WO2008095238A1 - Electrode reactivation in a microfluidic device - Google Patents

Electrode reactivation in a microfluidic device Download PDF

Info

Publication number
WO2008095238A1
WO2008095238A1 PCT/AU2008/000134 AU2008000134W WO2008095238A1 WO 2008095238 A1 WO2008095238 A1 WO 2008095238A1 AU 2008000134 W AU2008000134 W AU 2008000134W WO 2008095238 A1 WO2008095238 A1 WO 2008095238A1
Authority
WO
WIPO (PCT)
Prior art keywords
activation
activation pulse
pulse
electrodes
electrode
Prior art date
Application number
PCT/AU2008/000134
Other languages
French (fr)
Inventor
Cedric Robillot
Original Assignee
Cleveland Biosensors Pty Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from AU2007900537A external-priority patent/AU2007900537A0/en
Application filed by Cleveland Biosensors Pty Ltd filed Critical Cleveland Biosensors Pty Ltd
Publication of WO2008095238A1 publication Critical patent/WO2008095238A1/en

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/28—Electrolytic cell components
    • G01N27/30—Electrodes, e.g. test electrodes; Half-cells
    • G01N27/38—Cleaning of electrodes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
    • B01L3/00—Containers or dishes for laboratory use, e.g. laboratory glassware; Droppers
    • B01L3/50—Containers for the purpose of retaining a material to be analysed, e.g. test tubes
    • B01L3/502—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures
    • B01L3/5027—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip
    • B01L3/502707—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip characterised by the manufacture of the container or its components

