CN100473982C - Method for reducing interferences in an electrochemical sensor using two different applied potentials - Google Patents

Abstract

Translated fromChinese

本发明涉及降低分析物的测量中干扰化合物的影响的方法，更具体来说，涉及降低系统中干扰化合物的影响的方法，其中测试条(600)使用两个或更多个工作电极(12，14)。在本发明中，给第一个工作电极(12)施加第一个电位(E1)，给第二个工作电极(14)施加具有相同极性但是比第一个电位(E1)大的第二个电位(E2)。

The present invention relates to a method for reducing the effect of interfering compounds in the measurement of an analyte, and more particularly to a method for reducing the effect of interfering compounds in a system wherein a test strip (600) uses two or more working electrodes (12, 14). In the present invention, a first potential (E1) is applied to a first working electrode (12), and a second potential (E2) having the same polarity but greater than the first potential (E1) is applied to a second working electrode (14).

Description

Use two different current potentials that apply to reduce the method for the interference in the electrochemical sensor

Background of invention

Electrochemical glucose test strips is for example deriving from LifeScan, Inc.'s

Those electrochemical glucose test strips of using in the whole blood test kit are that design is used for measuring the concentration of glucose in diabetic's blood sample. the measurement of glucose is based on the specific oxidation of flavo-enzyme-glucose oxidase to glucose. between this reaction period, this enzyme has been reduced. by reacting with mediator ferricyanide, this enzyme is reoxidized, and in this process or between the reaction period, self is reduced the ferricyanide. these reactions are summarized as follows.

When using the current potential that between two electrodes, applies to carry out above-mentioned reaction, by electrochemical re-oxidation at the reduction amboceptor ion (ferrocyanide) of electrode surface, can produce electric current. therefore, because in ecotopia, amount at the ferrocyanide that produces during the above-mentioned chemical reaction is directly proportional with the amount that places two sample glucose between the electrode, so the electric current that produces will be directly proportional with the glucose content of sample. the redox mediators for example ferricyanide is at the oxidoreducing enzyme compound of exchange electronics between glucose oxidase and the electrode for example. when the concentration of glucose in the sample increases, the amount of the reduction amboceptor that forms also increases, therefore, have direct related between the electric current that generated and the concentration of glucose by reoxidizing of reduction amboceptor. particularly, the electron transfer of crossing electric interface causes flowing (every mole of oxidized glucose of 2 moles of electronics) of electric current. and therefore, the electric current that causes owing to the introducing of glucose is called glucose current.

Because know the concentration of glucose in blood, particularly the concentration in diabetes patient's blood may be very important, use above-mentioned principle can from the mediocrity, taking a sample at any time so developed, and the measuring instrument of measure glucose concentration. monitor the glucose current of generation by measuring instrument, and use the algorithm that sets in advance to change into the reading of concentration of glucose, described algorithm connects electric current and concentration of glucose by the simple mathematical formula.Generally speaking, measuring instrument and disposable band collaborative work, except enzyme (glucose oxidase) and amboceptor (ferricyanide), described band comprises sample room and at least two electrodes that place in the sample room. in use, the user hold up they finger or other cause and bleed in the position easily, and blood sample is introduced sample room, begins above-mentioned chemical reaction thus.

In electrochemical terms, the function of measuring instrument is dual. at first, its provide polarizing voltage (for

Approximately be 0.4V), this polarizing voltage polarizes electric interface, and allows electric current flow at the carbon working electrode surface. secondly, the electric current that flows in the external circuit of its measurement between anode (working electrode) and negative electrode (contrast electrode).Therefore, measuring instrument can be regarded as simple electro-chemical systems, and this electro-chemical systems also can use the 3rd or even the 4th electrode with the bipolar electrode mode operation in the reality, helps measure glucose and/or carry out other function in measuring instrument.

In most of the cases, the formula that provides above is considered to the sufficient approximation to the chemical reaction that carries out on test-strips, yet and the reading of measuring instrument is the enough accurate expression to the blood sample concentration of glucose., in some cases and for some purposes, it is favourable improving the degree of accuracy of measuring. for example, the one part of current of measuring on electrode is because other chemical substance or the compound that exist in the sample produce. when having so other chemical substance or compound, they can be described as interfering compound, and the other electric current that is caused can be described as interference current.

Current potential interfering chemicals (just for example find in the blood at physiological fluid, can produce the compound of interference current in the presence of electric field) comprises ascorbate, urate and paracetamol (Tylenol^TMOr Paracetamol). in the electrochemical measurement instrument (for example glucose meters) of the concentration that is used for measuring the physiological fluid analyte, a mechanism of generation interference current relates to the reduction by enzyme (for example glucose oxidase), the oxidation of one or more interfering compounds. in such measuring instrument, another mechanism of generation interference current relates to the reduction by amboceptor (for example ferricyanide), the oxidation of one or more interfering compounds. in such measuring instrument, another mechanism of generation interference current relates to the oxidation at one or more interfering compounds of working electrode. and therefore, the total current of measuring at working electrode is the stack of electric current that produces owing to analyte is oxidized and the electric current that produces owing to interfering compound is oxidized. and the oxidation of interfering compound can be and enzyme, amboceptor results of interaction or can directly take place at working electrode.

