Source: http://www.google.com/patents/US5556533?dq=6,977,809&ei=-AObT5vAOoSgiQL_5qznDg
Timestamp: 2016-02-06 09:53:28
Document Index: 697075258

Matched Legal Cases: ['Application No. 1', 'art 45', 'art 45', 'art 116', 'art 116', 'art 145', 'art 145', 'art 145']

Patent US5556533 - Voltage applying method for hydrogen-type enzyme electrode - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsA voltage applying method for a hydrogen type enzyme electrode in a chemical sensor and using a pair of working electrodes, a reference electrode and a counter electrode includes detecting a contact of a test specimen with the enzyme electrode; keeping a potential applied to the working electrodes at...http://www.google.com/patents/US5556533?utm_source=gb-gplus-sharePatent US5556533 - Voltage applying method for hydrogen-type enzyme electrodeAdvanced Patent SearchPublication numberUS5556533 APublication typeGrantApplication numberUS 08/471,779Publication dateSep 17, 1996Filing dateJun 6, 1995Priority dateAug 3, 1993Fee statusLapsedAlso published asDE4427363A1, US5741634Publication number08471779, 471779, US 5556533 A, US 5556533A, US-A-5556533, US5556533 A, US5556533AInventorsYoshiteru Nozoe, Kazuharu MurataOriginal AssigneeA & D Company LimitedExport CitationBiBTeX, EndNote, RefManPatent Citations (8), Referenced by (15), Classifications (13), Legal Events (5) External Links: USPTO, USPTO Assignment, EspacenetVoltage applying method for hydrogen-type enzyme electrode
US 5556533 AAbstract
A voltage applying method for a hydrogen type enzyme electrode in a chemical sensor and using a pair of working electrodes, a reference electrode and a counter electrode includes detecting a contact of a test specimen with the enzyme electrode; keeping a potential applied to the working electrodes at a first potential of substantially zero for a first preset time; applying a second potential that is higher than a hydrogen peroxide detect potential to the working electrodes for a second preset time; dropping the second potential to a third potential below zero potential; and sweeping from the first potential to a fourth potential higher than said hydrogen peroxide detect potential at a fixed rate. Other variations of the method are disclosed.
1. A voltage applying method for a hydrogen enzyme electrode having a pair of working electrodes, a reference electrode and a counter electrode comprising:detecting a contact of a test specimen with said enzyme electrode; keeping a potential applied to said working electrodes at a first potential of substantially zero for a first preset time; applying a second potential which is higher than a hydrogen peroxide detect potential to said working electrodes for a second preset time; dropping said second potential to a third potential below zero potential; sweeping from said third potential to a fourth potential higher than said hydrogen peroxide detect potential at a fixed rate. 2. A voltage applying method according to claim 1, wherein said detecting step comprising:applying a preset potential to said pair of working electrodes; detecting a preset current between said pair of working electrodes and said counter electrode to confirm as to whether enzyme electrode contacts said test specimen. 3. A voltage applying method according to claim 1, wherein said first preset time is substantially 15 to 40 seconds.
4. A voltage applying method according to claim 1, wherein said hydrogen peroxide detect potential is substantially 600 mV.
5. A voltage applying method according to claim 4, wherein said third potential is substantially -400 to -200 mV.
6. A voltage applying method according to claim 1, wherein said fixed rate is substantially 100 mV/sec.
7. A voltage applying method according to claim 1, further comprising said value:simultaneously with said sweeping step, detecting one of a peak value of current in the range of the voltage sweep to said fourth potential, a current value at a potential separated from a potential causing the peak current value by a preset potential value, and a current value at a specific potential; and converting said detected current value into a concentration of a substance in said test specimen by comparing with a calibration curve previously charted. 8. A voltage applying method for a hydrogen enzyme electrode having a pair of working electrodes, a reference electrode and a counter electrode comprising:detecting a contact of a test specimen with said enzyme electrode; keeping a potential applied to said working electrodes at a first potential of substantially zero for a first preset time; flowing a first current which is larger than a hydrogen peroxide detect current to said working electrodes for a second preset time; dropping to a second potential below zero potential; sweeping from said second potential to a third potential higher than said hydrogen peroxide detect potential at a fixed rate. 9. A voltage applying method according to claim 8, wherein said detecting step comprising:applying a preset potential to said pair of working electrodes; detecting a preset current between said pair of working electrodes and said counter electrode to confirm enzyme electrode contact with said test specimen. 10. A voltage applying method according to claim 8, further comprising:simultaneously with said sweeping step, detecting one of a peak value of current in the range of the voltage sweep to said fourth potential, a current value at a potential separated from a potential causing the peak current value by a preset potential value, and a current value at a specific potential; and converting said detected current value into a concentration of a substance in said test specimen by comparing said value with a calibration curve previously charted. 11. A voltage applying method according to claim 8, further comprising, before dropping to a second potential step, keeping a final potential that is reached when said preset time is passed at a third preset time.