Definitions

  • This invention relates to electrodes for microfluidic devices. In particular it relates to a process for reactivation (depassivation) of an electrode.
  • Microfluidic devices incorporating microchannels and detection zones are known for measurement of analytes in a fluid.
  • the detection zones may employ a variety of detection systems.
  • a novel microfluidic device is described in our co- pending international patent application number PCT/AU2005/001341.
  • a detection system is described that incorporates an interdigitated electrode.
  • An interdigitated electrode is based on two multi-finger electrodes, one cathode and one anode.
  • the materials used to produce the electrode can vary depending on the substrate and the electrochemical process employed, but gold and platinum are frequently used.
  • the geometry and dimensions of the electrode can also vary depending on the application including the number and shape of fingers, as well as their length, width, thickness and distance from each other.
  • Electrodes can be incorporated into the microfluidic device in a variety of ways.
  • One approach is to form the electrode on a separate element which is incorporated into the microfluidic device by flip-chip bonding techniques or by direct gluing.
  • Another approach is to form the electrode directly into the microfluidic device by vapor deposition or printing.
  • Electrodes are typically prone to passivation (reduction in sensitivity), by adsorption of chemicals (organics or inorganics) on the surface or by oxidation or reduction of the electrode material.
  • the activity of the electrode (and therefore the accuracy of measurements) will therefore vary depending on storage time, usage and operating conditions.
  • the shelf-life of the microfluidic detection device is directly related to the shelf-life of the electrodes so to obtain an accurate, sensitive and reproducible result, it is beneficial to re-activate (or depassivate) the electrode.
  • the invention resides in a method of depassivating electrodes in a microfluidic device by: flooding the electrodes with a conducting solution; applying a first activation pulse; applying a second activation pulse of inverse polarity to the first activation pulse; repeatedly applying the first activation pulse and the second activation pulse until the electrode is reactivated.
  • a rest period is provided after the first activation pulse and after the second activation pulse.
  • Fig 1 is a sketch of an interdigitated electrode
  • Fig 2 is a flowchart of the depassivation process
  • Fig 3 shows a depassivation cycle
  • Fig 4 shows the effect of depassivation
  • Fig 5 shows measured current and voltage of a depassivation cycle
  • Fig 6 demonstrates the reproducibility of a depassivated electrode
  • Fig 7 shows a first alternative depassivation cycle
  • Fig 8 shows a second alternative depassivation cycle
  • Fig 9 is a sketch of a first alternative to the electrode of Fig 1 ;
  • Fig 10 is a sketch of a second alternative to the electrode of Fig 1 ;
  • Fig 11 is a sketch of a third alternative to the electrode of Fig 1.
  • FIG 16 there is shown the interdigitated electrode depicted in FIG 16 of our co-pending international application number PCT/ AU2005/001341.
  • the electrode 10 consists of an anode 11 and a cathode 12.
  • the anode 11 is formed from a contact pad 13 and a number of anode fingers 14.
  • the cathode 12 is formed from a contact pad 15 and a number of cathode fingers 16.
  • the anode fingers 14 and cathode fingers 16 are interleaved.
  • FIG. 1 A flowchart outlining the reactivation (or depassivation) process is provided in Fig 2. Initially the electrode is flooded with a conductive solution. A first activation pulse is applied to the electrodes followed by a rest period. Then a reverse polarity activation pulse is applied followed by another rest period. The cycle is repeated until reactivation has been obtained to a desired level.
  • Each cycle consists of a positive high-current spike, followed by a resting phase at a potential close to zero, followed by a negative high-current spike, followed by a resting phase at a potential close to zero, as shown in Fig 3.
  • the conductive solution only needs to be conductive enough for the electrochemical process to take place (for example biological buffers containing enough salts would meet the requirements).
  • a typical buffer solution would be Tris or Phosphate Buffer 0.02M with 0.4M Sodium Chloride.
  • a typical activation current is in the ⁇ 5-50 ⁇ A range and the voltages applied can reach several volts.
  • the rest period may be 900 milliseconds after a pulse is applied for 100 milliseconds. The protocol will vary for different electrodes.
  • the reactivation protocol can be applied at the beginning of each new assay to ensure the maximal sensitivity is reached by the detection device. This avoids shelf-life issues and guarantees good reproducibility from device to device, which is especially important when these devices are disposable.
  • Fig 4 shows the effect of the reactivation process described.
  • the activity of an electrode is measured by chronoamperometry before and after activation.
  • the conductive solution in this example contains 2 ⁇ M ferrocyanide and 2 ⁇ M ferricyanide as a standard for the chronoamperometry measurement. It is clear from Fig 4 that the activity has been improved approximately three-fold.
  • the initial activity 41 is about 1OnA. After activation 42 the final activity 43 is about 3OnA.
  • Fig 5 displays the actual measured voltage and current for a typical activation sequence.
  • Fig 6 shows the activity of a 2 ⁇ M Ferrocyanide/ferricyanide standard solution. Each measurement of activity is made after activation using the process of Fig 2. The 46 measurements are spread in a range of only 7nA from 19nA to 26nA. The narrow distribution has a mean of 23.5nA and a standard deviation of 1.8nA. This demonstrates the reproducibility of the reactivation protocol.
  • the reactivation process outlined in Fig 2 obtains reproducible, accurate and sensitive signals from electrodes integrated into a microfluidic device.
  • the electrodes can be re-used multiple times and yet maintain sensitivity.
  • the process may be varied to suit particular electrode designs. For instance, the rest period may be varied over the activation cycle.
  • the pulse width, pulse intensity and pulse shape may increase or decrease over the activation cycle or from reactivation to reactivation.
  • An alternate pulse sequence is shown in Fig 7 where the pulse intensity and pulse width are varied throughout the sequence. For instance, it can be seen that the intensity of pulse 71 is greater that pulse 72.
  • Fig 8 there is shown a pulse sequence with different pulse shape.
  • Each pulse 80 has a saw-tooth shape rather than the square pulse of Fig 7.
  • the invention is not limited to this particular case. It may be that in certain applications there is advantage in a pulse sequence of two or more pulses of the same polarity followed by two or more pulses of the opposite polarity.
  • the invention is not limited to the particular electrode design shown in Fig 1.
  • Other electrode designs may include plate electrodes as shown in Fig 9.
  • the anode 91 is a flat plate.
  • the cathode 92 is another flat plate substantially parallel to, but separated from, the anode. This specific design can present some benefits in terms of sample volume and response time.
  • the anode 100 is a central disc.
  • the cathode 102 is a concentric electrode as shown in Fig 10. This electrode design is useful to minimize interference between the anode and cathode.
  • an array of micro-pillars 111 , 112 may also be particularly appropriate, as depicted in Fig 11.
  • the micro-pillars can have varying dimensions, and may be micro-dots.
  • the invention is not limited to the two- electrode designs. Three electrode designs (where one electrode is a reference electrode) may also re reactivated.
  • Pulse generators to produce the pulse sequences described may be obtained commercially, in the form of portable potentiostats/galavanostats such as the PG580 from Uniscan, or in the form of desktop systems such as the EC Epsilon from Bioanalytical Systems.

