Self cleaning electrochemical detector and cell for flowing stream analysis
First Claim
1. An electrochemical detector for detecting electroactive species in a flowing stream, comprising a detector cell having true wall-jet hydrodynamics, said detector cell having:
- a counter electrode;
a working electrode with a surface of nominal radius R;
a fluid inlet jet having an orifice with an outer diameter A and an inner diameter a aligned with the center of the surface of the working electrode for supplying substantially all of the flowing stream to the cell in a direction normal to the surface of the working electrode; and
an exit tube for the flowing stream to leave the cell;
wherein R is less than or equal to 1.5 millimeters, the ratio of R/a is greater than or equal to 4, and the ratio A/a is less than or equal to 4.
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Accused Products
Abstract
An improved electrochemical cell and detector which is especially suited for analysis of rapidly changing flowing streams such as found in high performance liquid chromatography is disclosed. A uniquely designed jet made of microbore drawn capillary tubing permits the construction of a cell for very low flow rates that still retains true wall-jet hydrodynamics. The invention prevents changes in cell response in time by periodically cleaning a working electrode in a novel way. Cleaning and detection are both accomplished on a time scale much shorter than the fastest liquid chromatograph peaks by means of a unique three electrode cell design utilizing a small diameter, low capacitance, metal working electrode situated close to a reference electrode. Cleaning is accomplished by means of a non-square wave periodic waveform which is effective in cleaning a wide variety of contaminants through the oxidation and reduction of the working electrode and/or solvent prior to application of one or more working potentials while providing a stable, reproducible detector. The detector thus provides improvements in both sensitivity and bandwidth over the prior art.
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Citations
27 Claims
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1. An electrochemical detector for detecting electroactive species in a flowing stream, comprising a detector cell having true wall-jet hydrodynamics, said detector cell having:
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a counter electrode; a working electrode with a surface of nominal radius R; a fluid inlet jet having an orifice with an outer diameter A and an inner diameter a aligned with the center of the surface of the working electrode for supplying substantially all of the flowing stream to the cell in a direction normal to the surface of the working electrode; and an exit tube for the flowing stream to leave the cell;
wherein R is less than or equal to 1.5 millimeters, the ratio of R/a is greater than or equal to 4, and the ratio A/a is less than or equal to 4. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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Specification