12. A voltage applying method according to claim 11, further comprising:simultaneously with said sweeping step, detecting one of a peak value of current in the range of the voltage sweep to said fourth potential, a current value at a potential separated from a potential causing the peak current value by a preset potential value, and a current value at a specific potential; and converting said detected current value into a concentration of a substance in said test specimen by comparing said value with a calibration curve previously charted. Description
This application is a divisional of U.S. patent application Ser. No. 08/284,116 filed Aug. 2, 1994.
The present invention relates to methods of applying voltage to chemical sensors for example, in a throwaway type chemical sensor.
A sensor which converts a given chemical substance contained in a test specimen into an electrical signal for measuring a concentration of the chemical substance has been known. This type of the sensor is called a chemical sensor. For the purposes of easy handling and improving the measuring accuracy, improved chemical sensors have been proposed. Some of the chemical sensor of this type have reached the stage of practical use.
FIG. 14 is a perspective view showing a sensor holder with a throwaway chemical sensor set thereto, which was proposed in Japanese Utility Model Application No. 1-141108 filed by the inventors of the present Patent Application. As shown in the drawing, the throwaway chemical sensor is a sensor collected body 50 containing a plural number (e.g., 10) of sensor elements S serially arrayed thereon. This sensor strip 50 is housed in a sensor holder 51. The foremost sensor element of these chained sensor elements of the sensor collected body 50 is exposed at the tip 51a of the sensor holder 51. The exposed sensor element is electrically connected to a not shown measuring instrument through a connector 52 and a cord 53. A test specimen is dropped on the exposed sensor element to measure the concentration of a given chemical substance thereof. After the measurement, a slider 54 of the sensor holder 51 is forwarded to project the used sensor element from the tip 51a of the holder so that the sensor element is cut out and thrown away. When the used sensor is cut out, a new sensor has already been placed at the tip 51a of the holder and ready for the next measurement. In this way, the process of cutting out and discarding the used or old sensor and another measurement using a new sensor are repeated for successive measurements.
It is desirable that the sensor collected body mounted in the holder has a lot of sensors so as to improve a workability, for example, reducing the number of setting the sensor collected body to the sensor holder. In the case of the sensor collected body illustrated in the drawing, an increase of the number of the sensor elements leads to an elongation of the sensor collected body. The length of the sensor collected body that is acceptable for the sensor holder is limited, so that the number of the sensor elements contained in the sensor collected body is also limited. Generally, the calibration value for the sensor is set up for each manufacturing lot, and input to the measuring instrument. Where the exchange of the sensor collected body with a new one is frequent, it is highly probable that an operator mistakenly uses the sensor collected body of another lot, and that calibration values are mistakenly input to the instrument.
Further, the sensor element is bent and cut out every measurement. During this cut-out work, the test specimen may accidentally be attached to other portions than the sensor element. A danger of contamination and infection by the specimen inevitably exists.
General chemical sensors easily lose their function by moisture. For this reason, a moisture-proof must be taken for the chemical sensors, particularly when these are not used. If the holder 51 is designed so as to have a completely sealed structure, it is very difficult to store the sensor collected body after unpacked for long time while keeping its performances.
In addition, enzyme electrodes of the current-detect type which detects a concentration of a glucose (dextrose) contained in blood or urine have been known. Some of the enzyme electrodes are of the throwaway type. An example of the enzyme electrode of this type is disclosed in Unexamined Japanese Patent Publication No. Hei. 2-245650. The enzyme electrode has such a structure that an electrode portion is formed on an insulating substrate, and an enzyme reaction layer is formed on the electrode. The enzyme reaction layer contains hydrophilic high polymer substance, oxidation reduction enzyme, and electron acceptor.
In the enzyme electrode thus structured, when a test specimen solution is dropped on the enzyme reaction layer, the oxidation reduction enzyme and the acceptor are dissolved into the test specimen solution so that the enzyme reacts with the substrate (glucose) in the specimen solution to deoxidize the receptor. The concentration of the substrate in the specimen solution is calculated using an oxidization current value obtained after the enzyme reaction completes. However, in the enzyme electrode thus structured, the oxidation reduction enzyme tends to bond to oxygen. Accordingly, the oxygen dissolved and existing in the specimen solution (this oxygen will be referred to as a dissolved oxygen) antagonistically act, so that the reaction progresses under the influence of the oxygen, and an error is caused in the measurement.
