measurements, where components are combined Monte Carlo Method (MCM) Taylor Series Approximation (TSM). MCM detailed simulation including iterative process involving in minimising deviations. On other hand, TSM approximate determination uncertainty. evaluation was successfully applied measuring buffers with 2.00, 4.00, 7.00, 10.00, standard 0.01. estimated values from both approaches metrologically compatible for 95% confidence level even when negligible contribution liquid junction potential is assumed. expanded uncertainty, level, between 0.26 0.51, depending on value inconsistencies. responsible up 87% quantified uncertainties average only 0.05 units larger than ones. Additional experimental tests should performed test models analysis laboratories solutions. • First measurements. Bottom-up proven valid confidence. Simulation least-squares minimisation. Described simplified equivalent. Measurements 10 0.26–0.51