pH Meter: Uses and How to Use It
pH Meter: Uses and How to Use It
A pH meter is an electronic instrument that measures the acidity or alkalinity of a solution (pH 0–14) from the potential difference between a glass electrode and a reference electrode. It must be calibrated with standard buffers before use, and the electrode is stored wet in storage solution.
What is a pH meter used for?
- Measuring the pH of solutions, water and wastewater.
- Adjusting buffer and media pH during preparation.
- Following potentiometric titrations.
- Quality control of food, drinks, cosmetics and pharmaceuticals.
Parts of a pH meter
- 1Display and keys – show pH, temperature and calibration status
- 2pH electrode – a thin glass bulb sensitive to H⁺ ions
- 3Electrode arm – holds the electrode over the beaker
- 4Temperature probe (ATC) – corrects for temperature automatically
How to use a pH meter
Calibrate with standard buffers
Calibrate every day of use with at least two buffers, starting with pH 7 (1), then pH 4 or 10 (2) depending on the sample range. Buffers and samples should be at the same temperature.
Rinse and blot dry; do not wipe
Rinse the electrode with distilled water from a wash bottle between solutions (1), then blot gently with tissue. Rubbing the bulb builds static and damages the glass.
Immerse, stir gently, wait for stability
Immerse the electrode so the bulb and reference junction are covered (1), stir gently or use a magnetic stirrer, and record the pH once the stability indicator appears.
Store the electrode in storage solution
When finished, rinse and fit the electrode cap filled with storage solution (usually 3 M KCl) (1). Never store the electrode dry or in distilled water.
Common mistakes
- Measuring without calibration or with expired buffers: readings drift.
- Storing the electrode in distilled water or letting it dry out: response slows and it fails early.
Care and safety
- Never pour used buffer back into the bottle; replace calibration buffers regularly.
- Refillable electrodes: keep the electrolyte topped up and open the fill hole while measuring.
SOP for using a pH meter
A summary of the standard operating procedure (SOP) for a pH meter that your laboratory can adapt. Each step is explained in the how-to section above.
1Protective equipment
- A buttoned, long-sleeved lab coat.
- Safety glasses; goggles where corrosive splashes are possible.
- Nitrile gloves suited to the chemicals handled; heat-resistant gloves for hot items.
2Before use
- Calibration buffers are in date, clean and at the same temperature as the samples.
- The electrode is uncracked, the bulb is wet and electrolyte is topped up (refillable electrodes).
- The ATC probe is connected or the sample temperature is entered manually.
3Procedure
4After use
- Rinse the electrode with distilled water and fit the cap with 3 M KCl storage solution.
- Close the fill hole, switch off and discard used buffer.
- Record the calibration slope and offset in the log.
5Verification & calibration
- Calibrate every day of use; an acceptable slope is usually 95–105% with offset near 0 mV.
- Measure a third buffer as a check; clean or replace the electrode if the slope is low or response slow.
6Emergencies
- Broken electrode: collect the glass with tongs; rinse skin with water if electrolyte contacts it.
- Chemical spill: warn people nearby, secure the area and clean up with a spill kit according to the SDS.
- Chemical on skin or in eyes: rinse with running water for at least 15 minutes (eyewash or safety shower), then report to the lab supervisor.
A print-ready version with purpose, scope, illustrated procedure, verification and sign-off boxes. Fill in your own document number and effective date.
Download the SOP (PDF, A4)Types and sizes
Benchtop pH meters suit laboratories, portable meters suit fieldwork and pocket testers suit quick checks. Glass combination electrodes are most common; there are also spear-tip electrodes for solid foods and special electrodes for protein-rich or hot samples.
pH Meter at AMI Scientific
Examples of pH meter available in our store. Prices exclude VAT.
AMI Scientific supplies laboratory glassware, instruments and chemicals with tax invoices and delivery across Indonesia.
Frequently asked questions
How do you calibrate a pH meter?
Rinse the electrode, immerse it in pH 7 buffer and store the value, rinse again and repeat with pH 4 or 10 buffer. A good slope is usually 95–105%.
Why should a pH electrode not be stored in distilled water?
Distilled water leaches ions from the glass gel layer and the reference electrolyte, making the electrode slow and unstable.
Related equipment
Compiled by the AMI Scientific team from standard laboratory practice. Illustrations: AMI Scientific. Updated: 06-11-2026.
Need a pH meter for your laboratory?
AMI Scientific supplies laboratory glassware, instruments and chemicals with tax invoices and delivery across Indonesia.
Available at AMI Scientific
pH Meter Benchtop Digital Infitek PH-B200EM
From Rp6.264.636