WO2016155709A1

WO2016155709A1 - Device and method for detecting an ionic analyte in a fluid in a qualitative and/or quantitative manner

Info

Publication number: WO2016155709A1
Application number: PCT/DE2016/100153
Authority: WO
Inventors: Martin Aicher
Original assignee: Martin Aicher
Priority date: 2015-04-02
Filing date: 2016-03-31
Publication date: 2016-10-06
Also published as: DE112016001536A5

Abstract

The invention relates to a device for detecting an ionic analyte (33), in particular ions of a species, in a fluid (31) in a qualitative and/or quantitative manner. The device has an ion-specific sensor (11) which has a first substrate (12) and a first signal transmission element (14). At least the first substrate (12) is brought into contact with the fluid (31), and the first substrate (12) has attachment locations (15, 16, 17) for the analyte (33). The device also has a conductivity sensor (21) which has a second substrate (22) and a second signal transmission element (24) and which is brought into contact with the fluid (31).

Description

description

Apparatus and method for the qualitative and / or quantitative determination of an ionic analyte in a fluid

The invention relates to a device for the qualitative and / or quantitative determination of an ionic analyte in a fluid, in particular ions of a species. It further relates to a method for the qualitative and / or quantitative determination of ionic analytes in a fluid, in particular of ions of a species. Sensors measure sum parameters such as conductivity, i. H. the sum of electrolytes of a fluid. Selective sensors measure a group of ions. They are therefore referred to as ion-selective sensors. Specific sensors can determine elements of a kind from the periodic table. They are therefore referred to as ion-specific sensors. Ion-specific sensors differ from ion-selective sensors in that they can measure an analy ion from the periodic table of the elements. By contrast, ion-sensitive sensors react cross-sensitively and cross-sensitively to neighboring ions in the periodic table and to the conductivity and pH of a fluid.

Conductivity sensors which measure the fluid conductivity with electrode structures are known from the prior art.

For the selective determination of ions in solutions, the potentiometric ion-selective electrode (ISE) is often used. Ion-selective electrodes are electrochemical sensors with which the concentration or the activity of certain ions can be determined by means of a potential difference. The ion-selective potential difference occurs at the phase boundary between the sensor membrane and the electrolyte and, according to the Nernst equation, depends on the activity of a particular ion in the solution. An example of such sensors are ion-selective field-effect transistors. ISEs are mostly selective, ie they measure a selection of different ions by their adverse cross-sensitivity and cross-sensitivity. In addition, ISEs are sensitive to the conductivity and pH of the fluid. Unlike resistance and capacitance, the absolute values of the electrical potential have no physical significance, since the potential can only be defined in relation to a reference value. In electrochemistry, such a reference value is usually supplied by the potential of the reference electrode. The necessity of a reference electrode is the decisive disadvantage in the use of potentiometric measurements for the determination of ionic activities in solution. Another fundamental limitation in the potentiometric analysis methods relates to the composition of the ion-selective membrane. The nature requirements of the specific binding and / or the complexing sites within the membrane are to be set so that the potential difference at the membrane / solution interface is specifically built up depending on the presence of a particular species in the solution. For example, this binding should not be too strong so that a sufficiently rapid exchange of the detected species between the membrane phase and the solution is possible. It is known from the prior art how such sensors are produced: on an inert substrate, a signal transmission element is applied as an IDES (Inter-Digital Electrode Structure). The IDES is filled to size with an ion-selective membrane. The membrane and the IDES form both a mechanical and an electrical bond on the substrate. During use, the ion-selective membrane interacts with the analyte and alters the electrical property of the electrolyte / membrane phase. The electrical behavior of the membrane is measured with the IDES. [BMBF Status Report 18.6.2012, Title "Printed Nanomaterials for Microsensors", page 17, Dr. Helmut Grothe, Martin Aicher].

Sensors that measure specifically, d. H. only measure the analyion, have a significantly lower cross-sensitivity and thus have a decisive advantage over selective measuring sensors. Sensors of the above type, that is to say the selectively measuring sensors, generally comprise an inert substrate as insulator, a signal transmission element in the form of an electrode structure as well as an ion-selective membrane and a reference electrode as potential reference. The analyte-selective membrane contains chemical coupling elements consisting of ligands embedded in a polymer matrix. The matrix consists of polymer, plasticizer and solvents. The polymer matrix adversely affects manufacturability and specificity. This membrane covers the electrode structure. During the measurement, these coupling elements enter into a complex with the analyte ions. The matrix itself shows an interference sensitivity, which manifests itself as cross and cross sensitivity. Another limitation is the membrane, it must be conditioned for several hours before use. In addition, the geometric reproducibility of membranes can be difficult to manufacture in terms of production, in particular during the printing of electrode structures by thick-film technology.

