JP2009276276A - Measuring device and measurement method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a measurement device, capable of accurately measuring conductivity of a sample liquid and concentration of at least a component contained in the sample liquid in a simple construction, and to provide a measurement method therefor. <P>SOLUTION: A measurement device includes a base, having a space communicating a first opening functioning as a sample liquid introduction hole and a second opening functioning as an air vent; an electrode system located on a first surface of a plurality of faces surrounding the space, containing at least tow electrodes, for measuring conductivity of the sample liquid introduced in the space and concentration of at least component contained in the sample fluid; and a reagent on a second surface, opposed to the first surface, of the plurality of the faces surrounding the space, located on a position opposed to the electrode system or a position closer to the air vent than that of the electrode system, containing at least an electron carrier. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a measuring device capable of measuring the conductivity of a sample solution and the concentration of at least one component contained in the sample solution, and a measuring method using the measuring device.

  Conventionally, the conductivity of a sample solution and the concentration of components contained in the sample solution are measured using an electrode system including two or more electrodes (see, for example, Patent Documents 1 and 2). .

  For example, in Patent Document 1, the electrical conductivity meter provided with a cell provided with a pair of electrodes is used to measure the electrical conductivity of a sample solution introduced into the cell, and the measured electrical conductivity is converted to a salinity concentration. A measurement method for conversion is disclosed.

  In Patent Document 2, a sensor including a substrate, an electrode system including a measurement electrode and a counter electrode disposed on the substrate, and a reagent layer including an enzyme and an electron carrier disposed on the electrode system is used in blood. Measuring the concentration of contained glucose is disclosed.

  Conventionally, it has been proposed to measure a plurality of items for a single sample solution using at least one electrode system (see, for example, Patent Documents 2, 3, and 4).

  In the above-mentioned Patent Document 2, using a single electrode system, blood as a sample liquid is introduced into the sensor, that is, detecting the presence of the sample liquid, and using the same electrode system, It is disclosed that the concentration of glucose contained in is measured. Specifically, a step of introducing blood into the electrode system by capillary action, a step of detecting that blood has been introduced into the electrode system by detecting a change in resistance value between the measurement electrode and the counter electrode, Disclosed is a measurement method including a step of waiting for a reaction between an enzyme and blood to progress, a step of measuring an oxidation current flowing between a measurement electrode and a counter electrode, and a step of converting the measured current value into a glucose concentration. ing.

  Patent Document 3 discloses a sensor including a main electrode system and a sub electrode system each having a measurement electrode and a counter electrode. In the sensor described in Patent Document 3, by combining an insulating substrate, a spacer, and a cover, a space portion, a sample supply hole communicating with one end portion of the space portion, and the other end portion of the space portion are provided. A communicating air hole is formed. The sub-electrode system is closer to the sample supply hole than the main electrode system in the space so that the sample solution introduced from the sample supply hole is introduced to the sub-electrode system before the main electrode system. A main electrode system and a sub-electrode system are arranged. Specifically, using a sensor in which a reagent layer containing an enzyme and an electron carrier is provided only on the main electrode, the step of introducing the sample liquid into the space from the sample supply hole, in the sample liquid in the sub-electrode system Discloses a measuring method including a step of measuring the concentration of ascorbic acid contained in the sample and a step of measuring the concentration of glucose contained in the sample solution in the main electrode system. In addition, in order to reduce the influence of hematocrit and to measure the glucose concentration with high accuracy, a space layer is formed from the sample supply hole using a sensor in which a reagent layer containing an enzyme and an electron carrier is provided only on the main electrode. The step of introducing the sample solution into the sub-electrode system, the step of detecting a change in impedance in the sub-electrode system when the sample solution is introduced into the sub-electrode system, the impedance in the main electrode system when the sample solution is introduced into the main electrode system A step of detecting a change in current, a step of measuring an oxidation current flowing between a measurement electrode and a counter electrode in the main electrode system, and a time when the measured current value and impedance change are detected in the sub-electrode system and the main electrode system And a measurement method including a step of obtaining a glucose concentration based on the difference between the two.