Generally speaking, the current potential interfering compound can be in electrode surface oxidation and/or oxidized by redox mediators. and the oxidation of interfering compound in the glucose measurement system causes that measured oxidation current is both relevant with glucose also relevant with interfering compound. therefore, if the concentration of interfering compound is significantly higher than concentration of glucose with efficient oxidation identical with glucose and/or interfering compound concentration, it can influence the concentration of glucose of measurement.

The co-oxidation of analyte (for example glucose) and interfering compound especially is a problem under following situation: the normal potential of interfering compound (being the current potential of compound when oxidized) is similar with the normal potential of redox mediators in size, causing owing to accounting for suitable ratio at the oxidized interference current that produces of interfering compound on the working electrode. the electric current that produces owing to the oxidation of interfering compound on working electrode can be called direct interference current. therefore, reducing that direct interference current maybe minimizes this influence for the influence of analyte concentration measurement will be favourable. reduce in the past or the method for eliminating direct interference current comprises, design can prevent that interfering compound from arriving working electrode, and reduction or elimination are by the direct interference current of the compound generation that is eliminated thus.

A strategy of influence that reduce to produce the interfering compound of direct interference current is the top that electronegative film is placed on working electrode. as an example, and can be with sulfonation fluorinated polymer NAFION for example^TMBe placed on above the working electrode, to repel all electronegative chemical substances. generally speaking, a lot of interfering compounds, comprise that ascorbate and urate have negative charge, therefore, when the surface of working electrode is covered by electronegative film, it is yet not oxidized thereby these interfering compounds are ostracised., for example paracetamol is not electronegative owing to some interfering compound, thereby and can pass through electronegative film, can not eliminate direct interference current so use electronegative film. another shortcoming that covers working electrode with electronegative film is, for example the ferricyanide is electronegative for redox mediators commonly used, and can not come and electrode exchange electronics by described film. the electronegative film of use also has a shortcoming to be on working electrode, the slowed down amboceptor of reduction of current potential is diffused on the working electrode, having increased Measuring Time thus. another shortcoming of the electronegative film of use is to have increased the production complicacy and the cost of the test-strips with electronegative film on working electrode.

Another strategy that can be used for reducing direct interference current is to lay a size Selection film at the working electrode top. as an example, can with 100 dalton's size exclusion films for example acetyl cellulose film be placed on the working electrode, to get rid of molecular weight greater than 100 daltonian compounds. in this embodiment, with oxidoreducing enzyme for example glucose oxidase be placed on the size exclusion film. in the presence of glucose and oxygen, glucose oxidase produces hydrogen peroxide, the amount of the hydrogen peroxide that produces is directly proportional with concentration of glucose. should be noted that, the molecular weight of glucose and most of redox mediators is greater than 100 dalton, yet and therefore can not pass through the size Selection film., the molecular weight of hydrogen peroxide is 34 dalton, therefore can pass through the size Selection film. generally speaking, the molecular weight of majority of compounds is greater than 100 dalton, thereby therefore can not be oxidized at electrode surface by exclusion. because some interfering compound has less molecular weight, therefore can pass through the size Selection film, can not eliminate direct interference current so use the size Selection film. on working electrode, use another shortcoming of size Selection film, increased the production complicacy and the cost of test-strips with size Selection film.

Another strategy that can be used for reducing the influence of direct interference current is to use the redox mediators with suboxides reduction potential, for example oxidation-reduction potential for pact-300mV extremely+redox mediators of 100mV (vs saturated calomel electrode). this makes it possible to apply lower current potential to working electrode, thereby has reduced interfering compound by the speed of working electrode oxidation.Yet the example that has than the redox mediators of suboxides reduction potential comprises osmium bipyridyl complexes, ferrocene derivatives and quinone derivative., the redox mediators that has than the suboxides reduction potential often is difficult to synthesize, and is unstable and more insoluble.

Another strategy that can be used for reducing the influence of interfering compound is, unite and use pseudo electrode and working electrode. can from the electric current of measuring at working electrode, deduct at the electric current that pseudo electrode is measured then, influence with the compensate for disturbances compound. if pseudo electrode is (just not covered by enzyme or amboceptor) of exposing, then the electric current of measuring at pseudo electrode will be directly proportional with direct interference current, if and will deduct from the electric current of measuring at working electrode at the electric current that pseudo electrode is measured and will reduce or eliminate the influence of the direct oxidation of interfering compound on working electrode. pseudo electrode covers with redox mediators, then the electric current of measuring at pseudo electrode will be direct interference current with because interfering compound reduces the combination of the interference current that causes with redox mediators. therefore, to from the electric current of measuring at working electrode, deduct at the electric current that the pseudo electrode that covers with redox mediators is measured with reduce or eliminate interfering compound direct oxidation influence and on working electrode because interfering compound reduces the influence of the interference that produces with redox mediators. in some cases, pseudo electrode also can cover with the oxidoreducing enzyme of inert protein or inactivation, the effect to spreading with simulation redox mediators and enzyme. because thereby test-strips preferably has little sample room and makes the diabetic need not to provide big blood sample, so sample room's volume when not using additional electrode to come Measurement and analysis thing (for example glucose), comprise that the additional electrode that makes sample room's volume increase may be disadvantageous. in addition, may be difficult to make that the electric current in the pseudo electrode measurement is directly related with the interference current of measuring at working electrode. last, because can cover pseudo electrode, so in a plurality of working electrode system, use pseudo electrode may increase the production cost and the complicacy of test-strips as the test-strips that reduces or eliminate the method for interfering compound influence with the material (for example redox mediators) different with the material that is used for covering working electrode (for example redox mediators and enzyme).

