Ambient desorption-optical emission spectroscopy using a microplasma desorption/excitation source
Described is an elemental analysis system and methods for use thereof that can be utilized in examination of samples in their native state. The systems utilize a liquid sampling—atmospheric pressure glow discharge (LS-APGD) device for ambient desorption sampling and excitation of a solid sample in combination with optical emission detection. This approach can find application across a broad spectrum of analytical challenges including metals, soils, and volume-limited samples.
1. A method for examining a sample comprising:
flowing an electrolyte solution through a first hollow tube from a first end to a second end of the first hollow tube;
flowing a gas through a second hollow tube from a first end to a second end of the second hollow tube, the second hollow tube comprising counter electrode;
forming a microplasma in a glow discharge space of a liquid sampling atmospheric pressure glow discharge (LS-APGD) device, the glow discharge space being defined between the second end of the first hollow tube and the second end of the second hollow tube;
contacting a solid sample within the glow discharge space with the microplasma and with the gas and thereby volatilizing the solid sample to release one or more components of the solid sample and exciting the released components, the excited components emitting a characteristic response within the glow discharge space; and
optically detecting the characteristic response as the emission occurs within the glow discharge space.
2. The method of claim 1 , wherein the solid sample comprises a metallic film.
3. The method of claim 1 , wherein the solid sample comprises a dried solution residue.
4. The method of claim 1 , wherein the solid sample comprises a metal.
5. The method of claim 1 , wherein the solid sample comprises a soil.
6. The method of claim 1 , wherein the method is carried out in the field.
7. The method of claim 1 , wherein the method is free of sample preparation.
8. The method of claim 1 , wherein the microplasma comprises a reference material, the reference material emitting a second characteristic response within the glow discharge space, the method further comprising optically detecting the second characteristic response.
9. The method of claim 1 , wherein the solid sample is electrically isolated from the LS-APGD device.
10. The method of claim 1 , wherein the solid sample is within an electrical circuit of the LS-APGD device.
11. The method of claim 1 , further comprising modifying the size and/or configuration of the glow discharge space by selective motion of the end of the first hollow tube or the counter electrode.
12. The method of claim 1 , wherein the gas that flows through the second hollow tube is an inert gas.
13. The method of claim 1 , the step of forming the microplasma comprising developing a voltage difference between the electrolyte solution expelled from the second end of the first hollow tube and the counter electrode.
14. The method of claim 1 , further comprising flowing a gas along at least a portion of the exterior surface of the first hollow tube.
15. The method of claim 1 , wherein the gas flowing through the second hollow tube comprises helium, nitrogen, or argon.
16. The method of claim 1 , the step of forming the microplasma comprising developing a voltage difference across the glow discharge space by use of a power supply selected from a direct current source, a radio frequency power source, or a microwave frequency power source.
17. The method of claim 1 , the step of optically detecting the characteristic response comprising directing light from the glow discharge space to an optical spectrometer.
18. The method of claim 1 , wherein the axis of the first hollow tube is at an angle of less than 90° to the axis of the second hollow tube.
19. The method of claim 1 , wherein the axis of the first hollow tube is at an angle of from 90° to 180° to the axis of the second hollow tube.
20. The method of claim 1 , wherein the axis of the first hollow tube is at an angle of from 90° to 120° to the axis of the second hollow tube.