JPH02134554A - Method and apparatus for measuring concentration of component of solution - Google Patents

Abstract

PURPOSE:To improve accuracy regardless of contamination of biosensors and time change by providing the first biosensor corresponding to the component of first solution and the second biosensor responding to the compositions of the first and second solution. CONSTITUTION:In a measuring container 2 which is arranged in a constant temperature device 1, a glucose sensor 3 and a cane-sugar sensor 4 are arranged so as to face each other. At first, a phosphate buffer having a specified concentration is injected into the container 2. An amplifier part 21 is adjusted. The difference between the outputs of the sensors 3 and 4 is made to be zero. The sensitivities of the sensors are calibrated. Then, at first, 1%-glucose standard liquid is injected into the container 2. The content is detected with a photosensor 19. The output ratio between the sensors 3 and 4 is operated in an operation control part 22 and stored. Then, the difference in outputs of the sensors 3 and 4 is obtained by using 3%-glucose standard liquid by the same way. The outputs of the sensors 3 and 4 are operated and stored for solution to be measured whose glucose concentration and cane-sugar concentration are unknown by the same way. In this way, the glucose concentration and the cane- sugar concentration of the solution to be measured are computed by a specified expression based on above described data.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method and apparatus for measuring the concentration of solution components using an enzyme sensor.

(Prior Art) In recent years, biosensors that use enzyme electrodes (enzyme sensors) and can easily and quickly measure components in living organisms have been widely used.

Conventionally, a glucose sensor for measuring glucose concentration, which combines glucose oxidase, an 02 electrode, a H2O2 electrode, a 15FET, etc., has already been disclosed, and glucose is present in a measurement solution such as blood or urine. Since glucose oxidase selectively reacts with oxygen, glucose concentration can be measured. By the way, since there are substances that are easily oxidized such as ascorbic acid and uric acid in blood and urine, these interferences cause errors in measurement values. A glucose sensor with an additional oxygen electrode of the same type has been proposed (Special Publication No. 62-1015
Publication No. 6).

As shown in FIG. 4, this glucose sensor includes a glucose oxidase electrode 100 and a glucose oxidase electrode 1.
An oxygen electrode 101 made of the same material as 00, and a platinum electrode 103 as a common counter electrode connected to a constant voltage power source 102.
It has And glucose oxidase electrode 10
0 and each output of the oxygen electrode 101 is detected by a detection circuit 104.
, 105, and the outputs of the detection circuits 104 and 105 are input to the cancellation circuit 106 to measure the concentration of only the glucose component.

(Problems to be Solved by the Invention) In the glucose sensor described above, the sensitivity of the glucose oxidase electrode 100 and the oxygen electrode 101 is
Since the detection accuracy varies depending on dirt on the 01 and changes over time, there is a drawback that the detection accuracy decreases. In addition, since the above-mentioned glucose sensor is interfered with by oxygen, by adding an oxygen electrode 101 and canceling out the respective outputs of the glucose oxidase electrode 100 and the oxygen electrode 101, in this case, only the glucose concentration can be measured. Therefore, it was not possible to measure the oxygen concentration.

The present invention was made for the purpose of solving the above-mentioned problems, and it is possible to measure the concentration of solution components with high accuracy even if the biosensor is contaminated or changes over time, and the concentration of two solution components can be measured simultaneously. The present invention aims to provide a measuring method and a concentration measuring device.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above-mentioned problems, the concentration measuring method according to the present invention includes: a first biosensor responsive to a first solution component; a solution component and a second biosensor responsive to the second solution component, the output ratio of the first and second biosensors with respect to the first solution component is determined, and this output ratio is determined as the output ratio of the first or second biosensor. After adjusting the output by multiplying the output of the biosensor to the same output, the concentration of the first solution component is determined from the output of the first biosensor, and the concentration of the second solution component is determined from the difference in output between the first and second biosensors. It is characterized by finding the concentration of.

Further, the concentration measuring device according to the present invention includes a first biosensor that responds to a first solution component, a second biosensor that responds to the first solution component and a second solution component, and a second biosensor that responds to the first solution component and the second solution component. a calibration means for calibrating the sensor sensitivities of the first and second biosensors; and calculating the concentrations of the first and second solution components by calculating the output ratio and output difference of the first and second biosensors. It is characterized by comprising a control calculation section.

(Function) According to the present invention, after calibrating the sensor sensitivities of the first and second biosensors, by calculating the output ratio and output difference of the first and second biosensors, each biosensor is contaminated with dirt. It is possible to simultaneously measure the concentrations of the first and second solution components with high precision while eliminating the influence of changes over time.

(Example) Hereinafter, the present invention will be described in detail based on an illustrated example.