Another type of the enzyme electrode is disclosed in Unexamined Japanese Patent Publication No. Hei. 2-129541. The enzyme electrode disclosed is of the called hydrogen peroxide type. In this electrode, a substrate (glucose) in a test specimen solution reacts with the dissolved oxygen using enzyme as catalyst to generate hydrogen peroxide. Measured is a current generated when the generated hydrogen peroxide is oxidized at the electrode. The current value thus measured is used for calculating the concentration of the substrate in the test specimen solution.
The enzyme electrode of the hydrogen peroxide type uses the dissolved oxygen in the test specimen solution. Therefore, it is not necessary to use the electron acceptor, which is indispensable to the enzyme electrode of the current-detect type. No antagonism between the dissolved oxygen and the acceptor takes place in the test specimen solution, thereby eliminating the measurement error problem by the antagonism. Such an advantageous enzyme electrode of the hydrogen peroxide type has still a following technical problem to be solved.
In the case of the enzyme electrode of the hydrogen peroxide type, the substrate reacts with the dissolved oxygen in a test specimen solution, using enzyme as catalyst. During the reaction process, hydrogen ions are generated. Also when the hydrogen peroxide is deoxidized, hydrogen ions are generated. By the generated hydrogen, the concentration of hydrogen ions is varied in the test specimen solution. When the concentration of hydrogen ions is varied, the reproducibility of a detected current and a detection sensitivity of the sensor become worse in accordance with the pH dependency of the enzyme reaction and the electrode reaction. An accuracy of detecting the concentration of a substance under measurement is degraded, and the resultant calibration curve has a poor linearity.
An object of the present invention is to provide a method for applying voltage to an enzyme electrode of the hydrogen peroxide type which is operable independent of the concentration of the dissolved oxygen, and expands a measurable range of the chemical sensor without a complicated electrode structure.
An example of a throwaway chemical sensor using the present invention includes: substantially disk-shaped sensor body; and a plurality of sensor elements radially extended outward from the circumference thereof, which is formed on the sensor body, each of the sensor having a detecting portion including a plurality of electrodes, and a terminal portion including a plurality of terminals corresponding to the electrodes; wherein the electrodes are electrically connected to the corresponding terminals.
In the example of a throwaway chemical sensor using the present invention, the sensor body has a plurality of notch portions forming a plurality of trapezoidal portion on which at least one of the electrodes of each of sensor element is provided.
In addition, in the example of a throwaway chemical sensor using the present invention, the throwaway chemical sensor is housed in a holder having supporting member for rotatably supporting the sensor body; upper and lower covering members for covering at least the sensor; an opening portion which is formed by notch portions of the members for exposing at least one of the sensor elements to an outside of the holder; rotating member for rotating the sensor body; positioning member which is engaged with the notch portion of the sensor body to rotate the sensor body at predetermined distance; terminal member which is contact with the terminal portion of the sensor element which is exposed to the outside of the holder from the opening portion.
Further, an enzyme electrode of an example of a chemical sensor using the present invention includes: electrode portion including a pair of working electrodes and counter electrode; first film formed on one of the working electrodes, which includes polyvinyl alcohol and surface-active agent; second film formed on the other working electrode, which includes polyvinyl alcohol, surface-active agent and enzyme; and overcoat film formed on the first and second film, which comprises high polymer electrolye including pH buffer.
A voltage applying method for a hydrogen type enzyme electrode having a pair of working electrodes and counter electrode according to the present invention includes: detecting a contact of a test specimen with the enzyme electrode; keeping a potential applied to the working electrodes at a first potential of substantially zero for a first preset time; applying a second potential which is higher than a hydrogen peroxide detect potential to the working electrodes for a second preset time; dropping the second potential to a third potential below zero potential; sweeping from the third potential to a fourth potential higher than the hydrogen peroxide detect potential at a fixed rate.
Since the sensor holder for a chemical sensor is thus constructed, an increased number of chemical sensors can be contained in the sensor holder, and there is eliminated a danger of contamination and infection by the test specimen attached to other portions than the sensor element. Further, a reliable moisture-proof structure of the sensor holder is secured.
In an exemplary enzyme electrode using the present invention, diffusion of a test specimen solution is accelerated by surface-active agent contained in the first and second films. A preparatory time before the measurement starts is reduced. Further, a pH buffer contained in the overcoat film reduces a variation of the concentration of hydrogen ions in the test specimen solution.
The voltage applying method of the invention provides the useful effects comparable with those when the dissolved oxygen is increased in the test specimen solution.
