How To Replace NH₄N Electrolyte & Troubleshoot Inaccurate Readings For PROBEST PINH3-900 & PISE Ammonia-Nitrogen Ion Electrodes

PROBEST PINH3-900 and PISE ammonia-nitrogen (NH₄⁺-N) ion-selective electrodes are widely used in water quality monitoring, wastewater treatment, environmental testing, and industrial process analysis. In daily operation, common issues such as drifting readings, unstable values, slow response, and inconsistent measurement results are mostly caused by deteriorated, depleted, contaminated, or air-bubble trapped internal electrolyte. Properly replacing the NH₄N electrolyte is the most effective and economical way to restore electrode performance, ensure measurement accuracy, and extend service life.

This article provides a complete technical tutorial for troubleshooting inaccurate probe readings and performing standard electrolyte replacement for PROBEST PINH3-900 and PISE electrodes.

1 Common Symptoms of Inaccurate Readings

Your PROBEST ammonia-nitrogen electrode may require electrolyte inspection or replacement if you observe:

• Continuous drifting that cannot stabilize

• Consistent high or low bias compared to standard solutions

• Significantly slow response and long equilibrium time

• Unstable signal, fluctuation, or electrical noise

• Calibration failure or electrode slope out of the acceptable range (typically 95%–105%)

• Visible contamination, crystallization, or air bubbles inside the electrode

Main Causes

• Electrolyte volatilization, concentration change, or contamination

• Fouling, aging, or damage of the gas-permeable membrane

• Air bubbles trapped near the sensitive membrane

• Dehydration due to improper dry storage

• Interference from suspended solids, oil, or high salinity in samples

2 Pre-Replacement Preparation

Tools & Consumables

• Original PROBEST specified NH₄N internal electrolyte

• Distilled or deionized water

• Lint-free cleaning wipes

• Small screwdriver (for certain models)

• Syringe or dropper for clean filling

• Ammonia-nitrogen standard solutions for calibration

Safety & Operation Notes

• Power off the meter and disconnect the electrode before maintenance

• Do not touch or scratch the sensitive ion-selective membrane

• Maintain a clean environment to avoid secondary contamination

• Dispose of used electrolyte according to local waste regulations

3 Step-by-Step Electrolyte Replacement for PROBEST PINH3-900 & PISE

Step 1 Disassemble the Electrode

• Remove the protective cap and take the electrode out of the holder or meter

• Open the filling port cap or screw seal (PINH3-900 / PISE structure)

• Carefully unscrew the membrane cap at the tip; keep all gaskets and small parts

Step 2 Empty and Clean the Inner Chamber

• Pour out all old, exhausted electrolyte completely

• Gently rinse the inner cavity and membrane cap with distilled water 2–3 times

• Shake lightly to remove residual liquid; do not strike forcefully

• Wipe the electrode body clean

Step 3 Fill with Fresh PROBEST NH₄N Electrolyte

• Hold the electrode at a 45° angle to prevent air bubbles

• Slowly inject fresh electrolyte up to the marked level or filling port

• Tap the electrode body lightly to release trapped air bubbles

• Ensure no bubbles remain near the sensitive membrane

Step 4 Reassemble the Electrode

• Clean any spilled electrolyte from the surface

• Reinstall O-rings and membrane cap; tighten securely to prevent leakage

• Close the filling port cap

Step 5 Polarization and Stabilization

• Place the reassembled electrode into ammonia-nitrogen standard solution

• Allow polarization for 10–30 minutes (per PROBEST specification)

• Do not calibrate or measure until the signal is fully stable

4 Post-Replacement Calibration & Verification

1. Rinse the electrode with distilled water and blot dry

2. Perform calibration with at least two standard solutions for PINH3-900 / PISE

3. Check the electrode slope; valid slope confirms successful replacement

4. Measure a quality control sample to verify accuracy

5. If problems continue, check for membrane fouling, air bubbles, or leakage

5 Troubleshooting Table (PROBEST PINH3-900 & PISE)

6 Daily Maintenance Best Practices

• Replace internal electrolyte every 1–3 months or when performance declines

• After use, rinse with distilled water and store in recommended solution

• Do not leave the electrode dry or in deionized water for long periods

• Increase cleaning frequency for high-fouling wastewater samples

• Calibrate before critical measurements

• Maintain maintenance logs: replacement date, slope, calibration results

7 Conclusion

Inaccurate, drifting, or unstable readings of PROBEST PINH3-900 and PISE ammonia-nitrogen electrodes can most often be resolved by replacing the NH₄N internal electrolyte. Following this standard tutorial will quickly restore accuracy, reduce downtime, and lower operating costs.

Always refer to the official PROBEST electrode manual for specific filling volume and polarization time. For further technical support, please contact our service team.