A redox electrode for the rapid detection of glucose in aqueous media and a method for its use are provided. The redox electrode comprises an electrically conductive member such as copper, and a redox membrane in direct contact with said electrically conductive member. The redox membrane comprises a polymer matrix such as PVC containing a plasticizer, and a complex of 7,7,8,8 -tetracyanoquinodimethane and tetrathiafulvalene with the complex having a burgundy-red coloration and characterized by a broad absorption from about 340 nm to about 550 nm and weaker absorption between about 650 nm to about 800 nm having about six small peaks with an absorption maximum at about 750nm. Glucose is rapidly assayed by bringing the redox electrode and a reference electrode into simultaneous contact with an aqueous medium containing KCl, phosphate buffer, glucose oxidase, peroxidase, and 3,3',5,5'-tetramethylbenzidine dihydrochloride. The potential of the redox membrane is then monitored until it is stable. A sample containing glucose is added to the aqueous medium, and the change of potential of the redox electrode, which is related to glucose concentration, is then observed. In a variant of this method, the redox electrode is treated with ascorbic acid before a glucose oxidation to magnify the potential difference generated, and after oxidation to rapidly collapse the potential and prepare the electrode for another analysis.
6776888 - Biosensor - Owned by Matsushita Electric Industrial Co., Ltd. (Osaka,JP)
The present invention provides a biosensor that enables highly-accurate measurement of a sample solution including a solid component like hemocytes and has a little variation in response. The biosensor includes: an insulating base plate, an electrode system having at least a working electrode and a counter electrode provided on the base plate, a cover member that is combined with the base plate to define a sample solution supply pathway for leading a sample solution from a sample supply unit to the electrode system, a reaction reagent system including at least an oxidation-reduction enzyme and an electron mediator, and a filter disposed between the electrode system and the sample supply unit in the sample solution supply pathway. The biosensor has a space that encircles surface of the filter in an area from one end of the filter close to the sample supply unit to the other end of the filter close to the electrode system. This arrangement effectively prevents the solid component like hemocytes from flowing into the electrode system without being filtered out by the filter.
A highly sensitive sensor for the amperometric assay of glucose in aqueous media having a face-to-face sandwich configuration is provided which comprises a sensing electrode strip containing a first redox mediator in an electrically conductive coating and a reference electrode strip in simultaneous contact with a reagent strip containing a second redox mediator which is sandwiched between the active electrode surfaces. An opening is provided in the reference electrode for the introduction of samples. In one embodiment, a whole blood separation membrane is interposed between the reference electrode and the reagent strip to filter red blood cells and other particles from whole blood to enable direct assay of glucose without sample preparation. The sensing electrode comprises a non-conductive support member having an electrically conductive layer containing the first redox mediator. The reference electrode is typically a Ag/AgCl electrode formed by coating an ink containing Ag/AgCl dispersed in a resin on a non-conductive base. The reagent strip is a porous or fibrous carrier, typically a paper, impregnated with a mixture containing the second redox mediator, glucose oxidase, horseradish peroxidase, at least one surfactant and at least one stabilizer comprising an aqueous thickening agent. In one version of the sensor, the sensing electrode comprises a support member of polyester film coated with an electrically conductive graphite composition containing dimethylferrocene as the first redox mediator and the second redox mediator comprises potassium ferrocyanide.
A self contained glucose sensor is provided that generally comprises a strip type glucose sensing electrode having an active surface comprising an organic conducting redox salt dispersed in a polymeric membrane, with the membrane coating a conductive strip and a strip type Ag/AgCl reference electrode having its active surface separated from physical contact with the strip type glucose sensor and a carrier strip of water absorbent paper or film containing an enzyme system and an oxidizable dye. The water absorbent carrier strip is in simultaneous contact with both the active surface of the strip type glucose electrode and the active surface of the strip type reference electrode. When an aqueous solution containing glucose is brought in contact with the carrier strip containing the enzyme system an electrical potential, proportional to the concentration of glucose in the solution, is created which can be detected by an electrometer or other suitable device.
The invention is concerned with a sensor for the determination of the concentration and the detection of an enzyme substrate in a liquid sample, the sensor comprising an enzyme capable of reacting with the enzyme substrate while producing a substance directly or indirectly detectable, a detection device for this substance and a cover membrane from a polymer permeable to the enzyme substrate, characterized in that the polymer is a polyvinyl chloride copolymer, i.e. a copolymer from vinyl chloride and a further monomer, the copolymer comprising hydrophilic groups. The sensor according to the invention may be provided as an optical sensor or as an amperometric sensor.
