JP2009258129A - Biosensor, measuring device for biosensor and determination method for substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a determination method for detecting that a sample liquid is supplied to a wrong place of a biosensor in the biosensor for determining a concentration of a substrate in the sample liquid. <P>SOLUTION: This biosensor includes a biosensor having a reagent layer specifically reacting with the substrate in a measuring sample and a measuring device for obtaining the quantity of the substrate contained in the measuring sample from a sample in which the measuring sample and the reagent layer react with each other. The measuring device includes a temperature measuring part for measuring the temperature when reaction of the measuring sample liquid and the reagent layer progresses and a temperature correction data storage part having two or more correction tables for measured values differing with every temperature region, wherein the correction table is selected according to the temperature measured by the temperature measuring part, and a correction value is calculated according to a measured value of the substrate to make correction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a biosensor for quantifying a substrate contained in a sample solution and a measurement apparatus for the biosensor, and particularly provides a novel quantification method for reducing measurement errors caused by the biosensor. Is.

  A biosensor is a sensor that uses the molecular recognition ability of biological materials such as microorganisms, enzymes, antibodies, DNA, RNA, etc., and applies the biological material as a molecular identification element to quantify the substrate content in a sample solution. . That is, the substrate contained in the sample solution is quantified using a reaction that occurs when the biological material recognizes the target substrate, for example, oxygen consumption due to respiration of microorganisms, enzyme reaction, luminescence, and the like. Among various biosensors, enzyme sensors have been put to practical use. For example, enzyme sensors that are biosensors for glucose, lactic acid, cholesterol, and amino acids are used in the medical measurement and food industries. This enzyme sensor, for example, reduces an electron carrier by electrons generated by a reaction between a substrate contained in a sample solution that is a specimen and an enzyme, and the measuring device electrochemically measures the reduction amount of the electron carrier. Thus, the quantitative analysis of the specimen is performed.

  Various types of biosensors have been proposed. Therefore, a biosensor Z that is a conventional biosensor will be described below. 16 (a) is an exploded perspective view of the biosensor Z, and FIG. 16 (b) is a diagram showing a configuration of an electrode portion formed at the tip of the biosensor Z. A method for quantifying the substrate of the sample solution in the thus configured biosensor Z will be described with reference to FIG. 16 (b).

  First, the biosensor Z is inserted into a measurement apparatus, and the sample liquid is supplied to the inlet 1106b of the sample supply path in a state where a constant voltage is applied between the counter electrode 1103a and the measurement electrode 1103b by the measurement apparatus. The sample liquid is sucked into the sample supply path by capillary action, passes through the counter electrode 1103a closer to the inlet 1106b, reaches the measurement electrode 1103b, and the reagent layer 1105 starts to dissolve. At this time, the measurement device detects an electrical change occurring between the counter electrode 1103a and the measurement electrode 1103b, and starts a quantitative operation. In this way, the substrate content of the sample solution is quantified.

  Specifically, the oxidoreductase and the electron acceptor supported on the reagent layer are dissolved in the sample solution, and the enzyme reaction proceeds with the substrate in the sample solution to reduce the electron acceptor. After completion of the reaction, the reduced electron acceptor is electrochemically oxidized, and the substrate concentration in the sample solution is measured from the oxidation current value obtained at this time.

  However, the conventional biosensor Z has a problem that is desired to be solved. In particular, when an electrical change in the reagent layer 1105 is detected, there is a problem that various factors affect the measurement accuracy and sensitivity of the measurement device.

  First, an erroneous operation by the user is caused. For example, 1) After the user has once supplied the sample solution to the sample supply path, before the quantification by the measuring device is completed, additional sample solution is supplied, and 2) Reuse using a biosensor that has already been used. There are means that can avoid user operation mistakes that affect measurement accuracy, such as trying to quantify, 3) supplying the sample solution to the wrong place, 4) inserting the biosensor into the measuring device in the wrong direction, etc. It was desired. In particular, a means capable of avoiding an erroneous operation by an elderly user is desirable.

  Second, the characteristics of the measurement object are attributed. For example, when the glucose concentration in blood taken from a human body is quantified using a biosensor, the viscosity of blood may affect the measurement accuracy. In general, hematocrit is known as an index of blood viscosity. Hematocrit is the percentage (%) of the volume of red blood cells in the blood. In general, in people without anemia, blood is 50-60% water and red blood cells are 40-50%. In chronic renal failure and renal anemia, the hematocrit is lowered and may fall below 15%. Therefore, in order to perform an appropriate therapeutic treatment, it is necessary to suppress the influence of blood hematocrit and to accurately measure the glucose concentration in blood in, for example, diabetic patients.

  Third, the influence of the environmental temperature on the measurement results. Currently, biosensor measuring devices are becoming more and more compact so that users can carry them. Therefore, when the user tries to measure immediately after moving from the outside to the indoor, the measurement may be started before the temperature in the measuring device is stabilized. The oxidation current value corresponding to the substrate concentration is affected by a sudden temperature change, and the measurement accuracy may be deteriorated. In addition, there is a concern that the temperature of the user's own hand etc. is conducted to the measuring device, and the temperature change due to the body temperature has an influence on the measurement accuracy.

  In view of the above, an object of the present invention is to provide a biosensor, a quantification method using the biosensor, and a measurement apparatus that are easy to operate for the user and have good measurement accuracy.

  In order to solve the above-described problems, according to the first aspect of the present invention, a support unit that detachably supports a biosensor having at least a pair of electrodes formed on an insulating substrate, and each of the electrodes is electrically connected. A biosensor for quantifying a substrate contained in a sample solution by inserting it into a measuring apparatus having a plurality of connection terminals to be connected and a driving power source for applying a voltage to each of the electrodes via the connection terminals. In addition, any one of the electrodes of the biosensor includes a first connection terminal and a second connection terminal provided in the measurement device only when the biosensor is inserted into the support unit of the measurement device in a predetermined direction. The electrode structure is connected to the connection terminal and is electrically connected between the first connection terminal and the second connection terminal when a voltage is applied by the driving power source.

  A conductive layer is formed on at least a part of the insulating substrate, and the conductive layer is divided by a slit to form the counter electrode and the measurement electrode, and further a detection electrode as necessary. You may do it.

  According to the second aspect of the present invention, the biosensor having at least a pair of electrodes formed on the insulating substrate is detachably supported, and the plurality of electrodes are electrically connected to the electrodes. A measurement device for a biosensor that has a connection terminal and a driving power source that applies a voltage to each of the electrodes through the connection terminal, and quantifies a substrate contained in a sample solution supplied to the biosensor, The measurement apparatus includes a first connection terminal and a second connection terminal that are connected to any one of the electrodes of the biosensor only when the biosensor is inserted into the support portion in a predetermined direction. The drive power supply applies a voltage to each of the first connection terminal and the second connection terminal to detect whether the first connection terminal and the second connection terminal are conductive. Yes.

  The measurement device may determine that the biosensor is not inserted in a predetermined direction when continuity between the first connection terminal and the second connection terminal is not detected.

  The measurement apparatus may further include an output unit that outputs a determination result to the outside when it is determined that the biosensor is not inserted in a predetermined direction.