FIG. 1 is a configuration diagram showing an apparatus for measuring the concentration of solution components according to the present invention. As shown in this figure, a glucose sensor 3 and a sucrose sensor 4 are placed facing each other as biosensors in a measurement container 2 arranged in a constant temperature facility 1. The glucose sensor 3 includes a platinum cathode 5, a silver/silver chloride anode 6.
1moΩ containing 1% carboxymethyl cellulose Na salt
Collagen/glucose oxidase membrane (thickness 50 μm) 10 is placed on the surface of the tetrafluoroethylene @8 of the oxygen electrode, which consists of / potassium chloride internal electrolyte solution 7, tetrafluoroethylene membrane (thickness 25 μm) 8, and vinyl chloride resin 9.
Further, a porous layer of a semipermeable membrane 11 having an asymmetric pore size distribution is disposed on the surface of the semipermeable membrane 11 so as to be in contact with the collagen/glucose oxidase membrane 10 (see FIG. 2).

On the other hand, the sucrose sensor 4 has a platinum cathode 5, a silver/silver chloride anode 6.
1 mo containing 1% carboxymethylcellulose Na salt
, Q/l potassium chloride internal electrolyte solution 7, tetrafluoroethylene membrane (thickness 25 μm) 8, vinyl chloride resin 9
A collagen membrane 12 containing three types of enzymes, glucose oxidase, invertase, and mutarotase, is disposed on the surface of the tetrafluoroethylene membrane 8 of the oxygen electrode.
Furthermore, a porous layer of a semipermeable membrane 11 having an asymmetric pore size distribution is disposed on its surface so as to be in contact with the collagen membrane 12 (see FIG. 3).

A stirrer 14 for stirring the solution 13 supplied into the measurement container 2 is arranged in the measurement container 2, and furthermore, each pipe 1 for supply and discharge is provided as a means for supplying and discharging the solution 13.
5a, 15b and pumps 16a, 16b are provided. The constant temperature equipment 1 also includes a heater 17 that adjusts the temperature of the solution 13 poured into the measurement container 2, a temperature sensor 18 that measures the temperature of the solution 13, and a photosensor 19 that detects the injection of the solution 13. A magnetic stirrer 20 for rotating the stirrer 14 is installed at the bottom of the constant temperature equipment 1.
is installed.

21 is an amplifier unit connected to the glucose sensor 3 and sucrose sensor 4; 22 is a control unit that measures the output of the glucose sensor 3 and sucrose sensor 4, and controls the temperature, supply/discharge control, stirring control, etc. of the solution 13; The calculation unit 23 is a display unit that displays the concentration measurement results of the glucose sensor 3 and sucrose sensor 4 calculated by the control calculation unit 22. In this way, the display section 22 is used as an output means for outputting the calculation results of the control calculation section 22.

Next, a method for measuring the concentration of solution components using the above-mentioned concentration measuring device will be explained.

First, 2 ml of a phosphate buffer solution (hereinafter referred to as buffer solution) having a pH of 6.5 is supplied into the measurement container 2 through the supply pipe 15a using the pump 16a. At this time, the temperature sensor 18 measures the liquid temperature, and the heater 17 adjusts the liquid temperature to 35.
℃, and the magnetic stirrer 20 is driven to rotate the stirring bar 14 to stir the buffer solution. Next, the output current value of the glucose sensor 3 is adjusted by the amplifier unit 21 to be synchronized with the output current value of the sucrose sensor 4, and the output difference between the glucose sensor 3 and the sucrose sensor 4 is made zero.

In this way, the buffer solution is used as a calibration means for calibrating the sensor sensitivities of the glucose sensor 3 and sucrose sensor 4.

Next, 50 μg of the 1% glucose standard solution is poured into the measurement container 2 and stirred. At this time, the injection of the glucose standard solution is detected by the photosensor 19, and the amplifier section 21 and the arithmetic control section 22 start measuring the outputs of the glucose sensor 3 and sucrose sensor 4. Then, when the outputs of the glucose sensor 3 and sucrose sensor 4 reach steady values approximately 2 minutes after injecting the glucose standard solution, the calculation control unit 22 determines the amount of change in the output current ΔI6 of each of the glucose sensor 3 and sucrose sensor 4. □.

ΔI Sgs and coefficient = ΔI5. /ΔIGg is calculated and stored.

Next, the solution (buffer solution and glucose standard solution) 13 in the measurement container 2 is passed through the discharge pipe 15b to the pump 16b.
After discharging the sample, the inside of the measurement container 2 is cleaned to remove the influence of the previous measurement.

Washing is performed by repeatedly discharging and supplying the buffer solution. When the inside of the measurement container 2 has been washed, a new buffer solution is supplied by the pump 16a through the pipe 15a. At this time, the liquid temperature is set to 35°C by the heater 17 as before.
The buffer solution is stirred by rotating the stirring bar 14 by driving the magnetic stirrer 20. Then, as described above, the output current value of the glucose sensor 3 is adjusted by the amplifier unit 21 to be synchronized with the output current value of the sucrose sensor 4, so that the output difference between the glucose sensor 3 and the sucrose sensor 4 is made zero.