From nanotechnology, membranes with synthetic nanochannels are known for the separation of substances such as ions, molecules, DNA and protein structures in measuring fluids and solutions. However, such nanochannels have no ion-specific coating in the form of coupling elements such as ligands. In addition, no nanostructured substrates in connection with a signal transmission element are known from the prior art.

The use of biological nanopores to detect single molecules is used in the living organism. Exemplary calcium channels are mentioned in the membranes of cells. In cell membranes, Ca ion channels are integrated. These channels on a nanoscale are of their geometry and surface charge only for a particular ion, eg. B. Ca ²⁺ , consistently. Out of bionics, this approach is applied to an inventive ion-specific sensor with synthetic channels and pores.

The disadvantages of the sensors with membranes and a potentiometric measuring principle can be listed as follows:

1. A fundamental limitation concerns the composition of the ion-selective membrane. The polymer matrix shows susceptibility to ions of other species.

2. There is a need to condition the membrane for several hours before use. 3. It is known from the prior art that immobilized membranes can be realized on signal transmission elements and substrates only by complicated process technology with regard to constant layer thickness and homogeneous material structure.

4. Another problem is an unavoidable sudden change in the dielectric constant of the sensitive membrane, depending on the composition of the solution to be analyzed.

5. They have limited long-term stability due to hydrolysis of the membrane composition.

6. A reference electrode means an additional device with variations in their reproducibility and life. The necessity of a reference electrode is the decisive disadvantage in the use of potentiometric measurements for the determination of ionic activities in solution.

The object of the invention is to eliminate the disadvantages of the prior art. In particular, a device is to be specified which enables an improved, in particular faster and more accurate, determination of an ionic analyte, in particular of ions of a species, in a fluid and at the same time reduces the expenditure on equipment. Furthermore, an ion-sensitive sensor, an arrangement with such an ion-specific sensor and a method are provided, which are suitable for the qualitative and / or quantitative determination of an ionic analyte, in particular ions of a species in a fluid.

This object is solved by the features of claims 1, 6, 11 and 13. Advantageous embodiments of the invention will become apparent from the features of the dependent claims.

According to the invention there is provided an apparatus for quantitatively and / or qualitatively determining an ionic analyte comprising an ion-specific sensor comprising a first substrate and a first signal transmitting element, wherein at least the first substrate is contacted with the fluid and wherein the first substrate Attachment sites for the analyte; and a conductivity sensor having a second substrate and a second signal transmission element and brought into contact with the fluid.

The first signal transmission element and the second signal transmission element may be identical. But they can also be different.

The device according to the invention requires no reference electrode. The substrate of the ion-specific sensor is brought into direct contact with the fluid. A membrane is therefore not required. The ion-specific sensor thus has no membrane. A coating, in particular an analyte-specific coating or a membrane-replacing coating, on the substrate of the ion-specific sensor is not required. The ion-specific sensor thus has no coating. Preferably, the ion-specific sensor has no electrolyte. Because the ion-specific sensor manages without membrane, it can consist only of the first substrate and the first signal transmission element. The conductivity sensor may also consist only of the second substrate and the second signal transmission element. The ion-specific sensor can be designed as a solid state sensor. The conductivity sensor may be formed as a solid state sensor.

The invention is based on the fact that the first substrate sensitively changes its electrical property upon contact with analyte ions, while the conductivity sensor has no sensitive electrical property change on contact with analyte ions. The conductivity sensor provides a reference signal that can be used to correct the measurement signal provided by the ion-specific sensor. The signal difference between the first and second signal transmission elements is a measure of the ion concentration or activity of the ionic analyte in the fluid.

