Milkotester Master Operation Manual

Appendices towards the Operation Manual of Ultrasonic milk analyzer Master

Measurement of pH

General information

PH probe is a unit, measuring the solution acidity or alkalinity degree. It is measured on

scale of 0 to 14. The term pH is derived from "p", the mathematical symbol for the negative

logarithm, and "H", the chemical symbol of Hydrogen. The formal definition of pH is the
negative logarithm of the Hydrogen ion activity.

pH Electrode

For pH measurement the milk analyzer needs a combination electrode, compatible with

most pH electrodes that have BNC connectors and zero potential (the pH where the mill volt
output of the electrode equals 0) near 7 pH.

Electrode part

The electrode is the most important part of the pH measurement. The electrode glass

membrane is fragile and must be handled with care. To protect the glass membrane and to

maintain activation, a protective rubber cap containing a suitable storage solution covers the
glass membrane.

Electrode care & Electrode maintenance

pH Electrodes are susceptible to dirt and contamination and need to be clean regularly

depending on the extent and condition of use. At no time should one touch or rub the glass
bulb as this causes the build-up of electrostatic charge.

Appendices towards the Operation Manual of Ultrasonic milk analyzer Master

Storage

For best results, always keep the pH bulb wet. An optimal storage solution for

combination electrode is pH 4 buffer with 225 grams of KCl per liter. Table salt, NaCl, can be

used if KCl is not really available. Other pH buffers or tap water are also acceptable storage

media, but avoid storage in de-ionized water. The protective rubber cap filled with the buffer

solution provides ideal storage for long periods.

After Use

After measurement is completed, follow the sequence below for storage.

- Wash the electrode and reference junction in de-ionized water.

- Close the refilling hole by returning its rubber sleeve or stopper cap.

(Necessary for only refillable electrode).

- Store the electrode as mentioned above (see section Storage).

Electrolyte Replacement (for refillable electrode only)

The reference electrolyte needs to be refilled when the electrode has been used for a

long period, or when the internal electrolyte has dried up. To accomplish this, follow the

procedure described below.

- Remove the protective rubber cap or sleeve;

- Remove the protective rubber sleeve to expose the filling port of the electrode;

- Remove the old reference electrolyte with a syringe;

- Fill the new reference electrolyte.

Appendices towards the Operation Manual of Ultrasonic milk analyzer Master

New electrolyte preparation

- Open the KCl container;

- Add in de-ionized water until it reaches the level of 20 ml;

- Close the container and shake it to dissolve the KCl;

- Add in fresh electrolyte until it reaches the level of the refilling port. The reference

electrolyte used should be 3M(Mol) KCl;

- Replace the rubber sleeve.

Re-use the electrode

- Rinse the liquid junction with de-ionized water.

If these steps fail to restore normal electrode response, you may attempt to

rejuvenate it (See: Electrode Rejuvenation).

Electrode cleaning

Electrodes which are mechanically intact can often be restored to normal performance

by one or combination of the following procedures.

- Salt deposits:

Dissolve the deposit by immersing the electrode in tap water for ten to fifteen minutes.

Then thoroughly rinse with de-ionized water. Wash the electrode pH bulb in a little

detergent and water. Rinse electrode tip in with de-ionized water.

- Oil/Grease films:

Wash electrode pH bulb in a little detergent and water. Rinse electrode tip with de-ionized
water.