Electrolysis: processes – compositions used therein – and methods – Electrolytic analysis or testing
Reexamination Certificate
2000-07-14
2003-10-28
Nguyen, Nam (Department: 1753)
Electrolysis: processes, compositions used therein, and methods
Electrolytic analysis or testing
C205S786500, C205S787000, C204S400000, C204S403020, C156S292000
Reexamination Certificate
active
06638415
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a device and method for measuring the level of an oxidant or antioxidant analyte in a fluid sample. The device comprises a disposable electrochemical cell containing a reagent capable of directly undergoing a redox reaction with the analyte.
BACKGROUND OF THE INVENTION
An oxidation reaction, broadly defined, involves the transfer of one or more electrons from one molecule or atom (the reducing agent or reductant) to another (the oxidizing agent or oxidant). Oxidation reactions occur in a broad range of systems, e.g., food products, living organisms, and drinking water, and may be detrimental or beneficial. Food products exposed to oxygen may undergo oxidative degradation, resulting in the generation of undesirable flavors and odors, the destruction of fat-soluble vitamins and essential fatty acids, and the production of toxic degradation products. Beneficial oxidation reactions in food products include those between natural or synthetic antioxidants and oxidants, whereby the oxidant is prevented from participating in a detrimental oxidation reaction.
Thus, it is desirable to be able to measure oxidant or antioxidant levels in liquid samples in many fields. For example, it is desirable in terms of manufacturing quality control as well as health monitoring to measure the level of preservatives such as sulfur dioxide in wine or food, the level of ascorbic acid in fruit, vegetables, beverages, and biological fluids, and the level of chlorine or peroxides in water. Most conveniently, these tests are fast and easy to use and be amenable to field as well as laboratory use.
Existing methods for measuring these components require either expensive laboratory apparatus or skilled operators in order for the method to be used successfully. For example, a sensor for detecting antioxidant agents in oil is disclosed in U.S. Pat. No. 5,518,590. However, this sensor is not designed for single, disposable use and does not use a redox agent. It is therefore desirable to have a sensor designed for single, disposable use that can detect oxidant or antioxidant levels in fluid samples through the use of a redox reagent.
SUMMARY OF THE INVENTION
The present invention provides a device and method for measuring oxidant and antioxidant analytes with a disposable sensing element, suitable for a single use, that can be combined with a meter to give a robust, fast, and easy to use test that is amenable to field as well as laboratory use. In particular, the invention relates to the use of an electrochemical sensor that utilizes a redox agent that reacts with the analyte of interest to produce an electrochemically detectable signal.
In one embodiment of the present invention, a device for detecting a presence or an absence of a redox reactive analyte in an aqueous sample is provided, the device including an electrochemical cell having a sensing chamber, a first electrode, a second electrode, an aperture for admitting the sample into the sensing chamber, and a reagent contained within the sensing chamber, wherein the electrochemical cell is designed to be disposed of after use in a single experiment, and wherein the reagent is capable of undergoing a redox reaction directly with the analyte to generate an electrical signal indicative of the presence or absence of the analyte.
In one aspect of this embodiment, the first electrode is a sensing electrode that may consist of platinum, palladium, carbon, indium oxide, tin oxide, gold, iridium, copper, steel, or mixtures thereof. The first electrode may also be silver. The first electrode may be formed by a technique such as sputtering, vapor coating, screen printing, thermal evaporation, ink jet printing, ultrasonic spraying, slot coating, gravure printing and lithography.
In another aspect of this embodiment, the second electrode is a counter electrode. The second electrode may include a metal in contact with a metal salt, for example, silver in contact with silver chloride, silver in contact with silver bromide, silver in contact with silver iodide, mercury in contact with mercurous chloride, or mercury in contact with mercurous sulfate. The second electrode may also be a reference electrode.
In another aspect of this embodiment, the electrochemical cell further includes a third electrode, such as a reference electrode. The third electrode may include a metal in contact with a metal salt, such as silver in contact with silver chloride, silver in contact with silver bromide, silver in contact with silver iodide, mercury in contact with mercurous chloride, and mercury in contact with mercurous sulfate.
In another aspect of this embodiment, the reagent is capable of oxidizing an analyte including an antioxidant. The reagent may include ferricyanide salts, dichromate salts, permanganate salts, vanadium oxides, dichlorophenolindophenol, osmium bipyridine complexes, and quinones.
In another aspect of this embodiment, the reagent is capable of reducing an analyte including an oxidant. The reagent may include iodine, triiodide salts, ferrocyanide salts, ferrocene, Cu(NH
3
)
4
2+
salts, and Co(NH
3
)
6
3+
salts.
In another aspect of this embodiment, the sensing chamber further includes a buffer contained within the sensing chamber. The buffer is selected from the group consisting of phosphates, carbonates, alkali metal salts of mellitic acid, and alkali metal salts of citric acid.
In another aspect of this embodiment, the device further includes a heating element. The heating element may include an electrically resistive heating element or an exothermic substance contained within the sensing chamber, such as aluminum chloride, lithium chloride, lithium bromide, lithium iodide, lithium sulfate, magnesium chloride, magnesium bromide, magnesium iodide, magnesium sulfate, and mixtures thereof.
In another aspect of this embodiment, the sensing chamber includes a support contained within the sensing chamber. Supports may include mesh, nonwoven sheet, fibrous filler, macroporous membrane, sintered powder, and combinations thereof. One or both of the reagent and buffer may be contained within or supported on the support.
In another aspect of this embodiment, the second electrode is mounted in opposing relationship a distance of less than about 500 microns from the first electrode, less than about 150 microns from the first electrode, or less than about 150 microns and greater than about 50 microns from the first electrode.
In another aspect of this embodiment, the device further includes an interface for communication with a meter. The interface may communicate a voltage or a current.
In another aspect of this embodiment, the electrochemical cell includes a thin layer electrochemical cell.
In a second embodiment of the present invention, a method for detecting a presence or an absence of a redox reactive analyte in an aqueous sample is provided which includes providing a device for detecting the presence or absence of an analyte in an aqueous sample, the device including an electrochemical cell having a sensing chamber, a first electrode, a second electrode, an aperture for admitting the sample into the sensing chamber, and a reagent contained within the sensing chamber, wherein the electrochemical cell is designed to be disposed of after use in a single experiment, and wherein the reagent is capable of undergoing a redox reaction directly with the analyte to generate an electrical signal indicative of the presence or absence of the analyte; providing an aqueous sample;allowing the sample to flow through the aperture and into the sensing chamber, such that the sensing chamber is substantially filled; and obtaining an electrochemical measurement indicative of the presence or absence of analyte present in the sample.
In one aspect of this embodiment, the electrochemical measurement is an amperometric measurement, a potentiometric measurement, a coulometric measurement, or a quantitative measurement.
In another aspect of this embodiment, the method includes the further step of heating the sample, wherein the heatin
Chatelier Ron
Hodges Alastair
Knobbe Martens Olson & Bear LLP
LifeScan, Inc.
Nguyen Nam
Olsen Kaj K.
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