As the core equipment of laboratory quantitative analysis, the stability of the titrator and the accuracy of data directly depend on the standardized daily maintenance and timely troubleshooting. This guide aims to systematically explain the key points of titrator maintenance and solutions to common problems to support the continued reliable operation of laboratory work.
Routine maintenance procedures
Routine maintenance of the system is the basis for preventing failures and extending the life of the instrument. Maintenance work should be recorded.
1. Maintenance of burette and liquid circuit system
The burette is a key component of the titrator. After each use, apply deionized water or a solvent that will be used in subsequent experiments to flush the tubing well to prevent crystallization or residue. For volatile or corrosive titrants, it is recommended to empty the burette after daily use and store it with an appropriate solvent. The sealing of the burette and connecting tube should be checked once a month for cracks or signs of aging. Lubrication of pistons should be carried out according to the manufacturer's recommended cycle, using the specified silicone grease, and the amount should be strictly controlled, too much may lead to contamination or blockage.
2. Electrode maintenance
The state of the electrode directly affects the titration endpoint judgment. After use, pH composite electrodes or metal electrodes should be rinsed with deionized water and immersed in the recommended storage solution depending on the measurement medium and electrode type. For example, pH electrodes are typically stored in 3 mol/L KCl solution. The sensitive membrane or metal surface of the electrode should avoid mechanical scratches. Regularly perform electrode performance checks, such as evaluating the slope of a pH electrode by measuring the potential response of a standard buffer, and its theoretical value can be described by the Nernst equation: E = E° - (RT/nF) ln Q, where E is the electrode potential, E° is the standard electrode potential, R is the gas constant, T is the thermodynamic temperature, n is the number of transferred electrons, F is the Faraday constant, and Q is the reaction quotient. The slope deviated significantly from the theoretical value, indicating that the electrode needed to be activated or replaced.
3. External and overall inspection of the instrument
Keep instrument surfaces and consoles clean and dry. Regularly check whether the power cord and data cable connection are secure. Ensure that the instrument is placed in a stable, free from strong vibration, away from heat sources and corrosive gases. For models with automatic injection or mixing devices, check the smoothness of the moving parts of the machine and clean them in a timely manner.
Common fault phenomena and troubleshooting methods
When the titrator is abnormal, the principle of simple to complex, from outside to inside can be followed. The following table lists typical failures and their handling ideas.
| Fault phenomenon | Possible causes and steps to eliminate |
| The titration flow rate is unstable or cannot be drained | Check whether the liquid level in the titrant bottle is too low; Check whether there are air bubbles in the pipeline and perform the emptying procedure; Check whether the burette outlet or needle is blocked, and use appropriate solvents to reverse rinse; Check the piston seal for wear or dryness. |
| Poor reproducibility of measurement results | Confirm whether the ambient temperature fluctuates too much; Check the status of the electrodes and clean, activate or replace them if necessary; Check whether the titrant concentration is accurate and whether decomposition occurs; Confirm whether the mixing speed is uniform and stable; Check if the sample is representative or if the response is complete. |
| The instrument does not recognize the endpoint or the endpoint is advanced/lagged | Check whether the electrode response is slow, clean or activate the electrode; Confirm whether the titration parameters (e.g., endpoint potential, incremental volume) settings are suitable for the current sample; Check for the presence of side reactions or interfering ions; For photometric titration, check whether the light source intensity and detector are normal. |
| The instrument does not respond or shows abnormalities when powered on | Check the connection between the power outlet and the power cord of the instrument; Confirm whether the main power switch of the instrument is turned on; Check whether the internal fuse of the instrument is blown. |
| The automatic control function failed | Try restarting the instrument; Check whether the method parameters are set correctly; If a robotic arm or valve is involved, check whether its physical movement is obstructed or whether the motor drive is normal. |
Notes:
Always turn off the instrument and unplug it before performing any maintenance operations, and operations involving circuit parts should be performed by qualified personnel. When cleaning with chemical solvents, wear personal protective equipment and perform in a well-ventilated area, and confirm the compatibility of the solvent with the instrument components. For replacement consumables, such as electrodes, seals, tubing, etc., it is recommended to use products approved by the instrument manufacturer or that meet the performance specifications. All maintenance, calibration, and troubleshooting procedures should be clearly documented, including dates, operations, observations, and performers, which can help track instrument status and perform periodic analysis.
Summary
The reliable operation of the titrator is based on the combination of active preventive maintenance and scientific troubleshooting. Laboratory personnel should have a deep understanding of instrument principles, strictly implement routine maintenance procedures, and be able to systematically conduct initial diagnosis when problems arise. When encountering complex faults that cannot be solved, professional technicians should be contacted in time. Through standardized management, the quality of titration analysis data and the work efficiency of the laboratory can be effectively guaranteed.
References
International Organization for Standardization, ISO 385:2005, Laboratory glass instruments — burettes.
National Standardization Administration of China, GB/T 601-2016, Chemical reagents - Preparation of standard titration solutions.
Skoog, D. A., West, D. M., Holler, F. J., & Crouch, S. R. "Fundamentals of Analytical Chemistry". (Related instrument principles and maintenance chapters)
Some instrument general maintenance principles are based on technical manuals and application guides published by many major laboratory instrument manufacturers.