In the following, the terms "analyte" and "analyte ion" are used interchangeably with the term "ionic analyte." The ionic analyte may be, for example, a cation or an anion In one embodiment of the invention, it is a cation The ionic analyte may be ions of a species, in particular ions of a species of the periodic table of the elements, for example the ionic analyte may be cations of a species, in particular cations of a species of the Periodic Table of the Elements or molecular compounds. If the analyte ion is a cation, the first substrate is a cation-specific substrate If the analyte ion is an anion, the first substrate is an anion-specific substrate Examples of cations which can be determined by means of the device according to the invention are H ⁺ , Na ⁺ , K ⁺ , Ca ²⁺ , Mg ²⁺ , NH ₄ ⁺ , but the list is not exhaustive Anions that can be determined by the device according to the invention are F ^" , Cl ^" , C0 ₃ ^{2 "} , P0 ₄ ^3" , the list is not exhaustive. The first substrate should be a specific ion specific substrate. The fluid may be, for example, a liquid, a gas or a mixture, with a liquid being preferred. Preferably, the fluid is water. The fluid is also referred to below as measuring fluid or measuring medium. The measuring fluid may be an electrolyte solution. By means of the device according to the invention it can be determined whether the measurement fluid contains a specific analyte. For the qualitative determination of the analyte, it is sufficient if it can be established that the measurement fluid contains or does not contain the analyte. For the quantitative determination of the analyte, it is determined in which concentration the analyte is contained in the measurement fluid. The measuring fluid may contain substances, in particular ions, which are not the analyte. The measurement fluid may contain ions that are different from the analyte. In this case, the measurement fluid (i) can contain only the analyte or (ii) contain only ions which differ from the analyte, or (iii) contain the analyte and ions which differ from the analyte. The measuring fluid may thus contain the same or different ions. If the analyte ions are dissolved in the measurement fluid, then it may be a measurement solution.

By a qualitative determination, the detection can be understood to mean that the fluid contains analyte ions. A quantitative determination can be understood to mean the determination of the concentration of the analyte ion in the fluid. According to the invention, the ion-specific sensor has a first substrate and a first signal transmission means. At least the first substrate is brought into contact with the measurement fluid when the ion-specific sensor is introduced into the measurement fluid. The first signal transmission means can also come into contact with the measurement fluid. That is not necessary. The statement that at least the first substrate is brought into contact with the fluid is to be understood such that the first substrate is intended to be brought into contact with the fluid.

The first substrate has attachment sites for the analyte. These attachment sites are attachment sites to which only the analyst but no other ion in the measurement fluid can attach. The attachment sites can thus be referred to as analyte-specific attachment sites. Due to the analyte-specific attachment sites, the first substrate is an ion-specific substrate.

The attachment sites may be selected from the group comprising pores, channels, surface functionalization, or combinations thereof. With regard to the attachment of an ionic analyte to the attachment sites, the pores may be referred to as ion pores and channels as ion channels. It is possible that the first substrate has only ion pores, only ion channels, or only surface functionalization. It is possible that the first substrate has only ion pores and ion channels. It is possible that the substrate has ion pores and ion channels and surface functionalization. It can be provided that the ion pores, the ion channels or both have a surface modification. In terms of their geometric dimensions, ion channels and ion pores are also referred to below as nanochannels or nanopores. Nanochannels and nanopores are also collectively referred to as nanostructures. With regard to this nanostructure, the first substrate together with the first signal transmission element can also be referred to as nanochannel electrode.

If the analyte ion is a cation, the first substrate is a cation-specific substrate. If the analyte ion is an anion, the first substrate is an anion-specific substrate.

The surface functionalization should allow an analyte-specific attachment of the analyte to the first substrate. By means of the surface functionalization, coupling elements, preferably chemical coupling elements, can be formed on the substrate surface. Chemical coupling elements allow chemical bonding between the coupling element and the analyte ion. The coupling elements may be, for example, ligands, cryptands, ionophores or combinations thereof. The layer thickness of the surface functionalization can be a few nanometers. Surface functionalization may be a chemical functionalization of the substrate surface.

If the substrate surface of the first substrate has ion pores, ion channels or both, then a geometric nanostructuring of the substrate surface is formed. The first substrate can thus be referred to as nanostructured substrate. If the first substrate has a surface functionalization, the first substrate may be referred to as a chemically functionalized substrate. If the first substrate has both (i) ion pores, ion channels, le or both and (ii) surface functionalization, it is thus a nanostructured and chemically functionalized substrate. Preferably, no coating is applied to the substrate surface of the first substrate, in particular no coating of an analyte-specific material and no coating which forms a membrane according to the prior art.

The nanopores and / or nanochannels may take various suitable forms. For a nanopore, a cylindrical shape or truncated cone shape is preferred. In this case, a truncated cone shape is particularly preferred in which the radius of the opening is smaller than the base of the nanopore. The radius of the opening of a conical nanochannel or a conical nanopore is preferably in the range of about 2 nm to about 500 nm. The depth of a nanostructure is the distance from the opening to the base of the nanostructure. The depth is preferably in the range of 10 nm to 100 μπι. The specificity of the ion-specific sensor for an analyte ion, in particular an ion of an element from the Periodic Table, can be made possible, for example, by one or more of the following measures: (i) individual dimensioning of the nanochannels and / or nanopores for the analyte ion;

(ii) a surface ionization specific to the analyte ion of the first substrate; and

(iii) a surface modification specific to the analyte ion of the surface of the nanochannels and / or the nanopores.