Use a plurality of working electrodes to come the Measurement and analysis thing, for example exist

Some test strip designs of the system that uses in the measuring system are favourable, this is because used two working electrodes. in such system, developing the method that reduces or eliminate the influence of interfering compound therefore will be favourable. more particularly, it will be favourable developing not using pseudo electrode, intermediate film or having the method that reduces under the situation of redox mediators of suboxides reduction potential or eliminate the influence of interfering compound.

Summary of the invention

The present invention relates in the measurement of analyte, reduce the method for the influence of interfering compound, more particularly, relate to test-strips therein and use the method that reduces the influence of interfering compound in the system of two or more working electrodes. in one embodiment of the invention, apply first current potential for first working electrode, apply second current potential for second working electrode, the polarity of described second current potential is identical with first current potential, but its size is bigger than first current potential. for the embodiment of using reduction current to come the Measurement and analysis substrate concentration, the size of second current potential also may be littler than first current potential. and in one embodiment, first working electrode and second working electrode can cover with specific enzyme reagent of analyte and redox mediators.Selection imposes on first current potential of first working electrode, make it be enough in the diffusion restriction mode with the redox mediators oxidation that is reduced, and select second current potential to make its size (being absolute value) bigger than first current potential, thereby make in the higher oxidation of luminous efficiency on second working electrode. in this embodiment of the present invention, the electric current of measuring at first working electrode comprises analyte current and interfering compound electric current, and the electric current of measuring in second work unit comprises analyte overpotential current and interfering compound overpotential current. should be noted that, the two is meant analyte current and analyte overpotential current and the corresponding electric current of analyte concentration, and this electric current is the oxidized result of reduction amboceptor. in one embodiment of the invention, electric current and the relation between the electric current of second working electrode at first working electrode can be passed through following formula definition

$A_1=\frac{W_2-{\mathrm{YW}}_1}{X-Y}$

A wherein₁Be analyte current at first working electrode, W₁Be the electric current of measuring at first working electrode, W₂It is the electric current of measuring at second working electrode, X is the analyte dependence voltage effects factors, and Y is the interfering compound dependence voltage effects factors. use above-mentioned formula in the methods of the invention, can reduce influence, and calculate the correcting current value that more can represent analyte concentration in the samples tested owing to the oxidation current that exists interfering compound to bring.

In one embodiment of the invention, the concentration of glucose that is placed in the sample on the test-strips can as described belowly calculate: sample is placed on the test-strips, described test-strips has first working electrode and second working electrode and contrast electrode, at least first working electrode and second combined thing of working electrode (for example enzyme and redox mediators) cover, when applying current potential between first working electrode and contrast electrode and between second working electrode and the contrast electrode, described compound is suitable for promoting the oxidation of glucose and electronics to transfer on first working electrode and second working electrode from the glucose of oxidation. according to the present invention, between first working electrode and contrast electrode, apply first current potential, select the size of first current potential, make it possible to be enough to guarantee that the size of the electric current that the oxidation owing to glucose in the sample produces only is subjected to the restriction of the factor (for example diffusion) except that applying voltage. according to the present invention, between second working electrode and contrast electrode, apply second current potential, the size of second current potential is bigger than first current potential, and in one embodiment of the invention, select second current potential to be increased in the oxidation of interfering compound on second working electrode. in another embodiment of the invention, can use following formula to reduce oxidation current that the existence owing to interfering compound produces for the influence that is used for calculating the electric current of concentration of glucose in the sample. particularly, can use the electric current A of calculating_1GDerive concentration of glucose, wherein

$A_{1G}=\frac{W_2-{\mathrm{YW}}_1}{X_G-Y}$

A wherein_1GBe glucose current, W₁Be the electric current of on first working electrode, measuring, W₂Be the electric current of on second working electrode, measuring, X_GBe the glucose dependence voltage effects factors, and Y is the interfering compound dependence voltage effects factors.

The accompanying drawing summary

New feature of the present invention especially provides in claims. and by the following detailed description that provides exemplary, the features and advantages of the present invention be can understand better, principle of the present invention and accompanying drawing wherein used:

Fig. 1 is the exploded perspective illustration that is used for test-strips embodiment of the present invention.

Fig. 2 is the diagram figure that is used for measuring instrument of the present invention and test-strips.

Fig. 3 is the dependent hydrodynamic force voltammogram that shows between the electric current of the voltage that applies and measurement.