FIG. 1 is a plan view showing a first embodiment of a sensor body utilizing the present invention;
FIG. 4 is a perspective view showing au upper portion of a sensor holder housing the sensor body;
FIG. 9 is a cross sectional view taken on line I--I' in FIG. 8;
FIG. 10 is a plan view showing a sensor body according to a second example of a sensor body using the present invention;
FIG. 11 is a cross sectional view taken on line II--II';
FIG. 15 is an exploded view in perspective of another exemplary chemical sensor holder using the present invention;
FIG. 18(a) is a plan view showing another exemplary sensor body using the present invention;
FIG. 19(a) is a plan view showing an enzyme electrode using the present invention;
FIG. 21 is a graph showing a calibration curve of the enzyme electrode using the invention;
A structure of a sensor is illustrated in FIGS. 1 to 3. As shown in FIG. 1, a disk-shaped sensor body 1 contains a plural number of elemental sensors 2 (referred to as sensor elements) radially extended outward from the circumference thereof. The sensor body 1 is made of a suitable insulating material, which is conventionally used for various types of substrate. The insulating material may be such plastics as epoxy resin or glass epoxy resin, or equivalent material. The circumferential portion of the sensor body 1 is shaped to have V-shaped notches 3 equidistantly and angularly arrayed therearound. Of these notches 3, the adjacent notches define a trapezoidal part. Thus, the notches 3 and trapezoidal parts are alternately arrayed on the circumference of the sensor body 1. The sensor elements 2 are formed in the trapezoidal parts, respectively.
A pattern of the sensor element 2 formed in the trapezoidal part is illustrated in detail in FIG. 3. Each of the sensor element 2 is formed by forming a circuit pattern of conductive material on the substrate, or the trapezoidal part, as of conventional sensors. A preferable conductive material may be platinum (Pt). A conventional, suitable plating technique, such as platinum plating process or conductive material printing process, may be used for forming the sensor circuit.
In the sensor circuit, a sensor portion is formed of a counter electrode 6, a reference electrode 7, a first working electrode 8, and a second working electrode 9. Reference numerals 10a, 10b, 10c, and 10d designate terminals of those electrodes. One sensor element 2 is formed by the sensor portions and the terminal portions. The sensor body 1 is shaped like a disk with the fringe made of a number of the trapezoidal parts each containing one sensor element 2 formed therein.
Reference numeral 4 designates a positioning plate coaxial with the sensor body 1. The positioning plate 4 is also used for containing desiccant therein. Accordingly, the positioning plate 4 need to be made of air-permeable material, such as plastic material with a number of perforations or air-permeable nonplastic material, e.g., hard unwoven fabric. The material have to be strong enough to withstand the operation of the positioning plate to be given later. The positioning plate 4 thus constructed is filled with desiccant. Grooves 4a are equidistantly formed in the circumferential outer face, so that the positioning plate 4 takes the form like a gear. The positioning plate 4 may consist of two half-circular plates, which are combined and fixed to the positioning-plate location on the sensor body 1. The positioning plate 4 may also be formed by fitting a positioning plate into an opening previously formed in the sensor body 1. A knob 5, which is coaxial with the sensor body 1, is provided to the surface of the sensor body 1 having the sensor element 2 formed thereon.
As illustrated in FIGS. 4 and 5, the sensor holder 11 becomes thin toward the fore end thereof (left side in the drawing). An opening 18 of a V-shaped (as viewed from top) cutout is formed at the fore end of the sensor holder 11. The opening 18 allows only one of the sensor elements 2 of the sensor body 1 contained in the holder 11 to be exposed in the outside of the holder.
The sensor body 1 is disposed in the holder 11 such that one of the plural number of sensor elements 2 forming the sensor body 1 is partly exposed to the outside of the holder 11 (FIG. 4). More specifically, the sensor part of the sensor element, which includes the electrodes 6, 7, 8, and 9, is exposed to the outside through the V-shaped opening 18 of the sensor holder 11. The terminals 10a to 10d of the sensor element 2 the sensor part of which is exposed outside are brought into contact with the connector terminals 17a of the connector 17, respectively. As a result, this sensor element 2 is electrically connected to the measuring instrument, through the connector 17 and the cords 19. The holder 11 containing the sensor body 1 thus set therein is placed in a state that the terminals of the sensor element 2 are located on the obverse side of the holder, as shown in FIG. 4. Then, for measurement, a test piece is attached to the sensor part of the sensor element 2.