In Patent Document 4, in FIG. 11 and paragraphs (0086) to (0087), a first electrode system composed of a pair of electrodes provided on one outer surface among a plurality of outer surfaces surrounding a substrate. And a second electrode system composed of a pair of electrodes provided on another outer surface is disclosed. Specifically, an example is disclosed in which salt concentration is measured by detecting conductivity using a first electrode system, and urine sugar or creatinine is measured using a second electrode system.
JP-A-1-203952 JP-A-4-357542 JP-A-5-340915 International Publication No. 2007/049607 Pamphlet

  However, the above-described conventional measurement method using a plurality of items has the following problems.

  First, in the method described in Patent Document 2, when blood introduced by capillary action reaches the electrode system, the reagent layer disposed on the electrode system dissolves in the blood, thereby transferring electrons contained in the reagent layer. Components such as the body ionize in the blood. For this reason, the resistance value detected by the electrode system is lower than the resistance value of blood as the sample liquid.

  In the method described in Patent Document 3, two electrode systems, that is, a main electrode system and a sub electrode system are necessary, so that the device structure is complicated.

  In the method described in Patent Document 4, the first electrode system and the second electrode system are necessary, so that the device structure is complicated as in the method described in Patent Document 3.

  Therefore, in view of the above-described conventional problems, the present invention has a simple configuration, and a measuring device capable of accurately measuring the conductivity of a sample solution and the concentration of at least one component contained in the sample solution, and the same It aims at providing the measuring method using.

  In order to solve the above-described conventional problems, the measurement device of the present invention includes a base having a first opening that functions as a sample solution introduction hole and a second opening that functions as an air hole, and the space. And a concentration of at least one component contained in the sample solution and disposed on the first surface of the plurality of surfaces surrounding the portion, including at least two electrodes and introduced into the space portion Of a plurality of surfaces surrounding the space portion, on a second surface facing the first surface, facing the electrode system or facing the electrode system And a reagent including at least an electron carrier, which is disposed at a position closer to the second opening than a position where the second electrode is opened.

Moreover, the measurement method of the present invention uses the measurement device,
(A) introducing the sample solution into the space through the first opening of the measurement device;
(B) measuring the conductivity of the sample solution using the electrode system after the sample solution reaches the electrode system;
(C) After the step B, waiting for the reagent dissolved in the sample solution to diffuse to the electrode system;
(D) After the step C, applying a voltage between at least two electrodes among the electrodes included in the electrode system;
(E) a step of measuring a value or amount of current flowing between the two electrodes to which a voltage is applied in the step D; and (F) based on the current value or amount of current measured in the step E, A step of determining a concentration of the component contained in the sample solution.

  According to the present invention, the conductivity of the sample solution and the concentration of at least one component contained in the sample solution can be accurately measured with a simple configuration.

  The measuring device of the present invention is characterized in that an electrode system and a reagent for measuring a component contained in a sample solution are arranged at positions separated via a space.

  More specifically, in the measurement device of the present invention, a reagent for measuring a component contained in the sample solution is arranged on a surface at a position facing the surface on which the electrode system is arranged.

  The measuring device of the present invention includes a base having a first opening that functions as a sample solution introduction hole and a second opening that functions as an air hole, and a first of a plurality of surfaces surrounding the space. An electrode system disposed on a surface, including at least two electrodes, for measuring the conductivity of the sample solution introduced into the space and the concentration of at least one component contained in the sample solution, and the space Among the plurality of surfaces surrounding the part, the second surface is opposed to the first surface and is closer to the second opening than the position facing the electrode system or the position facing the electrode system. A reagent comprising at least an electron carrier disposed at a position is provided.

  According to this configuration, electron transfer is performed on the second surface facing the first surface on which the electrode system is disposed, at a position facing the electrode system or closer to the air hole than a position facing the electrode system. Since the reagent containing the body is arranged, the sample solution introduced into the space from the first opening functioning as the sample solution introduction hole first contacts the electrode system before contacting the reagent. When the sample solution reaches the electrode system, the reagent is not dissolved in the sample solution in contact with the electrode system, so that the electron carrier does not affect the conductivity value of the sample solution. Therefore, when the sample solution reaches the electrode system, first, if the conductivity of the sample solution is measured using the electrode system, the conductivity of the sample solution can be accurately measured. Next, the sample solution reaches the position where the reagent is placed, and after the reagent dissolved in the sample solution diffuses in the sample solution and reaches the electrode system, it is the same as the electrode system used for the measurement of conductivity. Using the electrode system, the concentration of the measurement target component contained in the sample solution is measured. In this way, it is possible to accurately measure the conductivity of the sample solution and the concentration of the measurement target component contained in the sample solution using a single electrode system.