  Further, according to the third aspect of the present invention, an electrode part including a counter electrode, a measurement electrode and a detection electrode formed on at least a part of the insulating substrate, a sample supply path for supplying a sample liquid to the electrode part, A support part that detachably supports a biosensor having a reagent layer that reacts with a sample solution supplied through the sample supply path, and a connection terminal and a drive power source for applying a voltage to the electrode part. A substrate quantification method for quantifying a substrate contained in the sample solution by being inserted into a measurement device having the biosensor inserted into a support part of the measurement device, and the counter electrode and the A voltage is applied by the driving power source to the first set of measurement electrodes and the second set of measurement electrodes or counter electrodes and detection electrodes.

  In the biosensor, a detection electrode is formed on the most downstream side of the counter electrode, the measurement electrode, and the detection electrode along the sample supply path from the sample supply port toward the direction of flow of the sample. It is determined whether or not a sufficient amount of sample liquid necessary for measurement has been supplied, depending on whether or not each of the currents output from the first group and the second group exceeds a predetermined threshold value. It may be.

  If the current from the second set does not exceed the predetermined threshold within a predetermined elapsed time after the current from the first set exceeds the predetermined threshold, the sample liquid is insufficient. You may make it determine with it.

  When it is determined that the sample liquid is insufficient, a message to that effect may be output from the measuring device.

  If the current from the second set does not exceed the predetermined threshold within a predetermined elapsed time after the current from the first set exceeds the predetermined threshold, the measurer again You may make it wait for the step of a measurement temporarily for the operation | work which supplies additional sample liquid.

  In the sample supply path of the biosensor, the detection electrode is formed on the most downstream side of the counter electrode, the measurement electrode, and the detection electrode from the sample supply port in the direction of sample flow, and is further downstream from the detection electrode. A discharge port for accelerating the flow of the sample solution on the side, and the current from the second set exceeds the predetermined threshold before the first set. Thus, when the current from the first set does not exceed a predetermined threshold value within a predetermined elapsed time, it may be determined that the sample liquid has been accidentally sucked from the exhaust port.

  The electrode unit according to an elapsed time from when the current from the first set exceeds a predetermined threshold to when the current from the second set exceeds the predetermined threshold The quantitative value of the substrate corresponding to the current detected by may be corrected.

The measurement apparatus further includes a storage unit that stores calibration data indicating correspondence between the current detected by the biosensor and the content of the substrate contained in the sample solution,
The quantitative value of the substrate corresponding to the detected current may be determined by referring to the calibration data stored in the storage unit.

  When the substrate is quantified after the sample solution is supplied to the sample supply channel and then the reaction between the sample solution and the reagent layer is incubated for a certain period of time, the current from the first set exceeds a predetermined threshold value. The culture time may be changed according to the elapsed time from the detection of the fact until the current from the second set exceeds a predetermined threshold.

  The voltage application destination may be switched at regular intervals in either the first group or the second group.

  According to a fourth aspect of the present invention, there is provided a method for quantifying a substrate, wherein a biosensor having a reagent layer that specifically reacts with a substrate in a measurement sample is reacted with the measurement sample and a reagent in the reagent layer. A measuring device for determining the amount of the substrate contained in the measurement sample from the measured sample, and the measuring device measures the temperature when the reaction between the measurement sample solution and the reagent layer proceeds, and A temperature correction data storage unit having a plurality of measurement value correction tables, which are different for each temperature range, and selects a correction table corresponding to the temperature measured by the temperature measurement unit, and the measurement value of the substrate The correction value corresponding to is calculated and corrected.

  The biosensor has an electrode part including a counter electrode and a measurement electrode formed on at least a part of the insulating substrate, and the measurement device applies a voltage to the electrode part and outputs the voltage from the electrode. It is good also as a measuring device which detects the electric current.

  According to a fifth aspect of the present invention, there is provided a substrate quantification method for measuring a substrate contained in a sample solution supplied to a biosensor by a measuring device, wherein the measuring device measures a temperature in the device. Whether temperature change means is provided and the temperature change is detected from the temperature obtained prior to the measurement of the substrate and the temperature at the time of quantification of the substrate, and the substrate is measured based on this temperature change. A determination of whether or not is made.

  The temperature change between the temperature obtained prior to the substrate measurement and the temperature at the time of the substrate measurement is detected. If the temperature change exceeds a predetermined threshold, the substrate measurement is stopped. May be.

  You may make it perform the temperature measurement prior to the measurement of a substrate intermittently.

  According to the sixth aspect of the present invention, a bio having a counter electrode formed on at least a part of an insulating substrate, an electrode part including a measurement electrode, and a reagent layer that reacts with a sample solution supplied to the electrode part. A sensor, a support unit that detachably supports the biosensor, and a measuring device having a connection terminal for applying a voltage to each electrode of the electrode unit and a driving power source, and the electrode unit by the driving power source. A substrate quantification method for quantifying a substrate contained in the sample solution by detecting a current output by applying a voltage, wherein the measuring device is supported by the biometric unit supported by the support unit. A first potential is applied to the electrode portion of the sensor for a first period, and after the first potential is applied to the electrode portion in the first period, the first potential is applied in the standby period. Stop for a period of time After the elapse of time, the substrate is quantified by measuring a current output by applying a second potential to the electrode portion for a second period, and the first potential becomes larger than the second potential. Yes.

According to the present invention, it is possible to easily provide a biosensor, a quantitative method using the biosensor, and a measurement apparatus that are easy to operate for the user and have good measurement accuracy.

The figure which shows the biosensor system which concerns on embodiment of this invention Exploded perspective view of the biosensor according to the embodiment The figure which shows the combination of the identification part of the biosensor by the presence or absence of formation of the slit which concerns on the embodiment The figure which shows the structure of the biosensor and measuring device which concern on the embodiment The figure which shows the flow of a process of the biosensor and measurement apparatus at the time of quantifying the content of the substrate of a sample liquid The figure which shows the flow of a process of the biosensor and measurement apparatus at the time of quantifying the content of the substrate of a sample liquid The figure which shows the flow of a process of the biosensor and measurement apparatus at the time of quantifying the content of the substrate of a sample liquid The figure which shows the relationship between the correction factor which shows the ratio which corrects the measured base mass, and delay time Figure showing the profile of the preliminary measurement process Diagram showing the relationship between blood viscosity, reaction time between reaction reagent layer and blood, and measurement sensitivity The figure which shows the measurement result of the glucose concentration (mg / dl) of the conventional method and this preliminary measurement process The figure which shows an example of the calibration curve data CA The figure which shows an example of a temperature correction table Diagram showing the relationship between measurement temperature and measurement variation for each substrate concentration Diagram showing temperature change in measuring device Exploded perspective view of a conventional biosensor

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a biosensor system 1 according to an embodiment of the present invention. The biosensor system 1 includes a biosensor 30 and a measurement device 10 on which the biosensor 30 is detachably attached. The amount of the substrate contained in the sample spotted on the sample spotting portion 30 a located at the tip of the biosensor 30 is quantified by the measuring device 10.

  The measurement apparatus 10 includes, for example, a support unit 2 on which the biosensor 30 is detachably attached, and a display unit 11 that displays a quantitative result of a substrate contained in a sample solution spotted on the sample spotting portion 30a of the biosensor 30. have.

