• No : 4688
  • Displayed Date : 2020/12/17 13:08
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(GCMS) Chemical Ionization(CI, NCI) Reagent Gas Setup Procedure

(GCMS) Chemical Ionization(CI, NCI) Reagent Gas Setup Procedure
Category : 

Answer

Parts Number: 225-07776-91 PLUG KIT (Used as a stop cock when no reagent gas is used.)
 
1. Automatically stop the GC/MS in GCMSsolution.
  Wait until the "system shutdown" message appears
 
 
2. Connect the reagent gas to be used.
  For CI/NCI, a maximum of two types of reagent gas from among methane, isobutane and ammonia can be introduced from the two reagent gas introduction ports. Block the reagent gas introduction port of the CI that is not used with the plug provided with the system.
  NOTE: The reagent gas used for Smart EI/CI is limited to isobutane.
  CAUTION: Methane and isobutane are flammable gases and might explode when they accumulate. Also, ammonia is a toxic gas. Every effort has been made in the design of this instrument to prevent leakage of reagent gas. However, there is the possibility that small amounts of reagent gas in use may leak from the other unused port if the solenoid valve breaks or malfunctions, or if the gas pressure rises abnormally. When using CI/NCI, cover the unused reagent gas introduction port with the cap for the stop cock and take necessary safety precautions.
  
 
3. Install the required ion source.
  The ion source differs for when CI and NCI are used. The ion source for CI and NCI is installed and removed in the same way as for the EI ion source, except that the PTFE tube for introduction of standard sample (PFTBA) for instrument adjustment must be connected.
  For details on installing and removing the ion source, click here.
 
 
4. To be extra safe, check that the required reagent gas is connected correctly and that the required ion source is installed correctly.
 
 
5. Open the [GCMS Real Time Analysis] program window in GCMSsolution.
  Click [System Configuration] on the assistant bar to open the [System Configuration] sub-window.
 
 
6. Select [MS] at [Modules Used for Analysis] in the [System Configuration] sub-window.
  Click [Properties]. 
  
 
7. (1) Select the MS tab in the [Modules of Analytical Line#] sub-window.
  (2) Click the arrow to the right of the [Ion Source] dropdown list box, and select the type of currently installed ion source from EI, CI and NCI.(For Smart EI/CI ion source, select EI and select the [Perform QCI] checkbox.)
  (3) Click the arrow to the right of the [Port1] and [Port2] dropdown list boxes, and select the reagent gas to be used from each of their options. Select [None] for ion sources that are not to be connected. Note that auto tuning is performed based on this information.
  (4) Click [OK] to close the Properties sub-window. Click [Set] in the [System Configuration] sub-window to close it.
 
 
8. Automatically start up the GC/MS.
 
 
9. The [Instrument Monitor] view is displayed on the right side of the sub-window. If the [Instrument Monitor] view is not displayed, select [Instrument Monitor] on the [View] menu.
  The vacuum level can be monitored at the following two locations. In either case, the Pirani gauge indicates the low vacuum side and the ion gauge indicates the high vacuum side.
  The vacuum levels are displayed as a graph on the instrument monitor. The momentary value when the mouse cursor is aligned with the graphs is displayed as a numerical value.
  Click the [Detail] button at the instrument monitor. The [Monitor Settings] sub-window that is displayed indicates the vacuum level in real time.
  Check the vacuum level in the analysis tubes to make sure that there are no abnormalities. (The indicators for the vacuum level must indicate a green level.)
 
 
10. Click [Tuning] on the assistant bar and then click [Peak Monitor View]. The [Peak Monitor View] sub-window opens.
  Click [Instrument Control] on the [View] menu. Selection switches for the reagent gas port appear. Select the port of the reagent gas to be used from the dropdown list box.
  