  In the present invention, an insulating material such as glass, ceramic, rubber, ebonite, or plastic can be used as the base material.

  In the present invention, gold, platinum, palladium, copper, or the like can be used as a material for the electrode.

  The number of electrodes included in the electrode system may be at least two, and may be three or more. Here, it is preferable that the number of electrodes included in the electrode system is four.

  In the present invention, the sample liquid can be used without particular limitation as long as it is a liquid. The sample solution is preferably a biological sample such as blood or urine.

  In the present invention, as the electron carrier, ferricyanides such as potassium ferricyanide, phenazine compounds such as phenazine methosulfate, p-benzoquinone, methylene blue, ferrocene derivatives, and the like can be used. Among these, the electron carrier is preferably ferricyanide. Since ferricyanide has a function of directly reacting with creatinine to oxidize creatinine, when ferricyanide is used as an electron carrier, the concentration of creatinine contained in the sample solution can be measured.

  When the sample solution is urine, the electrolyte concentration in urine can be obtained by measuring the conductivity in urine using the measuring device of the present invention. Further, by measuring the creatinine concentration in urine using the measuring device of the present invention, and correcting the obtained urinary electrolyte concentration using the measured creatinine concentration, estimating the daily salt intake Is possible. Quantitative measurement of daily salt intake is useful for preventing hypertension.

  The reagent used in the present invention may contain a plurality of types of electron carriers.

The measurement method of the present invention uses the above measurement device,
(A) introducing the sample solution into the space through the first opening of the measurement device;
(B) measuring the conductivity of the sample solution using the electrode system after the sample solution reaches the electrode system;
(C) After the step B, waiting for the reagent dissolved in the sample solution to diffuse to the electrode system;
(D) After the step C, applying a voltage between at least two electrodes among the electrodes included in the electrode system;
(E) a step of measuring a value or amount of current flowing between the two electrodes to which a voltage is applied in the step D; and (F) based on the current value or amount of current measured in the step E, A step of determining a concentration of the component contained in the sample solution.

  According to this method, in Step B, since the reagent is not dissolved in the sample solution in contact with the electrode system, the conductivity of the sample solution can be measured with high accuracy. Next, in step D, since the reagent dissolved in the sample liquid diffuses in the sample liquid and reaches the electrode system, the same electrode system as that used for the measurement of conductivity is used. The concentration of the measurement target component contained in the liquid can be measured. Therefore, according to the measurement method of the present invention, it is possible to accurately measure the conductivity of the sample solution and the concentration of the measurement target component contained in the sample solution using a single electrode system.

  The distance δ at which the electron carrier dissolved in the sample solution diffuses during the time t is expressed by the following (Equation 1). However, D represents the diffusion coefficient of the electron carrier, and π represents the circumference.

  Here, when the distance between the first surface on which the electrode system is disposed and the second surface on which the reagent is disposed is L, the sample is transferred when the diffusion distance δ of the electron carrier becomes equal to L. The electron carrier dissolved in the liquid reaches the electrode system. Therefore, when time t when δ = L is assumed to be T, T is expressed by the following equation (Equation 2).

  In the measurement method of the present invention, the conductivity of the sample solution is measured using the electrode system in Step B from the time when the sample solution reaches the electrode system until the time T represented by the above formula (Equation 2) elapses. It is preferable.

  In this way, since the conductivity of the sample liquid is measured using the electrode system before the electron carrier dissolved in the sample liquid reaches the electrode system, the conductivity of the sample liquid must be accurately measured. Can do.

Moreover, the measuring method of the present invention comprises:
(G) It is preferable to further include a step of detecting that the sample solution has reached the electrode system using the electrode system before the step B.

  In this way, the time at which the sample solution reaches the electrode system can be accurately known, so that it is possible to know exactly when the measurement of the conductivity of the sample solution in Step B should be completed.

  The detection of the sample liquid in the process G can be performed, for example, by detecting a change in resistance between two electrodes included in the electrode system. When the sample solution reaches the electrode system, the resistance between the two electrodes contained in the electrode system decreases. Therefore, it is detected that the sample solution has reached the electrode system by detecting the change in resistance between the two electrodes. can do.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
The configuration of the measuring device 100 according to Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 is an exploded perspective view showing a configuration of a measuring device 100 according to the present embodiment.