Detailed Description Of The Invention

Though the present invention is particularly suitable for measuring the concentration of glucose in the blood, but it is evident that for ability city technician, the method of describing among the present invention can be suitable for improving the selectivity of other system of the electrochemical measurement that is used for the physiological fluid analyte. and can be suitable for using the inventive method to improve optionally the example of system and comprise and be used for measuring the physiological fluid lactate, alcohol, cholesterol, amino acid, the electrochemical sensor of the concentration of choline and fructosamine. the example that can contain the physiological fluid of such analyte comprises blood, blood plasma, serum, urine and interstitial fluid. should further understand, though the inventive method is measured therein electric current is to describe in the electro-chemical systems that produces by oxidation, and it is the system that produces by reduction that the present invention is equally applicable to wherein measured electric current.

The present invention relates to improve the optionally method of electrochemical measurement system, described method is specially adapted to blood sugar measuring system. more particularly, the present invention relates to improve the optionally method of blood sugar measuring system by the influence of partially or completely proofreading and correct direct interference current. in such system, selectivity is the ability that concentration of glucose in the physiological fluid sample is accurately measured by this system, described physiological fluid comprises that one or more can produce the compound of interference current. therefore, optionally raising can reduce the electric current that produces at working electrode owing to there is interfering compound (being that oxidation is to produce the compound except that glucose of interference current), and make the electric current of measuring more can represent concentration of glucose. particularly, the electric current of measuring can be the function of the oxidation of the interfering compound found usually in physiological fluid, and described interfering compound is paracetamol (Tylenol for example^TMOr Paracetamol), ascorbic acid, cholerythrin, dopamine, gentianic acid, glutathione, levodopa, ethyldopa, tolazamide, orinase and uric acid. such interfering compound can be oxidized by for example carrying out chemical reaction with redox mediators, and is perhaps oxidized by oxidation on electrode surface.

In system fully optionally, the oxidation current that will not produce by any interfering compound, and all oxidation current will produce by glucose oxidase.Yet, if the oxidation of interfering compound and the oxidation current that is produced can not be avoided, the invention describes the method for some or all influence of eliminating interfering compound, this is by quantitatively determining to be accounted for by the oxidation current that interfering compound produces the ratio of whole oxidation currents, and this magnitude of current deducted from whole oxidation currents realize. particularly, in the methods of the invention, use comprises the test-strips of first working electrode and second working electrode, apply two different potentials, and measure the oxidation current that on each working electrode, produces and come the shared separately oxidation current ratio of glucose estimator and interfering compound.

In an embodiment of the inventive method, employed test-strips comprises sample room, described sample room comprises first working electrode, second working electrode and contrast electrode. first working electrode, second working electrode and contrast electrode are covered by the glucose oxidase (enzyme) and the ferricyanide (redox mediators). when being placed on blood sample (physiological fluid) in the sample room, glucose oxidase is reduced by the glucose in the blood sample, produce gluconic acid. be reduced to ferrocyanide by the ferricyanide then, gluconic acid is oxidized, having produced the redox mediators of the reduction that its concentration is directly proportional with concentration of glucose. the example applicable to the test-strips of the inventive method is by LifeScan, Inc.of Milpitas, California sells

Test-strips. other test-strips is described among international open WO 01/67099A1 and the WO01/73124A2.

In an embodiment of the inventive method, apply first current potential for first working electrode, apply second current potential for second working electrode. in this embodiment, select the size of first current potential, make that the glucose current reaction is insensitive relatively for the current potential that applies, thereby be diffused into the quantitative limitation of the redox mediators of the reduction on first working electrode in the glucose current size on first working electrode. should be noted that, glucose is not by direct oxidation on working electrode, but by using oxidoreducing enzyme and redox mediators by indirect oxidation. in instructions of the present invention, glucose current is meant the oxidation of the redox mediators of the reduction relevant with concentration of glucose. in embodiments of the invention, when ferri/ferrocyanide is a redox mediators, and when carbon is working electrode, first current potential can be about 0 millivolt-Yue 500 millivolts, more preferably about 385 millivolts-Yue 415 millivolts, even more preferably about 395-405mV. applies second current potential for second working electrode, make second current potential greater than first current potential. wherein the current potential that is applied is greater than the required current potential of oxidizing glucose. in one embodiment of the invention, when ferri/ferrocyanide is a redox mediators, and when carbon is working electrode, second current potential can be about 50 millivolts-Yue 1000 millivolts, more preferably about 420 millivolts-Yue 1000 millivolts, even more preferably about 395-405mV.

Because along with the increase glucose current of current potential does not increase or only minimum degree ground increase; so the glucose current on second working electrode should equate basically with the glucose current on first working electrode; even the current potential on second working electrode is greater than the current potential on first working electrode. therefore; the any additional electric current of measuring on second working electrode is attributable to the oxidation of interfering compound. in other words; should cause that at the high potential on second working electrode the glucose overpotential current of measuring equals in size or is substantially equal to glucose current on first working electrode on second working electrode; because first is in the glucose current scope of restriction with current potential and second current potential; yet the glucose current of this scope is insensitive for the change that applies current potential.; in practice; other parameter may influence the electric current of measurement; for example; when applying higher current potential for second working electrode; result as IR potential drop or capacitive effect; increase a little through regular meeting in the total current on second working electrode. when having IR potential drop (both uncompensated resistance) in the system; the higher example that applies electric current that current potential causes measurement and increase the .IR potential drop can be first working electrode; second working electrode; contrast electrode; the nominal resistance of the physiological fluid between working electrode and the contrast electrode. in addition; apply higher current potential and cause forming bigger ion bilayer; this ion bilayer forms at the electrode/liquid interface, is increased in ion capacitance and formed electric current on first working electrode or second working electrode.

