JP4844817B2 - Electrochemical measurement assembly microelectrode for electrochemical measurement of a predetermined measurement object, electrochemical measurement aggregate microelectrode for electrochemical measurement of the predetermined measurement object, electrochemical measurement of the predetermined measurement object Electrochemical measurement method using assembly microelectrode for electrochemical measurement and electrochemical measurement apparatus provided with assembly microelectrode for electrochemical measurement for electrochemical measurement of the predetermined measurement object - Google Patents

Description

The present invention relates to a method for manufacturing an electrochemical measurement aggregate microelectrode for electrochemically measuring a predetermined measurement object, an electrochemical measurement aggregate microelectrode (hereinafter simply referred to as “aggregation”) for electrochemical measurement of the predetermined measurement object. Also referred to as a “microelectrode”.), An electrochemical measurement method using an assembly measurement microelectrode for electrochemical measurement of the predetermined measurement object, and an electrochemical for electrochemical measurement of the predetermined measurement object The present invention relates to an electrochemical measurement apparatus provided with a collective microelectrode for measurement.

  As is well known, there are two types of current flowing through the working electrode in the electrochemical measurement method, and one of them is the current flowing due to the electrochemical reaction of the measurement object that proceeds at the interface of the working electrode (hereinafter referred to as “signal current”). The other is the current that flows due to the composition of the base solution that dissolves the material of the working electrode and the measurement object (hereinafter referred to as “noise current”).

  In the present invention, “measurement” indicates a substance to be measured, and “analyte” indicates a solution obtained by dissolving the measurement in a base solution.

  In the amperometric analysis method (amperometry), coulometric analysis method (coulometry), and potentiometric analysis method (potentiometry), which are a type of electrochemical measurement method, the current flowing through the working electrode is the signal current including the noise current. Therefore, the ratio of the signal current S to the noise current N (hereinafter referred to as “S / N ratio”) must be sufficiently high. In particular, a low concentration analyte is analyzed with high accuracy. In cases it becomes very important.

  As a method for improving the S / N ratio, Non-Patent Document 1 described later uses a carbon paste electrode obtained by mixing carbon powder as a conductive material with liquid paraffin as an insulating material and kneading it as a working electrode. Is described. In the carbon paste electrode, carbon powder and liquid paraffin are kneaded and solidified at a specific ratio so that the carbon powders can be brought into contact with each other in liquid paraffin so that they can be energized. The signal current can be measured by bringing the resulting conductive portion into contact with the analyte. The carbon paste electrode is known to improve the S / N ratio because the noise current flowing due to the working electrode is kept small.

  In Non-Patent Document 2 described later, graphite powder was used instead of the carbon powder as a conductive material, and synthetic resin such as polychlorotrioethylene resin was used as an insulating material instead of the liquid paraffin. A Kel-F graphite electrode is described, and it is known that the same effect as the carbon paste electrode can be obtained by the Kel-F graphite electrode.

D.E.Weisshaar and D.E.Tallman, Anal.Chem., 55 (1983) 1146-1151, and references cited within. D.E.Tallman and D.E.Weisshaar, J.Liguid.Chromatography, 6 (12), 2157-2172 (1983)

  However, the carbon paste electrode described in Non-Patent Document 1 and the Kel-F graphite electrode described in Non-Patent Document 2 contain a certain amount or more of a powder of a conductive material in order to impart conductivity. As a result, the conductive material powder exposed on the surface cannot be intentionally adjusted, and as a result, the shape, quantity, or arrangement of the conductive material powder exposed on the surface and acting as an aggregated microelectrode This is a problem that it cannot be designed and manufactured arbitrarily. Along with this, there is also a problem that a stable quality cannot be maintained when commercialized.

  Therefore, the present inventor can freely design the shape of the conductive part in contact with the analyte and obtain a collective microelectrode with a high S / N ratio as a technical problem, and research to realize it. In the assembled microelectrode having an electrode layer that applies a voltage to the analyte in which the measurement object is dissolved, a plurality of strip-like conductive portions are provided over a predetermined range in the portion of the electrode layer that contacts the analyte. It is provided in a striped pattern with a space between each other, and the distance between adjacent band-shaped conductive portions in the portion of the electrode layer that contacts the analyte is set to be planar conductive over the predetermined range in the portion of the electrode layer that contacts the analyte. The thickness of the diffusion layer is determined based on the thickness of the diffusion layer that occurs when a predetermined time elapses after the analyte is brought into contact with the planar conductive portion of the virtual electrochemical measurement electrode provided with no gap and a pulse voltage is applied. Of the corrected diffusion layer obtained by multiplying the correction value by If the length is 200% or less, the S / N ratio can be improved, and a photolithographic method can be adopted as a manufacturing method in the case of an electrode layer composed of a conductive portion having such a shape. The inventors have obtained the remarkable knowledge that they can design freely, and have achieved the technical problem.

  Based on the above research, the reason why the fact that the S / N ratio can be improved by arranging the strip-like conductive portions in a striped condition under a predetermined condition will be described.

Conventionally width 2a _0, electrode strip conductive portion is provided with an electrode layer provided by one length L (L»2a ₀₎ (hereinafter, referred to as. "First conventional electrode") normal, the analyte by Research has been conducted on measurement by pulse voltammetry (Chronoamperometry) (J. Electroanal. Chem, 230 (1987) 61-67 and references cited within.). When the conventional studies are combined, the signal current I _F1 of the time change of the current flowing through the first conventional electrode can be approximately expressed as follows.
I _F1 = zFD * c2a ₀ L {(1 / (πDt) ^1/2 ) + (γ / 2a ₀ )} (1)
Here, z is the number of moving electrons, F is the Faraday constant, D is the diffusion coefficient of the measurement object, * c is the mother liquor concentration of the measurement object, and t is the time that has elapsed since the pulse voltage was applied to the analysis object. Further, γ is a correction value and is approximately expressed as follows.
γ = 1-1.1exp {−9.9 / ln12 (Dt / (2a ₀ ) ² )} (2)