  The measurement device 100 includes a first substrate 102, a second substrate 104 having air holes 106, and a spacer 108 disposed between the first substrate 102 and the second substrate 104 and having a slit 110. Yes. By combining the first substrate 102, the second substrate 104, and the spacer 108, the space formed at the position of the slit 110 functions as a sample solution holding unit. One end of the sample solution holding part is open, and the opening functions as the sample solution introduction hole 112. Further, the slit 110 communicates with the air hole 106. Here, the first substrate 102, the second substrate 104, and the spacer 108 correspond to the base in the present invention.

  On the first substrate 102, a first electrode 122, a second electrode 124, a third electrode 126, and a fourth electrode 128 are disposed at a position exposed to the sample holder. The first electrode 122, the second electrode 124, the third electrode 126, and the fourth electrode 128 constitute an electrode system 120. A reagent 130 including an electron carrier is disposed on the second substrate 104 at a position facing the electrode system 120. At least a part of the reagent 130 is exposed to the sample holder.

  A method for manufacturing the measuring device 100 will be described.

  As a material of the first substrate 102, the second substrate 104, and the spacer 108, for example, polyethylene terephthalate (hereinafter abbreviated as PET) is used. For example, after a Pd layer is formed on the first substrate 102 made of PET by sputtering, a part of the Pd layer is etched using laser trimming, whereby the first electrode 122, the second electrode 124, An electrode system 120 including a third electrode 126 and a fourth electrode 128 is formed.

  On the other hand, on the second substrate 104 made of PET, for example, an aqueous solution containing potassium ferricyanide as an electron carrier and carboxymethylcellulose as a hydrophilic polymer is dropped and air-dried to form the reagent 130.

  Finally, the first substrate 102 and the spacer are arranged so that the electrode system 120 provided on the first substrate 102 and the reagent 130 provided on the second substrate 104 face each other with the spacer 108 interposed therebetween. 108 and the second substrate 104 are bonded together, whereby the measuring device 100 is completed. Of the Pd layer provided on the first substrate 102, portions exposed without being covered by the second substrate 104 are the first terminal 132, the second terminal 134, the third terminal 136, And functions as the fourth terminal 138. In addition, among the Pd layer provided on the first substrate 102, the portions exposed in the slit 110 of the spacer 108 are the first electrode 122, the second electrode 124, the third electrode 126, and It functions as the fourth electrode 128. The first terminal 132, the second terminal 134, the third terminal 136, and the fourth terminal 138 are the first electrode 122, the second electrode 124, the third electrode 126, and the fourth electrode, respectively. 128 is connected.

  Next, the structure of the measuring apparatus 200 used in this Embodiment is demonstrated using FIG. FIG. 2 is a perspective view showing the configuration of the measuring apparatus 200 used in the present embodiment.

  The measurement apparatus 200 includes a housing 202, a display 204, and a measurement start button 206. The housing 202 has a measurement device insertion hole 208 into which the measurement device 100 is inserted.

  The configuration inside the housing 202 of the measuring apparatus 200 will be described with reference to FIG. FIG. 3 is a functional block diagram showing a configuration inside the housing 202 of the measuring apparatus 200.

  A constant current AC power supply 302, a voltage detector 304, a control unit 306, a timer unit 308, a storage unit 310, a DC power supply 312 and a current detector 314 are provided inside the housing 202 of the measuring apparatus 200.

  The constant current AC power supply 302 is fixed between the first electrode 122 and the fourth electrode 128 of the measurement device 100 inserted into the measurement device insertion hole 208 via the first terminal 132 and the fourth terminal 138. It has a function of applying an alternating current. The frequency of the alternating current applied can be set to any value within the range of 1 kHz to 100 kHz, and the current value of the alternating current can be set to any value within the range of 0.01 mA to 0.2 mA. Is possible.

  The voltage detector 304 has a function of detecting a voltage between the second electrode 124 and the third electrode 126 via the second terminal 134 and the third terminal 136.

  The DC power supply 312 has a function of applying a DC voltage between the second electrode 124 and the third electrode 126 via the second terminal 134 and the third terminal 136.

  The current detector 314 has a function of detecting a current value flowing between the second electrode 124 and the third electrode 126 via the second terminal 134 and the third terminal 136.