Abstract

A method of depassivating electrodes in a microfluidic device by flooding the electrodes with a conducting solution, then applying a first activation pulse followed by a second activation pulse of inverse polarity, and repeatedly applying the first and second activation pulses until the electrodes are reactivated.

Description

ELECTRODE REACTIVATION IN A MICROFLUIDIC DEVICE
This invention relates to electrodes for microfluidic devices. In particular it relates to a process for reactivation (depassivation) of an electrode.
BACKGROUND TO THE INVENTION
Microfluidic devices incorporating microchannels and detection zones are known for measurement of analytes in a fluid. The detection zones may employ a variety of detection systems. A novel microfluidic device is described in our co- pending international patent application number PCT/AU2005/001341. In one embodiment of the device a detection system is described that incorporates an interdigitated electrode.
An interdigitated electrode is based on two multi-finger electrodes, one cathode and one anode. The materials used to produce the electrode can vary depending on the substrate and the electrochemical process employed, but gold and platinum are frequently used. The geometry and dimensions of the electrode can also vary depending on the application including the number and shape of fingers, as well as their length, width, thickness and distance from each other.
Electrodes can be incorporated into the microfluidic device in a variety of ways. One approach is to form the electrode on a separate element which is incorporated into the microfluidic device by flip-chip bonding techniques or by direct gluing. Another approach is to form the electrode directly into the microfluidic device by vapor deposition or printing.
Electrodes are typically prone to passivation (reduction in sensitivity), by adsorption of chemicals (organics or inorganics) on the surface or by oxidation or reduction of the electrode material. The activity of the electrode (and therefore the accuracy of measurements) will therefore vary depending on storage time, usage and operating conditions. The shelf-life of the microfluidic detection device is directly related to the shelf-life of the electrodes so to obtain an accurate, sensitive and reproducible result, it is beneficial to re-activate (or depassivate) the electrode. However, once the electrode system is incorporated into the microfluidic device, it becomes impossible or very impractical to use known depassivation techniques.
As the range of applications of microchannel devices expands the demand on detection accuracy becomes more severe. It is necessary to be able to operate electrodes at a high and reproducible sensitivity.
OBJECT QF THE INVENTION
It is an object of the present invention to provide a process for depassivating electrodes in a microfluidic device.
Further objects will be evident from the following description.
DISCLOSURE OF THE INVENTION
In one form, although it need not be the only or indeed the broadest form, the invention resides in a method of depassivating electrodes in a microfluidic device by: flooding the electrodes with a conducting solution; applying a first activation pulse; applying a second activation pulse of inverse polarity to the first activation pulse; repeatedly applying the first activation pulse and the second activation pulse until the electrode is reactivated.
Suitably a rest period is provided after the first activation pulse and after the second activation pulse.
BRIEF DETAILS OF THE DRAWINGS
To assist in understanding the invention preferred embodiments will now be described with reference to the attached figures in which: Fig 1 is a sketch of an interdigitated electrode;
Fig 2 is a flowchart of the depassivation process;
Fig 3 shows a depassivation cycle;
Fig 4 shows the effect of depassivation; Fig 5 shows measured current and voltage of a depassivation cycle;
Fig 6 demonstrates the reproducibility of a depassivated electrode;
Fig 7 shows a first alternative depassivation cycle;
Fig 8 shows a second alternative depassivation cycle;
Fig 9 is a sketch of a first alternative to the electrode of Fig 1 ; Fig 10 is a sketch of a second alternative to the electrode of Fig 1 ; and
Fig 11 is a sketch of a third alternative to the electrode of Fig 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In describing different embodiments of the present invention common reference numerals are used to describe like features.
Referring to Fig 1 there is shown the interdigitated electrode depicted in FIG 16 of our co-pending international application number PCT/ AU2005/001341. The electrode 10 consists of an anode 11 and a cathode 12. The anode 11 is formed from a contact pad 13 and a number of anode fingers 14. Similarly, the cathode 12 is formed from a contact pad 15 and a number of cathode fingers 16. As is evident in FIG 1 , the anode fingers 14 and cathode fingers 16 are interleaved.