Therefore, to measure the analyte in the normal pulse voltammetry by a set microelectrodes having an electrode layer provided in stripes over a predetermined range in units m present per length the strip conductor section is a center-to-center distance 2b ₀ We discussed a signal current I _F when. At this time,
equivalent diffusion zone = 2b _D L (3)
b _D = a ₀ + γ {(πDt) ^1/2 / 2} (4)
Concept was introduced and the equation representing the signal current I _F from equation (1), expressed as follows: approximately divided into a large area and t is small region.
(A) When t is a small region b ₀ ≧ b _D (5)
I _F / q = (zFD * c) (a ₀ / b ₀ ) {(1 / (πDt) ^1/2 ) + (γ / 2a ₀ )} (6)
(B) In the case where t is large, b ₀ ≦ b _D (7)
I _F / q = (zFD * c) {1 / (πDt) ^1/2 } (8)
In addition, q is a surface area of the predetermined range, and is represented by q = m2b ₀ L.

Here, the equation (8) is an electrode having an electrode layer provided with a planar conductive portion having a surface area q known conventionally (hereinafter referred to as “second conventional electrode”. consistent with expression for the signal current _{I Cottrell} chemical measurement electrode "), the signal current _{I F} of the set microelectrode, under the conditions of the equation (7), the signal current _{I Cottrell} second conventional electrode It turned out to be the same.

In addition, when the equation (7) is modified,
2b ₀ -2a ₀ ≦ γδ (9)
(Note that δ = (πDt) ^1/2 )
This equation (9) is obtained by applying the pulse voltage by applying an analyte to the interval 2b ₀ -2a ₀ between adjacent strip-like conductive portions of the aggregate microelectrode and the planar conductive portion of the second conventional electrode, and then t This shows the relationship with the numerical value δ ′ (hereinafter also referred to as “corrected diffusion layer thickness”) obtained by multiplying the correction layer γ by the thickness δ of the diffusion layer generated during the lapse of time.

  From this, when the condition of the above formula (9) is satisfied, in other words, when the interval between adjacent strip-like conductive portions of the assembly microelectrode is equal to or less than the thickness of the correction diffusion layer, the analyte is detected by the assembly microelectrode. It was found that the signal current generated when measuring the same magnitude as the signal current generated when measuring the analyte with the second conventional electrode. It is understood that this is because the diffusion layer generated around each band-shaped conductive portion grows with the passage of time and overlaps each other and spreads uniformly over the entire electrode layer. On the other hand, since the total surface area of the conductive part in the aggregated microelectrode is narrower than the total surface area of the conductive part in the second conventional electrode, the noise current generated when the analyte is measured by the aggregated microelectrode is analyzed by the second conventional electrode. This is smaller than the noise current generated when measuring an object. As a result, the S / N ratio is dramatically improved.

  However, if the interval between the adjacent band-like conductive portions of the collective microelectrode is made too short than the thickness of the correction diffusion layer, the total surface area of the conductive portion in the collective microelectrode approaches the total surface area of the conductive portion in the second conventional electrode, As a result, the noise current generated in the collective microelectrode increases, and the S / N ratio is improved only slightly.

  On the other hand, if the condition of the formula (9) is not satisfied, in other words, even if the interval between adjacent strip-like conductive portions in the collective microelectrode is longer than the thickness of the correction diffusion layer, a certain length Then, although the signal current generated in the collective microelectrode is smaller than the signal current generated in the second conventional electrode, the total surface area of the conductive portion in the collective microelectrode is also larger than the total surface area of the conductive portion in the second conventional electrode. Accordingly, the noise current generated in the collective microelectrode is also reduced, and the S / N ratio is relatively improved.

  Therefore, next, the interval between adjacent strip-shaped conductive parts required for obtaining a collective microelectrode with improved S / N ratio and capable of detecting a signal current with high accuracy in actual electrochemical measurement. The range was examined.

  First, in order to find the lower limit value of the interval between adjacent strip-shaped conductive portions, the noise current that affects the decrease in the S / N ratio when the interval between adjacent strip-shaped conductive portions and the interval is made shorter than the thickness of the correction diffusion layer. The relationship was derived.

That is, the relationship between the gap between adjacent strip-shaped conductive portions and the thickness δ ′ of the correction diffusion layer in the collective microelectrode where the noise current is the smallest while maintaining the same signal current as that of the second conventional electrode is the above (9) From the equation
2b ₀ -2a ₀ = δ '(10)
It becomes. Further, when the interval between the adjacent band-shaped conductive portions in the state in which the width a ₀ of the band-shaped conductive portion is maintained is α times (α <1),
2b ₀ '-2a ₀ = αδ' (11)
It becomes. Here, 2b ₀ ′ is the center-to-center distance between the adjacent band-shaped conductive parts after multiplying the interval between the adjacent band-shaped conductive parts by α.
And when transforming (10) and (11),
(2a ₀ / 2b ₀ ) = 1 / {1+ (δ ′ / 2a ₀ )} (12)
(2a ₀ / 2b ₀ ′) = 1 / {1 + α (δ ′ / 2a ₀ )} (13)
Furthermore, since 2a ₀ is sufficiently smaller than δ ′, the equations (12) and (13) are approximately:
(2a ₀ / 2b ₀ ) ≈ (2a ₀ / δ ′) (14)
(2a ₀ / 2b ₀ ′) ≈ (2a ₀ / δ ′) (1 / α) (15)
It becomes. Here, noise current I _B in the set microelectrodes, a proportionality constant is k _B,
I _B / q = (a ₀ / b ₀ ) k _B (16)
Since the noise current I _B is proportional to a ₀ / b ₀ , the equations (14) and (15) are expressed as follows: when the alpha <1), the noise current I _B indicates that becomes 1 / alpha times.

