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The qualitative analysis of gas chromatography-mass spectrometry is very convenient, and it can be quickly qualitatively analyzed through the similarity search of its own database.
The gas chromatography-mass spectrometer also has a variety of acquisition modes, with high sensitivity and accurate quantification
.
The state of the instrument itself determines the accuracy of the sample analysis results.
Therefore, doing a good job in the maintenance of the gas chromatography-mass spectrometer is a very important task in the management and maintenance of the instrument
.
1 Mass spectrometer vacuum leak detection and tuning Mass spectrometer tuning is to obtain good mass spectrometer data, and mass spectrometer vacuum leak detection and tuning should be performed before sample testing
.
Tuning should be done after switching the machine on and off and changing the filament.
If the instrument is always on, tuning should be done once every 1-2 weeks
.
After tuning, make a new standard curve
.
Check the water peak and nitrogen peak.
If the peak height of nitrogen m/z 28 is more than twice the height of water m/z 18, there is a possibility of gas leakage
.
The possible reasons for the high nitrogen gas are as follows: (1) If the steel cylinder or carrier gas line filter has just been replaced, the nitrogen peak may be high at the beginning of the startup due to air mixed in the carrier gas line
.
The split ratio can be increased, and the air leakage check can be carried out after purging for 10 minutes
.
(2) If a helium filter is installed in the carrier gas pipeline, after a period of use, nitrogen will be released due to the saturation of the filter, which will result in a higher nitrogen peak during leak inspection.
At this time, a new helium filter needs to be replaced.
.
(3) If the purity of helium is not enough, the impurities may contain some nitrogen, and the nitrogen peak is slightly higher during peak detection
.
When a system leak is found, the leak point must be found
.
You can suck a small amount of petroleum ether with a syringe and inject it into the upper nut of the injection port, the joints at both ends of the chromatographic column and the front door of the ion source, and observe the peak height of 43 mass number.
Air leak
.
After you find the leak, screw it or reconnect it
.
After tuning is completed, evaluate the tuning report: (1) Check whether the peak shape has obvious bifurcation and symmetry; (2) Check whether the value of the peak width at half maximum is within the range of 0.
6 ± 0.
1; (3) Check whether the detector voltage is Over 1.
5kV, compared with the previous tuning data, a difference of 0.
2-0.
3kV is acceptable.
If the difference is too large, re-tuning is required; (4) The peak intensity is m/z 69, whether the peak intensity is the m/z 28 peak intensity 2 times; (5) Whether the relative intensity ratio of m/z 502 is greater than 2%
.
All of the above points are met, indicating that the tuning data is available for this time
.
2 Replacement of pump oil by mechanical pump The cycle of replacing pump oil by mechanical pump is 3000 hours
.
Change the pump oil after stopping the vacuum, powering off the workstation and the main unit
.
Put the mechanical pump above the ground, align the waste liquid bottle with the oil discharge port at the lower end of the mechanical pump, open the oil filling port at the upper end of the mechanical pump, unscrew the plug of the oil discharge port, and drain the pump oil
.
After all the pump oil is discharged, tighten the plug of the oil discharge port, slowly add new pump oil, and the liquid level of the added oil is close to the liquid level, tighten the plug, and put the mechanical pump in the original position
.
After the instrument starts normally, select the Reset Consumables dialog box to reset the pump oil usage time
.
3 Cleaning the ion source Contamination of the ion source will cause poor reproducibility, and the ion source should be cleaned in time
.
Clean gloves are required when handling the ion source
.
Cleaning the ion source is divided into the following three steps: (1) Take out the ion source
.
After stopping the vacuum, loosen the knob of the vacuum chamber, open the door, pull out the repeller shield with tweezers, move the wire to the left, put the ion source mounting rod on the ion source, and use a flat-blade screwdriver to remove the two ends of the ion source.
Loosen the two fixing screws one turn, and then use tweezers to move the fixing clamp of the ion source to the right and then down to the fixed position.
Use a flat-blade screwdriver to completely unscrew the two fixing screws, and use the mounting rod to take out the ion source
.
(2) Clean the ion source
.
Place the ion source on clean paper, remove the mounting rod, and separate the repeller set and ion source case
.
Wipe the inside of the ion source box and the round holes on both sides with abrasive sandpaper repeatedly, wipe the plane of the repelling electrode and the circumferential surface of the side, remove the surface dust with ear-washing balls, ultrasonically clean in acetone solution for 30 minutes, and then clean at 400°C.
aged for one hour in a muffle furnace
.
