Gas chromatography-mass spectrometerCompounds in complex samples are separated by gas chromatography, and the separated components are ionized and analyzed by mass spectrometry. Qualitative and quantitative analysis is achieved through mass to charge ratio.

Gas chromatography-mass spectrometerThe maintenance methods are as follows:

Carrier gas system:

Cylinder pressure inspection: Check the cylinder pressure daily to ensure that it is within the range of 0.5-0.9MPa. Keep at least 10% of the gas in the cylinder to avoid interference from impurities.

Filter maintenance: Regularly replace the molecular sieve filter and trap. Blockage can cause pressure fluctuations or increases.

Air tightness inspection: If the baseline is unstable or the noise increases, the air tightness of the gas path needs to be checked. After turning off the vacuum, open the main valve of the steel cylinder, adjust the pressure reducing valve to 700KPa, tighten the main valve and release the pressure reducing valve, and observe the pressure change. A decrease in the partial pressure gauge indicates a leak in the instrument end pipeline, while a decrease in the total pressure gauge indicates a leak in the cylinder end. It is necessary to locate and re tighten or replace the components with a leak detector.

Injection port:

Sample pad replacement: Replace the new sample pad after automatic injection 150 times or manual injection 50 times to avoid needle puncture debris contamination.

Glass liner maintenance: Replace the liner after 150 automatic injections, soak in methanol or acetone for 15-20 minutes during cleaning, blow dry with nitrogen, and reinstall. If there are scratches or coating peeling on the inner wall of the liner, it needs to be replaced immediately.

O-ring inspection: Regularly inspect the surface of the O-ring for damage and replace it if necessary.

Chromatographic column:

Pollution prevention: When using a polar chromatography column, it is necessary to remove oxygen from the carrier gas, avoid mixing air when replacing the gas cylinder, or install a helium purifier. Sample pretreatment should be thorough to prevent non-volatile components from entering the column.

Ghost peak treatment: If a ghost peak occurs, cut off the length of the front end of the chromatographic column and age the column according to the condition of "interface temperature>column temperature". If ineffective, cut off 30-50cm of the chromatographic column on the injection port side and age it again.

Storage method: When not in use, insert the ends of the chromatography column into discarded isolation pads to isolate the air and prevent coating damage.

Timing of replacement: When the separation efficiency decreases and the separation degree is insufficient, a new chromatographic column needs to be replaced.

Mass spectrometry vacuum system:

Vacuum leak detection: Record the vacuum level monthly. If the vacuum degree decreases, check if there are any leaks in the vacuum system or if the vacuum pump is malfunctioning.

Leakage point location: Use an injection needle to draw petroleum ether and inject it into the injection port nut, chromatographic column connector, and ion source front door. Observe the peak height of m/z 43, and the point where the peak height suddenly increases is the leakage point.

Whole machine cleaning: Clean the surface of the instrument daily to ensure that there are no organic reagent residues or stains.

Washing solution bottle and waste liquid bottle: Check if the washing solution bottle and waste liquid bottle are placed correctly, if the washing solution is sufficient and clean, and if the waste liquid has been dumped.