For glucose current and the actual relationship of determining on first working electrode, to measure between the glucose current of measuring on second working electrode, must develop suitable formula. should be noted that the glucose current on second working electrode also can be called glucose overpotential current. the proportional relation between glucose current and the glucose overpotential current can be described by following formula.

X_GXA_1G=A_2G(formula 1)

X wherein_GBe the glucose dependence voltage effects factors, A_1GBe the glucose current on first working electrode, A_2GBe the glucose current on second working electrode.

In one embodiment of the invention, when ferri/ferrocyanide is a redox mediators, and when carbon is working electrode, for glucose, the voltage effects factor can be expected to be about 0.95 to about 1.1. in this embodiment of the present invention, higher current potential has no significant effect for the glucose oxidase electric current, because and between the working electrode, redox mediators (ferrocyanide) but have electron transfer kinetics and inverted electron transfer feature fast. because the increase glucose current along with current potential does not increase after a fixed point, be saturated or in the situation of diffusion restriction so we can say glucose current.

In the embodiment of the invention described above, glucose is measured indirectly by iron protoxide prussiate on working electrode, and the ferrocyanide substrate concentration is directly proportional with concentration of glucose.For concrete galvanochemistry compound, normal potential (E °) value is the module of the ability of this compound and other compound exchange electronics. in the methods of the invention, be chosen in the current potential on first working electrode, make its normal potential (E °) greater than redox mediators. because select first current potential, make the E ° of value that is sufficiently more than redox couple, so along with the increase that applies current potential, oxidation rate does not significantly increase.Therefore, on second working electrode, apply bigger current potential and will can not be increased in second oxidation on the working electrode, and the electric current of any increase of measuring on the electrode of high potential must be because for example oxidation of interfering compound of other factors.

Fig. 3 is the dependent hydrodynamic force voltammogram that shows between the electric current of the voltage that applies and measurement, wherein ferri/ferrocyanide is a redox mediators, and carbon is working electrode. each data point on this figure is represented at least one experiment, wherein electric current is measured 5 seconds after applying voltage between working electrode and the contrast electrode. and Fig. 3 shows, at about 400mV, electric current has formed the beginning of land regions, because this voltage that applies is sufficiently more than E ° of value of ferrocyanide. therefore, as shown in Figure 3, when current potential reaches about 400mV, it is saturated that glucose current becomes, this be because the oxidation of ferrocyanide be diffusion restriction (ferrocyanide to the diffusion restriction of working electrode the size of the electric current measured, and be not subjected to the restriction of the electron transfer speed between ferrocyanide and the electrode).

Usually, the electric current that oxidation by interfering compound produces can be unsaturated because of the increase that applies voltage, and compare (ferrocyanide produces by the interaction of glucose and enzyme and enzyme and ferrocyanide) with the electric current that oxidation by ferrocyanide produces, show strong a lot to applying the dependence of current potential. interfering compound has usually than the slow electron transfer kinetics of redox mediators (being ferrocyanide). and the reason of this difference is the following fact, most of interfering compound experience endosphere electron transfer, and ferrocyanide experiences ectosphere electron transfer faster. typical endosphere electron transfer needed to take place chemical reaction before metastatic electron, for example hydride shifts.Different with it, the ectosphere electron transfer did not need chemical reaction before metastatic electron.Therefore, the endosphere electron transfer speed is slower than ectosphere electron transfer usually, because the chemical reaction step that they need add. it is an example of endosphere oxidation that Ascorbic Acid Oxidation is become hydroascorbic acid, and it need discharge two hydride parts. the ferricyanide is oxidized to the example that ferrocyanide is the ectosphere electron transfer.Therefore, when when high potential is tested, the electric current that is produced by interfering compound can increase usually.

Can describe by following formula at interfering compound electric current on first working electrode and the relation between the interfering compound overpotential current on second working electrode,

YxI₁=I₂(formula 2)

Wherein Y is the interfering compound dependence voltage effects factors, I₁Be the interfering compound electric current, and I₂Be the interfering compound overpotential current. because interfering compound dependence voltage effects factor Y depends on multiple factor, comprise the material that concrete interfering compound and working electrode are all, so for concrete system, test-strips, analyte and interfering compound, the calculating of the concrete interfering compound dependence voltage effects factor may need to test the voltage effects factor of optimizing for these standards. perhaps, under some conditions, can derive or describe the suitable voltage effects factor by mathematical method.