  Here, based on experience, the noise current generated when an analyte is measured by the collective microelectrode is measured by the collective microelectrode in which the distance between adjacent band-shaped conductive parts is the same as the thickness of the correction diffusion layer. If the current is larger than twice the noise current generated, it will be difficult to detect the signal current with high accuracy. Therefore, the distance between adjacent band-shaped conductive parts of the aggregate microelectrodes will be up to 50% of the thickness of the correction diffusion layer. You can see that it can be shortened.

  Next, in order to find the upper limit value of the interval between the adjacent strip-shaped conductive portions of the aggregated microelectrode, the S / N ratio is lowered when the interval between the adjacent strip-shaped conductive portions and the interval are longer than the thickness of the correction diffusion layer. The relationship with the influencing signal current was derived.

That is, when the interval between adjacent strip-like conductive parts is β times (β> 1),
2b ₀ -2a ₀ = βδ '(17)
And transforming equation (17),
2b ₀ = 2a ₀ + (β / 2) δ ′ + (β / 2) δ ′ (18)
It becomes. On the other hand, the signal current I _F in the case where the distance between the strip conductor portions adjacent in the set microelectrodes made longer than the thickness of the compensation diffusion layer may be represented by the general formula:.
I _F / q = (zFD * c) (1 / δ) {(2a ₀ + δ ′) / 2b ₀ } (19)
And when substituting (18) into (19) and transforming,
I _F / q = (zFD * c) (1 / δ) {1 / (1 + ((β−1) δ ′ / (2a ₀ + δ ′))}} (20)
It becomes. The part {1 / (1 + ((β−1) δ ′ / (2a ₀ + δ ′))} in the equation (20) is larger than 1 / β, and in particular, 2a ₀ is sufficiently larger than δ ′. smaller, approaching 1 / beta. This, when the beta times the thickness [delta] 'compensation diffusion layer spacing of the strip conductor portions adjacent set microelectrode (β> 1), the signal current I _F approximately 1 / β times.

  Here, empirically, the signal current generated when an analyte is measured by the collective microelectrode is measured by the collective microelectrode in which the distance between adjacent strip-shaped conductive portions is the same as the thickness of the correction diffusion layer. If the signal current is smaller than ½ times the signal current generated at this time, it is difficult to detect the signal current with high accuracy. Therefore, the interval between adjacent band-like conductive portions of the collective microelectrode is 200% of the thickness of the correction diffusion layer. It can be seen that the length can be increased.

  As described above, when the interval between the adjacent strip-like conductive portions of the assembly microelectrode is set to 200% or less of the thickness of the correction diffusion layer, the assembly microelectrode has an improved S / N ratio compared to the second conventional electrode. In addition, if the length is 50 to 200% of the thickness of the correction diffusion layer, the S / N ratio is improved, and the signal current can be detected with higher accuracy in actual electrochemical measurement. It was found that a collective microelectrode capable of

  The technical problem can be solved by the present invention as follows.

That is, the method for manufacturing a microelectrode for electrochemical measurement for electrochemical measurement of a predetermined measurement object according to the present invention includes an electrode layer for applying a voltage to an analyte in which the predetermined measurement object is dissolved. In a method for manufacturing a microelectrode for electrochemical measurement for electrochemical measurement of a predetermined measurement object, a state in which a plurality of strip-like conductive parts are spaced apart from each other over a predetermined range in a portion of the electrode layer that contacts the analyte The surface shape of the electrode for virtual electrochemical measurement in which the planar conductive portion is provided across the predetermined range in the portion of the electrode layer in contact with the analyte in the gap between the adjacent strip-shaped conductive portions. Obtained by multiplying the thickness of the diffusion layer by the correction value based on the thickness of the diffusion layer that occurs when 0.1 to 10 seconds elapses after the pulse voltage is applied by contacting the analyte in which the predetermined measurement object is dissolved in the conductive part. 50 to 200% or less of the thickness of the corrected diffusion layer age,
The correction value is
Dt / (2a ₀ ) ²
(D is the diffusion coefficient of the predetermined measurement object, t is the time elapsed since the analyte was brought into contact with the planar conductive portion of the virtual electrochemical measurement electrode and the pulse voltage was applied, and a ₀ is the width of the strip-shaped conductive portion. Is shown.)
And is a numerical value of 1 or less for correcting the thickness of the diffusion layer in accordance with the width of the strip-shaped conductive portion .

Further, the present invention provides a method for producing a microelectrode for electrochemical measurement for electrochemical measurement of the predetermined measurement object, wherein the correction value is:
1-1.1exp [-9.9 / ln12 (Dt / (2a ₀ ) ² )]
It is a numerical value calculated from

The electrochemical measurement aggregate microelectrode for electrochemically measuring a predetermined measurement object according to the present invention includes a predetermined measurement including an electrode layer that applies a voltage to an analyte in which the predetermined measurement object is dissolved. In a collective microelectrode for electrochemical measurement for electrochemically measuring an object, a plurality of strip-like conductive parts are provided in a striped manner over a predetermined range at a portion of the electrode layer that contacts the analyte. The gap between the adjacent band-shaped conductive portions in the portion of the electrode layer that contacts the analyte is virtually equal to the portion of the electrode layer that is in contact with the analyte over the predetermined range without any gap between the planar conductive portions. The thickness of the diffusion layer is determined based on the thickness of the diffusion layer that occurs when 0.1 to 10 seconds elapses after the pulse voltage is applied by bringing the analyte in which the predetermined measurement object is dissolved into contact with the planar conductive portion of the electrochemical measurement electrode. Correction diffusion obtained by multiplying the value by the correction value 50-200% of the thickness of has become a length,
The correction value is
Dt / (2a ₀ ) ²
(D is the diffusion coefficient of a predetermined measurement object, t is the time elapsed since the analyte was brought into contact with the planar conductive part of the electrode for virtual electrochemical measurement, and the pulse voltage was applied, a ₀ Indicates the width of the strip-shaped conductive portion. )
And a numerical value of 1 or less for correcting the thickness of the diffusion layer in accordance with the width of the strip-shaped conductive portion.