  In order to quantify the substrate content in the sample solution using the biosensor system 1, first, after the user inserts the biosensor 30 into the measuring device 10, the user uses the measuring device 10 to fix the electrode of the biosensor 30 described later. With the voltage applied, the sample solution is supplied to the sample spotting portion 30a. The spotted sample liquid is sucked into the biosensor 30 and dissolution of the reagent layer starts. The measuring apparatus 10 detects an electrical change occurring between the electrodes of the biosensor 30 and starts a quantitative operation.

  Here, the biosensor system 1 according to the present embodiment is particularly suitable for quantifying human blood as a sample solution and glucose, lactic acid, and cholesterol contained in blood as a substrate. . The quantification of the substrate contained in the body fluid of the human body is very important in the diagnosis and treatment of specific physiological abnormalities. Particularly for diabetic patients, it is necessary to frequently grasp the glucose concentration in the blood.

  In the following description, the disclosure of glucose contained in human blood is disclosed. However, the biosensor system 1 in the present embodiment quantifies lactic acid, cholesterol and other substrates by selecting an appropriate enzyme. It is also possible to do.

  Next, members constituting the biosensor 30 will be described with reference to FIG. FIG. 2 is an exploded perspective view of the biosensor 30. 31 is an insulating substrate made of polyethylene terephthalate or the like (hereinafter simply referred to as “substrate”), and the surface of the substrate 31 is made of an electrically conductive material such as noble metal such as gold or palladium, or carbon. The conductive layer is formed by a screen printing method or a sputtering vapor deposition method. The conductive layer may be formed on the entire surface of the substrate 31 or at least a part thereof. Reference numeral 32 denotes an insulating substrate provided with an air hole 33 in the center, and is arranged integrally with the substrate 31 with a spacer 34 having a notch interposed between the substrate 31 and the substrate 31.

  On the substrate 31, a conductive layer is divided by a plurality of slits to form a counter electrode 37, a measurement electrode 38, and a detection electrode 39. More specifically, the substantially arc-shaped slit 40 formed on the counter electrode 37, 41a and 41c formed in the direction perpendicular to the side surface of the substrate 31, the slits 41b, 41d and 41f formed in the direction parallel to the substrate 31, and V The conductive layer is divided by a slit 41e having a letter shape, and a counter electrode 37, a measurement electrode 38, and a detection electrode 39 are formed. Each electrode only needs to be formed on at least a part of the substrate 31, and the connection between the measuring apparatus 10 and each electrode may be a lead wire.

  The spacer 34 is disposed so as to cover the counter electrode 37, the measurement electrode 38, and the detection electrode 39 on the substrate 31, and the sample supply path 35 is formed by a rectangular notch provided at the center of the front edge of the spacer 34. Reference numeral 30a denotes an inlet of the sample supply path, and the sample liquid spotted on the inlet 30a is sucked toward the air hole 33 in a substantially horizontal direction (arrow AR direction in FIG. 2) by capillary action.

  A reagent layer 36 is formed by applying a reagent containing an enzyme, an electron acceptor, an amino acid, a sugar alcohol, or the like to the counter electrode 37, the measurement electrode 38, and the detection electrode 39 exposed from the notch portion of the spacer 34. It is.

  Here, glucose oxidase, lactate oxidase, cholesterol oxidase, cholesterol esterase, uricase, ascorbate oxidase, bilirubin oxidase, glucose dehydrogenase, lactate dehydrogenase, lactate dehydrogenase, etc. can be used as the enzyme.

  As the electron acceptor, potassium ferricyanide is preferable, but in addition to potassium ferricyanide, p-benzoquinone and derivatives thereof, phenazine methosulfate, methylene blue, ferrocene and derivatives thereof can be used.

  In the case of the biosensor system 1 according to the present embodiment, glucose oxidase is used as the oxidoreductase carried on the reagent layer 36 and potassium ferricyanide is used as the electron acceptor in order to measure the glucose concentration in the blood of the human body. . The oxidoreductase and the electron acceptor are dissolved in the sample liquid sucked into the sample supply channel (in the case of the present embodiment, blood taken from the human body), and the enzyme is exchanged with glucose as a substrate in the sample liquid. The reaction proceeds and the electron acceptor is reduced to produce ferrocyanide (potassium ferrocyanide in this embodiment). After completion of the reaction, the reduced electron acceptor is electrochemically oxidized, and the glucose concentration in the sample solution is measured from the current obtained at this time. Such a series of reactions mainly proceeds in the area from the slit 40 to the detection electrode 39 through the slit 41e, and the current accompanying the electrochemical change is read by the counter electrode 37, the measurement electrode 38, and the detection electrode 39. Will be.

  Reference numeral 42 denotes an identification unit for identifying a difference in output characteristics for each type of biosensor 30 and each manufacturing lot by the measuring apparatus 10. By forming a combination of slits 41g and 41h as shown in FIG. 2 in a portion corresponding to the identification portion 42 of the counter electrode 37 and the detection electrode 39, the measurement apparatus 10 can electrically identify the difference in output characteristics. Become.

  FIG. 3 shows a combination of the identification units 42 of the biosensor 30 depending on whether or not the slits 41g and 41h are formed. FIG. 3 shows seven types of combinations as an example.

  For example, FIG. 3A shows the identification unit 42 of the biosensor 30 in the case where cholesterol is a quantification target. In this case, the slits 41g and 41h are not provided.

  FIGS. 3B, 3C, and 3D show the identification unit 42 of the biosensor 30 when lactic acid is to be quantified. In FIG. 3B, the slit 41h is provided only in the counter electrode 37, and the correction unit 43 is formed. In FIG. 3C, the slit 41g is provided only in the detection electrode 39, and the correction unit 44 is formed. In FIG. 3D, slits 41 h and 41 g are provided in the counter electrode 37 and the detection electrode 39, respectively, and correction units 43 and 44 are formed. Further, FIGS. 3E, 3F, and 3G show the identification unit 42 of the biosensor 30 when glucose is a quantification target. In FIG. 3E, the slit 41g is provided only in the detection electrode 39, and the slit 41d is formed only up to the slit 41g. Therefore, the correction unit 44 and the measurement electrode 38 are integrally formed. In FIG. 3F, a slit 41h is further formed in the state of FIG. In FIG. 3G, the slit 41f is formed only up to the slit 41h in the state of FIG. Therefore, the correction parts 43 and 44 and the measurement electrode 38 are integrally formed.

  Thus, by changing the slit pattern of the identification unit 42, the area of the conductive portion with each electrode can be varied. Therefore, the measurement device 10 identifies the difference in output characteristics (glucose, cholesterol, and lactic acid concentration) of the biosensor 30 and the manufacturing error due to the manufacturing lot, and switches the data and the control program suitable for the substrate concentration measurement to obtain an accurate measurement value. Can be requested. As in the prior art, the user does not need to input correction data using a correction chip or the like, so that troubles can be eliminated and operational errors can be prevented. Note that although a biosensor having three electrodes is disclosed in this embodiment, the number of electrodes can be appropriately changed in other cases as long as it has at least a pair of electrodes. Further, as the slit formation pattern, a pattern other than the pattern described in FIG. 3 may be used.