 
11. First of all, air in the reagent gas flow path is extracted.
  (1) Make sure that the stop cock of the reagent gas cylinder is closed, and then click the [Reagent Gas] button on the [Instrument Control] bar to open the stop cock.
  (2) Next, click the [Reagent Gas] button to close the stop cock. (Repeat this operation 5 to 10 times.)
  NOTE: If the [Reagent Gas] button is clicked to open the stop cock and reagent gas is introduced to the ion source, the readouts of the Pirani gauge (low vacuum side indication) and ion gauge (high vacuum side indication) worsen.
  Alternatively, if the stop cock is closed, the readout of the ion gauge improves whereas the readout of the Pirani gauge momentarily suddenly worsens. The graph readouts sometimes go off the scale. However, there will be no problem if indications recover right away.
  Also, if the [Reagent Gas] button is clicked when the stop cock is closed, you will hear the solenoid valve in the reagent gas control unit operate a few times.
  
 
12. Open the stop cock of the reagent gas cylinder.
 
 
13. Open the pressure-regulating valve of the pressure regulator. (Set methane and ammonia to about 100 kPa and isobutane to about 20 kPa.)
Next, open the open/close valve of the pressure regulator.
 
 
14. Check for leakage from the reagent gas piping by the sealing test.
  Close the stop cock of the reagent gas cylinder.
 
 
15. Leave for 10 minutes, and then check to make sure on the pressure regulator that there is no pressure drop.
  If there is a pressure drop, a probable cause is leakage between the reagent gas cylinder and the GC/MS. Repeat the procedure starting from Step1.
  After performing this check, open the stop cock of the reagent gas cylinder.
 
 
16. Click the [Reagent Gas] button on the [Instrument Control] bar to open the valve.
The solenoid valve of the reagent gas control unit opens, and reagent gas is introduced from the selected port.
 
 
17. Check the vacuum level indicated on the high pressure side, and wait a while for the amount of introduced reagent gas to stabilize.
Adjust the pressure-regulating valve so that the vacuum level becomes less than 1 x 10-2Pa. The pressure of the pressure-regulating valve for attaining the above vacuum levels differs according to the type of gas.

  Reference pressure ranges for the pressure-regulating valve are as follows:
    Methane and ammonia: 100 to 300 kPa
    Isobutane: 20 to 80 kPa
  However, note that in the case of an NCI ion source, set a slightly higher pressure. (Methane and ammonia: 200 to 350 kPa, and isobutane: 40 to 80 kPa)

  When too much reagent gas is introduced, click here.
 
  CAUTION: The maximum operating pressure on this instrument is 400 kPa. So, limit the pressure of reagent gas used on this instrument to 400 kPa.
  NOTE: Adjust the amount of introduced reagent gas by the pressure cylinder of the pressure regulator attached to the reagent gas cylinder. When opening the pressure-regulating valve of the pressure regulator, open the valve a little at a time while checking the vacuum level.
 
 
18. In the [Peak Monitor] sub-window, set m/z and the scale factor as follows:
  
 
19. Click the [Filament] button to turn the filament ON.
  If the signals appear to be protruding off screen at the above scale factor settings, lower the [Detector] value so that they fit inside the screen.
 
20. Make sure that the following conditions are satisfied. If they appear not to be satisfied, adjust the pressure-regulating valve, check again to see if they are satisfied, and then perform auto tuning again.
  If adjustment of the pressure-regulating valve does not result in the conditions being satisfied even though reagent gas is being introduced, click here.
  (CI)
  Methane: I17 / I29 < 5
  Isobutane:  I43 / I57 < 1
  Ammonia:  I18 / I35 < 50
  I29: C2H5+ ion intensity
  I17: CH5+ ion intensity
  I57: CH9+ ion intensity
  I43: C37+ ion intensity
  I35: NH3NH4+ ion intensity
  I18: NH4+ ion intensity
 
  (NCI)
  Methan, Isobutane, Ammonia:
  Check that m/z 452 and 633 are detected.
 
  (Smart EI/CI)
  Isobutane: Check that m/z 57 is detected.
 
21. Auto Tuning Example
 
 
22. When using two lines of reagent gas, introduce gas also to the other line by the same method.