TWI656342B - An electrochemical sensing method for estimating the distribution status of a sample - Google Patents

Abstract

The electrochemical sensing method method comprises the following steps. A first voltage difference is formed between the first electrode and the second electrode for a first predetermined time, and a change in current with respect to time is recorded to obtain a current curve. Comparing at least one characteristic of the current curve with at least one standard value, and determining the distribution of the sample to be tested at one of the first electrode and the second electrode according to the at least one standard value.

Description

Electrochemical sensing method for judging sample distribution

The present invention relates to an electrochemical sensing method, and more particularly to an electrochemical sensing method for detecting the distribution of a sample.

If the blood glucose meter is not accurate enough, in addition to causing errors in blood glucose data, it will also affect treatment decisions. Common factors affecting accuracy include: improper human operation, improper calibration of the blood glucose meter, poor accuracy of the blood glucose machine itself, differences in test strips of different batches, chemical characteristics of the test strips, drug interference, and ambient temperature. The improper operation of human beings is the biggest factor affecting the accuracy of blood glucose machine; the lack of blood collection or excessively caused by improper operation of blood glucose machine is the main cause. The analyte concentration to be measured may be computationally inaccurate due to the surface area of the working electrode not being filled with the test fluid. When the surface area of the working electrode can be precisely controlled, whether the volume of the analyte to be tested is sufficient in the reaction zone becomes an important key factor.

Related prior art, for example, U.S. Patent Nos. 5,266,179 and 5,366,609, and European Patent No. EP 12728331, the main technical contents are: (1) measuring the current of the Cottrell Eq sensing current with additional components and design, thereby deducing the object to be tested The concentration is whether the detected sample appears in the Reaction zone. (2) In order to detect whether the sample is present in the reaction zone, when a sensitive test piece is properly inserted, a voltage is applied to the electrode, and the resistance of the reagent between the electrodes is high when no sample is present, but as long as the sample first contacts the reaction In the area, the resistance between the electrodes will decrease. The drop in this resistance allows a current to be detected as an indication that the sample is already present in the reaction zone. (3) Once the condition of the sample is mutated, the detection sample mechanism exceeds the preset value, and the problem of misjudgment will also occur.

Figure 1 shows a schematic view of the appearance of a conventional electrochemical test piece. Figure 2 shows an exploded view of the electrochemical test piece of Figure 1. As shown in FIGS. 1 and 2, the electrochemical test piece 100 is a blood glucose test piece including an electrode plate 110, a flow path plate 120, and a top plate 130. The electrode plate 110 includes a circuit layout 112 and a substrate 111, and is formed by printing a circuit layout 112 on a substrate 111 by a printing technique, and the circuit layout 112 has a plurality of electrodes and circuits. The flow passage plate 120 defines a notch 122 which is formed by penetrating the upper surface above the flow passage plate 120. In order to allow the blood to flow more smoothly, an opening 135 may be provided at the position of the notch 122 of the corresponding flow channel plate 120 of the top plate 130.

When the electrochemical test piece 100 is manufactured, the electrode plate 110, the flow path plate 120, and the top plate 130 need to be bonded together. The flow channel plate 120 is positioned between the electrode plate 110 and the top plate 130, and the electrode plate 110, the flow channel plate 120, and the top plate 130 collectively define a first-class track 150. The position of the flow path 150 corresponds to the position of the notch 122 of the flow path plate 120 and has an inlet 125 and an opening 135. During operation, the user drops blood at the inlet 125, and blood enters the flow channel 150 from the inlet 125. The blood flows through the flow channel 150 due to capillary action, and the gas in the flow channel 150 is discharged from the opening 135.

The circuit layout 112 includes a reference electrode 11a, a working electrode 11b and a detecting electrode 11c. The polarity of the voltage of the measuring electrode 11c and the reference electrode 11a are different; and the polarity of the voltage of the detecting electrode 11c and the working electrode 11b are different, so that the reference electrode 11a and the detecting electrode 11c form a voltage difference; the reference electrode 11a and the working electrode 11b form another A voltage difference.

