Electrophoretic device and method to separate and detect analyte ions
This invention is directed to an inexpensive, miniaturized, portable, low-power device and method for electrophoretic separation and electrochemical detection of an analyte, including different isotopes of the same element. The invention replaces a conventional or microfabricated capillary electrophoresis tube with a microchip comprising an array of parallel electrophoretic separation nanotubes or aligned hollow channels fabricated in a porous substrate.
1. A method for separating and detecting an analyte, comprising:
providing an electrophoretic device, the device comprising:
an array of aligned hollow channels in a porous substrate,
an injection electrode proximate the entrance of the array of aligned hollow channels,
a detection electrode proximate the exit of the array of aligned hollow channels, and
a power supply for applying an electrophoresis electric field between the entrance and the exit of the array of aligned hollow channels;
preconcentrating the analyte on the injection electrode;
electrodissolution of the preconcentrated analyte to provide at least two ionized species in a solvent;
injecting a pulse of the at least two ionized species into the array of aligned hollow channels;
electrophoretically separating the at least two ionized species in the electrophoresis electric field applied to the array of aligned hollow channels; and
electrochemically detecting the separated at least two ionized species at the detection electrode.
2. The method of claim 1 , wherein the analyte comprises isotopes of a chemical species.
3. The method of claim 1 , wherein the analyte comprises different chemical or biological species.
4. The method of claim 1 , wherein the analyte comprises a metal.
5. The method of claim 1 , wherein the at least two ionized species comprise at least two cations.
6. The method of claim 1 , wherein the hollow channels are less than 1 centimeter in length.
7. The method of claim 1 , wherein the hollow channels are less than 100 microns in cross-sectional dimension.
8. The method of claim 1 , wherein the substrate comprises metal oxide, carbonaceous material, polymer, glass, or semiconductor.
9. The method of claim 1 , wherein the array of aligned hollow channels comprise anodized aluminum oxide or a microchannel plate.
10. The method of claim 1 , wherein the aligned hollow channels further comprise a material deposited on the channel walls.
11. The method of claim 1 , wherein an electroosmotic velocity of the solvent is modified by capacitive charging of a dielectric layer on the interior walls of the hollow channels.
12. he method of claim 1 , wherein an electroosmotic velocity of the solvent is augmented by a pressure differential across the array that modifies the bulk flow of the solvent in the hollow channels.
13. The method of claim 1 , wherein the power supply applies an electrophoresis electric field between the entrance and the exit of the array of aligned hollow channels by applying a voltage between the injection and detection electrodes.
14. The method of claim 1 , further comprising at least one supplemental electrode proximate the entrance or exit of the array, wherein the power supply applies an electrophoresis electric field by applying a voltage between the at least one supplemental electrode and the injection or the detection electrode.
15. The method of claim 1 , further comprising a supplemental electrode proximate the entrance of the array and a supplemental electrode proximate the exit of the array, wherein the power supply applies an electrophoresis electric field by applying a voltage between the supplemental electrode proximate the entrance of the array and the supplemental electrode proximate the exit of the array.
16. The method of claim 1 , wherein the preconcentrating comprises electrochemical plating, electrochemical adsorption, chemical adsorption, or physical deposition of the analyte on the injection electrode.
17. The method of claim 1 , wherein the preconcentrating comprises depositing between 0.001 ng/cm 2 and 1 mg/cm 2 of analyte on the injection electrode.
18. The method of claim 1 , wherein the electrochemically detecting step comprises chronoamperometry.