ABSTRACT
Samples must be analyzed immediately, preferably at the sampling site. Avoid exposure to air because it can oxidize any reduced species present in the sample.
the sample is measured. e procedure for Eh determination is outlined below:
Eh can be determined from the following equation:
1 2 3Eh E E E= + −
where E1 is the sample potential relative to the reference electrode E2 is the theoretical Eh of the reference electrode and the redox stan-
dard solution relative to the standard hydrogen electrode (E2 may be calculated, see below)
E3 is the observed potential of the redox standard solution, relative to the reference electrode
E2, the theoretical Eh of the reference electrode, may be calculated from the stability constants. For each 1°C increase in temperature, the potential of K4Fe(CN)6-K3Fe(CN)6-KCl solution shows a decrease of about 2 mV. e Eh of this redox standard solution for the platinum electrode vs. Ag:AgCl reference electrode may be calculated as follows:
Eh(mV) 428 2.2( 25)T= − −
where T is the temperature of the solution.
