Appendix
Preparation of pH Buffer Solutions
The PHscan40 tester is packaged with the pH
4.01/7.00/10.01 buffer
sachets required for calibration.
1. Half fill a 250 ml volumetric flask with distilled water and add the
pH 7.00 buffer reagent.
2. Swirl the volumetric flask gently to dissolve the reagent and fill
to the mark with distilled water.
3. Cap and upend the volumetric flask several times to mix solution.
•
Preparation of pH 4.01 and 10.01 buffer solutions are the same
as above.
•
Prepared buffer solution should be stored in hermetically sealed
glass container and avoid direct sunlight.
Preparation of Electrode Storage Solution
Dissolve 24.6 grams of analytical grade KCl reagent in 100 ml distilled
water. Add pH 4.01 standard buffer and adjust solution to pH 4.
Optional Accessories
pH Electrode
Order Code
Description
E201-BNC
General purpose pH electrode, epoxy body, 12
mm
(0.47 in.) diameter. For liquids.
E202-BNC
Flat surface pH electrode, epoxy body, 12
mm
(0.47 in.) diameter. For semisolid samples.
P11
General purpose pH electrode, Glass body, 12
mm
(0.47 in.) diameter. For weak corrosive liquids.
5
I
PHscan40
250 ml
Electrode Maintenance
Cleaning the Electrode
Since pH electrode is susceptible to contamination, thoroughly clean
as necessary after each use.
•
General Cleaning
Rinse the pH electrode with distilled water and soak in 3M KCl
solution.
•
Salt Deposits
Dissolve the deposit by immersing the electrode in warm tap
water. Rinse the electrode with distilled water and soak in 3M
KCl solution.
•
Oil or Grease
Place the electrode in the detergent or ethanol solution for 15
minutes. Rinse the electrode with distilled water and soak in 3M
KCl solution.
•
Protein
(1) Add 1% pepsin to 0.1M HCl solution.
(2) Place the electrode in above solution for 15 minutes.
(3) Rinse the electrode with distilled water and soak in 3M KCl
solution.
•
Clogged Liquid Junction
(1) Heat a diluted KCl solution to 60° C (140° F).
(2) Place the electrode into the heated solution for 10 minutes.
(3) Allow the electrode to cool in unheated KCl solution.
Reactivating the Electrode
If the pH-sensitive membrane has dried out, the electrode response
will become sluggish. Immerse the electrode in a pH 4.01 buffer
solution for about 30 minutes to rehydrate. If this fails, the electrode
requires activation.
1. Soak the electrode in 0.1M HCl for 10 minutes.
2. Remove and rinse with distilled water, then place into 0.1M
NaOH for 10 minutes.
3. Remove and rinse again, and soak in 3M KCl solution for at least
6 hours.
If these steps fail to restore the response, replace the electrode.
Storing the Electrode
For best results, always soak the electrode in 3M KCl solution. If above
solution is not available, use a pH 4.01 buffer solution.
DO NOT store the electrode in distilled or deionized water that will
deplete the hydration layer of the pH-sensitive membrane and render
the electrode useless.
If you do not use the electrode for a period longer than 1 month, store
the electrode in storage solution.