Assemble the repeller set, install the repeller on the ion source box, and tighten the ion source mounting rod to the ion source box
.
(3) Install the ion source
.
Install the fixed ion source back into the instrument cavity, first tighten the two fixing screws of the ion source, and then loosen one turn, use tweezers to move the ion source clamp back in the order of first up and then to the left, and tighten the two Secure the nut and remove the ion source mounting rod
.
Use tweezers to put the wire back into the repeller, confirm that the wire of the repeller is in good contact, that the wire of the repeller and other wires cannot touch each other, confirm that the ion source clamp is in the initial position, and tighten the screws that fix the ion source
.
After closing the door and starting the instrument normally, in the workstation, reset the consumables dialog box and clear the ion source usage time
.
4 After the filament is replaced and the vacuum is stopped, loosen the knob of the vacuum chamber, open the door, carefully unplug the two wires to be replaced with tweezers, move the wires to the left, loosen the nut with a flat-blade screwdriver, and remove with tweezers Then use tweezers to remove the filament, replace it with a new filament, install the new filament with tweezers and fix it, use tweezers to install the filament's fixing nut and tighten it
.
Connect the two filament wires to the filament, and use tweezers to push the two wires towards the filament to make close contact without short-circuit
.
Close the door and tighten the vacuum chamber knob
.
After the instrument is in normal use, reset the usage time before the filament to zero
.
The factors that affect the service life of the filament are as follows: (1) Whether the vacuum degree is good
.
Under normal circumstances, the filament can be turned on after half an hour of vacuum startup.
Turning on the filament when the vacuum degree is not good will speed up the consumption of the filament
.
(2) Whether there is air leakage in the vacuum, vacuum air leakage will accelerate the oxidation and consumption of the filament
.
(3) The sample concentration will affect the life of the filament, and long-term analysis of high-concentration samples will speed up the consumption of the filament
.
(4) The filament and the ion source should be installed in the correct position.
If the position is deviated, the filament will be deformed and its life will be shortened
.
(5) The solvent removal time is not set properly.
Turning on the filament when the solvent is out will speed up the consumption of the filament
.
(6) When cleaning the ion source, the two electron introduction holes on the upper and lower sides of the ion source are not cleaned properly, which will reduce the efficiency of electron introduction and accelerate the consumption of the filament
.
The gas chromatography-mass spectrometer also has a variety of acquisition modes, with high sensitivity and accurate quantification
.
The state of the instrument itself determines the accuracy of the sample analysis results.
Therefore, doing a good job in the maintenance of the gas chromatography-mass spectrometer is a very important task in the management and maintenance of the instrument
.
1 Mass spectrometer vacuum leak detection and tuning Mass spectrometer tuning is to obtain good mass spectrometer data, and mass spectrometer vacuum leak detection and tuning should be performed before sample testing
.
Tuning should be done after switching the machine on and off and changing the filament.
If the instrument is always on, tuning should be done once every 1-2 weeks
.
After tuning, make a new standard curve
.
Check the water peak and nitrogen peak.
If the peak height of nitrogen m/z 28 is more than twice the height of water m/z 18, there is a possibility of gas leakage
.
The possible reasons for the high nitrogen gas are as follows: (1) If the steel cylinder or carrier gas line filter has just been replaced, the nitrogen peak may be high at the beginning of the startup due to air mixed in the carrier gas line
.
The split ratio can be increased, and the air leakage check can be carried out after purging for 10 minutes
.
(2) If a helium filter is installed in the carrier gas pipeline, after a period of use, nitrogen will be released due to the saturation of the filter, which will result in a higher nitrogen peak during leak inspection.
At this time, a new helium filter needs to be replaced.
.
(3) If the purity of helium is not enough, the impurities may contain some nitrogen, and the nitrogen peak is slightly higher during peak detection
.
When a system leak is found, the leak point must be found
.
You can suck a small amount of petroleum ether with a syringe and inject it into the upper nut of the injection port, the joints at both ends of the chromatographic column and the front door of the ion source, and observe the peak height of 43 mass number.
Air leak
.
After you find the leak, screw it or reconnect it
.
After tuning is completed, evaluate the tuning report: (1) Check whether the peak shape has obvious bifurcation and symmetry; (2) Check whether the value of the peak width at half maximum is within the range of 0.
6 ± 0.
1; (3) Check whether the detector voltage is Over 1.
5kV, compared with the previous tuning data, a difference of 0.
2-0.
3kV is acceptable.