It will be appreciated that the labeling as anode and cathode is somewhat arbitrary and merely for convenience. The anode and cathode have identical structures and are interchangeable. It will also be appreciated that the specific structure of Fig 1 is merely illustrative to assist with describing the invention. The invention is not limited to the particular electrode design shown in Fig 1. A flowchart outlining the reactivation (or depassivation) process is provided in Fig 2. Initially the electrode is flooded with a conductive solution. A first activation pulse is applied to the electrodes followed by a rest period. Then a reverse polarity activation pulse is applied followed by another rest period. The cycle is repeated until reactivation has been obtained to a desired level. Each cycle consists of a positive high-current spike, followed by a resting phase at a potential close to zero, followed by a negative high-current spike, followed by a resting phase at a potential close to zero, as shown in Fig 3. It will be appreciated that the resting phase is optional. The conductive solution only needs to be conductive enough for the electrochemical process to take place (for example biological buffers containing enough salts would meet the requirements). A typical buffer solution would be Tris or Phosphate Buffer 0.02M with 0.4M Sodium Chloride. A typical activation current is in the ±5-50 μA range and the voltages applied can reach several volts. As shown in Fig 3 the rest period may be 900 milliseconds after a pulse is applied for 100 milliseconds. The protocol will vary for different electrodes.
The reactivation protocol can be applied at the beginning of each new assay to ensure the maximal sensitivity is reached by the detection device. This avoids shelf-life issues and guarantees good reproducibility from device to device, which is especially important when these devices are disposable.
Fig 4 shows the effect of the reactivation process described. The activity of an electrode is measured by chronoamperometry before and after activation. The conductive solution in this example contains 2μM ferrocyanide and 2μM ferricyanide as a standard for the chronoamperometry measurement. It is clear from Fig 4 that the activity has been improved approximately three-fold. The initial activity 41 is about 1OnA. After activation 42 the final activity 43 is about 3OnA.
In practice the applied voltage and current do not have to be a perfect square wave as voltage can be regulated to reach the desired activation currents. Fig 5 displays the actual measured voltage and current for a typical activation sequence.
The inventors have found that the reactivation process can be repeated numerous times, thus significantly extending the life of the microfluidic device. The inventors have found that the reactivation process helps minimize electrode to electrode variation and therefore improve assay reproducibility. Fig 6 shows the activity of a 2μM Ferrocyanide/ferricyanide standard solution. Each measurement of activity is made after activation using the process of Fig 2. The 46 measurements are spread in a range of only 7nA from 19nA to 26nA. The narrow distribution has a mean of 23.5nA and a standard deviation of 1.8nA. This demonstrates the reproducibility of the reactivation protocol.
The reactivation process outlined in Fig 2 obtains reproducible, accurate and sensitive signals from electrodes integrated into a microfluidic device. The electrodes can be re-used multiple times and yet maintain sensitivity. The process may be varied to suit particular electrode designs. For instance, the rest period may be varied over the activation cycle. Similarly, the pulse width, pulse intensity and pulse shape may increase or decrease over the activation cycle or from reactivation to reactivation. An alternate pulse sequence is shown in Fig 7 where the pulse intensity and pulse width are varied throughout the sequence. For instance, it can be seen that the intensity of pulse 71 is greater that pulse 72.
In Fig 8 there is shown a pulse sequence with different pulse shape. Each pulse 80 has a saw-tooth shape rather than the square pulse of Fig 7.
Although the common case of alternating positive and negative pulses is shown in the figures the invention is not limited to this particular case. It may be that in certain applications there is advantage in a pulse sequence of two or more pulses of the same polarity followed by two or more pulses of the opposite polarity. As mentioned earlier the invention is not limited to the particular electrode design shown in Fig 1. Other electrode designs may include plate electrodes as shown in Fig 9. The anode 91 is a flat plate. Similarly, the cathode 92 is another flat plate substantially parallel to, but separated from, the anode. This specific design can present some benefits in terms of sample volume and response time.
Another electrode option is shown in Fig 10. The anode 100 is a central disc. The cathode 102 is a concentric electrode as shown in Fig 10. This electrode design is useful to minimize interference between the anode and cathode. For the microfluidic device application the inventor speculates that an array of micro-pillars 111 , 112 may also be particularly appropriate, as depicted in Fig 11. The micro-pillars can have varying dimensions, and may be micro-dots.
It will also be appreciated that the invention is not limited to the two- electrode designs. Three electrode designs (where one electrode is a reference electrode) may also re reactivated.
Persons skilled in the art will appreciate that the equipment required to work the invention is readily available. Pulse generators to produce the pulse sequences described may be obtained commercially, in the form of portable potentiostats/galavanostats such as the PG580 from Uniscan, or in the form of desktop systems such as the EC Epsilon from Bioanalytical Systems.
Throughout the specification the aim has been to describe the preferred embodiments of the invention without limiting the invention to any one embodiment or specific collection of features.