When the measurement progresses in this way and all of the sensor elements 2 of the sensor body 1 is used, an operator opens the back cover 12 of the sensor holder 11 so as to replace the old sensor body 1 with a new one. When the measurement is completed in a state that the sensor body 1 contains still the sensor elements 2 not yet used, the holder 11 is packed and stored in a moisture-proof state for another measurement.
In a case where the measurement is completed in a state that the sensor body 1 includes still new sensor elements 2, it is unsuggestible to take the sensor body 1 out of the holder 11. When it is taken out of the holder, the not yet used sensor elements 2 is touched with finger tips so as to reduce the reliability of the sensor elements 2. Accordingly, it is desirable to store the sensor body 1 in which the sensor body 1 has the not yet used sensor elements 2 is left to hold the sensor holder 11 therein. In the case of storing the sensor holder 11, the positioning plate 4 of the sensor body 1 preferably contains desiccant so that the inside of the holder 11 is kept in a satisfactorily dried state.
Second embodiment of a throwaway sensor according to the present invention will be described with reference to FIGS. 10 and 11.
While the first embodiment uses the positioning plate 4 for positioning the sensor part, the second embodiment uses for the positioning device in which the fringe of the sensor body 1 is configured to have the V-shaped notches 3 and the trapezoidal parts on which the sensor elements 2 are to be formed. A sensor body 1, shaped like a ring as viewed in plan, includes an opening la formed at the central part and key grooves 1b formed in the side wall.
The sensor holder 11 is provided with a device for rotatably supporting the sensor body 1. A main shaft 31 is rotatably planted on a bottom plate 11b of the holder 11. The top end of the main shaft 31 serves as a knob for turning the sensor body, which corresponds to the knob 5 in the first embodiment. An engaging shaft 32 is attached to the main shaft 31. The diameter of the engaging shaft 32 is substantially equal to the inner diameter of the opening 1a of the sensor body 1. A plural number of keys 32a are protruded from the side wall of the engaging shaft 32 so as respectively to engage the key grooves 1b of the sensor body 1. A support plate 33 is coaxial with the main shaft 31 and the engaging shaft 32. The support plate 33 is larger in diameter than the engaging shaft 32. The support plate 33 supports the sensor body 1 fit to the engaging shaft 32. The positioning member 14 is mounted at a location adjacent to the circumferential edge of the sensor body 1 on the bottom plate 11b so that the stopper 14b of the positioning member 14 engages any of the notches 3. When the stopper 14b engages one of the notches 3, a sensor element 2 specified by the notch engaging the stopper is set at the opening 18 of the sensor holder 11. In other words, the positioning member 14 positions the sensor body 1 in such a way.
After the sensor body 1 is set to the holder 11, a cover 30 is closed so that the main shaft 31 is partly protruded from the cover 30. As recalled, in the first embodiment, the cover is the back cover serving as the bottom plate. In the second embodiment, the bottom plate is integral with the holder 11, and the top surface of the holder is used for the cover 30. A desiccant 34 is located within the sensor holder 11. With use of the desiccant, the sensor body 1 in the holder 11 is protected from moisture as in the first embodiment.
In the figure, a reference numeral 3a designates a notch, reference numeral 40 designates a reference electrode; 41a, 41b, and 41c, counter electrodes; 42a and 42b, working electrodes; 43a, 43b, 43c, and 43d, terminals; and 44 lead wires for connecting those electrodes. A calibrating part 45 consists of a set of electrodes (in this instance, three electrodes forms one see of the electrodes). The calibrating part 45 is formed on one of the trapezoidal parts of the sensor body 1, and is provided for calibrating the sensor.
Next, FIG. 13 shows a plan view showing a moisture-proof cap to be attached to the chemical sensor holder 11. A moisture-proof cap 20 is made of high water-proof material, such as plastics. The moisture-proof cap 20 includes a pair of stopper pawls 20a and 20b formed at the opening for receiving the holder. A pair of stopper pawls 20a and 20b which is formed at the upper and lower of the holder receiving opening side, respectively, is engaged with a pair of groove 21 formed in the sensor holder 11 so that the moisture-proof cap 20 is airtightly connected with the holder 11. The moisture-proof cap 20 is very convenient for sealing the holder containing the sensor body having the not-yet-used sensor elements for a long time storage of the sensor. The moisture-proof cap 20 may also be made of water-proof and flexible material, such as rubber.
In this embodiments as mentioned above, the positioning plate 4 has two functions which are a water-proof function by desiccant and a positioning function for positioning the sensor body 1. If required, the desiccant is located at another place in the sensor holder 11, and the positioning plate 4 is used only for positioning the sensor body 1. In this case, the material of the positioning plate 4 is not limited to that referred to above.