Ferri/ferrocyanide is a redox mediators therein, and carbon is in the embodiment of the present invention of working electrode, and interfering compound dependence voltage effects factor Y can use about I₁And I₂The Tafel formula come to describe with mathematical measure,

$I_1=a\′\exp \left(\frac{{\mathrm{\η}}_1}{b\′}\right)$(formula 2a)

$I_2=a\′\exp \left(\frac{{\mathrm{\η}}_2}{b\′}\right)$(formula 2b)

η wherein₁=E₁-E °, η₂=E₂-E °, b ' is the constant that depends on concrete electroactive interfering compound, E₁Be first current potential, and E₂The value normal potential of interfering compound (concrete) that is second current potential .E ° is unessential, because it has been cancelled in the calculating of Δ η. can be altogether withformula 2,2a, 2b, and reset, obtain following formula,

$Y=\exp \left(\frac{\mathrm{\Δ\η}}{b\′}\right)$(formula 2c)

Δ η=E wherein₁-E₂. formula 2c provides the mathematical relation of the relation between description Δ η (being the difference between first current potential and second current potential) and the interfering compound dependence voltage effects factor Y.In one embodiment of the invention, Y can be about 1-about 100, more preferably about 1-10. in one embodiment of the invention, combination for concrete interfering compound or interfering compound, interfering compound dependence voltage effects factor Y can be determined by experiment. should be noted that, for interfering compound, interfering compound dependence voltage effects factor Y is usually greater than the voltage effects factor X of glucose_G. as described in following chapters and sections, a) interfering compound electric current I₁With interfering compound overpotential current I₂Between mathematical relation; And b) glucose current A_1GWith glucose overpotential current A_2GBetween mathematical relation make it possible to propose the glucose algorithm, this algorithm has reduced the influence of interfering compound for glucose measurement.

In one embodiment of the invention, developing the corrected glucose current that algorithm calculates the influence of interference-free thing (is A_1GAnd A_2G). after being added to sample on the test-strips, apply first current potential for first working electrode, apply second current potential for second working electrode. at first working electrode, measure first electric current, it can be described by following formula,

W₁=A_1G+ I₁(formula 3)

W wherein₁Be first electric current on first working electrode. in other words, first electric current comprises glucose current A_1GWith the interfering compound electric current I₁Stack. more particularly, the interfering compound electric current can be a direct interference current described above. at second working electrode, measure second electric current in second current potential or overvoltage, it can be described by following formula,

W₂=A_2G+ I₂(formula 4)

W wherein₂Be second electric current on second working electrode, A_2GBe glucose overpotential current second potential measurement, I₂Be interfering compound overpotential current second potential measurement. more particularly, the interfering compound overpotential current can be a direct interfering compound electric current described above. use to comprise 4 unknown quantity (A_1G, A_2G, I₁And I₂) above-described 4 formula (formula 1-4), can calculate the corrected glucose current formula of interference-free compounds affect.

As first step in deriving, can obtain followingformula 5 with being substituted in theformula 4 from the A2G offormula 1 with from the I2 offormula 2.

W₂=X_GA_1G+ YI₁(formula 5)

Next, formula 3 be multiply by the interfering compound dependence voltage effects factor Y of interfering compound, obtainformula 6.

YW₁=YA_1G+ YI₁(formula 6)

Formula 5 is deductedformula 6, obtain following form as shown in Equation 7

W₂-YW₁=X_GA_1G-YA_1G(formula 7)

With the formula 7 corrected glucose current As of rearrangement to find the solution in first potential measurement_1G, as shown inEquation 8.

$A_{1G}=\frac{W_2-{\mathrm{YW}}_1}{X_G-Y}$(formula 8)

Obtained corrected glucose current A byformula 8_1G, it has eliminated the influence of disturbing, and this only needs the output current (W for example of first working electrode and second working electrode₁And W₂), glucose dependence voltage effects factor X_GInterfering compound dependence voltage effects factor Y. with interfering compound

The glucose meters that will comprise electronic unit is electrically connected with glucose test strip with from W₁And W₂Measure electric current. in one embodiment of the invention, can be with X_GBe programmed in the glucose meters with Y, so only read storer. in another embodiment of the invention, can Y be passed to measuring instrument by calibration code chip. calibration code chip in its storer, have one group specific for X_GWith the value of Y,, can proofread and correct these values for a lot of concrete test-strips. this can explain may be at X_GWith the test-strips batch differences that takes place among the Y.

In another embodiment of the invention, to have only when surpassing some threshold values, the corrected glucose current in theformula 8 just can be used by measured instrument. for example, if W₂Compare W₁Go out greatly more than 10% or 10%, yet measuring instrument will useformula 8 to proofread and correct output current., if W₂Compare W₁Go out greatly below 10% or 10%, then interfering compound concentration is very low, so measuring instrument can be got W simply₁With W₂Between average current value, improve the accuracy and the degree of accuracy of measurement. in order to replace simply with electric current W₁And W₂On average, method can be to use W more accurately₂/ X_GCome average W₁, wherein considered glucose dependence voltage effects factor X_G(note, work as I₂When very low, according toformula 1 and 4, W₂/ X_GApproximate A_1G). the danger of only under wherein there is the situation of interfering compound of the level of signifiance in the sample in some, using the strategy offormula 8 to alleviate the glucose current excessive correction of measuring. should be noted that and work as W₂Compare W₁When enough big when (for example going out about 100% or more greatly), this is to have the very indication of the interfering compound of high concentration. under these circumstances, may wish output error message rather than dextrose equivalent, because very high-caliber interfering compound can cause breaking offormula 8 accuracy.

