Thermo Fisher liquid chromatography-mass spectrometry (LC-MS) is a crucial analytical equipment in laboratories, combining the high separation ability of liquid chromatography with the high sensitivity of mass spectrometry, playing an important role in multiple fields.

　　1、 Main application scenarios

1. Drug development and clinical research: In drug metabolism and pharmacokinetics research, liquid chromatography-mass spectrometry can accurately determine the mass and structure of constant, trace, and trace drugs and their metabolites, providing key data support for drug development.

2. Food safety testing: In the field of food analysis, this instrument can qualitatively and quantitatively detect drug residues in foods such as poultry, livestock, meat, and crops, providing structural information of the detected substances. It has high precision and good reproducibility, and can effectively eliminate false positive test results.

3. Environmental monitoring and protection: used for monitoring and analyzing environmental pollutants, capable of detecting various molecules in complex matrices, providing reliable data for environmental monitoring.

Proteomics and Bioanalysis: Suitable for sequence analysis of biomolecules such as peptides, proteins, nucleotides, polysaccharides, etc., it plays an important role in proteomics research.

　　2、 Core usage precautions

1. Mobile phase management: It is strictly prohibited to use non-volatile salts such as phosphates and borates. If buffering salts are required, only ammonium acetate and ammonium formate with a concentration of ≤ 20mmol/L should be selected. The mobile phase needs to be prepared and used immediately. The aqueous phase is prone to bacterial growth, and the acidic mobile phase may cause baseline drift if left for more than 12 hours.

2. Ion source maintenance: Rinse the atomization chamber with isopropanol and open the gas valve to vibrate the ESI source once a week; The sampling cone hole should be cleaned once every 2 weeks, and after disassembly, it should be sonicated with methanol: water: formic acid=45:45:10 for 10 minutes. Then, it should be sonicated with ultrapure water and methanol for 10 minutes each, and dried before installation.

3. Vacuum system maintenance: The mechanical pump needs to change oil every 6-12 months. Before changing oil, the vacuum should be emptied and the oil level should be kept between the scale lines. Open the shock valve for about 20 minutes per week to release dissolved gases and solvents from the pump oil.

4. Column protection: Before the experiment, if the mobile phase contains buffer salts, rinse the column with a salt free mobile phase until the baseline is stable; After the experiment, rinse with a salt free mobile phase with the same water content as the analysis for 30 minutes, and then rinse with 90% acetonitrile or methanol for 10 minutes to remove hydrophobic pollutants.

5. Cleaning of injection system: The sample needs to be filtered through a 0.22 μ m filter membrane. Immediately after the experiment, rinse the injection needle and injection valve with a methanol: water=1:1 solution at least 3 times. If acid or salt containing samples have been detected, increase the number of washings.

　　3、 Environmental and safety requirements

1. Environmental control: The laboratory temperature should be controlled between 15-28 ℃ and the humidity should be between 20% and 80%. Temperature fluctuations can cause inaccuracies in the quality axis, high humidity can lead to mold and corrosion, and low humidity can result in static electricity.

2. Power supply guarantee: It is necessary to connect a UPS stabilized power supply to avoid damage to the molecular turbine pump due to sudden power outages during power outages. Sudden power outage during operation of liquid chromatography-mass spectrometry may damage the circuit or affect the vacuum system.

3. Sample processing: The sample must undergo purification treatment, either by centrifugation at>10000rpm to remove solid impurities, or by filtration, otherwise impurities will clog the column and contaminate the ion source.

　　4、 Key points of daily maintenance

1. Regular tuning: tuning calibration must be carried out after startup and before testing, and the mass axis must be calibrated with instrument matching tuning solution to ensure that the target ion mass to charge ratio deviation is ≤ 0.1Da.

2. Flow rate control of mobile phase: The flow rate of ESI ion source should not exceed 0.5ml/min, and the flow rate of APCI should not exceed 1.0ml/min. Excessive flow rate can lead to poor atomization and residual solvent contamination of the ion source.

3. Regularly replace consumables: The mechanical pump oil should be changed every six months. If the pump oil is found to be blackened or contaminated, it should be replaced in a timely manner. Different brands of pump oil cannot be mixed, changing the oil costs only a few hundred yuan, and repairing the pump costs tens of thousands.

4. Data backup: Backup experimental data daily to prevent data loss caused by hard disk failures. Vulnerable parts such as spray needle, sampling cone, mechanical pump oil, etc. shall be stored in advance.

　　5、 Startup and shutdown specifications

1. Startup sequence: First turn on the gas (nitrogen/argon) → turn on the mechanical pump → wait for the vacuum degree to drop below 10Pa → turn on the molecular turbine pump, which must be evacuated for 12 hours. After turning on, it is necessary to perform tuning calibration, otherwise the quality number will be inaccurate and the result will be equivalent to a white test.

2. Shutdown process: After the experiment is completed, rinse the system thoroughly with a salt free mobile phase to ensure that the sample components, chromatographic column effluent, and buffer salts in the mass spectrometer are washed clean. Turn off the pump flow rate entering the mass spectrometer, purge with nitrogen for more than 5 minutes, and then turn off the instrument.

By strictly adhering to the above usage precautions and maintenance standards, the Thermo Fisher liquid chromatography-mass spectrometer can maintain long-term stable operation, providing reliable data support for scientific research and testing work.