The KOH rinse solution generator generates precise concentration KOH solution by electrolyzing pure water (commonly used in ion chromatography analysis). Unstable output (such as concentration fluctuations, abnormal flow rate, and sudden pressure changes) can cause chromatographic peak distortion and retention time drift, affecting the accuracy of analysis. The core issues are concentrated in five categories: electrolysis system, water and pipeline, control system, consumables status, and environmental interference, which require targeted investigation and resolution.

1、 Abnormal electrolysis module: the core cause of concentration output

Common reasons

The electrolysis module is the core component for generating KOH. If the electrode scales and the electrolysis voltage/current is unstable, it will cause fluctuations in ion generation efficiency

The electrode surface is covered with scale such as calcium carbonate and magnesium hydroxide (derived from trace impurity ions in pure water), which hinders the electrolysis reaction;

The electrolytic power module has malfunctioned, causing the output voltage/current to deviate from the set value (such as the rated 10V, which is actually only 8V), resulting in uneven ion generation;

Electrode wear or corrosion (platinum electrode coating peeling off after long-term use) reduces electrolysis efficiency.

Solution

Regular descaling maintenance: Disassemble the electrolysis module every 3 months, soak the electrode in 5% dilute hydrochloric acid for 30 minutes (to dissolve scale), rinse with ultrapure water until neutral (pH 7 ± 0.5), dry and reinstall;

Power calibration and replacement: Use a multimeter to check the output value of the electrolytic power supply. If the deviation exceeds ± 5%, contact the manufacturer for calibration or replacement of the power module; Avoid frequent starting and stopping of equipment in daily use to prevent power surges;

Electrode inspection and replacement: If there are obvious scratches or coating peeling on the surface of the electrode, immediately replace the original electrode (it is recommended to use platinum iridium alloy electrode, which has stronger corrosion resistance). After replacement, it needs to be verified by standard concentration (such as generating 10mmol/L KOH, confirming concentration deviation by titration method ≤ ± 2%).

2、 Waterway system pollution or blockage: dual effects of flow and purity

Common reasons

If the waterway system (including pure water inlet, water storage tank, filtration device) is contaminated or blocked, it will cause poor water inflow and a decrease in pure water purity, indirectly leading to unstable output:

The pure water inlet filter is blocked (intercepting sediment and microorganisms), resulting in insufficient inflow and water shortage for electrolysis reaction;

The water storage tank is not regularly cleaned, and microorganisms or residual KOH crystals grow on the inner wall, contaminating pure water;

The purity of pure water does not meet the standard (resistivity<18.2M Ω· cm), and impurities such as Na ⁺ and Ca ² ⁺ participate in electrolysis, interfering with the generation of KOH concentration.

Solution

Filter maintenance: Disassemble the inlet filter (usually a 0.22 μ m microporous membrane) every month. If the membrane changes color or becomes clogged, replace it directly; Suggest using 2-3 backup filter membranes to avoid downtime and waiting;

Cleaning of water storage tank: Empty the water storage tank every 2 months, wipe the inner wall with 10% hydrogen peroxide solution (sterilize), rinse with ultrapure water 3 times, air dry, and then refill with pure water (the water level of the water storage tank should be kept above 2/3 to avoid empty tank operation);

Pure water quality control: Ensure that the pure water connected to the generator has a resistivity of ≥ 18.2M Ω· cm. It is recommended to install a secondary purification column (such as an ion exchange column) at the pure water inlet, regularly monitor the purity of the pure water, and replace the purification column if it is not qualified.

3、 Leakage or blockage of pipeline system: key obstacles to pressure and flow

Common reasons

KOH solution is corrosive and long-term use can lead to pipeline aging, interface leakage, or crystal blockage of pipelines

Aging of sealing gaskets at pipeline interfaces (such as PE pipes and joints) (such as hardening of nitrile rubber gaskets), leading to leakage of KOH solution and pressure drop;

KOH crystals adhere to the inner wall of the pipeline (especially in low-temperature environments, the solubility of KOH decreases), narrowing the flow channel and causing a sudden decrease in flow rate;

One way valve failure (such as stuck valve core) causes solution reflux and disrupts output stability.

