In situ differential electrochemical mass spectrometer is a precision instrument that combines electrochemical testing and mass spectrometry analysis, used for real-time monitoring of volatile products (such as gases, vapors, etc.) generated in electrochemical reactions. Its maintenance needs to take into account the stability of the electrochemical system, the sensitivity of the mass spectrometer, and the synergy between the two. The following provides detailed explanations on daily maintenance, periodic maintenance, maintenance of key components, environmental control, and operational standards.

1、 Daily maintenance

1. Cleaning and Inspection of Electrochemical Systems

-Electrode surface treatment: After daily experiments, immediately rinse the working electrode, counter electrode, and reference electrode with ultrapure water to remove residual electrolytes or reaction products. If there is contamination on the electrode surface (such as oxide or polymer deposition), specialized polishing paper (such as Al ₂ O3 powder) or ultrasonic cleaning (in ethanol or deionized water medium) should be used to restore activity.

-Sealing of electrolytic cell: Check whether the O-ring of the electrolytic cell chamber is aging or deformed, ensure good sealing, and avoid short circuit or corrosion of the mass spectrometry pipeline due to liquid leakage.

-Reference electrode liquid level: Supplement the filling solution inside the reference electrode (such as KCl saturated solution) to prevent potential drift caused by salt bridge drying up.

2. Mass spectrometry maintenance

-Ion source cleaning: After daily experiments, wipe the mass spectrometry injection port with a dust-free cloth to prevent sample residue from blocking or contaminating the vacuum system. If the signal noise is detected to increase, the ion source (such as electron bombardment source or electric spray source) shall be disassembled and cleaned with ethanol or acetone before drying.

-Vacuum system inspection: Check whether the oil level of the mechanical pump is below the warning line, whether the molecular pump speed is normal (usually above 90% of the rated speed), and whether the vacuum degree meets the standard (such as 10 ⁻⁵ Pa level). If the vacuum degree decreases, it is necessary to check for pipeline leaks or replace the molecular pump bearings.

3. Maintenance of pipelines and interfaces

-Gas pipeline blowing: Use high-purity nitrogen gas (≥ 99.999%) to blow the capillary pipeline connecting the electrochemical cell and mass spectrometer in a forward direction every week, to remove adsorbed gases or condensates.

-Interface fastening: Check if the Swagelok connector or sleeve is loose to avoid air leakage or signal loss caused by vibration.

2、 Periodic maintenance (monthly/quarterly)

1. Electrochemical system calibration

-Reference electrode calibration: Use a standard buffer solution (such as KCl solution with pH=7) to calibrate the potential of the reference electrode, with an error controlled within ± 5 mV.

-Current voltage curve test: The double-layer stability of the working electrode is detected by cyclic voltammetry (CV). If the position of the oxidation-reduction peak shifts by more than 10 mV, the electrode surface needs to be reprocessed.

2. Performance verification of mass spectrometer

-Sensitivity calibration: Introduce standard gases (such as He, N ₂, or CO ₂), adjust the mass spectrometry resolution to the optimal state (such as R ≥ 1000), and ensure that the signal intensity of the target ion is linearly related to the concentration.

-Quality axis calibration: Use standard substances to correct the deviation of the quality axis, ensuring that the ion mass to charge ratio (m/z) positioning accuracy is ≤ 0.1 Da.

3. Replacement of consumables

-Electrolyte update: Replace the electrolyte in the electrolytic cell once a month (such as 0.1 M H ₂ SO ₄ or KOH solution) to avoid accumulation of impurities due to prolonged use.

-Filter replacement: The activated carbon filter at the mass spectrometry inlet should be replaced quarterly to prevent gas adsorption saturation from affecting detection sensitivity.

3、 Special maintenance of key components

1. Maintenance of mass spectrometer detector

-Electron multiplier protection: Avoid prolonged exposure to high concentration gases (such as>1000 ppm) to prevent fatigue of the multiplier. When shutting down, inert gas (such as Ar) should be used to blow and turn off the high-voltage power supply.

-Quality analyzer cleaning: Disassemble the quadrupole or time-of-flight (TOF) quality analyzer annually, wipe the internal components with ethanol, and remove any attached contaminants.

2. Temperature control system inspection

-Heating device testing: If the instrument contains an in-situ heating module (such as catalytic reaction testing), the resistance value of the heating wire should be checked (deviation ≤ 5%) to ensure temperature uniformity (within ± 1 ℃).

-Cooling circulating water maintenance: Regularly clean the filter screen of the chiller, replenish deionized water, and prevent scale blockage from affecting temperature control efficiency.

4、 Environmental Control and Operating Standards

1. Environmental requirements

-Temperature and humidity control: The laboratory temperature should be maintained at 20-25 ℃, with humidity ≤ 60%, to avoid circuit corrosion or abnormal mass spectrometry discharge caused by humidity.

-Dust prevention measures: Cover the instrument with a dust cover and regularly wipe the outer shell with non-woven fabric to prevent dust from entering the mass spectrometry vacuum chamber.

2. Precautions for operation

-Power on/off sequence: Start the mechanical pump first before turning on the molecular pump; Reverse operation during shutdown to avoid vacuum backflow.

-Sample processing: Before electrochemical reaction, the electrolyte needs to be degassed (such as passing high-purity N ₂ for ≥ 30 minutes) to reduce background interference.

-Emergency fault handling: If the mass spectrometry signal drops sharply, immediately check if the pipeline is blocked or if the electrode is short circuited. Do not forcefully increase the voltage.

5、 Maintain records and archive management

1. Log registration

-Record the maintenance content (such as electrode replacement, calibration of mass spectrometry), equipment operation status, and abnormal phenomena, and form traceability documents.

-Typical fault cases need to be recorded in detail (such as "Mass spectrometry signal drift on a certain day: resolved after replacing the molecular pump").

2. Spare parts management

-Common vulnerable parts: O-rings, capillaries, reference electrode solution, mass spectrometry filaments, etc., stored in a drying cabinet to prevent oxidation.

6、 Common troubleshooting

1. Abnormal electrochemical signal

-Reason: electrode contamination, unstable liquid contact potential, and damaged shielding wire.

-Solution: Polish the electrode, replace the reference electrode salt bridge, and check the grounding wire.

2. Decreased detection limit of mass spectrometry

-Reasons: ion source contamination, increased vacuum leakage rate, and detector aging.

-Solution: Clean the ion source, detect leaks and replace seals, adjust the detector voltage.