Maintenance and maintenance of GC/MS

What is a GC/MS?

Mass spectrometry can perform effective qualitative analysis, but the analysis of complex organic compounds is powerless; chromatography is an effective separation method for organic compounds, especially suitable for quantitative analysis of organic compounds, but qualitative analysis is more difficult. Therefore, the effective combination of the two will provide chemists and biochemists with a highly efficient qualitative and quantitative analysis tool for complex organic compounds. A technique that combines two or more methods is called a combination technique, and an instrument that combines a gas chromatograph and a mass spectrometer is called a gas-mass spectrometer.

The GC/MS can be seen as a combination of a capillary column gas chromatograph plus a mass detector. The problem it often comes up is also the sum of the two.

1. The tightness problem involved in the instrument

The GC/MS is a gas-operated system, so the tightness of the instrument is important.

(1) Changing the column: The length of the capillary column entering the mass spectrometer is not appropriate, too long or too short.

(2) The gasket should be tight and tight. If it is too loose, there will be a hidden danger. If it is too tight, the gasket will be crushed, and a new gasket will need to be replaced each time the column is replaced.

(3) Pay attention to the sealing property after opening the cavity when cleaning the ion source.

2, the use and preservation of the column

(1) When using the column, pay attention to the minimum and maximum temperatures indicated in the instruction manual, and do not exceed the upper temperature limit of the column. Otherwise, the fixed solution will be lost and the detector will be polluted. To set the maximum allowable temperature, the GC will automatically stop warming to protect the column if it is suddenly heated by human or for unknown reasons. Oxygen, inorganic acids and bases, and mineral acids can cause damage to the column fixative. These substances should be prevented from entering the column.

(2) After the column is removed, the two ends of the column are usually inserted into the unused sample pad. If it is only temporarily removed for a few days, it can be placed in the desiccator.

(3) Installation of the column

The installation of the column should be carried out according to the instructions. When cutting, special ceramic chips should be applied and the cutting surface should be flat. Different sizes of capillary columns are used for different sizes of graphite gaskets. Note that the graphite gasket used at one end of the inlet and the end of the mass spectrometer is different. Do not mix. The length of the capillary entering the end of the inlet depends on the liner used. The instrument company provides a special comparison tool. Similarly, the length of the capillary entering the end of the mass spectrometer also needs to be compared with the special tools provided by the instrument company. The column joint nut should not be too tight, too tight to crush the graphite ring, but it is easy to cause air leakage. Generally, the hand is tightened and then tightened with a wrench for a quarter turn. Turn on the mass before inserting the mass into the small beaker containing the organic solvent to see if there is any bubble overflow and the flow rate is equal to the set value. It is strictly forbidden to bake the column at a high temperature when no carrier gas passes, so as to avoid damage to the column caused by oxidation loss of the fixing solution.

3. Cleaning of ion source and pre-rod

Prepare the relevant tools and reagents before cleaning, then open the case, carefully unplug the cable connected to the ion source, loosen the screw, and remove the ion source. Remove the main quadrupole before taking the pre-rod, place it on the dust-free paper, and then remove the pre-rod to be washed. Be careful when handling the entire process. Second, avoid dust entering the cavity. The components of the ion source are separated, and the filaments, circuit boards, and black ceramic rings are not cleanable in all components of the ion source. The ion box and its support, three lenses, stainless steel heating block and pre-rod need to be scrubbed with alumina, and the 600-mesh alumina powder is adjusted into a paste with glycerin or deionized water, scrubbed with a cotton swab, and the components are scrubbed with emphasis. The inner surface, the passage of ions. After the alumina is scrubbed, rinse it with water, then soak it with deionized water, methanol and acetone, then ultrasonically clean it. After the ion source is combined, install the pre-rod and quadrupole, and then carefully install the ion source. Cover the chassis and clean it.