Next, 50 μΩ of a 3% sucrose standard solution is poured into the measurement container 2 and stirred. At this time, the photo sensor 19 detects the injection of the sucrose standard solution, and the amplifier section 21 and calculation control section 22 start measuring the outputs of the glucose sensor 3 and sucrose sensor 4. Then, about 2 minutes after injecting the sucrose standard solution, when the outputs of the glucose sensor 3 and sucrose sensor 4 reach steady values,
The calculation control unit 22 includes a glucose sensor 3 and a sucrose sensor 4.
Each output current change amount △I GS + △ISS, and coefficient A
=Δl5S−ΔIGS·K1 is calculated and stored.

Next, the solution (buffer solution and sucrose standard solution) 13 in the measurement container 2 is
is discharged through the pipe 15b by the pump 16b, and after repeated discharge and supply of the buffer solution for cleaning, the pipe 1
Fresh buffer is supplied by pipe 16a through 5a. At this time, the liquid temperature is also maintained at 35° C. by a heater, and the magnetic stirrer 20 is driven to rotate the stirring bar 14 to stir the buffer solution.

Next, a measurement solution (50 μl) with unknown glucose and sucrose concentrations is poured into the measurement container 2 and stirred. At this time, the injection into the measurement container is detected by the photosensor 19, and when the outputs of the glucose sensor 3 and sucrose sensor 4 reach steady values 2 minutes after the injection, the control calculation section 22 controls the output of the glucose sensor 3 and sucrose sensor 4. Each output current change amount ΔI o
, , ΔI, are calculated and stored.

In this way, the control calculation unit 22 has ΔI6. .

△IS, , = ΔI s-/Δ■CM・△IGS・
△ESS・A=I55−△I O5” Kl, △I
Since Gx*ΔISx is stored, the glucose concentration G8 and sucrose concentration S1 of the measurement solution can be determined from the following equations.

S, = (△l58−△Ia8・K+)
(%)...<2) Here, △■G8 is the amount of change in the output current of the glucose sensor 3 in the measurement solution, and △ISx is the amount of change in the output current of the glucose sensor 4 in the measurement solution.
The output current change amount, △Io, is the output current change amount of the glucose sensor 3 with 1% glucose standard solution, and K1 is △■s
, /△Ic- (△Is, is the amount of change in the output current of the sucrose sensor 4 with the 196 glucose standard solution), A is I, x-△■
ax”K1.

Therefore, using equations (1) and <2), the glucose concentration 68 and sucrose concentration S7 in the measurement solution can be calculated simultaneously by the control calculation unit 22, and the glucose concentration G calculated by the control calculation unit 22 and the sucrose concentration The density S8 is output to the display section 23 and displayed.

Furthermore, after washing the solution 13 in the measurement container 2, the output current values of the glucose sensor 3 and the sucrose sensor 4 in the buffer solution are adjusted to be the same.
Even if the sucrose sensor 4 becomes dirty or changes over time, it will not be affected by it, and highly accurate concentration measurement can be performed.

In the above embodiment, a glucose sensor and a sucrose sensor were used as the first and second biosensors, but the present invention is not limited to this. For example, a glucose sensor and an oxygen sensor may be used to simultaneously measure the glucose concentration and oxygen concentration. You can also.

[Effects of the Invention] As specifically explained above based on the examples, according to the present invention, the concentrations of two solution components can be measured simultaneously and
It is easy to measure, and since the effects of dirt on the biosensor and changes over time can be eliminated, highly accurate concentration measurement is possible.

In addition, by setting the output sensitivity of each biosensor to an appropriate value in advance and comparing the output sensitivities during measurement, it is possible to understand the state of each biosensor's dirt and changes over time.
It is possible to easily determine when to replace the biosensor.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing a solution component concentration measuring device according to the present invention, FIG. 2 is a sectional view showing a glucose sensor of the same device, and FIG. 3 is a sectional view showing a sucrose sensor of the same device. FIG. 4 is a configuration diagram showing a conventional solution component concentration measuring device. 2...Measurement container 3...Glucose sensor 4
... Sucrose sensor 10 ... Collagen/glucose oxylase membrane 12
...Collagen membrane 16a, 16b...Pump 21...Amplifier section 22...Control calculation section 23
...Display section

Claims (3)

[Claims] (1) A first biosensor that responds to a first solution component; and a second biosensor that responds to the first solution component and a second solution component; and the output ratio of the second biosensor, and after adjusting the output to the same output by multiplying the output ratio by the output of the first or second biosensor, calculate the output ratio of the first solution component from the output of the first biosensor. A method for measuring the concentration of a solution component, characterized by determining the concentration and also determining the concentration of a second solution component from the difference in output between a first and second biosensor. (2) a first biosensor that responds to a first solution component; a second biosensor that responds to the first solution component and the second solution component; and the first and second biosensors. comprising a calibration means for calibrating the sensor sensitivity, and a control calculation section for calculating the concentrations of the first and second solution components by calculating the output ratio and output difference of the first and second biosensors. A concentration measuring device for solution components, characterized by: (3) The solution component concentration measuring device according to claim (2), further comprising an output means for outputting the calculation result calculated by the control calculation section, and a supply unit for supplying and discharging the first and second solutions.・A device for measuring the concentration of solution components, characterized in that it is equipped with a discharge means.