Figure 3 shows a functional block diagram of a conventional electrochemical measuring device. The electrochemical measuring device 200 includes two electrodes 211 and 212, a reference voltage source 220, a current voltage conversion circuit 230, an analog digital conversion circuit 240, a processor 250, and a display 260. In an embodiment, a memory 270 may be further included. The electrode 211 is for electrically connecting the reference electrode 11a, and the electrode 212 is for electrically connecting the working electrode 11b and the detecting electrode 11c. The reference voltage source 220 can be a ground terminal. The reference electrode 11a is electrically connected to the reference voltage source 220 through the electrode 211, and the working electrode 11b and the detecting electrode 11c are electrically connected to the analog-to-digital conversion circuit 240, the current-voltage conversion circuit 230, and the processor 250 through the electrode 212. Display 260 is electrically coupled to processor 250. A plurality of materials can be stored in the memory 270.

Figure 4 shows a schematic view of the blood to be tested after entering the flow channel. As shown in FIG. 4, during operation, the user inserts the electrochemical test strip 100 into the electrochemical measuring device 200, such as a blood glucose meter, and drops the blood into the inlet 125, and the blood flows first along the flow path 150. The detecting electrode 11c flows through the working electrode 11b and finally flows through the reference electrode 11a. The reference electrode 11a and the detecting electrode 11c are used for detecting the amount of blood. When blood flows from the detecting electrode 11c to the reference electrode 11a, a voltage difference is generated between the reference electrode 11a and the detecting electrode 11c, and since the blood is a conductor, a blood flow is generated. After detecting the current I, the electrochemical measuring device 200 detects that the current I has been detected, and then it is known that the blood has flowed to the reference electrode 11a, and the blood glucose measuring program is started. During the blood glucose measurement procedure, the electrochemical measuring device 200 forms a voltage difference between the reference electrode 11a and the working electrode 11b, thereby measuring a current value and calculating the current value according to the current value. Blood glucose concentration.

Fig. 5A is a schematic view showing the distribution of blood in a flow channel in the case of insufficient blood in the prior art. Fig. 5B is a schematic view showing the distribution of blood in a flow channel in the case of insufficient blood in the prior art. As shown in FIG. 5A and FIG. 5B, due to the capillary phenomenon, in the case of blood deficiency, when blood flows in the flow channel 150, it is likely that a part of the blood has been located between the reference electrode 11a and the detecting electrode 11c, and is in the flow. There are also gaps in the road 150. In the case of insufficient blood, according to the conventional technique, the detection current I generated between the detection electrode 11c and the reference electrode 11a can be measured, and the blood glucose measurement program is started. However, due to insufficient blood in the flow channel 150, the error of the blood glucose concentration measured by the electrochemical measuring device 200 may also be excessive, which affects the measurement quality of the electrochemical measuring device 200.

Therefore, there is still room for improvement in the electrochemical test method according to the prior art.

According to an embodiment of the invention, an electrochemical sensing method is provided, which can be applied to an electrochemical test piece having a first electrode and a second electrode, and an electrochemical measuring device coupled to the electrochemical test piece. . The electrochemical sensing method method comprises the following steps. (a) providing a sample to be tested, and flowing the sample to be tested from the first electrode of the electrochemical test piece to the second electrode. (b) forming a first voltage difference between the first electrode and the second electrode for a first predetermined time, and recording a change in current with respect to time to obtain a current curve. (c) comparing at least one characteristic of the current curve with at least one standard value, and determining the sample to be tested at the first electrode according to the at least one standard value One of the second electrodes is distributed.

In an embodiment, the step of comparing the at least one characteristic of the current curve with the at least one standard value comprises: (f) determining at least one ratio of the at least one characteristic of the current curve to the at least one standard value, And determining, according to the at least one ratio, the distribution of the sample to be tested at the first electrode and the second electrode.

According to an embodiment of the present invention, the waveform comparison of the current curve can be performed using the blood volume deficiency and the full blood condition, and it can be known that the intensity value of the current curve when the blood is full and the blood is insufficient is different from the waveform slope. Using these differences, the distribution of blood volume can be predicted, and then the distribution status can be used to reinforce the existing blood volume judgment mechanism, thereby reducing the accuracy of the blood glucose machine due to improper human operation (such as insufficient blood volume or secondary blood injection). degree.