FIGS. 15 to 17 show a third embodiment of a chemical sensor holder according to the present invention. FIG. 15 is an exploded view in perspective of a chemical sensor holder according to the third embodiment. In a throwaway type chemical sensor 101, a sensor jacket 104 includes an upper cover 102 with a dropping part 116 and a lower cover 103. A sensor body 105 and a sensor cover 106 bonded to the sensor body 105 are sandwiched between the upper and the lower covers 102 and 103. A number of sensor elements 144 are radially mounted on the sensor body 105 as will be described later. The sensor cover 106 includes positioning grooves 107 formed in the circumferential edge thereof. When a protrusion 114 of a holder/sensor feed mechanism 118 (FIG. 17), which will be described with reference to FIG. 17, engages one of the positioning grooves 107, the sensor body 105 is turned in a given direction. The lower cover 103 is made up of a ratchet 109 for turning the sensor body 105 every groove while preventing reversal of the turn, a pushing portion 110, a hole 108 for receiving the protrusion 114, and a sensor rotation window 111. To assembly the chemical sensor 101, the upper and lower covers 102 and 103 are coupled and fastened by countersunk screws inserted into holes 112 of the upper cover 102 and holes 112 of the lower cover 103. The chemical sensor 101 thus assembled is illustrated in FIG. 16.
The chemical sensor 101 thus assembled is set to the holder/sensor feed mechanism 118 shown in FIG. 17. The holder/sensor feed mechanism 118 is provided with a contact portion 117, a sensor lever 115 for moving the sensor, and the protrusion 114. The protrusion 114, interlocked with the sensor lever 115, is set at an initial position by a spring which is not shown. When the sensor lever 115 is pushed, the protrusion 114 is moved in the direction of an arrow, viz., in the sensor moving direction, while resisting the resilient force of the spring. When the sensor lever 115 is released, the protrusion 114 is returned to the initial position by the resilient force of the spring. The protrusion 114 is obliquely raised to have a slanted surface and a vertical surface. When the chemical sensor 101 is set to the holder/sensor feed mechanism 118, the protrusion 114 engages at the vertical surface one of the positioning grooves 107 through the hole 108, and turns the disk-shaped sensor cover 106 unidirectionally. The contact portion 117 is brought into contact with the terminals of each sensor element on the sensor body 105 through a contact window 119. One of the sensor elements arrayed on the sensor body 105 is located at the dropping part 116 (FIG. 16). A test specimen is dropped onto the exposed sensor element. The result is transferred in the form of an electrical signal to a measuring instrument which is not shown.
A construction of the sensor body 105 of the throwaway chemical sensor is as shown in FIGS. 18(a) and 18(b). A plural number of sensor elements 144 each as shown in FIG. 18(b) are radially formed on a disk-shaped support member. As shown in the drawings, each of the sensor elements 144 includes a reference electrode 140, its terminal 143b, counter electrodes 141a, 141b, and 141c, first and second working electrodes 142a and 142b, and their terminals 143c and 143d. The functions of these electrodes have already been described in the above-mentioned embodiments, and hence no further description thereof will be given. The sensor body 105 has also a calibrating part 145 as in the previous embodiment. The calibrating part 145 also consists of a set of electrodes (in this instance, three electrodes forms one set of the electrodes). The calibrating part 145 is formed on one of the trapezoidal parts of the sensor body 105, and is provided for calibrating the sensor.
Since the sensor elements 144 are radially disposed on the disk-like support, the number of sensor elements is increased for a fixed size of the sensor body. The sensor body have to be infrequently set to the holder for its exchange with a new one. This improves the workability and reliability of the sensor. Additionally, the troublesome work to exchange the sensor element every measurement is eliminated. Since the test specimen will not be attached to other portions than the sensor element when it is exchanged, there is eliminated danger of contamination and inflection by the test specimen mistakenly attached.
These electrodes 204a to 204d are respectively connected to terminals 205 located on the left end portion. These terminals 205 are connected to a contact terminal of a measuring instrument, not shown, when a test specimen is subjected to a measurement. For the measurement, the test specimen is dropped on the electrode portion. An insulating film 206 having a substantially U-shaped when viewed from top, covers an area including a part of the counter electrode 204d and a portion for connecting the electrodes 204a to 204d to the terminals 205.
A first film 207 is layered on the first working electrode 204b. A second film 208 is layered on the second working electrode 204c. An overcoat film 209 (not shown) is further layered on both the first and second films 207 and 208. The first film 207 contains at least polyvinyl alcohol and surface-active agent. An example of the composition of the first film 207 is given below. In the composition, the components are expressed by weight for the unit area of 1 mm2 of the film.
