41
40
pH electrode activation (for glass bodied electrodes only)
WARNING:
Only qualified persons proficient with the safe handling of dangerous
chemicals should perform the procedure below. Provide proper containers, fume
hoods, ventilation, and waste disposal. Safety goggles and protective clothing must
be worn while performing this procedure. If possible, replace with another electrode
instead of performing this reactivation procedure.
1.
Dip or stir the pH electrode
in alcohol for 5 minutes.
2.
Leave the electrode in tap water
for 15 minutes.
3.
Dip and stir the electrode
in concentrate acid (such as HCl or H
2
SO
4
)
for five minutes.
4.
Repeat step 2.
5.
Dip and stir in strong base
(NaOH) for five minutes.
6.
Leave for 15 minutes
in distilled or deionized water.
7.
Now test with standard calibration buffer solutions
to see if the electrode yields
acceptable results. You may repeat step 3 through 6 up to three times for better
response. If the response does not improve, then your electrode is no longer
functioning. Replace with a new electrode.
9. Probe Care and Maintenance
Since your pH electrode is susceptible to dirt and contamination, clean it every one
to three months depending on the extent and condition of use.
NOTE:
for specialty electrode care, consult the instruction manual included with
your electrode.
pH electrode storage
For best results, always keep the pH bulb wet. Use the protective electrode storage
bottle or rubber cap filled with electrode storage solution to store your electrode.
Also, you can store in a pH 4 buffer with 1/100 part of saturated KCl. Other pH
buffers are OK for storage, but NEVER use distilled water for storage.
After measuring
1.
Rinse the pH electrode and reference junction in de-ionized water.
2.
Store the electrode as recommended above in “pH electrode storage,”
or as recommended by the manufacturer.
3.
Prior to next use, rinse the liquid junction with de-ionized water and tap dry—
never wipe electrode.
NOTE:
If this does not restore electrode to normal response, see
“Reactivating the pH electrode” section below.
pH electrode cleaning
Salt deposits:
dissolve the deposits by immersing the electrode in tap water for ten
to fifteen minutes. Ten thoroughly rinse with distilled water.
Oil/grease film:
wash electrode pH bulb gently in some detergent and water. Rinse
electrode tip with distilled water or use a general purpose electrode cleaner.
Clogged reference junction:
heat a diluted KCl solution to 60 to 80°C. Place the
sensing part of the electrode into the heated solution for about 10 minutes. Allow
the electrode to cool in some unheated KCl solution.
Protein deposits:
prepare a 1% pepsin solution in 0.1 M of HCl. Set the electrode in
the solution for five to ten minutes. Rinse the electrode with distilled water.
Reactivating the pH electrode
If stored and cleaned properly, your pH electrode should be ready for immediate
use. However, a dehydrated bulb may cause sluggish response. To rehydrate the
bulb, immerse the electrode in a pH 4 buffer solution for 10 to 30 minutes. If this
fails, the electrode requires activation. Never touch or rub glass bulb. Contact
builds up an electrostatic charge.
Содержание AP71
Страница 24: ...47 46...