100‧‧‧Electrochemical test piece

110‧‧‧electrode plate

111‧‧‧Substrate

112‧‧‧Circuit layout

11a‧‧‧reference electrode

11b‧‧‧Working electrode

11c‧‧‧Detection electrode

120‧‧‧flow channel board

122‧‧‧ gap

125‧‧‧ entrance

130‧‧‧ top board

135‧‧‧ openings

150‧‧‧ flow path

200‧‧‧Electrochemical measuring device

211‧‧‧electrode

212‧‧‧ electrodes

220‧‧‧reference voltage source

230‧‧‧current voltage conversion circuit

240‧‧‧ analog digital conversion circuit

250‧‧‧ processor

260‧‧‧ display

270‧‧‧ memory

300‧‧‧Electrochemical test piece

310‧‧‧electrode plate

311‧‧‧Substrate

312‧‧‧Circuit layout

31a‧‧‧ reference electrode

31b‧‧‧Working electrode

Figure 1 shows a schematic view of the appearance of a conventional electrochemical test piece.

Figure 2 shows an exploded view of the electrochemical test piece of Figure 1.

Figure 3 shows a functional block diagram of a conventional electrochemical measuring device.

Figure 4 shows a schematic view of the blood to be tested after entering the flow channel.

Fig. 5A is a schematic view showing the distribution of blood in a flow channel in the case of insufficient blood in the prior art.

Fig. 5B is a schematic view showing the distribution of blood in a flow channel in the case of insufficient blood in the prior art.

Fig. 6 is a view showing an electrode plate of an electrochemical test piece according to an embodiment of the present invention.

Figure 7 is a block diagram showing the function of an electrochemical measuring device according to an embodiment of the present invention.

Figure 8 shows a signal capture of the GC waveform of normal and abnormal blood.

Figure 9 shows a flow chart of an electrochemical test method in accordance with an embodiment of the present invention.

According to an embodiment of the invention, the electrochemical test strip 300 (shown in FIG. 7) is a blood glucose test strip comprising an electrode plate 310 (shown in FIG. 6), a flow channel plate 120, and a top plate 130 (FIG. 2). Shown). Fig. 6 is a view showing an electrode plate of an electrochemical test piece according to an embodiment of the present invention. As shown in FIG. 6, the electrode plate 310 includes a circuit layout 312 and a substrate 311, and is formed by a printed circuit layout 312 on a substrate 311 by a printing technique, and the circuit layout 312 has a plurality of electrodes and circuits. The electrode plate 310, the flow path plate 120, and the top plate 130 are bonded together. The flow channel plate 120 is positioned between the electrode plate 310 and the top plate 130, and the electrode plate 310, the flow channel plate 120, and the top plate 130 collectively define a first-class track 150. The circuit layout 312 includes a reference electrode 31a and a working electrode 31b.

In one embodiment, the reference electrode 31a and the working electrode 31b are formed on a same electrode plate 310, preferably formed on the same surface. Any of the conductive materials may be used for the electrodes. In the present embodiment, graphite may be used, but the invention should not be limited thereto. In one embodiment, the reference electrode 31a and the working electrode 31b have an enzyme, wherein the enzyme oxidizes or reduces the sample to be tested. In one embodiment, the sample to be tested is human blood, and the substance to be analyzed is blood glucose, and the enzyme comprises a glucose oxidase and other complexes.

Figure 7 is a block diagram showing the function of an electrochemical measuring device according to an embodiment of the present invention. As shown in FIG. 7, during operation, the user inserts the electrochemical test strip 300 into the electrochemical measuring device 200, such as a blood glucose meter, and drops the blood into the inlet 125, and the blood flows first along the flow path 150. The working electrode 31b finally flows through the reference electrode 31a. The electrochemical measuring device 200 forms a voltage difference between the reference electrode 31a and the working electrode 31b, records a change of the current with respect to time to measure a current curve, and determines a sample distribution state according to the current curve (step S02), when judging After the sample is filled in the flow path 150, another voltage difference is formed between the reference electrode 31a and the working electrode 31b, thereby measuring a current value, and calculating the blood sugar concentration of the blood based on the current value (step S04). However, the foregoing structure is not limited by the present invention. In one embodiment, the electrochemical sensing method of the present invention can also be applied to the structure of a conventional electrochemical measuring device as shown in FIG.