Claims

1. A method of depassivating electrodes in a microfluidic device by: flooding the electrodes with a conducting solution; applying a first activation pulse; applying a second activation pulse of inverse polarity to the first activation pulse; repeatedly applying the first activation pulse and the second activation pulse until the electrodes are reactivated.
2. The method of claim 1 including applying one or more further activation pulses after the first activation pulse or the second activation, the further activation pulses having the same polarity as the first activation pulse or second activation pulse respectively.
3. The method of claim 1 further including a rest period after at least the first activation pulse and/or after at least the second activation pulse.
4. The method of claim 1 wherein the electrodes are an interdigitated array.
5. The method of claim 1 wherein the electrodes are a pair of parallel plates.
6. The method of claim 1 wherein the electrodes are a pair of concentric plates.
7. The method of claim 1 wherein the electrodes are a micropillar array.
8. The method of claim 1 wherein the electrodes include a reference electrode.
9. The method of claim 1 wherein the first activation pulse and the second activation pulse are nominally square wave pulses.
10. The method of claim 1 wherein the first activation pulse and the second activation pulse are nominally saw-tooth wave pulses.
11. The method of claim 1 wherein the current of the first activation pulse and the second activation pulse is in the range ±5-50 μA.
12. The method of claim 1 wherein the voltage of the first activation pulse and the second activation pulse is up to 2.5 volts.
13. The method of claim 1 wherein voltage is regulated to achieve a desired activation current.
14. The method of claim 1 wherein the pulse duration of the first activation pulse and the second activation pulse is up to 200 milliseconds.
15. The method of claim 1 wherein the pulse duration of the first activation pulse and the second activation pulse is 100 milliseconds.
16. The method of claim 3 wherein the rest period is up to 2000 milliseconds.
17. The method of claim 1 wherein the rest period is 900 milliseconds.
18. The method of claim 1 wherein an activity of the electrodes is increased by at least a factor of two.
19. The method of claim 1 wherein the conducting solution is a salt buffer.
PCT/AU2008/000134 2007-02-05 2008-02-05 Electrode reactivation in a microfluidic device WO2008095238A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AU2007900537A AU2007900537A0 (en) 2007-02-05 Electrode reactivation in a biochip
AU2007900537 2007-02-05

Publications (1)

Publication Number Publication Date
WO2008095238A1 true WO2008095238A1 (en) 2008-08-14

