A120/130
I
18
Appendix
Preparation of ORP Standard Solutions
Quinhydrone solution A: Dissolve 3 grams of quinhydrone reagent in
500 ml of the pH 4.01 buffer solution, stir the solution for 10 minutes.
Undissolved quinhydrone reagent must be present. If necessary, add
the reagent.
Temperature
Potential (± 10 mV)
20° C
268 mV
25° C
263 mV
30° C
260 mV
Quinhydrone solution B: Dissolve 3 grams of quinhydrone reagent in
500 ml of the pH 7.00 buffer solution, stir the solution for 10 minutes.
Undissolved quinhydrone reagent must be present. If necessary, add
the reagent.
Temperature
Potential (± 10 mV)
20° C
94 mV
25° C
87 mV
30° C
80 mV
Due to the quinhydrone solution is susceptible to air oxidation in
storage, make sure to prepare the fresh solution before use.
Preparation of Electrode Storage Solution
•
Dissolve 29.8 grams of analytical grade potassium chloride (KCl)
reagent in 100 ml distilled water.
•
Add pH 4.01 standard buffer and adjust solution to pH 4.