Hereinafter, the method of detecting the distribution state of the sample in the above step S02 will be described in more detail. In the present invention, the distribution status is classified into normal blood intake (that is, blood volume is full or full), blood volume is insufficient, and secondary blood is introduced.

The Cottrell equation describes the change in current versus time in an electrochemical experiment. Specifically, it describes the current response when the potential is a step function. In one embodiment, the electrochemical measuring device 200 measures the change of the sensing current with respect to time by using the existing GC measuring waveform and the Cottrell current equation to obtain a current curve, and determines whether the sample is full of the flow according to the current curve. Road 150. More specifically, it is detected whether the sample has been filled in the reaction zone S between the reference electrode 31a and the working electrode 31b in the flow path 150. In one embodiment, electrochemical measurements The device 200 calculates the intensity value of the current curve and the slope of the waveform to determine whether the sample has been filled in the flow channel 150.

According to an embodiment of the invention, an electrochemical sensing method is applied to an electrochemical test strip 300 having a working electrode 31b (first electrode) and a reference electrode 31a (second electrode) and an electrochemical test piece coupled thereto. An electrochemical measuring device 200 of 300. The electrochemical sensing method method comprises the following steps.

Step S20: providing a sample to be tested, and flowing the sample to be tested from the working electrode 31b of the electrochemical test piece to the reference electrode 31a. The sample to be tested can be human blood.

Step S22: A first voltage difference is formed between the working electrode 31b and the reference electrode 31a for a first predetermined time, and a change of the current with respect to time is recorded to obtain a current curve.

Step S24: performing waveform comparison on the current curve and the standard curve. Preferably, at least one characteristic of the current curve and at least one standard value are compared to determine whether an abnormality occurs in the blood inlet condition corresponding to the current curve. In an embodiment, preferably, the distribution of the sample to be tested at one of the working electrode 31b and the reference electrode 31a is determined according to the at least one standard value. In an embodiment, step S24 includes determining at least one ratio between the at least one characteristic of the current curve and the at least one standard value, and determining the sample to be tested at the working electrode 31b and the reference electrode 31a according to the at least one ratio. The distribution status. At least one characteristic of the current curve is derived from at least one intensity value. In one embodiment, at least one characteristic of the current curve includes at least one of an intensity value and a slope of the waveform obtained using the intensity value and the time. Preferably, at least one characteristic of the current curve is a combination of intensity values and waveform slopes.

Step S26: when it is determined that the sample to be tested is at the working electrode 31b and the reference electrode 31a When the cloth condition is full, a concentration of a substance in the sample to be tested is measured by the working electrode 31b and the reference electrode 31a.

Figure 8 shows a signal capture of the GC waveform of normal and abnormal blood. As shown in Fig. 8, there are differences in the measurement of the waveforms of different blood intakes. In an embodiment, at least one threshold value (standard value) can be obtained by using the current curve of the normal blood inlet of FIG. 8, for example, a threshold value of the current intensity value and a threshold value of the waveform slope obtained from the intensity value and the time. At least one of them. Moreover, by using these threshold values, it is possible to measure the abnormal blood wave pattern generated by different blood feeding modes such as the second blood inflow and the insufficient blood in FIG.

Comparing the current curve of the normal blood in Fig. 8; and the current curve of the second blood in Fig. 8, it can be known that two peaks are generated when the blood is introduced twice. Therefore, in one embodiment, the slope of the measured waveform after one second can be calculated, and the slope of the measured waveform and the preset threshold of the waveform slope can be compared to eliminate the operation error of the second blood.

For different blood shortages, set thresholds for different full blood conditions, perform multiple experiments, and perform waveform comparison of different current curves. The proportions of the correctness and abnormal warnings are sorted out and are shown in Table 1 below.

