Plasmas and methods of using them
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 device comprising:
a torch body;
an inductive device surrounding the torch body and configured to provide inductively coupled radio frequency energy into the torch body; and
at least one capacitive device separate from the inductive device and positioned between a first end of the inductive device and an end of the torch body, wherein the capacitive device is configured to provide capacitively coupled radio frequency energy into the torch body simultaneously with the provided inductively coupled radio frequency energy from the inductive device to sustain a plasma within the torch body.
2. The device of claim 1 further comprising a single power source to provide power to the inductive device and the capacitive device.
3. The device of claim 1 further comprising a first power source configured to provide power to the inductive device and a second power source configured to provide power to the capacitive device.
4. The device of claim 1 in which the inductive device is configured to generate a loop current.
5. The device of claim 1 in which the inductive device is configured as a helical induction coil that surrounds the torch body.
6. The device of claim 1 in which the capacitive device comprises a first plate and a second plate, the first plate positioned substantially parallel to the second plate, and the torch body positioned between the first plate and the second plate.
7. The device of claim 1 further comprising a detector configured for detection of optical emission.
8. The device of claim 1 further comprising a detector configured for detection of atomic absorption.
9. The device of claim 1 further comprising a detector configured for mass spectroscopy.
10. The device of claim 1 , wherein inductive device comprises a helical induction coil configured to provide the inductively coupled radio frequency energy into the torch and wherein the capacitive device comprises a first plate and a second plate together configured to provide the capacitively coupled radio frequency energy into the torch.
11. The device of claim 1 , wherein inductive device comprises a first plate electrode and a second plate electrode together configured to provide the inductively coupled radio frequency energy into the torch and wherein the capacitive device comprises a first plate and a second plate together configured to provide the capacitively coupled RF energy into the torch.
12. The device of claim 1 , further comprising a mass analyzer fluidically coupled to the torch body.
13. The device of claim 10 , in which the first plate and the second plate of the capacitive device are positioned within the inductive device and between the first end of the inductive device and the end of the torch body.
14. The device of claim 1 , further comprising a plasma sensor optically coupled to the torch body to allow light from the plasma in the torch body to be incident on the plasma sensor.
15. The device of claim 14 , wherein the plasma sensor is configured to shut down the inductive device and the capacitive device if the plasma in the torch body is extinguished.
16. The device of claim 1 , wherein the capacitive device is configured as two copper foil plates, and wherein the inductive device is electrically coupled to the capacitive device.
17. The device of claim 16 , wherein the inductive device and capacitive device are configured together to provide a plasma with an ionization potential of at least 60 eV.