  Next, a measurement method according to the present embodiment using the measurement device 100 and the measurement apparatus 200 will be described.

  First, after the measurement device 100 is inserted into the measurement device insertion hole 208 so that the sample solution introduction hole 112 side of the measurement device 100 is exposed, the measurement apparatus 200 is activated by pressing down the measurement start button 206.

  Next, when the sample solution is brought into contact with the sample solution introduction hole 112 of the measurement device 100, the sample solution is introduced into the sample solution holding portion from the sample solution introduction hole 112 by capillary action.

  When the sample solution reaches the electrode system 120, the second electrode 124 and the third electrode 126 are brought into conduction through the sample solution, so that the resistance between the second electrode 124 and the third electrode 126 decreases. When the voltage detector 304 detects this resistance change, the controller 306 controls the timer 308 to start measuring time.

  Simultaneously with the start of measurement by the time measuring unit 308, the control unit 306 controls the constant current AC power supply 302, and the first electrode 122 to the fourth electrode are connected via the first terminal 132 and the fourth terminal 138. A constant alternating current is applied between 128. While the alternating current is applied, the voltage detector 304 detects the voltage between the second electrode 124 and the third electrode 126. The control unit 306 calculates the conductivity of the sample solution based on the current value applied by the constant current AC power supply 302 and the voltage value detected by the voltage detector 304.

  When the calculation of the conductivity of the sample solution is completed, the control unit 306 controls the constant current AC power supply 302 to stop the application of the AC current. At this time, when the sample solution reaches the position of the reagent 130, the reagent 130 is dissolved in the sample solution, and potassium ferricyanide contained in the reagent 130 is ionized and begins to diffuse toward the electrode system 120. Further, when the reagent 130 is dissolved in the sample solution, the ferricyanide ion functions as an oxidizing agent to oxidize creatinine contained in the sample solution, so that the ferricyanide ion reduced form of ferricyanide ion is contained in the sample solution. Russian ion is generated.

  When the control unit 306 detects that the time T represented by the above equation (Equation 2) has elapsed from the start of measurement by the time measuring unit 308, the control unit 306 controls the DC power supply 312 to control the second terminal 134. A DC voltage is applied between the second electrode 124 and the third electrode 126 via the third terminal 136. By application of the DC voltage, ferrocyanide ions accumulated in the sample solution are oxidized in the electrode system 120.

  While the DC voltage is applied, the current detector 314 detects the value of the current flowing between the second electrode 124 and the third electrode 126. The concentration of ferrocyanide ions in the sample solution is proportional to the concentration of creatinine contained in the sample solution. Therefore, when a DC voltage is applied, the value of the oxidation current that flows based on the oxidation of ferrocyanide ions is proportional to the creatinine concentration. The control unit 306 reads the correlation data indicating the correlation between the current value and the creatinine concentration stored in the storage unit 310, refers to the correlation data, and determines the current based on the current value detected by the current detector 314. The value is converted into the concentration of creatinine contained in the sample solution.

  Finally, the control unit 306 displays the creatinine concentration obtained on the display 204.

  According to the measuring device 100 according to the present embodiment, the reagent 130 is disposed on the second substrate 104 facing the first substrate 102 on which the electrode system 120 is disposed, at a position facing the electrode system 120. Therefore, the sample liquid introduced into the sample liquid holding part from the sample liquid introduction hole 112 first contacts the electrode system 120 before contacting the reagent 130. When the sample solution reaches the electrode system 120, the reagent 130 is not dissolved in the sample solution in contact with the electrode system 120. Therefore, potassium ferricyanide as an electron carrier affects the conductivity value of the sample solution. Never give. Therefore, when the sample solution reaches the electrode system 120, the conductivity of the sample solution can be measured with high accuracy by first measuring the conductivity of the sample solution using the electrode system 120.

  Next, after the sample liquid reaches the position where the reagent 130 is disposed, and the reagent 130 dissolved in the sample liquid diffuses in the sample liquid and reaches the electrode system 120, the second electrode 124-third. Since a DC voltage is applied between the electrodes 126 and the value of the current flowing between the second electrode 124 and the third electrode 126 is measured by applying the DC voltage, the concentration of creatinine contained in the sample solution is accurately measured. It can be measured well. Therefore, according to the present embodiment, the conductivity of the sample solution and the concentration of the measurement target component contained in the sample solution can be accurately measured using a single electrode system.