  Next, details of the configuration of the measuring apparatus 10 will be described. FIG. 4 shows the configuration of the biosensor 30 (top view) and the measurement apparatus 10. In the biosensor 30, the detection electrode 39 is formed on the most downstream side of the counter electrode 37, the measurement electrode 38, and the detection electrode 39 along the sample supply path 35 in the direction in which the sample flows from the sample spotting portion 30 a. Has been. The arrangement order of the counter electrode 37 and the measurement electrode 38 may be switched. In addition, by providing a predetermined distance between the measurement electrode 38 and the detection electrode 39 via the slits 41c and 41e, the sample liquid can be surely and sufficiently provided due to the change in current accompanying the electrical change of the substrate. It is determined whether or not the amount has been aspirated.

  In the measuring apparatus 10, 12, 13, 14, 15, 16, and 17 correspond to areas A, B, C, D, E, and F, respectively, in which the identification unit 42 of the biosensor 30 is divided into six. Connector to be connected. The areas A, B, C, D, E, and F are divided so as to correspond to the slits 41d and f and the slits 41g and h. Area A corresponds to the measurement electrode 38, area C corresponds to the detection electrode 39, and area E corresponds to the counter electrode 37. Area B is formed integrally with area A, and areas D and F correspond to correction units 43 and 44 in FIG. In addition, 18, 19, 20, 21, and 22 are connectors 13, 14, 15, 16, and 17, respectively, and ground (which means a constant potential, and need not necessarily be “0”. The same applies hereinafter. There is a switch between them. In this ground, the voltage applied to each electrode can be variably controlled. Each connector 13, 14, 15, 16, 17 is connected in parallel to the ground so that a necessary connector can be selected from the connectors 13-17 by on / off control of each switch 18-22 and used at the time of measurement. Become.

  Reference numeral 23 denotes a current / voltage conversion circuit which is connected to the connector 12 and converts the current flowing between the measurement electrode 38 and other electrodes into a voltage and outputs the voltage. Reference numeral 24 denotes a current / voltage conversion circuit 23 which is connected to the current / voltage conversion circuit 23. An A / D conversion circuit 25 that converts the voltage value from 23 into a pulse, 25 controls each switch on / off, or calculates the substrate content of the sample solution based on the pulse from the A / D conversion circuit 24 A CPU 11 is an LCD (liquid crystal display: output unit) that displays measurement values calculated by the CPU 25. Reference numerals 26 and 28 denote temperature measuring units for measuring the temperature in the measuring apparatus 10. One of the temperature measuring units 26 and 28 is connected to the ground, and the other is connected in parallel between the connector 12 and the current / voltage conversion circuit 23 via the switches 27 and 29.

  In the measurement apparatus 10 according to the present embodiment, a change in current between the electrodes is detected using a voltage value (mv) obtained by converting the current flowing between the electrodes of the biosensor 30 by the current / voltage conversion circuit 23. Is done. That is, the voltage value is an index indicating the magnitude of the current between the electrodes.

  Hereinafter, the operations of the biosensor 30 and the measurement apparatus 10 when quantifying the content of the substrate of the sample solution by the quantification method using the biosensor 30 according to the embodiment of the present invention will be described with reference to FIGS. To do.

  First, it is determined whether or not the biosensor 30 has been securely inserted into the support unit 2 of the measurement apparatus 10 (step S1). Specifically, it is determined whether or not the biosensor 30 is inserted by a switch (not shown) in the connector of FIG. When the biosensor 30 is inserted (step S1; Yes), next, conduction detection between the areas A and B (measurement electrode 38) is performed (step S2). As shown in FIG. 3, the measurement electrode 38 is not provided with a slit for insulating one electrode like the slits 41h and 41g. Since the connectors 12 and 13 are connected to the measurement electrodes 38 in the areas A and B, respectively, the biosensor 30 is oriented in such a direction (predetermined direction) that the conductive layer of the biosensor 30 is positioned in the normal direction. When it is inserted into the measuring apparatus 10, it always becomes conductive between the areas AB.

  Therefore, the front and back of the biosensor 30 can be determined by turning on the switch 18 and confirming the presence or absence of conduction between the areas AB. If continuity cannot be detected between the areas AB (step S2; No), it is recognized that the biosensor 30 is inserted reversely, and the measurement process is terminated as a front / back discrimination error (step S3). When a front / back discrimination error is detected, it is preferable to warn the user by displaying an error on the display unit 11 or generating a warning sound from a speaker. As a result, it is possible to easily prevent the user from spotting blood on the biosensor 30 by mistake while the biosensor 30 is inserted upside down.

  If continuity can be detected between the areas AB (step S2; Yes), it is determined whether or not the voltage value detected between the area A and the areas C and E is greater than 5 (mv) (step S4). The switch switching control is performed so that both the switches 19 and 21 are turned on, and the voltage value is detected between the areas C and E which are considered to be electrically integrated with the area A, and thus inserted in step S1. It is determined whether or not the detected biosensor 30 has already been used. This is because if the biosensor 30 has been used, the reaction between the reagent layer 36 and glucose in the blood has already progressed, and the detected voltage value tends to increase.

  When it is determined that the voltage value detected between the area A and the areas C and E is larger than 5 (mv) (step S4; Yes), it is recognized that the used biosensor 30 has been inserted and used. The measurement process is terminated as a completed error (step S5). When a used error is detected, it is preferable to warn the user by displaying an error on the display unit 11, generating a warning sound from a speaker, or the like. Accordingly, it is possible to easily prevent the user from spotting blood on the biosensor 30 by mistake while the used biosensor 30 is inserted.

  Next, when it is determined that the voltage value detected between the area A and the areas C and E is 5 (mv) or less (step S4; No), the identification unit of the biosensor 30 detected by insertion in step S1 By identifying the 42 slit patterns, the CPU 25 switches data and programs suitable for output characteristics based on the identification result (steps S6 to S10). In the case of the present embodiment, there are three types of slit patterns in FIGS. 3E, 3F, and 3G in the blood glucose level sensor that measures the glucose concentration in the example of FIG. Specifically, first, continuity detection between the areas AD is performed (step S6). By performing switch switching control so that the switch 20 is turned on and detecting continuity between the area A and the area D, the biosensor 30 is not a sensor for lactic acid or cholesterol but a blood glucose level sensor. It becomes possible to determine whether or not.

  If conduction between the areas AD is not confirmed (step S6: No), it is determined that the biosensor 30 for the blood glucose level sensor is not compatible, and an error display and warning sound on the display unit 11 is output from the speaker. The user is warned by sounding or the like and the measurement process is terminated (step S7). Thereby, it is possible to avoid in advance that the user erroneously quantifies and misidentifies the quantification result as the glucose concentration.

  If conduction between the areas AD is confirmed (step S6: Yes), conduction detection between the areas AF is performed (step S8). The switch switching control is performed so that the switch 22 is turned on, and the continuity detection is executed between the area A and the area F, so that the biosensor 30 corresponding to the blood glucose level sensor further depends on the production lot. Differences in output characteristics can be identified. The CPU 25 automatically switches data and programs in which output characteristics according to manufacturing lots are considered in advance without using a correction chip.

  Therefore, not only the operability is improved, but also the measurement accuracy can be improved. When there is continuity detection between the areas AF (step S8; Yes), the result record “I” is stored in a memory (not shown) assuming that the type of the biosensor 30 is FIG. 3G (step S9). When there is no continuity detection between the areas AF (step S8; No), the result record “II” is stored in a memory (not shown) on the assumption that the type of the biosensor 30 is FIG. 3 (e) or FIG. 3 (f). (Step S10).