As shown in Table 1 above, in the case of full blood (ie, normal blood flow), the correct rate is 100%. In the case of insufficient blood volume and only 0.6 (uL), the abnormal warning reached 77.6%. In the case of insufficient blood volume and only 0.5 (uL), the abnormal warning reached 98.33%, and most of the abnormalities have been detected. It can be proved that the electrochemical sensing method according to an embodiment of the present invention can effectively detect the distribution of blood between the reference electrode 31a and the working electrode 31b.

Figure 9 shows a flow chart of an electrochemical test method in accordance with an embodiment of the present invention. According to an embodiment of the invention, an electrochemical sensing method, at least one standard value of the current curve is obtained by the following steps.

Step S02: Prepare a plurality of sample blood. Preferably, the sample blood has a different and known hematocrit ratio and an actual blood glucose concentration value.

Step S04: continuously collecting current signal values during a measurement period, and measuring a normal blood volume blood glucose concentration and a current curve thereof (which may be an electrochemical reaction waveform) according to the obtained signal value.

Step S06: According to the actual current curve measured by the sample blood and the blood glucose concentration measurement value of the sample blood, the regression analysis is used to obtain the actual normal blood volume under a normal blood volume (or called full A relationship between the actual blood type of blood glucose and the measured value of blood glucose concentration.

Step S08: determining at least one characteristic of the current curve according to the current curve measured in step S22 (step S82), determining at least one standard value in step S24 according to the relationship (step S84), and comparing At least one characteristic of the current curve and at least one standard value to determine whether an abnormality occurs in the blood inlet condition corresponding to the current curve.

Step S10: When an abnormality occurs, the display 260 is caused to display an abnormality.

Step S12: When the waveform is normal (i.e., no abnormality has occurred), the display 260 is caused to display a normal measurement value.

Hereinafter, a specific embodiment of the present invention for waveform comparison of blood deficiency and full blood conditions will be described in more detail. According to the current curve of the normal blood flow, a relationship is obtained, and the relationship is stored in the electrochemical measuring device 200. As shown in FIG. 8, a plurality of time points are selected, for example, X1-X8 of FIG. 8, wherein the interval between the first half of the time points is smaller than the interval between the second half of the time points, because the characteristics of the previous period are Can display more abnormal waveforms. Based on the current curve, the intensity value (or blood glucose concentration) of the current value at the time points X1-X8 is obtained; and the waveform slope is used as a plurality of features of the current curve (step S82). Substituting the time points X1-X8 into the relational expression to obtain the intensity value of the current value at the time points X1-X8; preferably, the relationship is further differentiated to obtain the time points at the time points. The slope of the waveform at X1-X8 is taken as a plurality of standard values (step S84). In addition, in an embodiment, a plurality of ratios of the two corresponding values in step S82 and step S84 may be obtained, and the distribution of blood is determined according to the ratios.

In an embodiment, as shown in FIG. 8, the linear relationship expressed by the algorithm of an embodiment of the present invention is used to intercept abnormal blood waves generated by different blood feeding modes, and two blood ingestions are generated when the blood is introduced twice. The peak value is calculated by calculating the waveform difference of one second before and after all the signal values to eliminate the operation error of the second blood injection. Waveform comparison was performed using blood deficiency and full blood conditions. It was found that the intensity value and waveform slope of the measured full blood and insufficient blood flow were different, and affected by GC concentration and Hct, so the slope (y=ax+) b), polynomial (y=ax+bz+cw+d) and complex regression (Y=β0+β1X1+β2X2 +...+βnXn+ε) at least one relationship, and set the threshold to intercept the blood wave pattern generated by different blood feeding modes. When detecting a blood shortage and abnormal blood feeding, the reading value is misjudged. The rate has been significantly reduced.

Using the foregoing examples, a plurality of experiments were conducted, and the experimental results are shown in Table 2 below. Table 2 shows the statistical results of the abnormal blood test after analysis using the algorithm.

As shown in Table 2, the analysis result of the algorithm using an embodiment of the present invention shows that the judgment rate of abnormal blood intake is 99.85%.