A surface functionalization specific to the analyte ion is present when only the analyte ion can attach to the surface of the first substrate. A specific surface modification for the analyte ion is present if only the analyte ion can bind to the surface of the nanochannels and / or nanopores. In any case, it must be ensured that only the analyte ion, but not other ions, can attach to the attachment sites of the first substrate.

The nanostructures may be formed by irradiating the surface of the first substrate with ions and then selectively chemical etching the ion trace areas in the first substrate. In addition, the electrochemical interaction with the analyte ions on the surface of the first substrate and in the first substrate can be improved by a functionalized wetting of the surface of the first substrate by performing a functionalized wetting of the surface of the first substrate and / or the surfaces of the nanostructures with ligands becomes. The surface of the nanopores and / or of the nanochannels can be modified in order to change the surface properties, for example the electrical charge density, hydrophobicity or hydrophilicity of the respective surfaces. For example, coupling elements, preferably chemical coupling elements, can be formed on the surfaces of the nanostructures by means of the surface modification. Chemical coupling elements allow chemical bonding between the coupling element and the analyte ion. The coupling elements may be, for example, ligands, cryptands, ionophores or combinations thereof, wherein ligands are preferred. The surface modification may correspond to the surface functionalization described above, provided that the surface functionalization is formed on the surface of the respective nanostructure. The functionalized wetting is a form of surface modification. For example, in one embodiment of the invention, the first substrate has nanostructures with modified surfaces. The modification consists of functional coupling elements in the form of ligands attached to the inner surface of the nanostructure. Thus, an ion-specific sensor is obtained, which is for detecting ions by measuring the change of an electrical property of the first substrate, for. Resistivity and capacitance of the first substrate, upon binding of the analyte ion to the ligands that are on the surface of the nanopore.

The first substrate can be made, for example, from glass, Si, Si0 ₂ , Si ₃ N ₄ , quartz, alumina, nitrides, metals, polymers or other suitable materials. In one embodiment of the invention, the first substrate is made of a polymer.

For the permselectivity of the ion-specific sensor, it is of interest to influence the interaction between the analyte ions, the first substrate and the boundary layer fluid / electrode structure. For a specific ion measurement it can be very advantageous to exercise control over the properties of the nanostructure, consisting of nanopores and / or nanochannels, ie to functionalize the inner surface of the nanostructure in such a way that specific requirements with regard to hydrophobicity, selectivity and interaction with through the channel einlagernde analyte ions are met. For example, by wetting the inner surfaces of the nanostructure with ligands, the specificity for the ion measurement can be improved.

The first signal transmission element is in communication with the first substrate. The first signal transmission element may be in the form of an IDES (Inter-Digital Electrode Structure). The IDES may be an IDES made of an interdigitated thin-film metal electrode structure of Ni, Pt or Au deposited on the first substrate. The first signal transmission element may be in the form of rods, wires, meshes or IDE (Interdigital Electrodes). The first signal transmission element may be free-standing, applied to the substrate or embedded in the substrate. Preferably, the first signal transmission element is formed by one or more interdigital electrodes. Details of the configuration of the first signal transmission element in the form of an IDE (Inter-Digital Electrode) or an IDES (Inter-Digital Electrode Structure) can be found in the prior art. Suitable arrangements of the signal transmission element in the form of electrodes and related modifications are made in DE 44 37 274 AI. The first substrate may be formed as a shaped body. In this case, the first substrate together with the first signal transmission element form a shaped body. It can be provided that the first substrate with the IDES is designed as a 2D or 3D shape, wherein different 2D and 3D shapes are possible.

The IDES of the ion-specific sensor can consist, for example, of platinum, gold, silver, nickel or tungsten. But it can also consist of any other electrically conductive material, for example carbon, a semiconductor (eg silicon) or an electrically conductive polymer (eg polyanaline). The IDES may be applied to the first substrate, for example, by thick film technology. The first signal transmission element in the form of an IDES may have a comb structure with a plurality of electrode fingers. Two interdigital electrodes (IDE) or conduction bands can be applied to the second substrate. The conduction band can be a polymer band, glass, ceramic, sapphire or silicon. The electrode materials of the first signal transmission element may consist of ionic, electronic or semiconductive materials.

