Potentiometry measurement uncertainties

MCM-41, olefin epoxidation, 418, 421-2 MCM-48, olefin epoxidation, 418 MDA see Malondialdehyde Measurement uncertainties analytical methods, 624 potentiometry, 663 Meat... 

Potentiometry biosensors, 664 fitness for purpose, 663 hydrogen peroxide determination, 650-1 iodine-iodide buffer, 699 measurement uncertainties, 663 peroxide value, 663-4 transition metal peroxides, 1069 POV see Peroxide value POZ see Primary ozonides Precipitation waters, hydrogen peroxide determination, 637... 

The non-linearity in accumulation of errors can clearly be seen from Table 8-2. The measurement combinations At, Ct and pH, /(COz) are obviously unsuitable for calculation of other CO2 system parameters since the uncertainties in the measurements are magnified during the calculation. The results suggest, however, that with the right choice of measured parameters. At and Cj can be calculated with precision similar to that achieved in direct measurement (this also applies to pH measured by potentiometry). In contrast, /(CO2) cannot be calculated with the precision which can be achieved in direct measurement. 

Keeping in view the above serious anomalies commonly encountered with direct potentiometry, such as an element of uncertainty triggered by liquid junction potential (E.) and high degree of sensitivity required to measure electrode potential (E), it promptly gave birth to the phenomenon of potentiometric titrations,... 

Potentiometry is an electrochemical technique in which the electrical potential of an "inert" electrode is measured against that of a reference electrode while both are immersed in an aqueous solution. A problem in potentiometry is that the measured potential may be slow to achieve a steady value. This is especially common in attempts to measure the Eh of solutions that are poorly poised, as is the case with most natural waters, and it is not uncommon for measured redox potentials to drift for many hours Q, 2). The long equilibration times, together with published reports of large discrepancies between platinum Eh values and actual solution compositions (2), have led to a great deal of uncertainty and skepticism about the use of Eh measurements. 

Potentiometric titrations are always more accurate than direct potentiometry because of the uncertainties involved in potential measurements. Whereas accuracies of better than a few percent are rarely possible in direct potentiometry, accuracies of a few tenths of a percent are common by potentiometric titration. We can make some general statements concerning potentiometric titrations ... 

---