  After the confirmation of the type of the biosensor 30 is completed, it is determined again whether or not the voltage value detected between the area A and the areas C and E is larger than 5 (mv) (step S11). The switch switching control is performed so that both the switches 19 and 21 are turned on, and the current is detected between the area A and the areas C and E, so that the sample is prepared by the user before the measurement apparatus 10 is ready for quantification. It is determined whether or not the liquid has been spotted. Thereby, not only the use of the used biosensor 30 can be surely avoided, but also the spotting of the sample liquid by the user before the preparation for quantification is completed on the measuring apparatus 10 side can be detected.

  When it is determined that the voltage value detected between the area A and the areas C and E is larger than 5 (mv) (step S11; Yes), it is determined that the sample liquid has been spotted before the measurement preparation is completed. Then, the measurement process is terminated as a spotting error (step S12). When a spotting error is detected, it is preferable to warn the user by displaying an error on the display unit 11, generating a warning sound from a speaker, LED display (not shown), or the like. Accordingly, it is possible to reliably avoid user operation errors that affect measurement accuracy, and to maintain measurement accuracy with high accuracy.

  When it is determined that the voltage value detected between the area A and the areas C and E is 5 (mv) or less (step S11; No), the sample liquid is not spotted by the user before the preparation for quantification is completed. And the user is notified of the completion of quantitative preparation by LED display or the like (step S13). When a used error is detected, it is preferable to notify the user not only by LED display but also by display on the display unit 11 and sounding an alarm sound from a speaker. The user who has confirmed this notification collects blood as a sample liquid from his / her own human body, and deposits the collected blood on the sample spotting portion 30a of the biosensor 30 inserted in the measuring apparatus 10.

  Next, it is determined whether or not a sufficient amount of the sample liquid has been sucked through the sample supply path from the sample spotting portion 30a (steps S14 to S20). In the biosensor 30, the counter electrode 37, the measurement electrode 38, and the detection electrode 39 are formed along the sample supply path 35 from the sample spotting portion 30 a toward the sample flow direction, and the detection electrode 39 is located on the most downstream side. Is formed. Therefore, the measurement is performed by selecting any one of the pair of the counter electrode 37 and the measurement electrode 38 and the pair of the measurement electrode 38 and the detection electrode 39 at a constant period and applying a voltage to each electrode of the selected set. It is determined whether or not a sufficient amount of sample liquid necessary for the test has been supplied. As in the prior art, only by identifying the change in current between the measurement electrode 38 and the detection electrode 39, the measurement is not started despite the sample liquid being injected into the sample supply path, or the amount necessary and sufficient for the measurement. On the other hand, it was difficult to identify the cause of whether the sample liquid injection amount was insufficient and the measurement was not performed.

  Specifically, in the case of a pair of the counter electrode 37 and the measurement electrode 38, the switch 19 is turned off and the switch 21 is turned on so that a potential difference is generated between the areas AE. In the case of the set of the measurement electrode 38 and the detection electrode 39, the switch 19 is turned on and the switch 21 is turned off so that a potential difference is generated between the areas AC between the areas AC. Thus, by controlling the switches 19 and 21 respectively, it is possible to easily select and switch between the pair of the counter electrode 37 and the measurement electrode 38 or the pair of the measurement electrode 38 and the detection electrode 39. It becomes. For convenience of explanation, in the following description, when a potential difference is generated in the pair of the counter electrode 37 and the measurement electrode 38, a potential difference is generated in the pair of the measurement electrode 38 and the detection electrode 39 that generates a potential difference between the areas AE. The generation of a potential difference is referred to as generating a potential difference between the areas AC.

  Furthermore, in this embodiment, as an example, switching control between the areas AE and AC is performed every 0.2 (seconds), and 0.2 V is applied to each. Whether or not the voltage value measured between the areas AE and AC has reached 10 (mv) (a predetermined threshold value) is detected. These numerical values can be appropriately changed according to the type of biosensor.

  Returning to the flowchart of FIG. First, a potential difference of 0.2 V is generated between the areas AE located on the upstream side of the sample supply path, and it is determined whether or not the voltage value measured between the areas AE has reached 10 mV or more (step S14). . If the voltage value measured between the areas AE does not reach 10 mv or more (step S14; No), a potential difference of 0.2V is generated between the areas AC on the downstream side, and the voltage value measured between the areas AE is 10 mv. It is determined whether or not the above has been reached (step S15).

  If the voltage value measured between the areas AC does not reach 10 mV or more (step S15; No), it is determined in step S14 whether or not 3 minutes have elapsed since the potential difference was generated between the areas AE (step S14). S16). If it has not reached 3 minutes (step S16; No), the processing from step S14 is repeated again. If the voltage value does not reach 10 mv for 3 minutes between areas AE and AC (step S16; Yes), the measurement process is terminated.

  When it is determined that the voltage value has reached 10 mv between the areas AE (step S14; Yes), it is determined whether or not the voltage value has reached 10 mv between the areas AC (step S17). If the voltage value measured between the areas AC does not reach 10 mv (step S17; No), whether or not 2 seconds (predetermined period) has elapsed since it was determined that the voltage value reached 10 mv between the areas AE. Is determined (step S18). If 10 seconds have not elapsed, the processes in steps S17 and S18 are repeated until the voltage value measured between the areas AC reaches 10 mv until 10 seconds have elapsed (during step S18; No). It becomes a temporary standby state. In this case, since there is a high probability that the spotted sample liquid is insufficient, the error message is displayed on the display unit 11 or the like in order to prompt the user to run out of the sample liquid and follow up the sample liquid. Is preferably displayed or a warning sound is pronounced. If the voltage value measured between the areas AC does not reach 10 mv even after 10 seconds have elapsed (step S18; Yes), the measurement process is terminated as a sample shortage error (step S19).

  Here, the fact that the final measurement accuracy deteriorates when the user catches up the sample solution during 10 seconds after the voltage value between the areas AE is determined to have reached 10 mv in step S14. The inventors of the invention have found. Specifically, while the user is following up, the enzyme reaction is proceeding between the substrate in the sample solution previously deposited and the enzyme in the reagent layer 36. It has already occurred. Thereafter, when the substrate is quantified after the added sample solution reaches between the areas AC, it is influenced by the reductant that has already been generated, so that the voltage value apparently tends to increase. . That is, the influence on the measurement accuracy increases as the elapsed time increases since it is determined in step S14 that the voltage value between the areas AE has reached 10 mv.

  In order to eliminate the measurement error due to the addition of the sample liquid, in the measurement apparatus 10 of the present embodiment, it is determined in step S14 that the voltage value between the areas AE has reached 10 mv. The base mass corresponding to the measured voltage value is corrected according to the elapsed time (hereinafter referred to as delay time) until it is determined that the voltage value has reached 10 mv.

  FIG. 8 is a sensitivity correction table showing the relationship between the correction rate indicating the ratio of correcting the measured base mass and the delay time. The vertical axis represents the correction factor, and the horizontal axis represents the delay time. For example, in the case of a delay time of 5 seconds, a 10% lower correction is made with respect to the measured base mass, and as a result, 90% of the measured base mass becomes the corrected base mass. Such a sensitivity correction table is stored in a memory (not shown) of the measuring apparatus 10 and is referred to when the final base mass is calculated.

