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Thermo Fisher Scientific

Plasma Will Not Ignite on iCAP Qnova Series


Plasma will not ignite


  • iCAP Q
  • iCAP Qnova Series


When the plasma won’t ignite, the following steps can be taken in order to try and determine what the source of the ignition failure is:


1)    Have any sample introduction components been changed, i.e. torch, o-rings, etc either right before or since the issue started occurring? If so, did you use Thermo Scientific parts? If components have been changed since the last time the plasma successfully ignited, then the components which have been changed could be defective. Please replace them with the original component and see if the plasma ignites then.

If no components have been changed since the plasma ignition issue started occurring, it would be a good idea to troubleshoot the torch. Namely, it would be a good idea to replace the torch, injector and torch body and see if the plasma ignites then. Please make sure you use genuine Thermo Scientific parts for these components.

2)    Has the torch been inserted properly into the torch holder, see Figure 1? The torch should be inserted into the body to the point where the red marker on the torch is positioned inside the indentation in the body.

a)    Is the top of the base of the injector tube holder flush with the base of the torch body, see Figure 1 again? It is possible for the center tube holder to be cross threaded when screwing it into the torch holder. Therefore, please verify that the injector tube holder is seated flush throughout the entire circumference with the torch holder. There should be no gap anywhere between the torch holder and the injector tube holder.

b)    Are the o-rings located on the coolant and auxillary gas inputs to the torch holder in place, see red box in Figure 1?

 Qnova Torch Assembled Correctly.png

Figure 1: The torch has been inserted properly into the holder


3)    When is the last time the chiller water was changed? It is important that the chiller water is changed at least once per year. If you are running the instrument 8 hours a day / 5 days a week or more, the chiller water should be changed every 6 months. If the chiller water needs to be changed, please do so using distilled water with a conductivity below 1000 micro Siemens.

4)    Check the sample introduction for leaks by removing the spray chamber from the center tube holder, sealing the center tube holder inlet with tape, and then try lighting plasma. If it lights, a leak should be suspected somewhere in the sample introduction system before the ball joint (i..e. seal securing nebulizer in spray chamber, nebulizer gas line, etc.).

Qnova Torch Taped Over.jpg

5)    Check the load coil alignment:                                                                                                                                        

Run a 1mm Allen wrench or wooden Q-tip around the space between the coil and outer quartz tube and see if resistance is encountered anywhere. If it is, suspect that the coil is touching the torch in that area. Gently bend the coil in a manner so that the coil is no longer touching the torch and re-check spacing.

The distance between the right-hand side of the load coil and the top of the inner quartz tube should be 1mm. If it is not, gently bend the coil so that this distance is met.

Qnova Load Coil Spacing.png


6)    Did the plasma ignition issue start happening after the Argon gas supply changed? If so, bad Argon gas should be suspected and the gas should be replaced.


7)    Are there any leaks in the argon line running from the argon supply to the instrument? All junctures should be especially scrutinized. This can easily be done by dispensing about a quarter sized amount of liquid soap into a beaker, filling the beaker with about 20 mL of DI water and then using a 1” paint brush to whip the solution so that suds appear. The suds (none of the liquid) can then be applied using the paint brush to all of the junctures in the Argon line to the instrument. If the bubbles start to get bigger at any juncture, a leak should be suspected and subsequently corrected.


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