  In the first embodiment, the measurement apparatus 300 includes the constant current AC power supply 302, and the constant current AC power supply 302 measures the first electrode 122-second of the measurement device 100 when measuring the conductivity of the sample solution. Although an example in which a constant alternating current is applied between the electrodes 128 via the first terminal 132 and the fourth terminal 138 has been described, the present invention is not limited to this example. Instead of this configuration, the measuring apparatus includes a constant current DC power source, and the constant current DC power source is connected between the first electrode and the second electrode of the measuring device when measuring the conductivity of the sample solution. A constant direct current may be applied via the terminal and the fourth terminal.

(Embodiment 2)
Next, the configuration of the measuring device 400 according to Embodiment 2 of the present invention will be described with reference to FIG. FIG. 4 is an exploded perspective view showing the configuration of the measuring device 400 according to the present embodiment.

  In the measurement device 400 according to the present embodiment, unlike the measurement device 100 according to the first embodiment, the electrode system 420 is composed of two electrodes, a first electrode 422 and a second electrode 424. Further, when the first substrate 102, the spacer 108, and the second substrate 104 are bonded together, the exposed portion of the Pd layer formed on the first substrate 102 substrate is the first terminal. 432 and the second terminal 434 function. The first terminal 432 and the second terminal 434 are connected to the first electrode 422 and the second electrode 424, respectively. Since other configurations are the same as those of the measurement device 100 according to the first embodiment, the same reference numerals as those in the first embodiment are given and description thereof is omitted.

  Next, the structure inside the housing 202 of the measuring apparatus 500 used in this embodiment will be described with reference to FIG. FIG. 5 is a functional block diagram showing a configuration inside the housing 202 of the measuring apparatus 500.

  In the housing 202 of the measuring apparatus 500 used in the present embodiment, a constant current AC power supply 302, a voltage detector 304, a control unit 306, a time measuring unit 308, a memory are stored in the same manner as the measuring apparatus 200 used in the first embodiment. Unit 310, DC power supply 312, and current detector 314.

  The constant current AC power supply 302 is fixed between the first electrode 422 and the second electrode 424 of the measurement device 400 inserted into the measurement device insertion hole 208 via the first terminal 432 and the second terminal 434. It has a function of applying an alternating current. Similar to the measuring apparatus 200 used in Embodiment 1, the frequency of the alternating current to be applied can be set to any value within the range of 1 kHz to 100 kHz, and the current value of the alternating current is 0.01 mA. It is possible to set an arbitrary value within a range of ~ 0.2 mA.

  The voltage detector 304 has a function of detecting a voltage between the first electrode 422 and the second electrode 424 through the first terminal 432 and the second terminal 434.

  The DC power supply 312 has a function of applying a DC voltage between the first electrode 422 and the second electrode 424 through the first terminal 432 and the second terminal 434.

  The current detector 314 has a function of detecting a current value flowing between the first electrode 422 and the second electrode 424 through the first terminal 432 and the second terminal 434.

  Next, a measurement method according to the present embodiment using the measurement device 400 and the measurement apparatus 500 will be described.

  First, after the measurement device 400 is inserted into the measurement device insertion hole 208 so that the sample liquid introduction hole 112 side of the measurement device 400 is exposed, the measurement apparatus 500 is activated by depressing the measurement start button 206.

  Next, when the sample solution is brought into contact with the sample solution introduction hole 112 of the measuring device 400, the sample solution is introduced into the sample solution holding portion from the sample solution introduction hole 112 by capillary action.

  When the sample solution reaches the electrode system 420, the first electrode 422 and the second electrode 424 are brought into conduction through the sample solution, so that the resistance between the first electrode 422 and the second electrode 424 is reduced. When the voltage detector 304 detects this resistance change, the controller 306 controls the timer 308 to start measuring time.

  Simultaneously with the start of measurement by the time measuring unit 308, the control unit 306 controls the constant current AC power supply 302, and the first electrode 422 to the second electrode via the first terminal 432 and the second terminal 434. A constant alternating current is applied between 424. While the alternating current is applied, the voltage detector 304 detects the voltage between the first electrode 422 and the second electrode 424. The control unit 306 calculates the conductivity of the sample solution based on the current value applied by the constant current AC power supply 302 and the voltage value detected by the voltage detector 304.