  Further, in the biosensor 30 shown in FIG. 2, if the counter electrode 37 is formed so that the slit 41f formed on the substrate 31 extends in the slit 41c direction and is completely connected to the slit 41b, the sample solution is mistakenly generated. It becomes possible to detect a spotting position error that is spotted on the air hole 33. In the flowchart of FIG. 6, when it is determined that the voltage value has reached 10 mV or more between the areas AC first, not between the areas AE (step S15; Yes), between the areas AE within 0.2 seconds thereafter. It is determined whether or not the voltage value has reached 10 mV or more (step S20). When the voltage value does not reach 10 mV or more between the areas AE, it is determined that the sample liquid is spotted at the wrong position of the sample liquid, and the measurement process is ended (step S50).

  As normal, the sample liquid spotted on the sample spotting part 30a is sucked toward the air hole 33 so as to be immersed in the order of the counter electrode 37, the measurement electrode 38, and the detection electrode 39 along the sample supply path 35. . However, when the voltage value only between the areas AC changes greatly, there is a high probability that the user has accidentally spotted the sample liquid on the air holes 33. In such a case, it is determined that it is difficult to perform accurate measurement, and the measurement process is forcibly terminated as a spotting position error. As a result, it is possible to reliably eliminate measurement errors due to user's erroneous operations.

  Further, when it is determined that the voltage value has reached 10 mv between the areas AC (step S17; Yes), or when it is determined that the voltage value has reached 10 mv or more between the areas AE (step S20; Yes), the sample A sufficient amount of liquid is detected, and a preliminary measurement process for quantifying the substrate is started, and time is counted by a timer (not shown) of the measurement apparatus 10 (step S21).

  Next, continuity detection is performed between the area AFs (step S22). Switch switching control is performed so that the switch 22 is turned on, and conduction detection is performed between the area A and the area F. When continuity is detected between the areas AF (step S22; Yes), in step S9, it is determined whether the result record “I”, which is the type of the biosensor 30, is stored in the memory (step S23). When the result record “I” which is the type of the biosensor 30 is stored (step S23; Yes), it is determined that the type of the biosensor 30 is FIG. A calibration curve F7 is set as calibration curve data for specifying the glucose concentration in the sample solution from the voltage value obtained when chemically oxidizing (step S24).

  On the other hand, when the result record “II” is stored (step S23; No), it is determined that the type of the biosensor 30 is FIG. 3E, and the calibration curve F5 is set as the calibration curve data (step). S25). When there is no continuity detection between the areas AF (step S22; No), it is determined that the type of the biosensor 30 is FIG. 3F, and a calibration curve F6 is set as calibration curve data (step S26).

  Thus, according to the slit of the identification part 42 of the biosensor 30, the difference in the output characteristic of the biosensor 30 is automatically recognized, and calibration curve data suitable for the characteristic is automatically selected and set. The calibration curve data in which the output characteristics of the production lot are taken into consideration in advance is automatically switched by the CPU 25 without using the correction chip. Therefore, erroneous measurement using erroneous data by the user can be avoided, and high measurement accuracy can be maintained.

  After the calibration curve is set in steps S24 to S26, preliminary measurement processing is started (steps S27 to S29). First, the preliminary measurement process will be described with reference to FIG. FIG. 9 shows a profile of the preliminary measurement process in the present embodiment.

  In the profile in FIG. 9, the preliminary process is started at time t0. Specifically, the time when the time counting is started by the timer (not shown) of the measuring apparatus 10 is shown. The profile of the preliminary process includes three continuous periods, for example, a first potential period from time t0 to t1, a standby period from time t1 to t2, and a second potential period from time t2 to t3.

  In the first potential period, the potential V1 is applied to the areas A, C and E, and the enzyme reaction proceeds, so that the voltage value obtained by electrochemically oxidizing the produced ferrocyanide increases exponentially. I will do it. Next, in the standby period, the potential V1 applied in the first potential period is set to zero. During this time, the ferrocyanide is not electrochemically oxidized, and the enzymatic reaction continues and the amount of ferrocyanide accumulates. In the second potential period, the potential V2 is applied to the areas A, C, and E, and the ferrocyanide accumulated during the standby period is oxidized at a stretch, so that the amount of emitted electrons increases, so that it is high at time t2. The response value is shown. The voltage value showing a high response value decreases with time, and finally, at time t3, the stabilized voltage value i3 is measured. In the preliminary measurement process, the switches 19 and 21 are both turned on in the measurement apparatus 10 so that the potential is applied to the counter electrode 37 and the detection electrode 39 as a unit.

  Here, as a specification required for biosensors in recent years, reduction of measurement time has been desired. The inventors of the present invention have found that when a substrate is quantified at high speed by a biosensor, the viscosity of the sample solution greatly affects the measurement accuracy. In particular, when human blood is used as a sample liquid, the measurement sensitivity is lowered in the case of blood having high viscosity (high Hct: hereinafter, high viscosity), and the viscosity of blood having low viscosity (low Hct: hereinafter, low viscosity) is measured. In the case, the measurement sensitivity becomes high. This phenomenon is derived from the dissolution rate of the reaction reagent layer and blood. Since the dissolution is slow in high-viscosity blood and the dissolution is fast in low-viscosity blood, the measurement sensitivity by the biosensor is affected.

  FIG. 10 is a diagram showing the relationship between the viscosity of blood, the reaction time between the reaction reagent layer and blood, and the measurement sensitivity. The data shown in FIG. 10 is measured by a conventional measurement method. The conventional technique is a technique in which a potential is applied only during a period corresponding to the second potential period in FIG. 9 and its voltage value is measured. As is clear from FIG. 10, it can be seen that the shorter the reaction time, the greater the influence of the measurement sensitivity due to the difference in viscosity (in the case of blood, Hct). In particular, during the reaction time of about 5 seconds, there is a large difference in measurement sensitivity between low-viscosity blood and high-viscosity blood.

  Therefore, in the conventional measuring method, there is a tendency that the measurement error due to the viscosity of blood becomes conspicuous.

  Therefore, in the first potential period of the preliminary measurement process, the reaction product generated at the initial stage of dissolution with the reagent layer 36 is forcibly consumed by applying the potential V1. In the first potential period, low-viscosity blood has a faster enzyme reaction rate than high-viscosity blood, so that more reaction products are generated and more reaction products are consumed. However, if the potential is applied for an excessively long time, the reaction product is excessively consumed, and the responsiveness of the voltage value detected in the second potential period may be deteriorated. Thus, the effective first potential period length t1-t0 can be 3 to 13 seconds, but it is preferable to further increase the applied potential to 2 to 10 seconds. The potential V1 is preferably 0.1V to 0.8V.

Next, in the standby time, the enzyme reaction proceeds again, and the product from the low-viscosity blood consumed in the first potential period is also quickly recovered and accumulated in substantially the same amount as the high-viscosity blood. However, the influence on the final measurement sensitivity differs if the length of the waiting time is too long or too short.
When the standby time is too short, the response value of the voltage value i3 measured at time t3 becomes too low, and the measurement error increases. If the waiting time is too long, the difference in enzyme reaction rate between low-viscosity blood and high-viscosity blood may further spread. Therefore, the length of the waiting time is determined so that the difference in the enzyme reaction rate between the low-viscosity blood and the high-viscosity blood does not increase further. Therefore, the length of the standby period t2-t1 can be 1 to 10 seconds, but more preferably 2 to 10 seconds.

