1、 Daily calibration standards

Calibration frequency: High frequency use (such as daily testing) requires daily calibration; It is recommended to calibrate at least once a week for low-frequency use; Calibration must be carried out immediately after replacing the electrode or solution.

Calibration steps:

Two point calibration: prioritize using pH 6.86 (midpoint) and pH 4.01 (acidic) or pH 9.18 (alkaline) buffer solutions. Insert the electrode into the buffer solution, wait for the reading to stabilize, and follow the instrument prompts to enter the standard value at the current temperature (such as pH 6.86 at 25 ℃) to complete the positioning calibration; Repeat the steps to calibrate the slope using the second point buffer.

Three point calibration: suitable for a wide measurement range, increasing pH 4.00 or pH 9.18 buffer to improve linear accuracy.

Notes:

Before calibration, check if the electrode is dry. If it has not been used for a long time, soak it in a 3mol/L KCl solution and activate it for 2-4 hours.

To avoid cross contamination, rinse the electrode with distilled water and dry it after calibration.

2、 Electrode cleaning method

Daily cleaning: Rinse the electrode head with distilled water after measurement, and dry the water with filter paper (do not wipe to prevent damage to the sensitive membrane).

Special pollution treatment:

Oil/organic matter: Soak in a 0.1% sodium dodecyl sulfate solution for 15-30 minutes and rinse thoroughly.

Protein: Soak in 1g gastric protease+100mL 0.1mol/L hydrochloric acid solution for 1-2 hours, rinse and soak in 3mol/L KCl solution for 15 minutes.

Sulfides/heavy metals: Soak in 10% thiourea solution or 0.1mol/L EDTA solution for 30 minutes and rinse thoroughly.

3、 Common troubleshooting

Unstable reading:

Reasons: electrode aging, temperature changes, electromagnetic interference.

Solution: Check the lifespan of the electrode (replace if the slope is below 85%), ensure that the sample temperature is stable, and stay away from strong magnetic fields.

Unable to calibrate:

Reason: Buffer failure, insufficient electrode filling solution, internal malfunction.

Solution: Replace with fresh buffer solution, check the electrode filling solution (such as 3mol/L KCl solution), and contact the manufacturer for repair.

Delayed electrode response:

Reason: Sensitive membrane contamination, liquid interface blockage.

Solution: Soak the electrode in 0.1mol/L HCl or enzyme cleaning solution, and reverse rinse the liquid interface (such as ceramic core).

No display on screen:

Reason: Power failure, instrument damage.

Solution: Check the power cord and socket, replace the battery or contact a professional for repair.

4、 Summary of Maintenance Points

Storage: When not in use for a short period of time, immerse the electrode in a 3mol/L KCl solution; Long term non use requires dry storage, avoid soaking with detergent.

Environment: Keep away from temperature (<5 ℃ or>40 ℃), strong electromagnetic interference, and use the original packaging box during transportation.

Record: Establish a "PH Meter Maintenance Calendar" to record calibration, cleaning, and storage times for easy traceability of issues.