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Metrological Aspects of Activity Measurements in Mixed Electrolytes by Ion‐Selective Electrodes
Author(s) -
Wunderli Samuel,
Andres Hanspeter
Publication year - 2008
Publication title -
electroanalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 128
eISSN - 1521-4109
pISSN - 1040-0397
DOI - 10.1002/elan.200704051
Subject(s) - analyte , electrolyte , metrology , measurement uncertainty , analytical chemistry (journal) , diffusion , ion , electrode , range (aeronautics) , stability (learning theory) , chemistry , standard uncertainty , biological system , thermodynamics , materials science , statistics , mathematics , physics , chromatography , computer science , organic chemistry , machine learning , biology , composite material
Based on the model equation for the measurand analyte activity, all significant sources of uncertainty are identified, their magnitude estimated from published and experimental data and finally combined to give the uncertainty in the reported value of the analyte activity. It is found that the combined uncertainty is dominated by the uncertainties in the diffusion potential E J and the time‐dependent response behavior κ of the sensor. Using Henderson's approach E J is calculated not to vary more than 150 μV for physiological analytes in contact with a 3 M KCl reference solution. The stability of the reference electrode as well as the flow characteristics in the vicinity of the sensing element greatly influence the response time of the sensor. By minimizing the mentioned contributions of E J and κ in the uncertainty budget, combined uncertainties for activity values in the range of 2% are feasible for univalent ions.