Voltammetry in high-voltage fields
Herein are described an instrument and a method for using the same. The instrument comprises a fluid channel fluidly connected to at least a first fluid reservoir and a second fluid reservoir; a counter electrode (CE), a reference electrode (RE), and a working electrode (WE); and a potentiostat. The CE, RE, and WE are all disposed within the fluid channel; the potentiostat is isolated from earth ground by at least one isolator and is powered by a floating power supply; and the CE, RE, and WE are each electrically connected to the potentiostat.
1. An instrument comprising:
a fluid channel fluidly connected to at least a first fluid reservoir and a second fluid reservoir, wherein the fluid channel comprises a capillary tube;
a counter electrode (CE), a reference electrode (RE), and a working electrode (WE); and
a potentiostat; wherein:
the CE, RE, and WE are all disposed within the capillary tube;
the potentiostat is isolated from earth ground by at least one isolator and is powered by a floating power supply;
the CE, RE, and WE are each electrically connected to the potentiostat; and
an access hole defined within a wall of the capillary tube, wherein the RE is removably disposed within the access hole.
2. The instrument of claim 1 , further comprising at least a first lead and at least a second lead.
3. The instrument of claim 2 , wherein the first lead is disposed in the first fluid reservoir.
4. The instrument of claim 2 , wherein the first lead is disposed in the second fluid reservoir.
5. The instrument of claim 2 , wherein the at least a first lead and at least a second lead create a high-voltage electric field across the capillary tube.
6. The instrument of claim 5 , wherein the high-voltage electric field is a field of about 100 V/cm to about 3000 V/cm.
7. The instrument of claim 1 , wherein the capillary tube is a microchannel or a nanochannel.
8. The instrument of claim 1 , wherein each of the CE, RE, and WE independently comprises Ti, Au, Pt, C, or Ag.
9. The instrument of claim 1 , wherein the capillary tube is made from a material which is an insulator.
10. The instrument of claim 1 , wherein the capillary tube is made from a polymer, an epoxy, glass, or fused silica.
11. The instrument of claim 1 , wherein each of the CE, RE, and WE independently is less than 300 μm wide.
12. The instrument of claim 1 , wherein the CE, RE, and WE are all disposed within 1 mm of each other.
13. The instrument of claim 1 , wherein the CE, RE, and WE are all disposed within 0.5 mm of each other.
14. The instrument of claim 1 , wherein the at least one isolator is a galvanic isolator.
15. The instrument of claim 1 , wherein the floating power supply is a battery.
16. The instrument of claim 1 , wherein the CE, RE, and WE are all disposed within the capillary tube at a distance from each end of the capillary tube equal to at least an eighth of a length of the capillary tube.
17. The instrument of claim 1 , wherein the CE and WE are disposed on a surface of the capillary tube opposite the access hole, such that when the RE is disposed within the access hole, the RE is oriented:
generally perpendicular to the CE and WE; and
above a gap between the CE and WE.
18. The instrument of claim 17 , wherein the access hole is disposed:
at approximately a midpoint of the capillary tube between a first end and second end of the capillary tube; or
at approximately a quarter length of the capillary tube away from either the first end or the second end of the capillary tube.
19. The instrument of claim 1 , wherein the potentiostat comprises:
a first operational amplifier (op amp) having an output connected to the CE and at least one input connected to a virtual ground, wherein the virtual ground is a local potential in a fluid within the capillary tube;
a second op amp having at least one input connected to the RE; and
a third op amp having a first input connected to the WE and a second input connected to the virtual ground.
20. The instrument of claim 1 , wherein a fluid flows freely from the first fluid reservoir through the capillary tube into the second fluid reservoir without leaking from the instrument.
21. An instrument comprising:
a fluid channel fluidly connected to at least a first fluid reservoir and a second fluid reservoir, wherein the fluid channel comprises a capillary tube;
a counter electrode (CE), a reference electrode (RE), and a working electrode (WE); and
a potentiostat; wherein:
the CE, RE, and WE are all disposed within the capillary tube;
the potentiostat is isolated from earth ground by at least one isolator and is powered by a floating power supply;
the CE, RE, and WE are each electrically connected to the potentiostat;
the CE and WE are oriented in an opposed configuration such that the CE and WE extend into the capillary tube from opposing sides of the capillary tube;
the CE extends through only one wall of the capillary tube; and
an access hole defined within a wall of the capillary tube, wherein the RE is removably disposed within the access hole.
22. The instrument of claim 21 , wherein:
each of the CE and WE are disposed within the capillary tube at approximately a same distance from an end of the capillary tube;
the WE extends through only one wall of the capillary tube; and
an end of the CE and an end of the WE terminate within the capillary tube forming a gap between the end of the CE and the end of the WE.