  When the calculation of the conductivity of the sample solution is completed, the control unit 306 controls the constant current AC power supply 302 to stop the application of the AC current. At this time, when the sample solution reaches the position of the reagent 130, the reagent 130 is dissolved in the sample solution, and potassium ferricyanide contained in the reagent 130 is ionized and begins to diffuse toward the electrode system 420. Further, when the reagent 130 is dissolved in the sample solution, the reaction between creatinine contained in the sample solution and potassium ferricyanide contained in the reagent 130 proceeds.

  When the control unit 306 detects that the time T represented by the above equation (Equation 2) has elapsed from the start of measurement by the time measuring unit 308, the control unit 306 controls the DC power supply 312 to control the first terminal 432. A DC voltage is applied between the first electrode 422 and the second electrode 424 through the second terminal 434. While the DC voltage is applied, the current detector 314 detects the value of the current flowing between the first electrode 422 and the second electrode 424. The control unit 306 reads the correlation data indicating the correlation between the current value and the creatinine concentration stored in the storage unit 310, refers to the correlation data, and determines the current based on the current value detected by the current detector 314. The value is converted into the concentration of creatinine contained in the sample solution.

  Finally, the control unit 306 displays the creatinine concentration obtained on the display 204.

  According to measurement device 400 according to the present embodiment, reagent 130 is disposed on second substrate 104 facing first substrate 102 on which electrode system 420 is disposed and at a position facing electrode system 420. Therefore, similarly to the measurement device 100 according to the first embodiment, it is possible to accurately measure the conductivity of the sample solution and the concentration of the measurement target component contained in the sample solution using a single electrode system. it can.

  In order to investigate the diffusion speed of the electron carrier in the sample liquid holding part, the following experiment was performed. The configuration of the measurement device 600 used in this experiment will be described with reference to FIG. FIG. 6 is an exploded perspective view showing the configuration of the measurement device 600 used in this experiment.

  In the measurement device 600 used in this experiment, unlike the measurement device 400 according to the second embodiment, the reagent 130 is not arranged in the sample holder. Since other configurations and manufacturing methods are the same as those of the measurement device 400 according to Embodiment 2, the description thereof is omitted.

  In this experiment, nine types of measuring devices A to I having different spacers 108 were manufactured. The thicknesses of the spacers 108 of the measuring devices A to I are 45, 70, 95, 120, 145, 208, 238, 270, and 313 μm, respectively. As the sample solution, an aqueous solution containing 20 mM each of potassium ferricyanide and potassium ferrocyanide was used.

  The first electrode so that the potential of the first electrode 422 is higher than that of the second electrode 424 at the same time as the sample solution is introduced into the sample solution holding part 112 of each measurement device A to I. A DC voltage of 0.5 V was applied between 422 and the second electrode 424. For each of the measuring devices A to I, the value of the current flowing between the first electrode 422 and the second electrode 424 was measured 5 seconds after the start of application of the DC voltage. The measurement results are shown in FIG. In FIG. 7, the horizontal axis represents the thickness of the spacer 108, and the vertical axis represents the measured current value.

  As can be seen from FIG. 7, the measured current values for the measuring devices D to I in which the thickness of the spacer 108 is 120 μm or more were substantially the same value. On the other hand, the current value decreased in the measurement devices A to C in which the thickness of the spacer 108 is 95 μm or less. This result can be explained as follows.

  In the first electrode 422, ferrocyanide ions are oxidized to generate ferricyanide ions. Ferricyanide ions generated on the first electrode 422 by application of voltage are diffused toward the second substrate 104 arranged to face the first substrate 102. That is, the diffusion layer of ferricyanide ions grows from the first substrate 102 toward the second substrate 104 as time elapses from the voltage application. The diffusion at this time is called semi-infinite diffusion. In the state where the diffusion of electrolyte ions is a semi-infinite diffusion, the value of the current flowing between the electrodes is constant.

  When the end of the ferricyanide ion diffusion layer reaches the second substrate 104, the diffusion layer cannot grow any further in the direction from the first substrate 102 toward the second substrate 104. The diffusion at this time is called finite diffusion. It is known that when the diffusion of electrolyte ions shifts from semi-infinite diffusion to finite diffusion, the value of the current flowing between the electrodes decreases with this shift.