The ion-specific sensor does not require a membrane because the first substrate is brought into direct contact with the measurement fluid. For this reason, the ion-specific sensor may consist of only two components, namely the first substrate and the first signal transmission element. The invention thus enables the reduction of the components from three to two components, which considerably simplifies the reproducible production of the ion-specific sensor.

In one embodiment of the invention, the first substrate of the ion-specific sensor together with the first signal transmission element forms a nanochannel electrode. The nanochannel electrode is formed by the first substrate interspersed with nanopores and / or nanochannels and the first signal transmission element. The first substrate of the nanochannel electrode may further have a surface functionality. A nanochannel electrode can be manufactured rationally and reproducibly, for example, together with a signal transmission element. The first signal transmission element is applied to the first substrate or embedded in the first substrate. The specificity of the sensor to an analyte ion, for example to ions of a species, in particular to ions of a species or molecules of the elements from the Periodic Table, is made possible by an individual dimensioning and surface functionalization of the nanochannels / nanopores for the analyte ion.

According to the invention, the conductivity sensor has a second substrate and a second signal transmission element. The second substrate is preferably an inert substrate. In this way it should be prevented that ions, including the analyte ions, attach to the second substrate. The second substrate should have no ion pores, no ion channels and no surface functionalization. The second substrate should thus have no analyte-specific properties. The statement that the conductivity sensor is brought into contact with the fluid is to be understood such that the conductivity sensor is intended to be brought into contact with the fluid.

The second substrate may consist of an inert material, in particular an insulating, inert material. The second substrate can be made, for example, from glass, Si, Si0 ₂ , Si ₃ N ₄ , quartz, alumina, nitrides, metals, polymers or other suitable materials. In one embodiment of the invention, the second substrate is a polymer.

The second signal transmission element is in communication with the second substrate. The second signal transmission element may be in the form of an IDES (Inter-Digital Electrode Structure). The IDES may be an IDES made of an interdigitated thin-film metal electrode structure of Ni, Pt or Au deposited on the second substrate. The second signal transmission element may be in the form of rods, wires, Mesh or IDE (interdigital electrodes) may be formed. The second signal transmission element may be free-standing, applied to the substrate or embedded in the substrate. Alternatively, the second signal transmission element does not require a substrate. Preferably, the second signal transmission element is formed by one or more interdigital electrodes. Details of the configuration of the second signal transmission element in the form of an IDE (Inter-Digital Electrode) or an IDES (Inter-Digital Electrode Structure) can be found in the prior art. Suitable arrangements of the signal transmission element in the form of electrodes and related modifications are made in DE 44 37 274 AI.

The second substrate may be formed as a shaped body. In this case, the second substrate together with the second signal transmission element form a shaped body. It can be provided that the second substrate with the IDES is designed as a 2D or 3D shape, wherein different 2D and 3D shapes are possible.

The IDES of the conductivity sensor can be made of platinum, gold, silver, nickel or tungsten, for example. However, it can also consist of any other electrically conductive material, for example carbon, a semiconductor (eg silicon) or an electrically conductive polymer (eg polyanaline). The IDES may be applied to the second substrate, for example, by thick film technology. The second signal transmission element in the form of an IDES may have a comb structure with a plurality of electrode fingers. Two interdigital electrodes (IDE) or conduction bands can be applied to the second substrate. The conduction band can be a polymer band, glass, ceramic, sapphire or silicon. The electrode materials of the second signal transmission element may consist of ionic, electronic or semiconductive materials.

The first substrate and the second substrate may be of the same material, wherein the first substrate comprises either (i) a nanostructure of nanopores and / or nanochannels or (ii) surface functionalization or (iii) both while the second substrate is inert. However, it is not required that the first substrate and the second substrate be made of the same material. The first signal transmission element and the second signal transmission element may be made of the same material. This is preferred, but not required. Both signal transmission elements may be an IDES with the same structure and / or the same shape. The device according to the invention may comprise a transmitter, which is connected via electrical conduction means to the ion-specific sensor and the conductivity sensor. For this purpose, the first and the second signal transmission element can have plus and minus poles for the electrical connection of the two signal transmission elements to the transmitter. The conduit means may also be referred to as connection means. The transmitter preferably has measuring electronics or is connected to measuring electronics. The measuring electronics can form an evaluation device or be part of an evaluation device. The evaluation device is used to evaluate the signals that are supplied by the ion-specific sensor and the conductivity sensor. The signal difference between the first and the second signal transmission element is a measure of the ion concentration of the ionic analyte. The invention makes it possible to determine an ionic analyte present in solution, in particular cations, quantitatively and / or qualitatively by means of an absolute measurement, without the use of reference electrodes, and at the same time to eliminate disturbing interference from interfering ions and membranes. At the same time the measuring accuracy is increased and the detection limit is lowered. Required for this purpose are two sensors, namely the ion-specific sensor according to the invention and the conductivity sensor according to the invention.