Further, the present invention provides an electrochemical measurement aggregate microelectrode for electrochemically measuring the predetermined measurement object, wherein the correction value is:
1-1.1exp [-9.9 / ln12 (Dt / (2a ₀ ) ² )]
It is a numerical value calculated from

Further, according to the present invention, in the collective microelectrode for electrochemical measurement for electrochemical measurement of any one of the predetermined measurement objects, the distance between adjacent band-shaped conductive portions in the portion of the electrode layer that contacts the analyte is corrected and diffused. The length is 100% of the thickness of the layer.

Further, according to the present invention, in the collective microelectrode for electrochemical measurement for electrochemical measurement of any one of the predetermined measurement objects , the plurality of strip-like conductive parts can be all energized in the portion of the electrode layer that does not contact the analyte. It is connected to.

In addition, the electrochemical measurement method according to the present invention uses an electrochemical measurement collective microelectrode for electrochemically measuring any one of the predetermined measurement objects .

  In the electrochemical measurement method according to the present invention, the analyte is advanced along the longitudinal direction of the strip-shaped conductive portion in the portion of the electrode layer that contacts the analyte.

  In the electrochemical measurement method of the present invention, the electrochemical reaction of the analyte is completed while the analyte passes through the portion of the electrode layer that contacts the analyte.

In addition, an electrochemical measurement apparatus according to the present invention includes an electrochemical measurement collective microelectrode for electrochemically measuring any one of the predetermined measurement objects .

  Furthermore, as another form of the collective microelectrode according to the present invention, a conductive portion is provided between adjacent strip-shaped conductive portions, and even if the conductive portion cannot pass through any of the strip-shaped conductive portions. Good. In addition, a portion of the electrode layer that does not come into contact with the analyte may be covered with an insulating material.

  According to the present invention, in the aggregated microelectrode, a plurality of strip-like conductive portions are provided in a striped manner in a state where they are spaced apart from each other over a predetermined range in the portion of the electrode layer that contacts the analyte, Apply a pulse voltage by contacting the analyte to the planar conductive portion of the electrode for virtual electrochemical measurement in which the planar conductive portion is provided over the predetermined range without gaps in the portion of the electrode layer that contacts the analyte. Since the length of the corrected diffusion layer obtained by multiplying the thickness of the diffusion layer generated after a lapse of a predetermined time by the correction value is 200% or less, the S / N ratio is improved.

  Further, if the interval between adjacent strip-like conductive portions of the aggregated microelectrode is 50 to 200% of the thickness of the correction diffusion layer, the S / N ratio is improved, and high accuracy is obtained in actual electrochemical measurement. Can detect the signal current.

  Furthermore, since the collective microelectrode according to the present invention can be manufactured by a photolithography method, the shape of the conductive portion can be freely designed.

  Therefore, it can be said that the industrial applicability of the present invention is very high.

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

Embodiment 1 FIG.

  FIG. 1 is a plan view showing a collective microelectrode according to the present embodiment. FIG. 2 is an AA end view showing the assembled microelectrode shown in FIG. FIG. 3 is a plan view showing a virtual electrochemical measurement electrode (the above-mentioned “second conventional electrode”). FIG. 4 is an end view showing a manufacturing procedure of the collective microelectrode shown in FIG. In these drawings, reference numeral 1 denotes an insulating layer 2 made of an insulating material, an electrode layer 3 formed by laminating a conductive material on the insulating layer 2, and an electrode layer 3 formed by laminating an insulating material on the electrode layer 3. It is a collective microelectrode provided with a cover layer 4 that partially covers.

  As an insulating material for forming the insulating layer 2, a synthetic resin such as ceramic, glass, acrylic, or silicon may be used. The insulating layer 2 may be a plate-like material formed by molding an insulating material, or a film-like material obtained by laminating an insulating material on a substrate. The thickness of the plate-like insulating layer 2 is not particularly limited, but is preferably 100 μm to 200 μm in view of convenience, and may be thicker.

  The electrode layer 3 includes a portion 5 (shown by a solid line in FIG. 1) that contacts the analyte and a portion 6 (shown by a dotted line in FIG. 1) that does not contact the analyte. In the portion 5 of the electrode layer 3 that is in contact with the analyte, a plurality of strip-like conductive portions 7 made of a conductive material laminated on the insulating layer 2 are striped in a state where the gap Y is spaced from each other over a predetermined range X. It is provided in the shape. In the portion 6 of the electrode layer 3 that does not come into contact with the analyte, a pair of terminal conductive portions 8, 8 made of a conductive material are bridged across both ends of each strip-shaped conductive portion 7 so that all the strip-shaped conductive portions 7 can be energized. Has been. The pair of terminal conductive portions 8 and 8 extend so as to be further extended from the strip-shaped conductive portion 7 located at the end, and the extended portions serve as terminals.

  The plurality of strip-like conductive portions 7 in the portion 5 in contact with the analyte of the electrode layer 3 is such that the interval Y between the adjacent strip-like conductive portions 7 is within a predetermined range X in the portion 5 in contact with the analyte of the electrode layer 3 shown in FIG. Instead of providing a plurality of strip-like conductive portions 7 over a predetermined range, a predetermined time is elapsed after the analyte is brought into contact with the virtual electrochemical measurement electrode 10 provided with the planar conductive portion 9 over the predetermined range X and a pulse voltage is applied. Multiply the thickness of the diffusion layer generated during the lapse (hereinafter simply referred to as “the thickness of the diffusion layer”) by a correction value of 1 or less for correcting the thickness of the diffusion layer in accordance with the width of the strip-shaped conductive portion. 200% or less of the thickness of the corrected diffusion layer obtained (hereinafter simply referred to as “corrected diffusion layer thickness”), preferably 50 to 200%, more preferably 50 to 150%. It has become.