  In the second potential period, the voltage value is not stabilized immediately after time t2 when the application of the potential V2 is started, and an elapsed time is required for the voltage value to stabilize. In addition, it is not necessary to apply the same potential as that in the first potential period, and a potential lower than the potential V1 in the first potential period is preferable. Any voltage that is sufficiently low to oxidize potassium ferrocyanide is sufficient. Therefore, the length t3-t2 of the second potential period is preferably 2 to 10 seconds. The potential V2 is preferably 0.05 to 0.6V. Finally, the voltage value i3 between areas A, C, and E at time t3 is read, and the amount of substrate (glucose) in the sample solution is calculated from the read voltage value i3.

  Such time setting is a biosensor using a noble metal electrode such as palladium, and the reagent prescription uses not only glucose oxidase or / and glucose dehydrogenase and potassium ferricyanide but also a biosensor containing amino acid and sugar alcohol. It is particularly suitable for quantitative measurement. Moreover, it is suitable when an organic acid is included.

  When the substrate is quantified after the sample solution is supplied to the sample supply path 35 and the reaction between the sample solution and the reagent layer 36 is incubated for a certain period of time, the voltage value measured between the areas AE in step S14 is The incubation time is changed according to the elapsed time from when the threshold value (10 mv or more) is detected until the voltage value measured between the areas AC exceeds the predetermined threshold value (10 mv) in step S17. You may make it make it.

  FIG. 11 is a diagram showing measurement results of glucose concentration (mg / dl) between the conventional method and the preliminary measurement process using blood with hematocrit (hereinafter referred to as Hct) of 25%, 45%, and 65%. . R in FIG. 11 is a measurement result by this preliminary treatment, and the measurement result when the reaction time is 15 seconds and 30 seconds using the conventional method is shown. In this preliminary process, the first potential period is 6 seconds long, the potential V1 is 0.5 V, the standby time length is 6 seconds, the second potential period is 3 seconds long, and the potential V2 is 0.2 V. ing. When measured with reference to Hct 45% and glucose concentration 100 mg / dl, if the blood becomes Hct 25% low-viscosity blood or Hct 65% high-viscosity blood, the measurement results will vary greatly. The higher the blood viscosity, the lower the response value.

  Furthermore, the shorter the reaction time, the greater the variation. In the case of a reaction time of 15 seconds, the variation occurs 10% higher (low viscosity blood with 25% Hct) and 10% lower (low viscosity blood with 65% Hct). In the case of a reaction time of 30 seconds, the variation occurs 5% higher (low viscosity blood of Hct 25%) and 5% lower (low viscosity blood of Hct 65%). In this preliminary treatment, variations of 3% higher (Hct25% low-viscosity blood) and 3% lower (Hct65% low-viscosity blood) occur. Although the total reaction time is equal to the measurement result of the reaction time of 15 seconds, the variation due to Hct can be reduced.

  Returning to FIG. 7 again, the description of the measurement process is continued. Preliminary measurement processing is started, and a potential of 0.5 V is applied between areas A, C, and E as a first potential period for 6 seconds (step S27). Then, after the end of the first potential period, a standby state of 6 seconds is entered, during which the potential is removed (step S28). After the standby period, as a second potential period, a potential of 0.2 V is applied between areas A, C, and E for 3 seconds (step S29), and after 3 seconds, voltage value i3 at that time is read (step S30). ).

  After the voltage value i3 is read in step S30, the temperature in the measuring device 10 is measured by controlling the temperature measuring unit 26 and its switch 27, the temperature measuring unit 28 and the switch 29 arranged in the measuring device 10. To be implemented. Specifically, the switch 27 is turned on, and the temperature is measured by the temperature measurement unit 26 (step S31). Subsequently, the switch 27 is turned off and the switch 29 is turned on, and the temperature is measured by the temperature measuring unit 28 (step S32).

  The two temperature measurement results measured by the temperature measurement unit 26 and the temperature measurement unit 28 are compared, and it is determined whether or not the difference is within a predetermined threshold value (step S33). If the difference is not within the threshold range, the measurement process is terminated assuming that one of the temperature measuring units 26 and 28 is out of order (step S33; No). A plurality of temperature measuring units 26 and 28 are installed in the measuring apparatus 10, and the measurement results are compared to enable accurate and easy failure detection. As a result, measurement errors due to irregular temperature measurement can be avoided. The timing for measuring the temperature is immediately after the voltage value is read in step S30. For example, the temperature measurement may be performed at the timing when the preliminary measurement process is started in step S21.

  When the difference between the two temperature measurement results is within a predetermined threshold (step S33; Yes), the temperature measurement result is temporarily stored in a memory (not shown). At this time, any one of the temperature measuring units 26 and 28 may be selected and stored, or an average value of two measured temperatures may be stored. Then, a calibration curve to which the voltage value i3 measured in step S30 should be referred is specified (step S34). The calibration curve set in steps S24, 25, and 26 is referred to, and in the case of the biosensor 30 corresponding to step S24, the calibration curve F7 is referenced (step S35). Similarly, in the case of the biosensor 30 corresponding to step S25, the calibration curve F5 is referred to (step S36). In the case of the biosensor 37 corresponding to step S26, the calibration curve F6 is referred to (step S37).

  FIG. 12 shows an example of calibration curve data CA measured in steps S34, 35, and 36. In the calibration curve CA, the voltage value measured in step S30 and the concentration (mg / dl) of the substrate contained in the sample solution are defined for each of the output characteristics F1 to F7 of the biosensor 30. For example, if the measured voltage value is 25 (mv), 14 (mg / dl) is stored in the memory as the substrate concentration if the biosensor corresponds to the calibration curve F5.

  Next, the concentration of the substrate extracted in step S35, S36 or S37 is corrected according to the correction rate corresponding to the delay time obtained in steps S14 and S17 and stored in the memory (step S38). Specifically, it is corrected by the following equation (1).

D1 = (concentration of extracted substrate) × {(100−sensitivity correction factor) / 100}
Here, D1 represents the concentration of the substrate after correction. Thereby, the measurement error accompanying the sample liquid follow-up operation by the user is surely eliminated.

  Next, the concentration of the substrate corrected in step S38 is corrected according to the temperature measured in steps S31 to S33 (step S39). Specifically, the temperature stored in the memory in step S33 (hereinafter, measured temperature) is read, and the temperature correction rate for the substrate concentration D1 is determined by referring to the temperature correction table shown in FIG. .

  FIG. 13 is a diagram illustrating an example of the temperature correction table. In FIG. 13, as an example, T10 shows a temperature correction table when the measured temperature is 10 ° C. Hereinafter, similarly, T15 indicates a temperature correction table when the measured temperature is 15 ° C., and T20 indicates a temperature correction table when the measured temperature is 20 ° C. Each temperature correction table defines the relationship between the substrate concentration D1 in the sample solution and the temperature correction rate. The temperature correction rate is set on the basis of the substrate concentration at a temperature of 25 ° C., and indicates a rate of correction to the corresponding substrate concentration. Specifically, temperature correction is performed according to the following equation (2).

D2 = D1 × (100−Co) / 100
Here, D2 is the substrate concentration after temperature correction, D1 is the substrate concentration calculated in step 38, and Co is the temperature correction rate specified with reference to the temperature correction table.