The existing in the prior art disadvantage of susceptibility due to the electrolyte conductivity is overcome by the invention. The invention is based on the fact that the analyte ion forms a compound with the first substrate, which may also be referred to as a complex. The connection of the analyte to the first substrate causes ionic conductivity of the first substrate. The principle of action can be explained as follows. The analyte ions present in a measurement fluid attach to anolyte-specific attachment positions of the first substrate. These can be, for example, ion channels and / or ion pores into which the analyte ions are incorporated, and / or a surface functionalization of the first substrate which leads to the formation of chemical complexes when the analyte ions attach to the functionalized surface of the first substrate. By recording the indications, at least one electrical property of the first substrate changes, for example the resistance, the ionic conductivity, the admittance or the impedance, as well as the boundary layer between the first substrate and the measurement fluid. The first substrate, which is specifically sensitive to the analyte ion, is in communication with the first signal transmission element in the form of an electrode structure. The change of an electrical characteristic, for example the impedance change, is measured and forwarded via the signal transmission element. This signal is superimposed by the conductivity of the measuring fluid. The second sensor, which has a second substrate and a second signal transmission element, measures the conductivity of the measurement fluid. Measuring electronics are used to calculate the difference between the signals from the ion-specific sensor and the conductivity sensor. The signal difference is a measure of the concentration of the analyte ion in the measurement fluid.

Also, the existing in the prior art second disadvantage due to the membrane is overcome by the invention by the membrane is eliminated. The actual membrane function takes over the first substrate according to the invention. In order to ensure the required specificity of the ion-specific sensor for the analyte ion, the first substrate has analyte-specific attachment sites. For this purpose, the first substrate can be, for example, geometrically nano-structured and / or chemically functionalized. The analyte-specific attachment sites having, for example, nanostructured and / or chemically functionalized substrate allows the specific measurement of the analyte ion. The analy ion combines with the first substrate, thereby changing the electrical resistance and capacitance of the first substrate. Due to this novel first substrate, the membrane is unnecessary. The first signal transmission element forwards the electrical change as a measuring signal to an evaluation unit, for example to a measuring electronics.

The present invention provides a measurement signal that correlates with analyte concentration. The device according to the invention and the measuring principle according to the invention make it possible to omit a reference electrode. A preferred construction of the ion-specific sensor is based on the use of microelectronic chips with the required number of interdigital electrodes forming the first signal transmission element on the first substrate. If the analyte ion is a cation, the first substrate is a cation-specific substrate. If the analyte ion is an anion, the first substrate is an anion-specific substrate. A preferred construction of the conductivity sensor is based on the use of microelectronic chips with the required number of interdigital electrodes forming the second signal transmission element on the second substrate. Thus, both sensors can be based on the use of microelectrical chips with the required number of interdigital electrodes forming the respective signal transmission element on the respective substrate. Such a construction has the advantage of technological compatibility with microelectronic chip technologies as well as the simplicity of miniaturization.

The ion-specific sensor provided according to the invention can also be used independently of the device according to the invention. According to the invention, an ion-specific sensor is thus provided for the quantitative and / or qualitative determination of an ionic analyte in a fluid, wherein the ion-specific sensor has a first substrate and a first signal transmission element, wherein at least the first substrate is brought into contact with the fluid and wherein the first substrate has attachment sites for the analyte. The ion-specific sensor may consist of the first substrate and the first signal transmission element.

The ion-specific sensor according to the invention has been described above in connection with the device according to the invention. Further features of the ion-specific sensor according to the invention can thus be taken from the description of the device according to the invention.

The ion-specific sensor according to the invention may be part of an arrangement which, in addition to the ion-specific sensor according to the invention, comprises a conductivity sensor. According to the invention, an arrangement is thus provided for the quantitative and / or qualitative determination of an ionic analyte in a fluid which has the ion-specific sensor according to the invention and a conductivity sensor for determining the conductivity of the fluid.

The conductivity sensor can be a prior art conductivity sensor or, preferably, the conductivity sensor described above in connection with the device according to the invention. Further features of the conductivity sensor can thus be taken from the description of the device according to the invention.