  Since the thickness of the spacer 108 corresponds to the distance between the first substrate 102 and the second substrate 104, the current value decreases when the thickness of the spacer 108 is between 95 and 120 μm as shown in FIG. Therefore, in this experiment, it can be considered that the diffusion layer of ferricyanide ions grew to about 95 to 120 μm within 5 seconds from the voltage application.

  On the other hand, if the distance δ in which ferricyanide ions are diffused in 5 seconds using the above formula (Equation 1) is theoretically obtained, it becomes 97 μm. It was. However, the diffusion coefficient D of ferricyanide ions is expressed by the following formula (Equation 3).

  Therefore, the conductivity of the sample liquid is measured using the electrode system from the time when the sample liquid reaches the electrode system until the time T represented by the above formula (Equation 2) elapses. Is used to measure the concentration of the components contained in the sample solution, and before the electron carrier dissolved in the sample solution reaches the electrode system, the conductivity of the sample solution is measured using the electrode system. Since the concentration of the components contained in the sample liquid is measured using the electrode system after the transmitter has reached the electrode system, the conductivity of the sample liquid and the liquid contained in the sample liquid are measured using a single electrode system. It can be seen that the concentration of the measurement target component can be measured with high accuracy.

  The present invention relates to measuring the conductivity of a sample solution and the concentration of a component contained in the sample solution, and particularly measuring the conductivity of a biological sample such as urine and the concentration of a component such as creatinine contained in the biological sample. Useful for.

1 is an exploded perspective view showing a configuration of a measuring device according to an embodiment of the present invention. The perspective view which shows the structure of the measuring apparatus used in the same embodiment Functional block diagram showing the internal configuration of the measurement device The disassembled perspective view which shows the structure of the measuring device which concerns on other embodiment of this invention. Functional block diagram showing the configuration inside the housing of the measuring apparatus used in the same embodiment The disassembled perspective view which shows the structure of the measuring device used in one Example of this invention. Graph showing the relationship between the current value measured using the measurement device and the spacer thickness

Explanation of symbols

100, 400, 600 Measuring device 102 First substrate 104 Second substrate 106 Air hole 108 Spacer 110 Slit 112 Sample liquid introduction hole 120,420 Electrode system 122,422 First electrode 124,424 Second electrode 126 Second electrode 126 3 electrode 128 4th electrode 130 reagent 132,432 1st terminal 134,434 2nd terminal 136 3rd terminal 138 4th terminal 200,500 measuring device 202 casing 204 display 206 measurement start button 208 measurement Device insertion hole 302 Constant current AC power supply 304 Voltage detector 306 Control unit 308 Timekeeping unit 310 Storage unit 312 DC power supply 314 Current detector

Claims (5)

A substrate having a space communicating with a first opening that functions as a sample solution introduction hole and a second opening that functions as an air hole;
At least one component included in the sample liquid and the conductivity of the sample liquid introduced into the space part, which is disposed on the first surface among the plurality of faces surrounding the space part and includes at least two electrodes An electrode system for measuring the concentration of the electrode, and a position on the second surface facing the first surface of the plurality of surfaces surrounding the space portion, or the position facing the electrode system or the electrode system A measurement device comprising a reagent including at least an electron carrier, which is disposed at a position closer to the second opening than a position opposed to the second opening. The measuring device according to claim 1, wherein the electron carrier is ferricyanide. Using the measuring device according to claim 1 or 2,
(A) introducing the sample solution into the space through the first opening of the measurement device;
(B) measuring the conductivity of the sample solution using the electrode system after the sample solution reaches the electrode system;
(C) After the step B, waiting for the reagent dissolved in the sample solution to diffuse to the electrode system;
(D) After the step C, applying a voltage between at least two electrodes among the electrodes included in the electrode system;
(E) a step of measuring a value or amount of current flowing between the two electrodes to which a voltage is applied in the step D; and (F) based on the current value or amount of current measured in the step E, A measurement method comprising a step of determining the concentration of the component contained in a sample solution. From the time when the sample liquid reaches the electrode system until the time T represented by the following formula (Equation 1) elapses, the conductivity of the sample liquid is measured using the electrode system in the step B. The measurement method according to claim 3.

However, in the above formula (Equation 1),
L is the distance between the first surface and the second surface;
D is the diffusion coefficient of the electron carrier,
π represents the circumference ratio. (G) The measurement method according to claim 4, further comprising a step of detecting that the sample liquid has reached the electrode system using the electrode system before the step B.

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