Plasmas and methods of using them
View Patent ↗Plasma devices and methods for using such plasma devices in analytical measurements are disclosed. In certain examples, a low flow plasma may be operative using a total argon gas flow of less than about five liters per minute, and in some embodiments, a plasma argon gas flow of less than about four liter per minute. In other examples, a plasma produced using inductive and capacitive coupling is disclosed.
1. A method of generating a plasma in a torch, the method comprising:
igniting a plasma using an argon gas flow at a first flow rate and using coupling of both inductive and capacitive coupled RF energies; and
introducing a non-argon barrier gas flow into the torch.
2. The method of claim 1 , further comprising reducing the argon gas flow in the torch from the first flow rate to a second flow rate that is less than the first flow rate.
3. The method of claim 1 further comprising selecting the non-argon barrier gas flow to be nitrogen.
4. The method of claim 1 further comprising replacing about 75% of the argon gas flow with the non-argon barrier gas flow.
5. The method of claim 1 further configuring the capacitive coupling to increase ionization potential of the plasma to at least about 25 eV.
6. The method of claim 1 further comprising configuring the torch with a first plate and a second plate to provide the capacitive coupling.
7. A method comprising providing inductive coupling and capacitive coupling to a plasma to increase the ionization potential of the plasma.
8. The method of claim 7 further comprising configuring the capacitive coupling to increase ionization potential of the plasma to at least about 25 eV.
9. The method of claim 7 further comprising configuring a torch with a first plate and a second plate to provide the capacitive coupling.
10. A method of generating a low flow plasma in a torch, the method comprising:
igniting a plasma using an argon gas flow at a first flow rate and using coupling of both inductive and capacitive coupled RF energies;
introducing a non-argon barrier gas flow into the torch; and
reducing the first flow rate to less than or equal to five liters/minute.
11. The method of claim 10 , further comprising selecting the non-argon barrier gas to be nitrogen.
12. The method of claim 10 , further comprising configuring the capacitive coupling to increase ionization potential of the plasma to at least about 25 eV.
13. The method of claim 10 , further comprising configuring the torch with a first plate and a second plate to provide the capacitive coupling.
14. The method of claim 13 , further comprising configuring the first plate to be substantially parallel to the second plate.
15. The method of claim 10 , further comprising the reducing the first flow rate to less than four liters/minute.
16. The method of claim 15 , further comprising configuring the non-argon gas flow to be about four liters/minute to about five liters/minute.
17. The method of claim 10 , further comprising selecting the non-argon barrier gas to be air.
18. The method of claim 10 , further comprising sustaining the plasma in the torch using a loop current.
19. A method of generating a plasma comprising:
igniting a plasma in a torch using an argon gas flow at a first flow rate, in which the torch comprises an inductive device and a capacitive device, the capacitive device comprising at least one plate to provide capacitive coupling that increases ionization potential of the plasma to at least about 25 eV;
introducing a non-argon barrier gas flow into the torch; and
reducing the first flow rate to a second flow rate that is less than the first flow rate.
20. The method of claim 19 , in which the inductive device comprises at least one plate electrode.