By the analyte ions to be detected in contact with the first substrate, as described above, a detectable change of at least one electrical property of the first substrate is caused. A change in an electrical property, such as the impedance, admittance, or other electrical property of the first substrate described above, may be indicated as a function of the interactions with the detected analyte ions, for example, with the detected ion species. The specificity and sensitivity of the determination can be improved by the conductivity sensor whose second signal Transmission element provides a comparison signal to the ion-specific sensor with the first signal transmission element. This also applies in the case of the device according to the invention.

In addition, the arrangement according to the invention can have a transmitter which is connected via electrical conduction means to the ion-specific sensor and the conductivity sensor. For this purpose, the first and the second signal transmission element can have plus and minus poles for the electrical connection of the two signal transmission elements to the transmitter. The transmitter preferably has measuring electronics or is connected to measuring electronics. The measuring electronics can form an evaluation device or be part of an evaluation device. The evaluation device is used to evaluate the signals that are supplied by the ion-specific sensor and the conductivity sensor. The signal difference between the first and the second signal transmission element is a measure of the ion concentration of the ionic analyte.

Finally, in accordance with the invention, a method is provided for the quantitative and / or qualitative determination of an ionic analyte, in particular of ions of a species, in a fluid by means of the device according to the invention or the arrangement according to the invention. The method comprises:

(a) contacting the first substrate of the ion-specific sensor with the fluid;

(b) contacting the conductivity sensor with the fluid; and

(C) quantitative and / or qualitative determination of the analyte in the fluid from signals of the ion-specific sensor and the conductivity sensor.

It can be provided that step (c) comprises the sub-steps:

(c 1) determining an electrical property of the first substrate; and

(c2) determining the electrical conductivity of the fluid by means of the conductivity sensor. It may be provided in step (a) that the first substrate is brought into contact with the fluid together with the first signal transmission element of the ion-specific sensor. Thus, the first substrate alone or the first substrate can be immersed in the fluid together with the first signal transmission element.

It can be provided that the electrical property is selected from the group comprising the resistance, the electrical conductivity, the capacitance, the admittance and the impedance. Preferably, the impedance of the first substrate is measured.

Further features of the method according to the invention have been described above in connection with the device according to the invention. They can thus be taken from the description of the device according to the invention. The invention has numerous advantages over the prior art. In particular, no reference electrode is needed, since the measurements of electrical properties such as conductivity or admittance, in contrast to z. B. potential measurements in the potentiometry, absolute measurements are. The omission of the membrane and thus the disadvantages of the membrane matrix improves the sensitivity, allows the dispensing with conditioning for hours and leads to an improved sensor response. By eliminating the membrane, the invention makes it possible to reduce the ion-specific sensor from three to two components, which considerably simplifies the reproducible production of the ion-specific sensor. In the case of sensors with membranes, the membrane must cover the electrode structure in order to exclude cross-sensitivity to the conductivity. The limited reproducibility of the membrane thickness during manufacture leads to a large variance of the sensitivity and the sensor cell constant.

Further advantages of the invention are that the signal of the conductivity sensor compensates for the interference of the conductivity of the measurement fluid. In addition, the ion-specific sensor, the conductivity sensor or both can be constructed as highly integrated solid-state complete systems. This allows a high degree of miniaturization and ensures compatibility with microelectronics. If the first signal transmission means, the second signal transmission means or both are implemented in the form of an IDE, the advantage of using an IDE is the possibility of the dense arrangement of the electrodes. The dimensions of the electrode spacings can be reduced down to the submicron scale while at the same time providing a high sensitive substrate surface, which leads to an increase in sensitivity in a small area. The sensor design enables a thin and flexible design. Free-form surfaces in 3D are possible with the sensor design. The sensor design enables a design as a highly integrated solid state complete system. This allows a high degree of miniaturization and ensures compatibility with microelectronics.

The attachment sites provided according to the invention, in particular in the form of nanochannels and nanopores in combination with the surface functionalization, allow the specific measurement of ions of an element from the periodic table as opposed to a membrane-shaped coating which is selective, ie. H. are cross-sensitive to a group of ions and show cross-sensitivity. The conductivity sensor forms an inert reference sensor, the sum parameter conductivity of the measuring fluid, d. H. the sum of all ions of the measuring fluid, measures. The signal difference between the selective sensor, d. H. the ion-specific sensor, and the reference sensor, d. H. the conductivity sensor, eliminates the cross-sensitivity to the conductivity. With the design of the device or arrangement according to the invention, the measurement accuracy can be improved and the detection limit can be reduced.