If the difference is too large, re-tuning is required; (4) The peak intensity is m/z 69, whether the peak intensity is the m/z 28 peak intensity 2 times; (5) Whether the relative intensity ratio of m/z 502 is greater than 2%
.
All of the above points are met, indicating that the tuning data is available for this time
.
2 Replacement of pump oil by mechanical pump The cycle of replacing pump oil by mechanical pump is 3000 hours
.
Change the pump oil after stopping the vacuum, powering off the workstation and the main unit
.
Put the mechanical pump above the ground, align the waste liquid bottle with the oil discharge port at the lower end of the mechanical pump, open the oil filling port at the upper end of the mechanical pump, unscrew the plug of the oil discharge port, and drain the pump oil
.
After all the pump oil is discharged, tighten the plug of the oil discharge port, slowly add new pump oil, and the liquid level of the added oil is close to the liquid level, tighten the plug, and put the mechanical pump in the original position
.
After the instrument starts normally, select the Reset Consumables dialog box to reset the pump oil usage time
.
3 Cleaning the ion source Contamination of the ion source will cause poor reproducibility, and the ion source should be cleaned in time
.
Clean gloves are required when handling the ion source
.
Cleaning the ion source is divided into the following three steps: (1) Take out the ion source
.
After stopping the vacuum, loosen the knob of the vacuum chamber, open the door, pull out the repeller shield with tweezers, move the wire to the left, put the ion source mounting rod on the ion source, and use a flat-blade screwdriver to remove the two ends of the ion source.
Loosen the two fixing screws one turn, and then use tweezers to move the fixing clamp of the ion source to the right and then down to the fixed position.
Use a flat-blade screwdriver to completely unscrew the two fixing screws, and use the mounting rod to take out the ion source
.
(2) Clean the ion source
.
Place the ion source on clean paper, remove the mounting rod, and separate the repeller set and ion source case
.
Wipe the inside of the ion source box and the round holes on both sides with abrasive sandpaper repeatedly, wipe the plane of the repelling electrode and the circumferential surface of the side, remove the surface dust with ear-washing balls, ultrasonically clean in acetone solution for 30 minutes, and then clean at 400°C.
aged for one hour in a muffle furnace
.
Assemble the repeller set, install the repeller on the ion source box, and tighten the ion source mounting rod to the ion source box
.
(3) Install the ion source
.
Install the fixed ion source back into the instrument cavity, first tighten the two fixing screws of the ion source, and then loosen one turn, use tweezers to move the ion source clamp back in the order of first up and then to the left, and tighten the two Secure the nut and remove the ion source mounting rod
.
Use tweezers to put the wire back into the repeller, confirm that the wire of the repeller is in good contact, that the wire of the repeller and other wires cannot touch each other, confirm that the ion source clamp is in the initial position, and tighten the screws that fix the ion source
.
After closing the door and starting the instrument normally, in the workstation, reset the consumables dialog box and clear the ion source usage time
.
4 After the filament is replaced and the vacuum is stopped, loosen the knob of the vacuum chamber, open the door, carefully unplug the two wires to be replaced with tweezers, move the wires to the left, loosen the nut with a flat-blade screwdriver, and remove with tweezers Then use tweezers to remove the filament, replace it with a new filament, install the new filament with tweezers and fix it, use tweezers to install the filament's fixing nut and tighten it
.
Connect the two filament wires to the filament, and use tweezers to push the two wires towards the filament to make close contact without short-circuit
.
Close the door and tighten the vacuum chamber knob
.
After the instrument is in normal use, reset the usage time before the filament to zero
.
The factors that affect the service life of the filament are as follows: (1) Whether the vacuum degree is good
.
Under normal circumstances, the filament can be turned on after half an hour of vacuum startup.
Turning on the filament when the vacuum degree is not good will speed up the consumption of the filament
.
(2) Whether there is air leakage in the vacuum, vacuum air leakage will accelerate the oxidation and consumption of the filament
.
(3) The sample concentration will affect the life of the filament, and long-term analysis of high-concentration samples will speed up the consumption of the filament
.
(4) The filament and the ion source should be installed in the correct position.
If the position is deviated, the filament will be deformed and its life will be shortened
.
(5) The solvent removal time is not set properly.
Turning on the filament when the solvent is out will speed up the consumption of the filament
.
(6) When cleaning the ion source, the two electron introduction holes on the upper and lower sides of the ion source are not cleaned properly, which will reduce the efficiency of electron introduction and accelerate the consumption of the filament
.