As described above, according to an embodiment of the present invention, the waveform comparison of the current curve can be performed using the blood shortage and the full blood condition, and it can be known that the intensity value of the current curve and the waveform slope are different when the blood is full and the blood is insufficient. . Using these differences, the distribution of blood volume can be predicted, and then the distribution status can be used to reinforce the existing blood volume judgment mechanism, thereby reducing the accuracy of the blood glucose machine due to improper human operation (such as insufficient blood volume or secondary blood injection). degree. In one embodiment, the distribution of blood can be measured without the detection electrode being included in the circuit layout 312. The configuration of the circuit layout 312 can be simplified, and the interference of the detection electrode on the blood glucose measurement can be eliminated.

Claims (10)

An electrochemical sensing method is applied to an electrochemical test piece having a first electrode and a second electrode, and an electrochemical measuring device coupled to the electrochemical test piece, the method comprising: providing a sample to be tested And flowing the sample to be tested from the first electrode of the electrochemical test piece to the second electrode; forming a first voltage difference between the first electrode and the second electrode for a first predetermined time, and recording a current curve with respect to time to obtain a current curve; according to the current curve, a plurality of time points are obtained, wherein an interval between two points of the front portion of the time points is less than between two points of the latter part of the time points Intervals; determining a plurality of features according to the time points and the current curve, the features corresponding to the plurality of intensity values and the at least one waveform slope, and obtaining a plurality of standard values corresponding to the time points; The features of the curve and the standard values are determined, and the distribution of the sample to be tested at one of the first electrode and the second electrode is determined according to the standard values. The electrochemical sensing method of claim 1, wherein the step of comparing the characteristics of the current curve with the standard values comprises: determining between the features of the current curve and the standard values a plurality of ratios, and determining the distribution of the sample to be tested at the first electrode and the second electrode according to the ratios. An electrochemical sensing method is applied to an electrochemical test piece having a first electrode and a second electrode, and an electrochemical measuring device coupled to the electrochemical test piece, the method comprising: providing a sample to be tested And flowing the sample to be tested from the first electrode of the electrochemical test piece to the second electrode; forming a first voltage difference between the first electrode and the second electrode for a first predetermined time, and recording a change in current with respect to time to obtain a current curve, and the current curve a continuous curve; according to the current curve, obtaining a plurality of time points; determining a plurality of features according to the time points and the current curve, the features corresponding to the plurality of intensity values and the at least one waveform slope, and obtaining corresponding a plurality of standard values of the time points; comparing the characteristics of the current curve with the standard values, and determining the distribution of the sample to be tested at one of the first electrode and the second electrode according to the standard values. The electrochemical sensing method according to claim 3, wherein an interval between two points of a front portion of the time points is smaller than an interval between two points of a later portion of the time points, and the current curve These features are derived from the intensity values. The electrochemical sensing method according to any one of claims 1 to 4, wherein the step of obtaining a plurality of standard values corresponding to the time points includes a relationship according to the electrochemical measurement device and At the time points, the standard values are obtained, and the features of the current curve include: the intensity values; and the slope of the at least one waveform obtained by using the intensity values. The electrochemical sensing method of any one of claims 1 to 4, wherein the characteristics of the current curve comprise: the intensity values and the slope of the at least one waveform obtained using the intensity values; Comparing the characteristics of the current curve with the standard values, including determining that the two peaks are generated by the features, determining the distribution is a secondary blood flow. The electrochemical sensing method according to any one of claims 1 to 4, further comprising: when it is determined that the distribution of the sample to be tested is full at the first electrode and the second electrode, The first electrode and the second electrode measure one of a substance in the sample to be tested concentration. The electrochemical sensing method according to any one of claims 1 to 4, wherein the first electrode and the second electrode are located on a same electrode plate of the electrochemical test piece. The electrochemical sensing method according to any one of claims 1 to 4, wherein the first electrode and the second electrode have an enzyme, wherein the enzyme oxidizes or reduces the sample to be tested. An electrochemical measuring device adapted to couple an electrochemical test piece having a first electrode and a second electrode, wherein the electrochemical measuring device is configured to perform the method according to any one of claims 1 to 9. Electrochemical sensing method.