Solution

Interface sealing inspection and maintenance: Check the pipeline interface weekly, and if any leaks are found, replace the alkali resistant sealing gasket (recommended fluororubber material, resistant to KOH corrosion); During installation, ensure that the depth of the pipeline insertion joint meets the standard (such as PE pipe insertion of 3-5mm), and fix it with clamps;

Pipeline crystallization treatment: If the flow rate decreases, rinse the pipeline in reverse with ultrapure water at around 50 ℃ (from the outlet to the inlet) to dissolve the crystals; After daily use, it is necessary to perform the "pipeline cleaning program" (built-in function of the generator) to avoid residual KOH crystallization;

One way valve maintenance: Disassemble the one-way valve every 6 months and check if the valve core is flexible (manually pushing the valve core should have no jamming). If it is stuck, clean it with ultrapure water and ultrasonic for 15 minutes, or replace the one-way valve directly.

4、 Drift or malfunction of control system parameters: core failure of precise regulation

Common reasons

The control system (such as PLC, concentration sensor, flow sensor) is responsible for monitoring and adjusting the output. Parameter drift or failure can directly lead to control misalignment:

The calibration of the concentration sensor has expired, resulting in a large deviation between the detected value and the actual concentration (such as displaying 12mmol/L when the actual concentration is 15mmol/L), leading to incorrect calibration instructions;

The flow sensor is dirty (with KOH residue attached), and the deviation between the detected flow rate and the actual flow rate exceeds ± 5%;

Control program disorder (such as sudden power outage causing parameter loss), unable to adjust electrolysis and flow according to the set logic.

Solution

Regular calibration of sensors: calibrate the concentration sensor monthly with standard KOH solution (such as 10mmol/L, 20mmol/L, verified by titration) to ensure a detection deviation of ≤± 2%; Clean the flow sensor probe with calibration solution every week to remove any residue;

Program reset and backup: If the program is disrupted, reset the parameters through the device's built-in "factory reset" function. After resetting, the target concentration and flow rate (such as 1.0mL/min) need to be reset; Daily weekly backup of control parameters to USB drive to prevent data loss;

Control system detection: If the parameters are still unstable after calibration, use specialized diagnostic software to detect the operating status of the PLC. If there is a fault code, contact the manufacturer's technical personnel for troubleshooting (such as replacing the faulty signal acquisition module).

5、 Environmental condition fluctuations: easily overlooked factors of external interference

Common reasons

The KOH rinse solution generator is sensitive to temperature, humidity, and voltage stability, and environmental fluctuations can indirectly affect equipment operation:

Low (<15 ℃) or high (>30 ℃) ambient temperature: Low temperature leads to a decrease in KOH solubility (easy crystallization), while high temperature accelerates electrode corrosion and microbial growth;

Voltage fluctuations in the power grid (such as rated 220V but actual 190V or 240V) affect the stability of the electrolytic power supply and control system power supply;

The environmental humidity is greater than 75%, which causes moisture in the internal circuit of the equipment and leads to control module failure.

Solution

Environmental temperature and humidity control: Place the equipment in a constant temperature and humidity laboratory (temperature 20 ± 2 ℃, humidity 45% ± 5%), avoiding proximity to air conditioning vents or heat sources; Insulation covers can be installed around the equipment in low-temperature environments (non sealed to prevent poor heat dissipation);

Stabilized power supply configuration: Equip the generator with a high-precision stabilized power supply (such as a 1kVA stabilized power supply) to ensure that the input voltage is stable at 220V ± 5%; Avoid sharing the same circuit with high-power equipment such as centrifuges and air compressors;

Moisture protection: When the humidity exceeds the standard, place desiccants (such as silicone desiccants, replace once a month) inside the equipment, and regularly clean the equipment's heat dissipation holes with a hair dryer (cold air) to prevent moisture accumulation.

The solution to the unstable output of the KOH rinse solution generator needs to follow the logic of "first investigating the core components (electrolysis, water circuit), and then dealing with control and environment". Through regular maintenance (descaling, calibration, cleaning) and standardized operation (avoiding frequent start stop and ensuring pure water quality), the frequency of failures can be significantly reduced. It is recommended to establish a "maintenance ledger" in daily use to record the cause and solution of each malfunction, providing reference for rapid troubleshooting and ensuring long-term stable service of the equipment for ion chromatography analysis.