Following chapters and sections will be described the possible test-strips embodiment that can use with the algorithm that the present invention shown in theformula 8 proposes. and Fig. 1 is the exploded perspective illustration of test-strips 600, it comprises 6 layers that are arranged on thesubstrate 5. these 6 layers areconductive layers 50,insulation course 16, reagent layer 22,bonding coat 60,hydrophilic layer 70 andtop layer 80. test-strips 600 can be made in series of steps, for example wherein use the screen cloth printing method withconductive layer 50,insulation course 16, reagent layer 22,bonding coat 60 is arranged on thesubstrate 5.hydrophilic layer 70 andtop layer 80 can be from coiled material (roll stock) thus take out and be laminated on thesubstrate 5. the test-strips of assembling forms and can receive the sample receiving chamber that blood sample makes that blood sample can be analyzed fully.

Conductive layer 50 comprisescontrast electrode 10, first workingelectrode 12, second workingelectrode 14,13, second contact points 15 of first contact point (contact), reference contact point 11 and test-strips check-out console 17.The suitable material that can be used for forming conductive layer is the tin oxide of Au, Pd, Ir, Pt, Rh, stainless steel, doping, carbon etc. preferably, the material that is used for conductive layer can be carbon ink (carbon ink) for example describe at US5653918 those.

Insulation course 16 comprises otch (cutout) 18, it has exposed can be by the wetting a part ofcontrast electrode 10 of liquid sample, first workingelectrode 12 and second workingelectrode 14. as limiting examples, insulation course (16 or 160) can be can be available from Ercon, the Ercon E6110-116 Jet Black Insulayer Ink. of Inc

Reagent layer 22 can be arranged on a part ofconductive layer 50 and the insulation course 16.In an embodiment of the present invention, reagent layer 22 can comprise optionally and the chemical substance of glucose response for example oxidoreducing enzyme and redox mediators. between this reaction period, can produce the redox mediators of the reduction of certain proportion amount, can measure it with electrochemical means, thereby can calculate concentration of glucose. the example that is applicable to reagent formulation of the present invention or ink can be referring to US patent 5,708,247 and 6,046,051; The International Application No. WO 01/67099 and the WO01/73124 that publish, they all are incorporated herein by reference.

Bonding coat 60 comprises first adhesive pad 24, secondadhesive pad 26 and the 3rd adhesive pad 28.First adhesive pad 24 adjacent with reagent layer 22 and the lateral edges of secondadhesive pad 26 define the wall of sample receiving chamber respectively. in an embodiment of the present invention, bonding coat can comprise the water based acrylic copolymer contact adhesive, this bonding agent can be from TapeSpecialties LTD in Tring, Herts, United Kingdom (part ﹠amp; Num; It is A6435) commercially available.

Hydrophilic layer 70 comprises thehydrophilic pad 32 in distally and thehydrophilic pad 34 of nearside.As limiting examples,hydrophilic layer 70 can be to have for example polyester of antifogging coating of a water-wetted surface, it can be commercially available from 3M. should be noted that, thehydrophilic film 32 in distally and thehydrophilic film 34 of nearside all are transparent, thereby make the user can observe the liquid sample of filling the sample receiving chamber.

Top layer 80 comprises thattransparent part 36 andopaque section 38.top layers 80 are arranged on thehydrophilic layer 70 and is bonding with it. as limiting examples, top layer 40 can be a polyester. should be noted that,transparent part 36 is overlapping basically with proximalhydrophilic pad 32, this make the user visually the validation sample receiving chamber enough fills full.opaque section 38 help users observe for example degree of contrast between the zone of opacity of blood and teleblem of the interior band look fluid of sample receiving chamber.

Fig. 2 is the simple diagram figure that shows the measuringinstrument 500 that is connected with test-strips 600. measuringinstrument 500 has 3 electrical pickofves, these 3 electrical pickofves form and being electrically connected of first workingelectrode 12, second workingelectrode 14 andcontrast electrode 10. particularly,connector 101 connectsvoltage source 103 and first workingelectrode 12,connector 102 connectsvoltage source 104 and second workingelectrode 14, andcommon connector 100 is connected with 104voltage source 103 with contrast electrode 10.When testing, thevoltage source 103 in the measuringinstrument 500 applies first current potential E between first workingelectrode 12 andcontrast electrode 10₁,voltage source 104 applies second current potential E between second workingelectrode 14 andcontrast electrode 10₂. apply blood sample, first workingelectrode 12, second workingelectrode 14 andcontrast electrode 10 are covered by blood like this. and this causes reagent layer 22 hydrations, produce the ferrocyanide that the glucose that exists in its amount and the sample and/or interfering compound concentration are directly proportional. apply 5 seconds behind the sample, the oxidation current of measuringinstrument 500 first workingelectrodes 12 of measurement and second workingelectrode 14.

In above-mentioned first and second test-strips embodiment, first workingelectrode 12 and second workingelectrode 14 have equal area. should be noted that, the invention is not restricted to have test-strips of the same area. for the embodiment of the different above-mentioned test-strips of area wherein, the output current of each working electrode must be carried out naturalization to area. because output current is directly proportional with area, so the term among the formula 1-8 can be represented with the current potential (electric current) of ampere or the ampere (being current density) in every current potential area.