  The interval between adjacent strip-shaped conductive portions 7 in the aggregated microelectrode 1 will be described in detail. When the interval between adjacent strip-shaped conductive portions 7 is 100% or less of the thickness of the correction diffusion layer, the aggregated microelectrode 1 The signal current generated when the analyte is measured with the electrode 1 has the same magnitude as the signal current generated when the analyte is measured with the virtual electrochemical measurement electrode 10, while the conductive portion 7 of the collective microelectrode 1 Since the total surface area is narrower than the total surface area of the conductive portion 9 in the virtual electrochemical measurement electrode 10, noise current generated when the analyte is measured with the aggregated microelectrode 1 is generated in the virtual electrochemical measurement electrode 10. It is smaller than the noise current that occurs when the analyte is measured. Therefore, the S / N ratio is always improved when the interval between the adjacent belt-like conductive portions 7 is set to a length of 100% or less of the thickness of the correction diffusion layer.

  Moreover, since the total surface area of the conductive portion 7 in the collective microelectrode 1 gradually becomes narrower as the distance between the adjacent band-shaped conductive portions 7 in the collective microelectrode 1 is gradually increased from the thickness of the correction diffusion layer, The noise current generated when the analyte is measured with the collective microelectrode 1 gradually decreases. However, the signal current generated when the analyte is measured with the collective microelectrode 1 is also applied to the virtual electrochemical measurement electrode 10. The signal current generated in the measurement is gradually reduced, and when the interval between the adjacent strip-like conductive portions 7 becomes too long, the S / N ratio is relatively lowered. For this reason, in order to obtain the collective microelectrode 1 capable of detecting the signal current with high accuracy, the upper limit value of the interval between the adjacent strip-like conductive portions 7 is set to a length of 200% or less of the thickness of the correction diffusion layer. Need to be restricted.

  Further, when the interval between the adjacent band-like conductive portions 7 in the collective microelectrode 1 is gradually shortened from the thickness of the correction diffusion layer, the magnitude of the signal current generated when the analyte is measured by the collective microelectrode 1. However, since the total surface area of the conductive portion 7 in the collective microelectrode 1 gradually increases, noise current generated when the analyte is measured by the collective microelectrode 1 causes the virtual electrochemical measurement electrode 10 to generate the analyte. It approaches the noise current that occurs when measured. For this reason, in order to obtain the collective microelectrode 1 capable of detecting a signal current with high accuracy in actual electrochemical measurement, the lower limit value of the interval between the adjacent strip-like conductive portions 7 is set to 50 of the thickness of the correction diffusion layer. % Should be limited.

  The narrower the width of the band-like conductive portion 7, the smaller the surface area of the entire conductive portion in the electrode layer 3, so that the noise current generated when the analyte is measured using the collective microelectrode 1 decreases.

  As a method of applying a pulse voltage by bringing an analyte into contact with the virtual electrochemical measurement electrode 10, a method of applying a pulse voltage to the analyte by bringing a stationary analyte in contact with the electrode in advance, In contrast, there is a method in which a constant voltage is applied in advance to bring a flowing analyte into contact with the electrode. In the present invention, adding a pulse voltage means that a constant voltage is instantaneously applied and then the constant voltage is maintained.

  In addition, the predetermined time is a time from when a pulse voltage is applied to an analyte generally used in electrochemical measurement until the measurement is performed. It is known that a highly accurate analysis result can be obtained by measuring when ˜10 s has elapsed. Note that if it is earlier than 0.1 s, the noise current tends to be detected, and if it is later than 10 s, the signal current tends to be small.

The correction value is expressed by a mathematical formula having at least Dt / (2a ₀ ) ² as a parameter. For example, as shown in the above formula (2), 1-1.1exp {−9.9 / ln12 (Dt / (2a ₀ ) ² )}
It can be expressed as. Note that equation (2) is approximately expressed.

  As the conductive material for forming the electrode layer 3, platinum, gold, carbon, tin dioxide, palladium-chrome alloy, or the like may be used.

  The cover layer 4 does not allow the terminal conductive parts 8 not arranged in stripes in the electrode layer 3 to come into contact with the analyte so that the analyte comes into contact only with the strip-like conductive parts 7 arranged in stripes in the electrode layer 3. Is covered. As an insulating material for forming the cover layer 4, an epoxy resin (including a photosensitive epoxy resin) or the like may be used.

  Next, a method for manufacturing the collective microelectrode according to the present embodiment will be described.

  First, an untreated electrode layer 11 is formed by laminating a conductive material on the insulating layer 2 made of an insulating material (see FIG. 4A). Next, a conductive layer to be obtained on the resist layer 12 is formed on the untreated electrode layer 11 after forming a resist layer 12 made of a negative type resist that cures in response to ultraviolet rays (see FIG. 4B). A mask pattern 13 for concealing a portion other than the portion corresponding to the shape is stacked (see FIG. 4C). Subsequently, after irradiating ultraviolet rays from above the mask pattern 13 to cure the portion of the resist not hidden by the mask pattern of the resist layer 12, the mask pattern 13 is removed and the resist layer 12 is ultraviolet cured. By removing the remaining resist, the resist layer remains only on the portion corresponding to the shape of the conductive portion to be obtained on the untreated electrode layer 11 (see FIG. 4D). Finally, a solvent for dissolving the conductive material is sprayed from above the resist layer 12 to dissolve the conductive material located in a portion of the untreated electrode layer 11 that is not covered with the resist layer 12 ((e in FIG. 4). )), And by removing the resist layer 12, the electrode layer 3 formed into the shape of the conductive part to be obtained is obtained (see (f) of FIG. 4). Thereafter, the portion of the electrode layer 3 that does not come into contact with the analyte is covered with an insulating material to form the cover layer 4 to obtain the aggregated microelectrode 1.