  Further, the inventors of the present invention have found from experiments that measurement accuracy is affected by a combination of measurement temperature and substrate concentration. The influence on measurement accuracy will be specifically described. FIG. 14 is a diagram showing the relationship between the measurement temperature and measurement variation (bias) for each glucose concentration as the substrate concentration. The measurement variation in FIG. 13 indicates the rate at which the glucose concentration measured at a measurement temperature of 25 ° C. varies with the change in measurement temperature. FIG. 14A is a diagram showing the relationship between measurement variation and measurement temperature when the glucose concentration is 50 mg / dl at 25 ° C. FIG. Similarly, FIG. 14B shows a glucose concentration of 100 mg / dl at 25 ° C., FIG. 14C shows a glucose concentration of 200 mg / dl at 25 ° C., and FIG. In the case of 300 mg / dl, FIG. 14 (e) shows the relationship between the measurement variation and the measurement temperature in the case of a glucose concentration of 420 mg / dl at 25 ° C. and FIG. 14 (f) in the case of a glucose concentration of 550 mg / dl at 25 ° C. Indicates.

  From these experimental data, the following two trends are clear. First, it can be seen that the variation in measurement increases as the difference in measurement temperature from the reference temperature of 25 ° C. increases in relation to the same glucose concentration. Specifically, the measurement variation tends to increase in the negative direction as the measurement temperature is lower than the reference temperature, and the measurement variation tends to increase in the positive direction as the measurement temperature is higher than the reference temperature. Second, it can be seen that even if the glucose concentration is increased, the measurement variation converges with the glucose concentration being 300 mg / dl as a boundary. Specifically, for example, in FIG. 14A, the measurement variation at a measurement temperature of 40 ° C. is about 28%, about 50% in FIG. 14C, about 60% in FIG. In FIG. 14F, the transition is about 50%. There is a similar tendency even in a low temperature region such as a measurement temperature of 10 ° C.

  Therefore, such a tendency is reflected in the temperature measurement table shown in FIG. Specifically, in the relationship of the same glucose concentration, the measurement variation increases as the difference in measurement temperature from the reference temperature 25 ° C. increases, and even when the glucose concentration is increased, the glucose concentration is 300 mg / dl. As shown in the table, the measurement variation is considered to converge. By making corrections by referring to the temperature correction table according to the combination of the measurement temperature and the substrate concentration, the measurement accuracy can be greatly improved rather than simply making corrections according to the measurement temperature.

  Note that a temperature correction table in units of 1 ° C. may be provided in the operating temperature range of the biosensor 30 (in this embodiment, as an example, 10 ° C. to 40 ° C.), or a predetermined temperature range (for example, 5 ° C.). ). When a measured temperature located in the middle of a predetermined temperature range is detected, the temperature correction factor may be calculated by performing linear interpolation using a temperature correction table that sandwiches the detected measured temperature.

  Returning to the flowchart of FIG. 7, the substrate concentration D2 after such temperature correction is performed is output to the display unit 11 of the measurement apparatus 10 as the final substrate concentration (step S40). In this way, since the base mass is quantified taking into account the additional time, measurement temperature, the combination of measurement temperature and substrate concentration, or the viscosity of the Hct sample solution, the measurement accuracy is greatly improved compared to conventional methods. Can be planned.

  In order to further suppress the measurement error due to temperature, the following method is also possible. The temperature measurement is continuously performed in advance in a state where the biosensor 30 is not inserted in the measurement apparatus 10, and the measured temperature is accumulated. After the biosensor 30 is inserted, the measured temperature measured in steps S31 to S32 may be compared with the temperature accumulated in advance. If there is a large difference between the temperature accumulated in advance and the measured temperature measured in steps S31 to S32, the measurement process is forcibly terminated because there is a temperature change that affects the measurement error. Will be able to.

  Since the portable biosensor system like this embodiment is easy to carry, it is exposed to various temperature changes depending on the external environment. For example, there are cases in which the temperature of the user's hand and the environmental temperature when the user moves indoors from the outdoors are rapidly changed. While the change in the environmental temperature is rapid, it takes a considerable time for the temperature change in the measuring apparatus 10 to stabilize.

  For example, FIG. 15 is a diagram illustrating a temperature change in the measurement apparatus 10. The diagram shown in FIG. 15 shows the temperature change in the measuring apparatus 10 when the measuring apparatus 10 is moved from a temperature of 10 ° C. to a temperature of 25 ° C. and when it is moved from a temperature of 40 ° C. to a temperature of 25 ° C. FIG. 15 shows that it takes about 30 minutes for the temperature once generated at the use temperature of 10 ° C. to 40 ° C. to stabilize. If temperature correction is performed while the temperature is changing, there may be cases where accurate temperature correction cannot be performed.

  Therefore, if there is a large difference between the temperature accumulated in advance and the measured temperature measured in steps S31 to S32, the measurement process is forcibly determined that there is a temperature change that affects the measurement error. There is a need to quit. Thereby, the accuracy of temperature correction in the measuring apparatus 10 can be further improved. In addition, the prior measurement of the temperature in a state where the biosensor 30 is not inserted in the measurement apparatus 10 may be performed at a predetermined time (for example, 5 minutes) cycle, or may be performed continuously. Further, when the degree of temperature change is determined and the temperature change is large, the measurement process may not be executed even if the user attempts to perform the measurement.

DESCRIPTION OF SYMBOLS 1 Biosensor system 2 Support part 10 Measuring apparatus 11 Display part 30 Biosensor 30a Sample spotting part 35 Sample supply path 36 Reagent layer 37 Counter electrode 38 Measurement electrode 39 Detection electrode 42 Identification part CA Calibration curve T10 T15 T20 Temperature correction table

Claims (5)

A biosensor having a reagent layer that specifically reacts with the substrate in the measurement sample, and a measurement device that determines the amount of the substrate contained in the measurement sample from the sample obtained by reacting the measurement sample with the reagent in the reagent layer. The measurement device includes a temperature measurement unit that measures a temperature when the reaction between the measurement sample solution and the reagent layer proceeds, and temperature correction data that includes a plurality of measurement value correction tables that differ for each temperature range. A storage unit, selecting a correction table corresponding to the temperature measured by the temperature measuring unit, calculating a correction value corresponding to the measured value of the substrate, and correcting the substrate Quantification method. The biosensor has an electrode part including a counter electrode and a measurement electrode formed on at least a part of the insulating substrate, and the measurement device applies a voltage to the electrode part and outputs the voltage from the electrode. The quantification method according to claim 1, wherein the quantification method is a measurement device that detects a current that is generated. A substrate quantification method for measuring a substrate contained in a sample solution supplied to a biosensor with a measuring device,
The measuring device includes temperature measuring means for measuring the temperature in the device, and detects the temperature change from the temperature obtained prior to the measurement of the substrate and the temperature at the time of quantification of the substrate. A substrate quantification method characterized by determining whether or not to measure the substrate based on a temperature change. The temperature change between the temperature obtained prior to the measurement of the substrate and the temperature at the time of measurement of the substrate is detected, and when the temperature change exceeds a predetermined threshold value, the measurement of the substrate is stopped. The substrate quantification method according to claim 3, wherein the substrate is quantified. The method for quantifying a substrate according to claim 3 or 4, wherein the temperature measurement prior to the measurement of the substrate is intermittently performed.

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