Will be appreciated that, for the structure that illustrates herein and describe, can substitute equivalent constructions, and described embodiment of the present invention is not the unique structure that can use in the present invention. in addition, be to be understood that, above-mentioned each structure has function, though and such structure can be described as the means of implementing this function. represented and described the preferred embodiments of the invention, but for the technician of ability city, it is evident that, it only is to illustrate for example that such embodiment is provided. to those skilled in the art, in the case of without departing from the present invention, can make a lot of changes, variation and alternative. be to be understood that, the multiple replacement scheme of embodiment of the present invention described herein can be used for implementing the present invention. and following claims limit scope of the present invention, and the method and structure in these claim scopes and be equal to absorption and should be included in these claim scopes.

Claims (5)

Translated fromChinese

1.降低电化学传感器中的干扰的方法，所述方法包括：1. A method of reducing interference in an electrochemical sensor, the method comprising:给第一个工作电极施加第一个电位；Apply the first potential to the first working electrode;给第二个工作电极施加第二个电位，其中所述第二个电位大于所述第一个电位的绝对值；applying a second potential to the second working electrode, wherein the second potential is greater than the absolute value of the first potential;测量在所述第一个工作电极上的第一个电流，所述第一个电流包括分析物电流和干扰化合物电流；measuring a first current at the first working electrode, the first current comprising an analyte current and an interfering compound current;测量在所述第二个工作电极上的第二个电流，所述第二个电流包括分析物超电位电流和干扰化合物超电位电流，其中所述分析物超电位电流与所述分析物电流具有第一个正比关系，并且其中所述干扰化合物超电位电流与所述干扰化合物电流具有第二个正比关系；和Measuring a second current on the second working electrode, the second current comprising an analyte overpotential current and an interfering compound overpotential current, wherein the analyte overpotential current and the analyte current have a first proportional relationship, and wherein said interfering compound overpotential current has a second proportional relationship to said interfering compound current; and使用公式计算代表分析物浓度的校正电流值，所述公式是所述第一个电流、所述第二个电流、所述第一个正比关系和所述第二个正比例关系的函数；calculating a corrected current value representative of the analyte concentration using a formula that is a function of said first current, said second current, said first proportional relationship, and said second proportional relationship;其中所述分析物是葡萄糖，对于包括碳工作电极和亚铁氰化物氧化还原介体的所述电化学传感器，所述第一个电位是385毫伏-415毫伏，所述第二个电位是420毫伏-1000毫伏。Where the analyte is glucose, for the electrochemical sensor comprising a carbon working electrode and a ferrocyanide redox mediator, the first potential is 385 mV-415 mV and the second potential It's 420mV-1000mV.2.权利要求1的方法，其中所述公式是2. The method of claim 1, wherein said formula is${\mathrm{<span><span>A</span>A</span>}}_{\mathrm{<span><span>1</span>1</span>}}<span><span>=</span>=</span>\frac{{\mathrm{<span><span>W</span>W</span>}}_{\mathrm{<span><span>2</span>2</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>YW</span>YW</span>}}_{\mathrm{<span><span>1</span>1</span>}}}{\mathrm{<span><span>X</span>x</span>}<span><span>-</span>-</span>\mathrm{<span><span>Y</span>Y</span>}}$其中A₁是所述分析物电流，W₁是所述第一个电流，W₂是所述第二个电流，X是分析物电压效应因子，且Y是干扰化合物电压效应因子。where_A1 is the analyte current,_W1 is the first current,_W2 is the second current, X is the analyte voltage effect factor, and Y is the interfering compound voltage effect factor.3.权利要求1的方法，其中所述干扰化合物电流是由于至少一种选自下列的化合物的氧化而产生的：扑热息痛、抗坏血酸、胆红素、多巴胺、龙胆酸、谷胱甘肽、左旋多巴、甲基多巴、妥拉磺脲、甲苯磺丁脲和尿酸。3. The method of claim 1, wherein said interfering compound current is generated due to the oxidation of at least one compound selected from the group consisting of paracetamol, ascorbic acid, bilirubin, dopamine, gentisic acid, glutathione, L- Dopa, methyldopa, tolazamide, tolbutamide, and uric acid.4.权利要求1的方法，其中所述第一个正比关系是4. The method of claim 1, wherein said first proportional relationship isXxA₁＝A₂XxA₁ =A₂其中X是所述分析物电压效应因子，A₁是所述分析物电流，且A₂是所述分析物超电位电流。where X is the analyte voltage effect factor,_A1 is the analyte current, and_A2 is the analyte overpotential current.5.权利要求1的方法，其中所述第二个正比关系是5. The method of claim 1, wherein said second proportional relationship isYxI₁＝I₂YxI₁ =I₂其中Y是所述干扰化合物电压效应因子，I₁是所述干扰化合物电流，且I₂是所述干扰化合物超电位电流。where Y is the interfering compound voltage effect factor,_I is the interfering compound current, and_I is the interfering compound overpotential current.

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