JPS62168045A - Component measuring method - Google Patents

Abstract

PURPOSE:To take a measurement an irreducible time after a power source is turned on by detecting and storing the degree of variation in the offset of the output of a sensor, and calibrating a next detected electric signal value into a measured value according to the degree of variation. CONSTITUTION:A biosensor 1 equipped with a Pt electrode where oxygen is fixed and a counter electrode of Ag/AgCl is dipped in a buffer solution which is stirred by a rotator 3 rotated by a magnetic stirrer 2. A current which flows between both electrodes is converted by a current-voltage converter 6 into a voltage, which is A/D-converted 7 and inputted to an arithmetic part 8. Then the degree of variation in the offset of the output of the sensor 1 is detected and stored in a storage part 10, and the offset value of the sensor 1 as a measured value is extrapolated from plural offset values of the output of the sensor 1 before the stat of measurement by linear or hyperbolic approximation and the extrapolated value is subtracted from the detected electric signal value to obtain the measured value.

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to a component measuring method using a sensor.

[Background technology]

Biosensors are used to measure body fluids such as blood, urine, food components, etc., and are excellent in terms of substrate specificity, reaction specificity, high sensitivity, and quick response, and are suitable for clinical testing. Practical use is progressing mainly in the fields of, and it is becoming widespread.

Generally, many biosensors have enzymes immobilized on the surface of an electrode.

Electrode-type biosensors require a considerable amount of time after the power is turned on until the output offset becomes constant, and measurements cannot be taken immediately in many cases. In the third part, curve C shows how the output of an electrode-type biosensor changes depending on the elapsed time after the power is turned on. As shown in the figure, when the power is initially turned on, a large offset current flows, as shown in part a in the figure, and decreases with time until the song '! /Ac approaches a certain level. If a sample is injected when the offset is decreasing, the output will rise once and then decrease as the offset decreases (portion C in the figure).

Conventionally, the offset value y1 at the time when the sample is injected is stored in the storage unit, and Δ is set after seconds (for example, Δt=10
) was read, and )'-)'l was used as the measured value. That is, the offset value at the time of measurement was set to a straight line P parallel to the time axis.

However, the offset value further decreases during this Δ second, and only a value smaller than the true value is obtained.

For this reason, in the past, measurements were not accepted until the offset reduction rate was below a certain value. However, with this method, it is not possible to measure immediately after power is turned on. Furthermore, in order to perform emergency measurements, it is necessary to keep the biosensor in a measurable state at all times.

[Purpose of the invention]

In view of the above, an object of the present invention is to provide a component measuring method that can perform component measurement using a sensor in as short a time as possible after turning on the power.

[Disclosure of the invention]

In order to achieve the above object, the present invention includes a method of detecting a detected component with a sensor, converting it into an electrical signal, and measuring the detected component, in which the degree of offset variation in the output of the sensor is detected. The gist is a component measurement method characterized by storing the measured values and calibrating the next detected electric signal value based on the degree of variation to obtain the measured value.

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

FIG. 2 shows the apparatus (
Here is an example of a component measuring device.

As shown in FIG. 2, the biosensor 1 is immersed in a buffer solution 4 that is being stirred by a rotor (Pj1 stirrer) 3 that is rotated by a magnetic stirrer 2. Biosensor 1 includes a Pt electrode on which an enzyme is immobilized and an Ag/AgC
It has the opposite polarity of 1. A constant voltage source 5 applies a constant voltage between the Pt electrode and the counter electrode. The current flowing between these two electrodes is converted into a voltage by a current-voltage converter 6, converted into a numerical value by an A-D converter 7, and then inputted into an arithmetic unit 8. The calculation unit 8 includes a program storage unit 9 and a data storage unit 10 that are read at the same time as the power is turned on.
, and a calculation result display section 11 are connected.

In FIG. 3, an example of the output of the biosensor 1 is plotted by a curve C.

This will be explained below with reference to FIGS. 2 and 3.

When the power is initially turned on, a large offset current flows as shown in part a of curve C, and this decreases over time and approaches a constant level. After turning on the power, the degree of variation of the offset value is read from the time when the offset is in the section a, and is stored in the storage unit 1o. When a sample is injected at the time when the offset value is decreasing, the output rises once and then decreases as the offset decreases (section C in FIG. 3). The detected electric signal value (output value) y after a predetermined time Δ is read from the time when the rise of the output is detected. On the other hand, the output value y is calibrated by estimating the offset value at the time b+Δt when the output value y is read from the degree of variation in the offset value immediately before the time when the rise of the output is detected, and is displayed on the display unit 11 as a measured value. do.