  When electrochemical measurement is performed using the collective microelectrode 1 according to the present embodiment, an electrolytic cell including the collective microelectrode 1 as a working electrode and a reference electrode and a counter electrode is manufactured. The three-electrode type electrochemical measurement may be performed by putting the analyte into the sample and connecting these three electrodes to a commonly used electrochemical measurement device. Depending on conditions and purposes, electrochemical measurement may be performed by a two-electrode system in which the reference electrode and the counter electrode are shared by one electrode.

  When applying a pulse voltage by bringing an analyte into contact with an aggregate microelectrode, a pulse voltage is applied while the aggregate microelectrode is in contact with an analyte in a stationary state in advance, or a constant voltage is applied to the aggregate microelectrode in advance. The added analyte may be brought into contact with the fluidized state. In the latter case, it is preferable that the flow direction of the analyte coincides with the longitudinal direction of the strip-like conductive portion 7 in the collective microelectrode 1. This is because when the flow direction of the analyte is made to coincide with the short direction of the strip-shaped conductive portion in the collective microelectrode, the analyte passes through the portion of the collective microelectrode that contacts the analyte in the strip-shaped conductive portion. Will pass alternately through the part where the electrode is laminated and the part where the band-like conductive part is not laminated, and the reaction will not proceed smoothly, while the flow direction of the analyte will change the length of the band-like conductive part in the collective microelectrode. When matched with the direction, the analyte always touched the part where the band-like conductive part was laminated or the part where the band-like conductive part was not laminated when passing through the part of the aggregated microelectrode contacting the analyte. This is because the reaction proceeds smoothly and the design proceeds easily.

  In addition, the assembly microelectrode and the electrode are configured so that the electrochemical reaction of the measurement object is completed between the time when the analyte in the fluidized state is brought into contact with the portion of the assembly microelectrode that is in contact with the analyte and the passage through the portion. If a cell that accommodates is designed, analysis can be performed with high accuracy by coulometry. In this case, the thickness and width of the cell, the concentration of the analyte, the flow rate and flow velocity when flowing the analyte, the length of the strip-shaped conductive portion of the portion of the assembly microelectrode that contacts the analyte, and the like are adjusted. There is a need.

  The method for manufacturing the aggregated microelectrode according to the present invention is not limited to the etching method used in the first embodiment, and may be formed by another photolithography method such as a lift-off method. Further, when the width of the strip-like conductive portion is 1 μm or less, it may be produced by a production method using X-rays. In addition, it is not limited to these manufacturing methods, It can manufacture also by other methods, such as an electron beam (EB) processing method and a focused ion beam (FIB) processing method.

  The collective microelectrode according to the present invention is designed based on a measurement value obtained by normal pulse voltammetry, but is not limited to normal pulse voltammetry, and has a high S / V even when used in other electrochemical measurement methods. The signal current can be detected by the N ratio.

Embodiment 2. FIG.

  The present embodiment is a modification of the electrode layer in the first embodiment. FIG. 5 is a plan view showing the collective microelectrode according to the present embodiment. In this figure, the same reference numerals as those in FIGS. 1 to 4 denote the same or corresponding parts.

  As shown in FIG. 5, in the electrode layer of the collective microelectrode according to the present embodiment, island-shaped conductive portions 14 made of a conductive material are formed between adjacent strip-shaped conductive portions 7. Cannot be energized with the belt-like conductive portion 7.

  Also in the present embodiment, the same operational effects as in the first embodiment can be obtained.

  First, a phosphate buffer solution of pH 7.0 0.1 mol / l is prepared as a basal solution, ferrocenecarboxylic acid 0.5 mmol / l is prepared as an analyte, and a solution in which the analyte is mixed into the basal solution as an analyte is prepared. Prepare a silver / silver chloride electrode (Ag / AgCl / 3.0 mol / l NaCl) (part number: RE-1B, manufactured by BAS) as the reference electrode, and prepare a platinum wire with a diameter of 1.0 mm as the counter electrode. As a measuring device, Elecrochemical Analyzer 624B (manufactured by ALS) was prepared.

Example 1.

Next, a gold thin film having a thickness of 1 to 1.5 μm was laminated on an insulating layer made of an alumina substrate having a thickness of 200 μm by a sputtering method to form an untreated electrode layer. Next, a resist solution was applied onto the untreated electrode layer by using a spin coating method, and then dried at 60 ° C. for 3 hours to form a resist layer. Next, the diffusion coefficient D of phyrocenecarboxylic acid D = 5 × 10 ⁻⁶ cm ² s ⁻¹ , the width a ₀ of the band-shaped conductive part in the assembly microelectrode scheduled to be completed, a ₀ = 10 μm, and Comparative Example 1 in which the analyte is described later Time (t = 1 s) elapsed from applying a pulse voltage to contact with the electrode ("virtual electrochemical measurement electrode" in the present invention) and measuring the thickness of the diffusion layer is substituted into equation (2). After calculating a correction value of 0.9, the correction value was multiplied by the diffusion layer thickness of 40 μm generated at t = 1 s to obtain a correction diffusion layer thickness of 36 μm. Then, a mask pattern in which positions corresponding to the shape of the electrode layer in which a plurality of strip-shaped conductive portions having a width of 10 μm, which are designed with reference to the thickness of the correction diffusion layer are arranged at intervals of 50 μm, is vacant is formed on the resist layer. After the lamination, ultraviolet rays were irradiated from above the mask pattern so that the integrated exposure amount was 300 mJ, and the portion of the resist layer not covered with the mask pattern was cured. Next, after removing the uncured portion of the resist layer by immersing it in a 35 ° C KOH solution for 1 minute, spray it with ferric chloride at 40 ° C for several tens of seconds and cover it with the resist layer of the untreated electrode layer. The part which was not done was removed. Finally, the remaining resist layer was removed by exposure treatment, and after forming an electrode layer in which strip-shaped conductive portions having a width of 10 μm were arranged in stripes at intervals of 50 μm, the strip-shaped conductive portions of the electrode layer were provided. The assembly microelectrode of Example 1 was obtained by covering the other part with epoxy resin while leaving the part in contact with the analyte 1 cm in length and 1 cm in width (width). The interval 50 μm between adjacent strip-like conductive portions is 140% of the correction diffusion layer thickness of 36 μm.

