Compared with GC-MS, the advantages of GC-MSMS are below:
1. With cascade function, strong qualitative ability and quantitative ability, MRM signal-to-noise ratio is higher than SIM of GC-MS;
2. In addition to general ion scanning functions, it also has functions such as SRM, MRM, precursor ion scanning, and neutral loss (not for ion traps);
3. It is very helpful for the structural research of characteristic groups;
4. The sample does not need to be derivatized;
5. Achieve confirmatory quantitation in a single analysis;
6. Low detection limit in complex and dirty matrix, improving laboratory efficiency and output rate.

Reply: Both can be disassembled from the front for cleaning. LC-MSMS can be quickly disassembled, and the ion source can be disassembled without tools. For GC-MSMS, the ion source can be turned on from the front. It can prevent the quadrupole from being exposed to the ambient air of the laboratory for a long time, causing contamination.

Reply: There is a conversion column in front of the ion source, and the gas chromatographic column can be replaced without breaking the vacuum by closing the valve.

Reply: The vacuum degree of the 5231 collision cell can generally reach 3.7*E-5 Torr, and the EI source chamber can reach the level of E-6 Torr. (Note: 1 Torr means 1 mm Hg column)

Reply: Usually, it will take more than 8 hours, suggest the overnight.

Reply: Yes, the sample detection in DAD will not damage the sample, but entering the mass spectrometer will destroy the molecular structure, so it can be used in series after the advanced DAD detection and then enter the mass spectrometry detection.

Reply: No, we need to consider the stability of the compound.

Reply: Nitrogen blowing apparatus, fast solvent extraction apparatus, parallel concentration, solid phase extraction apparatus, pulverizer, homogenizer, shaker, etc.

Reply: It can be used with most common pretreatment equipment, such as headspace, purge trap, thermal analysis, thermal cracking and solid phase extraction, solid phase microextraction, etc.

Reply: The hardware advantages are: Efficient ESI ion source, unique ion transmission system (exclusive), pure molybdenum gold-plated quadrupole (exclusive), axial acceleration collision cell, detector with stronger response signal.

Reply:
1. Rinse the system and clean the spray chamber with isopropanol solution every day, and regularly open the shock valve to shock the gas (for the ESI source, at least once a week; for the APCI source, once a day) to ensure that the capillary is clean.
2. Mobile phase flow rate should not be too high, ESI ion source should not exceed 0.5 mL/min, and APCI should not exceed 1.0 mL/min.
3. The pump oil of the mechanical pump needs to be replaced regularly, usually once every half a year. If the pump oil looks very dirty, it needs to be replaced in advance.
4. Control the environment of the sample running, including temperature and humidity.
5. After the experiment, the injection needle and injection valve should be cleaned. After using the mobile phase containing too much acid, the chromatography column and ion source should be washed with methanol / water.
6. Clean the sample cone hole regularly, close the partition valve, and remove the sample cone hole.
7. Regularly replace the electron multiplier.

Reply:
1. Daily maintenance of the gas chromatography part
 (1) Carrying gas and flow path system: Check the cylinder pressure every day, with a pressure range of 0.5~0.9MPa, generally 0.6MPa. Regularlly check molecular sieve filters and traps for clogging, which can cause pressure fluctuations or increases. Regularly use leak detection fluid to check carefully, determine the location of the air leak, and re-tighten or replace the new pressure reducing valve.
(2) Chromatographic column: Remove the oxygen from the carrier gas when using the column, especially the polar column, Be careful not to mix with air when changing the cylinders, A helium purifier can also be installed in the gas flow path.
2. Daily maintenance of mass spectrometry
(1) Mass spectrometer vacuum leak detection and tuning: The tuning of the mass spectrometer is to obtain good mass spectrometry data, and the vacuum leak detection and tuning of the mass spectrometer must be performed before the sample test.
(2) Replace the mechanical pump pump oil regularly.
(3) Clean the ion source regularly.