Corrosion resistant electrodes for electrophoretic mobility measurements and method for their fabrication
An electrode for use in instruments capable of measuring the electrophoretic mobility of particles in solution is disclosed. The electrode is comprised of an inexpensive support member, generally made of titanium, onto a flat surface of which has been connected, generally by microwelding, a flat electrically conductive but chemically inert foil member, preferably platinum. A uniform texture can be generated on the exposed surfaces of the electrode by various means including tumbling the electrode with an abrasive. An oxide layer can be generated on the support member by soaking the composite electrode in an appropriate medium, protecting the exposed surface of the support member from fluid contact with the sample solution, while the foil member, unaffected by the oxidation process, is able to contact the sample solution.
1 . A corrosion resistant electrode for use with an electrophoretic mobility detector comprising
a) an electrically conductive support member
b) a chemically inert, electrically conductive foil member connected to said conductive support member.
2 . The electrode of claim 1 wherein said electrically conductive support member is comprised of titanium
3 . The electrode of claim 1 wherein said electrically conductive foil member is comprised of platinum.
4 . The electrode of claim 3 wherein said platinum foil member is disc shaped.
5 . The electrode of claim 1 further comprising an o-ring groove.
6 . The electrode of claim 4 wherein said support member is welded to said foil member about the perimeter of said foil member.
7 . The electrode of claim 4 where said platinum foil is 100±5 μm thick permitting the foil to be cleaned with mild abrasives without damage.
8 . The electrode of claim 1 wherein at least said electrically conductive foil member is etched to provide a relatively uniform surface texture.
9 . The electrode of claim 8 wherein said etching is achieved by the application of hydrofluoric acid.
10 . The electrode of claim 8 wherein said etching is achieved by ion beam etching applied to the exposed side of the electrically conductive foil member.
11 . The electrode of claim 8 wherein said etching is achieved by mechanically tumbling said electrode with an abrasive.
12 . The electrode of claim 1 wherein said support member is comprised of a material whose surface, when exposed to a strong oxidizer causes an oxide layer to grow thereupon, and wherein said foil member is comprised of a material whose surface, when exposed to a strong oxidizer is resistant to an oxide layer forming thereupon.
13 . The electrode of claim 12 wherein an oxide layer is generated upon the exposed surface of said support member by means of an oxidation agent.
14 . The electrode of claim 13 wherein an oxide layer is caused to grow upon the exposed surface of the support member by soaking said electrode in a solution comprised of hydrogen peroxide and water.
15 . The electrode of claim 14 wherein said solution is composed of about 30% hydrogen peroxide and 70% water.
13 . The electrode of claim 12 wherein an oxide layer is generated upon the exposed surface of said support member by means of passing an electrical current through said electrode while it is bathed in a salt solution.
16 . A method for the fabrication of an electrode for use with an electrophoretic mobility detector comprising the steps of
A. providing an electrically conductive support member;
B. providing a chemically inert, electrically conductive foil member;
C. welding said foil member to said conductive support member about the perimeter of said foil member, forming, thereby a composite electrode;
D. mechanically tumbling said composite electrode with an abrasive, providing thereby a uniform surface texture to the exposed surfaces of each of said conductive support member and said foil member; and
E. soaking said composite electrode in a solution comprised of hydrogen peroxide and water, providing thereby an oxide layer on the conductive support member.