Mass spectrum instrument

How to correctly shut down the GC-MS (gas chromatography-mass spectrometer)

(1) In the control menu of the instrument, click the “View” menu and select “Vacuum control” to enter the diagnosis and vacuum control page.

(2) Select “Empty” in the vacuum menu; then, the workstation sets the column temperature at 30℃, and turns off the auxiliary heating. This course needs about 40 min.

(3) Upon completion of emptying, quit the workstation, and power off the computer.

(4) Never turn off the power supply of gas chromatograph and mass spectrum.

(5) Shut off the carrier gas He.

Use and storage of chromatographic column

(1) When using the chromatographic column, notice the minimum and maximum temperatures indicated in the manual, and never use the chromatographic column at the temperature over the upper limit, in order to avoid loss of stationary liquid and prevent the detector from pollution. The maximum allowable operating temperature shall be set; in case of sudden temperature rise due to man-made or unknown cause, GC will stop temperature rise automatically in order to protect the chromatographic column. Oxygen, inorganic acid and alkali, and mineral acid can damage the stationary liquid of chromatographic column to it is necessary to prevent those materials from entering the chromatographic column.

(2) After being dismantled, both ends of chromatographic column shall be inserted in the unused sample inlet gasket. If the chromatographic column is just dismantled for days, it can be placed in the dryer.

(3) Installation of chromatographic column

The chromatographic column shall be installed according to the manual, and cut by the dedicated ceramic blade to ensure that the cut face is flat. The capillary columns of different sizes shall be provided with the graphite washers of different sizes. The graphite washer used on the side connected to the sample inlet is different from that used on the side connected to the mass spectrum so they must not be mixed. The length of capillary column entering the sample inlet shall be determined according to the adopted lining; the instrument company provides the special comparison tool. Similarly, the length of capillary column entering the mass spectrum side shall also be compared with the special tool supplied by the instrument company. The adapter nut of the column must not be tightened extremely; otherwise, the graphite washer may be crushed, resulting in gas leakage; normally, the nut shall be tightened first by hand, and then turned for 1/4 of turn by the wrench. Before connecting the mass spectrum, it is required to turn on the instrument, insert the end of column into a small beaker containing organic solvent, and check if there are bubbles and the flow rate is equivalent to the setting. It is forbidden to bake the chromatographic column at a high temperature without carrier gas, for fear of damaging the chromatographic column due to oxidization and loss of stationary liquid. 

How to guarantee the tightness of GC-MS?

GC-MS is a gas operating system so its tightness is vital.

(1) Replace the column: The length of capillary column entering the mass spectrum chamber is unsuitable; both extremely long and extremely short are forbidden.

(2) The tightness of washer shall be suitable; there may be gas leaking if the washer is very loose, and the washer may be crushed if it is very tight; the seal washer must be renewed every time when the chromatographic column is replaced.

(3) When cleaning the ion source, notice the tightness after the chamber is opened.