Means of introducing an analyte into liquid sampling atmospheric pressure glow discharge
A liquid sampling, atmospheric pressure, glow discharge (LS-APGD) device as well as systems that incorporate the device and methods for using the device and systems are described. The LS-APGD includes a hollow capillary for delivering an electrolyte solution to a glow discharge space. The device also includes a counter electrode in the form of a second hollow capillary that can deliver the analyte into the glow discharge space. A voltage across the electrolyte solution and the counter electrode creates the microplasma within the glow discharge space that interacts with the analyte to move it to a higher energy state (vaporization, excitation, and/or ionization of the analyte).
1. A liquid sampling, atmospheric pressure, glow discharge (LS-APGD) device comprising:
an electrolyte solution source;
a first hollow tube extending from the electrolyte solution source to a first discharge end of the first hollow tube, the first hollow tube comprising a wall surrounding an interior space and further comprising a conductive element, the first hollow tube being in fluid communication with the electrolyte solution source and being configured to carry a flow of a liquid electrolyte solution within the first hollow tube and deliver the electrolyte solution out of the first discharge end;
a second hollow tube the second hollow tube comprising a wall surrounding an interior space and the second hollow tube including a terminal portion at a second discharge end, the terminal portion comprising a counter electrode, the second discharge end being disposed at a distance of from about 0.1 millimeters to about 5 millimeters from the first discharge end;
a glow discharge space being external to the first discharge end of the first hollow tube and external to the second discharge end of the second hollow tube and within an electric field established between the conductive element and the counter electrode;
a power source in electrical communication with the conductive element and the counter electrode, the power source being configured to establish the electric field; and
an analysis instrument in communication with the glow discharge space.
2. The LS-APGD device of claim 1 , further comprising a pump in fluid communication with the electrolyte solution source.
3. The LS-APGD device of claim 1 , wherein the first discharge end of the first hollow tube comprises the conductive element.
4. The LS-APGD device of claim 1 , wherein the first discharge end of the first hollow tube comprises a non-conductive material, a metal, a polymer, a glass, fused silica, or silicon.
5. The LS-APGD device of claim 1 , further comprising a conduit surrounding the first discharge end of the first hollow tube, the conduit defining an annular space surrounding the first discharge end.
6. The LS-APGD device of claim 1 , the conductive element extending into the interior space of the first hollow tube.
7. The LS-APGD device of claim 1 , wherein the analysis instrument detects optical emission signals in the glow discharge space.
8. The LS-APGD device of claim 1 , wherein the analysis instrument comprises a mass spectrometer.
9. The LS-APGD device of claim 8 , wherein the mass spectrometer is configured to extract ionic species from the glow discharge space.
10. The LS-APGD device of claim 1 , wherein the interior space of the first hollow tube defines an inside diameter of from about 0.1 millimeter to about 2 millimeters.
11. The LS-APGD device of claim 1 , wherein the interior space of the second hollow tube defines an inside diameter of from about 0.1 millimeter to about 2 millimeters.