Family

ID=39681178

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/AU2008/000134 WO2008095238A1 (en) 2007-02-05 2008-02-05 Electrode reactivation in a microfluidic device

Country Status (1)

Country Link
WO (1) WO2008095238A1 (en)

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005024408A1 (en) * 2003-08-21 2005-03-17 Colorado State University Research Foundation Direct determination of carbohydrates, amino acids and antibiotics by microchip electrophoresis with pulsed amperometric detection

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005024408A1 (en) * 2003-08-21 2005-03-17 Colorado State University Research Foundation Direct determination of carbohydrates, amino acids and antibiotics by microchip electrophoresis with pulsed amperometric detection

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
FANGUY ET AL.: "Pulsed amperometric detection of carbohydrate on an electrophoretic microchip", ANALYST, vol. 127, 2002, pages 1021 - 1023, Retrieved from the Internet <URL:http://www.rsc.org/delivery/_ArticleLinking/DisplayArticleForFree.cfm?doi=b205980k&JournalCode=AN> *
LI: "Microfluidic Lab-on-a-Chip for Chemical and Biological Analysis and Discovery", CRC PRESS, CHROMATOGRAPHIC SCIENCE SERIES, vol. 94, 2006, Retrieved from the Internet <URL:http://www.***.com/books?id=we1gmMOW_ukC> *

Similar Documents

Publication Publication Date Title
Pecková et al. Boron-doped diamond film electrodes—new tool for voltammetric determination of organic substances
Tokuda et al. Voltammetry at partially covered electrodes: Part III. Faradaic impedance measurements at model electrodes
TWI227066B (en) Electrochemical cell
JP2002514744A5 (en)
Moldenhauer et al. Rapid and direct determination of diffusion coefficients using microelectrode arrays
DK0986748T3 (en) Electrodes for measuring analytes in small sample volumes
US20120326732A1 (en) Nanosensor and method of detecting target molecule by using the same
CA2474912A1 (en) Electrochemical biosensor strip for analysis of liquid samples
DE60220035D1 (en) SENSOR ARRAY DEVICE AND METHOD FOR MONITORING ELECTROCHEMICAL CORROSION
Vázquez et al. Dual contactless conductivity and amperometric detection on hybrid PDMS/glass electrophoresis microchips
RU2015112598A (en) ELECTROCHEMICAL ANALYTICAL TEST STRIP WITH NON-COATED ELECTRODES FOR AN INTERFERING COMPONENT
Sairi et al. Chronoamperometric response at nanoscale liquid–liquid interface arrays
US20190086356A1 (en) Electrochemical measurement method, electrochemical measurement apparatus and transducer
EP3315957A1 (en) Bio-sensor and bio-sensor array
Johirul et al. Microchip capillary electrophoresis with a cellulose‐DNA‐modified screen‐printed electrode for the analysis of neurotransmitters
JP6619367B2 (en) Sample concentration measurement
Raj et al. Poly-melamine film modified sensor for the sensitive and selective determination of propranolol, a β-blocker in biological fluids
WO2008095238A1 (en) Electrode reactivation in a microfluidic device
Al Mamun et al. Vertically aligned carbon nanofiber based biosensor platform for glucose sensor
US10041900B2 (en) Controlled electrochemical activation of carbon-based electrodes
Kim et al. Array of ultramicroelectrodes for the simultaneous detection of nitric oxide and peroxynitrite in biological systems
WO2009128346A1 (en) Electrode module
Le Drogoff et al. Effect of the Microelectrode Geometry on the Diffusion Behavior and the Electroanalytical Performance of Hg‐Electroplated Iridium Microelectrode Arrays Intended for the Detection of Heavy Metal Traces
Mahanthesha et al. Selective determination of norepinephrine at SAOS/MWCNT/MCPE: A voltammetric study
Sultana et al. Practical implications of using nanoelectrodes for bioanalytical measurements

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 08700429

Country of ref document: EP

Kind code of ref document: A1

DPE2 Request for preliminary examination filed before expiration of 19th month from priority date (pct application filed from 20040101)
NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 08700429

Country of ref document: EP

Kind code of ref document: A1