Composition of the first film 207
______________________________________1)   Polyvinyl alcohol of 300 to 3000                      0.3 &#956;g to 3.0 &#956;gin polymerization degree2)   SDS (surface-active agent)                      0.5 &#956;g to 1.5 &#956;g3)   Sodium alginate       0.12 &#956;g to 0.4 &#956;g4)   Phosphoric acid buffer*Dipotassium hydrogen phosphate                      0 &#956;g to 11.8 &#956;g*Sodium hydrogen phosphate                      0 &#956;g to 4.5 &#956;g______________________________________
The reason why the polymerization degree of the polyvinyl alcohol is selected in the range of 300 to 3000 is as follows. Polyvinyl alcohol is hard to be dissolved into water, if its polymerization degree is high. Surface-active agent (SDS: dodecyl sodium sulfate) and phosphoric acid buffer are nonuniformly mixed so that the polyvinyl alcohol is separated out of the solution. Particularly, when the polymerization degree exceeds 3000, these components are separated out of a solution suitable for film formation even at the lower limit value (0.3 μg) of the composition example. The film components are nonuniformly distributed to cause an error in measurement. If its polymerization degree is low, the solubility of polyvinyl alcohol is increased so that it fails to grasp enzyme within a measuring time. As a result, the measurement reproducibility is deteriorated.
Composition of the overcoat film 209
______________________________________1)  Sodium alginate (high polymer electrolyte)                        5 &#956;g to 20 &#956;g2)  Phosphoric acid buffer composition by    molar ratio    *Dipotassium hydrogen phosphate:    Sodium hydrogen phosphate (sodium    phosphate) = 1:1 to 9:1    *Dipotassium hydrogen phosphate                        32 &#956;g to 236 &#956;g    *Sodium hydrogen phosphate                        4.5 &#956;g to 90 &#956;g______________________________________
The high polymer electrolyte of the overcoat film 209 may be any other suitable material than alginic acid, for example, polystyrene sulfonic acid or polyacrylic acid. The surface-active agent used for the first and second films 207 and 208 may be any other suitable material than SDS, e.g., any of negative ion active agents, such as higher fatty acid alkaline salts and alkyl aryl sulfonic acid salts, or any of nonionic surface-active agents, such as polyethylene glycol alkyl phenyl ether and sorbitan fatty acid ester.
The pH buffer may be not only the phosphoric acid but also a reagent satisfying the following conditions. Positive ions having a valence of 2 or more are not contained. When it is dissolved into a test specimen solution, the concentration of hydrogen ions is between 5 and 8. The reagent does not hinder the enzyme reaction and the electrode reaction. Use of the pH buffer not containing the positive ions having a valence of 2 or more is preferable since the pH buffer containing such positive ions makes the coating work of gelatinized alginic acid difficult.
A. Components of the first film 207
______________________________________1)   Polyvinyl alcohol of 500 in polymerization                          2.8 mg/mldegree2)   SDS (surface-active agent)                          2.5 mg/ml3)   Sodium alginate           0.5 mg/ml4)   Phosphoric acid buffer    30 mM*Dipotassium hydrogen phosphate                          3.5 mg/ml*Sodium hydrogen phosphate                          1.2 mg/ml______________________________________
C. Components of the overcoat film 209
______________________________________1)   Sodium alginate (high polymer electrolyte)                          10 mg/ml2)   Phosphoric acid buffer    0.6 MPhosphoric acid buffer composition bymolar ratio*Dipotassium hydrogen phosphate:Sodium hydrogen phosphate (sodiumphosphate) = 2:1*Dipotassium hydrogen phosphate                          116 mg/ml*Sodium hydrogen phosphate                          40 mg/ml______________________________________
Further, in the enzyme electrode of the hydrogen peroxide type, which includes the enzyme electrode of the invention, a range allowing a substrate to be measured is limited by the dissolved oxygen in the test specimen solution. To expand this range, the inventor excogitated some inventive and unique methods of applying voltage to the enzyme electrode, which can expand this range. These methods applied to the electrode will be described with reference to FIGS. 22 to 25.
The first potential for causing no current to flow into the electrode portion 204 may be realized by setting the potential applied to the electrode portion 204 at substantially 0, or disconnecting a potential applying device (power source) from the electrode portion 204. At this time, the same may also be realized by using such a voltage as to cause an extremely smaller current than the measurement detection current. The preset time t1, usually 15 to 40 seconds, preferably 30 to 40 second, is determined by the composition and the thickness of the enzyme film, the structure of the electrode, and the like. This time may be reduced by reducing the film thickness as thin as possible, constructing the electrode structure as to swiftly guide the test specimen onto the surface of the enzyme film, using such a material as to well absorb the test specimen, or the like.