Example 2

  A correction value of 0.8 was calculated under the same conditions as in Example 1 except that the width of the strip-like conductive portion in the assembly microelectrode to be completed was set to 3 μm, and a correction diffusion layer thickness of 32 μm was obtained. Then, using a mask pattern that is designed with reference to the thickness of the correction diffusion layer and that has a pattern corresponding to the shape of the electrode layer in which a plurality of strip-shaped conductive portions having a width of 3 μm are arranged at intervals of 40 μm. After forming an electrode layer in which strip-shaped conductive portions having a width of 3 μm are arranged in stripes at intervals of 40 μm by the same production method as in Example 1, the portion of the electrode layer provided with the strip-shaped conductive portions is used as an analyte. The other part was covered with an epoxy resin while leaving 1 cm in length and 1 cm in width (width) as a part to be contacted to obtain an assembled microelectrode of Example 2. The interval 40 μm between adjacent strip-like conductive portions is 125% of the correction diffusion layer thickness of 32 μm.

Comparative Example 1

  After forming the electrode layer provided with the planar conductive portion by the same manufacturing method as in Example 1, the portion provided with the planar conductive portion of the electrode layer is defined as 1 cm in length × width as the portion in contact with the analyte. (Width) 1 cm was left, and the other part was covered with an epoxy resin to obtain an electrode of Comparative Example 1 (“electrode for virtual electrochemical measurement” in the present invention).

  Then, the following measurement experiments were performed using Examples 1 and 2 and Comparative Example 1.

  First, the aggregated microelectrode, silver-silver chloride electrode, and platinum wire of Example 1 connected to the electrochemical measurement apparatus are immersed in the stationary analyte, and the potential sweep rate is 10 mV / s and the voltage (E) is 0 to 0.6 V. The phylocene carboxylic acid was measured by cyclic voltammetry under the following conditions. Similarly, phylocenecarboxylic acid was measured by cyclic voltammetry using the electrode of Comparative Example 1. A cyclic voltammogram obtained by this measurement is shown in FIG. In FIG. 6, the horizontal axis indicates the potential of the collective microelectrode based on the silver-silver chloride electrode of Example 1, and the vertical axis indicates the current flowing through the collective microelectrode. The measurement result of the microelectrode is shown by a solid line, and the measurement result of the electrode of Comparative Example 1 is shown by a dotted line.

  According to FIG. 6, even when the aggregated microelectrode is measured, a reversible current-potential curve similar to that of the electrode of Comparative Example 1 conventionally used as an electrode for electrochemical measurement appears, and the strip-shaped conductive portion It can be seen that normal electrochemical measurement is possible even in an assembled microelectrode having an electrode layer provided in a striped pattern.

  Next, the aggregated microelectrode, silver-silver chloride electrode, and platinum wire of Example 1 connected to the electrochemical measurement apparatus were immersed in a basal solution in a stationary state, and the potential sweep rate was 10 mV / s and the voltage (E) was 0 to 0.6. Voltammograms were measured by cyclic voltammetry under conditions of V. Similarly, the voltammogram was measured by cyclic voltammetry using the electrode of Comparative Example 1. A cyclic voltammogram obtained by this measurement is shown in FIG. In FIG. 7, the horizontal axis indicates the potential of the collective microelectrode based on the silver-silver chloride electrode of Example 1, and the vertical axis indicates the current flowing through the collective microelectrode. The measurement result of the microelectrode is shown by a solid line, and the measurement result of the electrode of Comparative Example 1 is shown by a dotted line.

  According to FIG. 7, compared with the case where the electrode of Comparative Example 1 was measured, the value of the current when measured with the collective microelectrode of Example 1 was smaller. From this, it can be seen that in a collective microelectrode provided with an electrode layer in which strip-like conductive portions are provided in stripes, the noise current generated from the base solution, which causes a decrease in the S / N ratio, can be kept small.

  Next, the aggregated microelectrode, silver-silver chloride electrode, and platinum wire of Example 1 connected to the electrochemical measurement apparatus are immersed in the stationary analyte, and pulsed under the conditions of applied voltage of 0.6 V and current sampling time of 1 s. -Ferrocene carboxylic acid was measured by voltammetry. Similarly, ferrocenecarboxylic acid was measured by pulse voltammetry using the assembled microelectrode of Example 2 or the electrode of Comparative Example 1. A calibration curve in which the signal current value obtained by this measurement is plotted against the concentration of ferrocenecarboxylic acid is shown in FIGS. 8 to 10, the horizontal axis indicates the concentration of ferrocenecarboxylic acid, the vertical axis indicates the signal current value, the circle indicates an average of five measurement results, and two circles are sandwiched between the circles. The horizontal line of the book indicates the confidence limit.

When the detection limit of ferrocenecarboxylic acid at each electrode is calculated using the 3s _B method with reference to FIGS. 8 to 10, the detection limit of Example 1 is 1.3 μmol / l, and the detection limit of Example 2 is 0.31 μmol / l. The detection limit of Comparative Example 1 is 5.2 μmol / l, and it can be seen that the detection limit of the assembled microelectrodes of Examples 1 and 2 is improved as compared with the electrode of Comparative Example 1.

