Thermo Fisher Scientific CyberScan pH 10/pH 100 - Manual (Page 53)

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11.2 Electrode Cleaning
Electrodes that are mechanically intact can be restored to normal performance by one or
combination of the following procedures.
a) Salt deposits:
Dissolve the deposit by immersing the electrode in tap water for ten to fifteen minutes. Then
thoroughly rinse with deionized water.
b) Oil / Grease Films:
Wash electrode pH bulb in a little detergent and water. Rinse electrode tip with deionized
water.
c) Clogged Reference Junction:
Heat a dilute KCl solution to 60-80 °C. Place the sensing portion of the pH electrode into the
heated KCl solution for approximately 10 minutes. Allow the electrode to cool while immersed
in some unheated KCl solution.
d) Protein Deposits:
Prepare a 1% pepsin solution in 0.1M HCl. Allow the electrode to stand in this solution for five
to ten minutes. Rinse the electrode with deionized water.
11.3 Electrode Activation
Generally, if the procedure of storage and maintenance had been closely followed, the
electrode can be used immediately. However, should the electrode response become
sluggish, it may be possible that the bulb has dehydrated. The bulb can be re-hydrated by
immersing the electrode in an ideal storage solution (e.g. buffer pH 4 solution) for 1- 2 hours. If
this fails, the electrode may require re-activation.
At no time should one touch or rub the glass bulb as this causes the build-up of electrostatic
charge.
If the above procedure does not re-activate the electrode to acceptable status, try rejuvenating
the electrode by following the procedure outlined below.
11.4 Rejuvenation Procedure
a) Dip and stir the electrode in freon or alcohol for 5 minutes.
b) Leave the electrode in tap water for 15 minutes.
c) Dip and stir the electrode in concentrated acid (e.g. HCl, H
2
SO
4
) for 5 minutes.
d) Repeat Step b.
e) Dip and stir in strong base (NaOH) for 5 minutes.
f) Leave for 15 minutes in tap water.