In this way, the component measurement method of the present invention calibrates the detected electrical signal value based on the degree of variation in the offset value in the output of the sensor immediately before the start of measurement. However, measurement errors can be eliminated or reduced. Therefore, even if the offset value fluctuates, its influence can be reduced, and the detected component can be measured with high accuracy. Of course, accurate measurements can be made even when the offset value does not change at all or hardly changes. In addition, it can be measured even at the beginning of power-on, when the offset in the sensor output is unstable.
The warm-up time of the measuring device is reduced. Therefore, it is no longer necessary to always keep the measuring device in a measurable state in order to perform urgent measurements.

In the above description, a biosensor is used as the sensor, but any sensor other than the biosensor may be used as long as it detects a detected component and converts it into an electrical signal. Also, sensors other than electrode types may be used. Components to be detected include components contained in body fluids such as blood, components in urine1 foods, and other substances, and may be contained in other than liquids.Next, we will explain based on more specific examples. FIG. 1 is a flowchart showing one embodiment of the main part of the present invention.

This will be explained below with reference to FIGS. 1 to 3.

When the power is initially turned on, a large offset current flows as shown in part a of curve C, and as time passes, this decreases and approaches a constant level. After turning on the power, reading of the offset value is started at predetermined time intervals. The read offset value first enters the storage unit (1) and is sequentially stored in the storage unit (1).
2) Enter... When the offset value reaches memory unit (4), the data in memory unit fl) is erased and the data in memory unit (2) is erased.
) to (4) are sequentially sent to the previous storage section, and the next data is then stored in the empty storage section (4). This operation is repeated at predetermined time intervals (for example, but not limited to one second).

Next, at the time when the sample is injected, the offset value after Δt (for example, 10 seconds, but not limited to this. The same applies hereinafter) is calculated by straight line Q from the four offset values immediately before that.
The value y2 is obtained by approximation and stored in the storage unit (5). From the moment the sample is injected, Δt (for example, 1
Read the detected electrical signal value (output value) y after 0 seconds). This reading may be performed two or more times and the average value may be calculated. y-Yz is used as the measurement value.

Even more precisely than in the example just described, the measurement time point (b+Δ
In order to estimate the true offset value at t), from the four offset values immediately before the sample injection time,
It is preferable to extrapolate using hyperbolic R approximation. Subtracting the offset value y3 obtained by this method from the detected electrical signal value y,
V'! Use s as the measurement value.

In the above two embodiments, in order to estimate the true offset value at the time of measurement in order to calibrate the detected electrical signal value, four offset values immediately before the time of sample injection were used. As long as it is above, the number is not limited. In order to estimate the true offset value, a method of extrapolation using linear approximation or hyperbolic approximation has been adopted, but extrapolation may be performed using other curve approximation.

Note that this invention is not limited to the above embodiments.

〔Effect of the invention〕

As described above, the component measurement method according to the present invention stores the degree of offset variation in the output of the sensor, and uses the degree of variation to calibrate the next detected electric signal value to obtain the measured value. , the influence of offset value fluctuations can be reduced and measurements can be made with high accuracy. Additionally, measurements can be made even when the offset value is unstable at the beginning of power-on, and warm-up time can be shortened.

[Brief explanation of drawings]

Fig. 1 is a flowchart showing an embodiment of the main part of the method of this invention, Fig. 2 is a block diagram showing an example of an apparatus used to carry out the method of this invention, and Fig. 3 is a flowchart showing an example of a device used to carry out the method of this invention. This is a graph showing the output characteristics. 1... Biosensor agent Patent attorney Takehiko Matsumoto, Figure i1 Figure 2

Claims (5)

[Claims] (1) In a method of measuring the detected component by detecting the detected component with a sensor and converting it into an electrical signal, the degree of offset variation in the output of the sensor is detected and stored, and the degree of variation determines the following: A component measurement method characterized by calibrating a detected electrical signal value to obtain a measured value. (2) Calibrating the detected electrical signal value involves extrapolating the offset value in the sensor output at the time of measurement from a plurality of offset values in the sensor output immediately before the start of measurement, and calculating the extrapolated value from the detected electrical signal value. A component measuring method according to claim 1, which is carried out by subtracting. (3) The component measuring method according to claim 2, wherein the extrapolation is performed by linear approximation. (4) The component measuring method according to claim 2, wherein the extrapolation is performed by hyperbolic approximation. (5) Claim 1 in which the sensor is a biosensor
Component measurement method according to any one of Items 1 to 4.