FIG. 3 is a plan view showing the collective microelectrode according to the first embodiment. FIG. 2 is an AA end view showing the assembled microelectrode shown in FIG. 1. It is the top view which showed the electrode for virtual electrochemical measurements. It is the end elevation which showed the preparation procedure of the assembly | stacking microelectrode shown in FIG. FIG. 5 is a plan view showing a collective microelectrode according to a second embodiment. 2 is a cyclic voltammogram in which an analyte is measured with the assembled microelectrode of Example 1 and the electrode of Comparative Example 1. FIG. 2 is a cyclic voltammogram of the basal solution measured by the assembled microelectrode of Example 1 and the electrode of Comparative Example 1. FIG. 2 is a calibration curve obtained by measuring an analyte with the collective microelectrode of Example 1. FIG. 3 is a calibration curve obtained by measuring an analyte with the collective microelectrode of Example 2. FIG. 2 is a calibration curve obtained by measuring an analyte with the electrode of Comparative Example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Collective microelectrode for electrochemical measurements 2 Insulating layer 3 Electrode layer 4 Cover layer 5 Part in contact with analyte 6 Part in non-contact with analyte 7 Strip-like conductive part 8 Terminal conductive part 9 Planar conductive part 10 For virtual electrochemical measurement Electrode 11 Untreated electrode layer 12 Resist layer 13 Mask pattern 14 Island-like conductive part

Claims (10)

In the method of manufacturing an aggregate microelectrode for electrochemical measurement for electrochemical measurement of a predetermined measurement object having an electrode layer for applying a voltage to an analyte in which the predetermined measurement object is dissolved, A plurality of strip-shaped conductive portions are provided in a striped pattern in a state where they are in contact with each other over a predetermined range, and the interval between adjacent strip-shaped conductive portions is extended to the portion in contact with the analyte of the electrode layer over the predetermined range. Occurred 0.1 to 10 seconds after applying a pulse voltage by bringing an analyte in which a predetermined measurement substance is dissolved into contact with the planar conductive portion of the electrode for virtual electrochemical measurement in which the planar conductive portion is provided without gaps. The length of the corrected diffusion layer obtained by multiplying the thickness of the diffusion layer by the correction value with reference to the thickness of the diffusion layer is 50 to 200% or less,
The correction value is
Dt / (2a ₀ ) ²
(D is the diffusion coefficient of a predetermined measurement object, t is the time elapsed since the analyte was brought into contact with the planar conductive part of the electrode for virtual electrochemical measurement, and the pulse voltage was applied, a ₀ Indicates the width of the strip-shaped conductive portion. )
Electrochemical measurement for electrochemical measurement of a predetermined measurement object, characterized in that the numerical value is based on the above and is a numerical value of 1 or less for correcting the thickness of the diffusion layer in accordance with the width of the strip-like conductive portion For producing a microelectrode for an assembly. The correction value is
1-1.1exp [-9.9 / ln12 (Dt / (2a ₀ ) ² )]
The method for producing an assembled microelectrode for electrochemical measurement for electrochemical measurement of a predetermined measurement object according to claim 1, which is a numerical value calculated from: A portion of an electrode layer in contact with an analyte in an electrochemical measurement aggregate microelectrode for electrochemically measuring a predetermined measurement object having an electrode layer for applying a voltage to an analyte in which the predetermined measurement object is dissolved A plurality of strip-shaped conductive portions are provided in a striped manner in a state of being spaced apart from each other over a predetermined range, and the interval between adjacent strip-shaped conductive portions in the portion of the electrode layer that contacts the analyte is analyzed in the electrode layer. A pulse is obtained by bringing an analyte in which a predetermined measurement substance is dissolved into contact with a planar conductive portion of an electrode for virtual electrochemical measurement in which a planar conductive portion is provided over the predetermined range with no gap at a portion in contact with the target. Based on the thickness of the diffusion layer that occurs when 0.1 to 10 seconds elapses after the voltage is applied, the thickness of the diffusion layer is multiplied by the correction value to be 50 to 200% of the corrected diffusion layer thickness. And
The correction value is
Dt / (2a ₀ ) ²
(D is the diffusion coefficient of a predetermined measurement object, t is the time elapsed since the analyte was brought into contact with the planar conductive part of the electrode for virtual electrochemical measurement, and the pulse voltage was applied, a ₀ Indicates the width of the strip-shaped conductive portion. )
Electrochemical measurement for electrochemical measurement of a predetermined measurement object, characterized in that the numerical value is based on the above and is a numerical value of 1 or less for correcting the thickness of the diffusion layer in accordance with the width of the strip-like conductive portion Assembly microelectrode. The correction value is
1-1.1exp [-9.9 / ln12 (Dt / (2a ₀ ) ² )]
The collective microelectrode for electrochemical measurement for electrochemically measuring a predetermined measurement object according to claim 3, which is a numerical value calculated from: 5. The predetermined measurement object according to claim 3, wherein an interval between adjacent band-shaped conductive portions in a portion in contact with the analyte of the electrode layer is 100% of the thickness of the correction diffusion layer. Collective microelectrode for electrochemical measurements for electrochemical measurements. 6. For electrochemical measurement for electrochemical measurement of a predetermined measurement object according to any one of claims 3 to 5, wherein all of the plurality of strip-like conductive parts are connected so that they can be energized in a portion of the electrode layer that does not contact the analyte. Aggregated microelectrode. An electrochemical measurement method using an assembled microelectrode for electrochemical measurement for electrochemical measurement of the predetermined measurement object according to any one of claims 3 to 6. 8. The electrochemical measurement collective microelectrode for electrochemically measuring a predetermined measurement object according to claim 7, wherein the analyte is advanced along the longitudinal direction of the strip-shaped conductive portion in the portion of the electrode layer that contacts the analyte. Had electrochemical measurements. 9. The electrochemical measurement aggregate microparticle for electrochemical measurement of a predetermined measurement object according to claim 8, wherein the electrochemical reaction of the measurement object is completed while the analyte passes through a portion of the electrode layer that contacts the analyte. Electrochemical measurement method using electrodes. An electrochemical measurement apparatus comprising an assembled microelectrode for electrochemical measurement for electrochemical measurement of the predetermined measurement object according to any one of claims 3 to 6.

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