FIG. 23 is a graph explaining a second method of applying voltage to the enzyme electrode according to the present invention. Only the different portions of the second voltage applying method from the first voltage applying method will be described. The second voltage applying method includes first to fourth steps as the first voltage applying method. Of those steps, the first, second, and fourth steps are the same as those of the first voltage applying method.
Patent CitationsCited PatentFiling datePublication dateApplicantTitleUS4528270 *Oct 27, 1983Jul 9, 1985Kabushiki Kaisya Advance Kaihatsu KenkyujoElectrochemical method for detection and classification of microbial cellUS4935105 *Oct 18, 1989Jun 19, 1990Imperial Chemical Industries PlcMethods of operating enzyme electrode sensorsUS5407545 *Apr 25, 1994Apr 18, 1995Kyoto Daiichi Kagaku Co., Ltd.Method for measuring sample by enzyme electrodesUS5409583 *Sep 28, 1993Apr 25, 1995Matsushita Electric Industrial Co., Ltd.Method for measuring concentrations of substrates in a sample liquid by using a biosensorUS5411647 *Jan 25, 1994May 2, 1995Eli Lilly And CompanyTechniques to improve the performance of electrochemical sensorsUS5496452 *Jan 4, 1993Mar 5, 1996The Secretary Of State For Defence In Her Britannic Majesty's Government Of The United Kingdom Of Great Britain And Northern IrelandSubstrate regenerating biosensorJPH0380353A * Title not availableJPS62156555A * Title not available* Cited by examinerReferenced byCiting PatentFiling datePublication dateApplicantTitleUS5672256 *Dec 8, 1995Sep 30, 1997Lg Semicon Co., Ltd.Multi-electrode biosensor and system and method for manufacturing sameUS6176989Dec 28, 1998Jan 23, 2001Teledyne Technologies Incorp.Electrochemical gas sensorUS7664607Oct 4, 2005Feb 16, 2010Teledyne Technologies IncorporatedPre-calibrated gas sensorUS8052619 *Jan 30, 2007Nov 8, 2011Panasonic CorporationBlood sensor and blood test apparatus having the sameUS8191396May 3, 2007Jun 5, 2012Bayer Healthcare LlcTest-sensor packagingUS8444576Sep 20, 2011May 21, 2013Panasonic CorporationBlood test apparatus having blood sensorUS8679309Jul 30, 2008Mar 25, 2014Bayer Healthcare LlcTest sensors and methods of using side mounted meter contactsUS20040084307 *Jan 22, 2003May 6, 2004Kim Hyo-KyumBiosensor, biosensor array, and method for manufacturing a plurality of biosensorsUS20050125162 *Dec 3, 2003Jun 9, 2005Kiamars HajizadehMulti-sensor device for motorized meter and methods thereofUS20090043227 *Jan 30, 2007Feb 12, 2009Matsushita Electric Industrial Co., Ltd.Blood sensor and blood test apparatus having the sameUS20100206747 *Jul 30, 2008Aug 19, 2010Bayer Healthcare LlcTest Sensors and Methods of Using Side Mounted Meter ContactsEP1225449A1 *Jan 19, 2001Jul 24, 2002Apex Biotechnology CorporationNon-enzymatic disposable electrode strip comprising a surfactant for detecting uric acid or hemoglobin; method for producing the same and its useEP1936375A1 *Jan 19, 2001Jun 25, 2008Apex Biotechnology CorporationNon-enzymatic disposable electrode strip comprising a surfactant for detecting uric acid or hemoglobin; method for producing the same and its useWO2007133455A2 *May 3, 2007Nov 22, 2007Bayer Healthcare LlcTest-sensor packagingWO2009017732A1 *Jul 30, 2008Feb 5, 2009Bayer Healthcare LlcTest sensors and method of using side-mounted meter contacts* Cited by examinerClassifications U.S. Classification205/777.5, 204/412, 435/817International ClassificationC12Q1/00, G01N27/403, G01N33/487Cooperative ClassificationY10S435/817, G01N33/4875, C12Q1/002, C12Q1/001European ClassificationG01N33/487E, C12Q1/00B2, C12Q1/00BLegal EventsDateCodeEventDescriptionMar 6, 2000FPAYFee paymentYear of fee payment: 4Feb 10, 2004FPAYFee paymentYear of fee payment: 8Mar 24, 2008REMIMaintenance fee reminder mailedSep 17, 2008LAPSLapse for failure to pay maintenance feesNov 4, 2008FPExpired due to failure to pay maintenance feeEffective date: 20080917RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services