Cations sensor

In one embodiment, the invention relates to an embodiment of the device according to the invention or the arrangement according to the invention called a cation sensor. The cation sensor consists of two sensors, namely an ion-specific sensor and a conductivity sensor. The ion-specific sensor has: a first, ion-specific substrate with ion channels, with ion pores and a surface functionalization for attaching the ion species to be analyzed, ie the analyte ion, in a measurement solution; and a signal transmission element in the form of an IDES (Inter-Digital Electrode Structure) in communication with the first ion-specific substrate.

The conductivity sensor has a second signal transmission element on an inert substrate. The ion-specific sensor and the conductivity sensor have positive and negative poles for electrical connection to a transmitter with measuring electronics. The signal difference of the two signal transmission elements is a measure of the ion concentration or ion activity of the ion species in a measurement solution.

It may be provided in the cation sensor that the first, ion-specific substrate changes its electrical property sensitive upon contact with cations of an ionic species and that the first signal transmission element is in communication with the first, ion-specific substrate.

It is provided in the cation sensor that the membrane function is integrated or integrated into the first, ion-specific substrate and that the cation sensor according to the invention is realized without a membrane.

It may be provided in the cation sensor that the cation measurement is realized without a reference electrode.

It may be provided in the cation sensor that the first substrate is formed with ion-specific ion channels and with ion pores, so that change by specific cation recording the electrical properties such as resistance, capacitance, admittance or impedance of the substrate. It can be provided that the ion channels and the ion pores have a surface functionalization with ion-specific coupling elements, so that change the electrical properties such as resistance, capacitance, admittance or impedance of the substrate by a specific cation uptake. Alternatively, it may be provided in the cation sensor, that the first substrate is equipped without ion channels and ion pores, but has a surface functionalization with ion-specific coupling elements, so that change by specific cation recording the electrical properties such as resistance, capacitance, admittance or impedance of the substrate.

It may be provided in the cation sensor that the conductivity sensor, in which the second signal transmission element is arranged on an inert substrate, has no sensitive electrical property change, so that it acts as a reference signal transmission element to the ion-specific sensor. Finally, it can be provided that the ion-specific sensor and the conductivity sensor are connected via a measuring electronics, so that the difference of the signals from the first and second signal transmission element can be calculated for the purpose of compensating the cross-sensitivity by the fluid conductivity. Anion Sensor

The anion sensor corresponds to the cation sensor except that the ion species to be analyzed, i. H. the analyte is an anion. The Amonen sensor consists of two sensors, namely an ion-specific sensor and a conductivity sensor. The ion-specific sensor comprises: a first, ion-specific substrate with ion channels, with ion pores and a surface functionalization for attaching the ion species to be analyzed, ie the analyte ion, in a measurement solution; and a signal transmission element in the form of an IDES (Inter-Digital Electrode Structure) in communication with the first ion-specific substrate.

The conductivity sensor has a second signal transmission element on an inert substrate. The ion-specific sensor and the conductivity sensor have positive and negative poles for electrical connection to a transmitter with measuring electronics. The signal difference of the two signal transmission elements is a measure of the ion concentration of the ion species in a measurement solution.

It may be provided in the amino-sensor that the first, ion-specific substrate changes its electrical property sensitively upon contact with anions of an ion species and that the first signal transmission element is in communication with the first, ion-specific substrate.

It is provided in the case of the amonorm sensor that the membrane function is combined or integrated into the first, ion-specific substrate, and that the amonep sensor according to the invention is realized without a membrane.

It can be provided in the Amonen sensor that the Anionenmessung is realized without a reference electrode.

It may be provided in the amonotransducer, that the first substrate is formed with ion-specific ion channels and with ion pores, so that change the electrical properties such as resistance, capacitance, admittance or impedance of the substrate by specific Anionenaufnahme. It can be provided that the ion channels and the ion pores have a surface functionalization with ion-specific coupling elements, so that change the electrical properties such as resistance, capacitance, admittance or impedance of the substrate by a specific Anionenaufnahme. Alternatively, it can be provided in the amino-sensor that the first substrate is equipped without ion channels and ion pores, but has a surface functionalization with ion-specific coupling elements, so that the electrical properties such as resistance, capacitance, admittance or impedance of the substrate change by specific cation uptake.

It may be provided in the amono sensor that the conductivity sensor in which the second signal transmission element is disposed on an inert substrate has no sensitive electrical property change, so that it acts as a reference signal transmission element to the ion-specific sensor. Finally, provision may be made for the ion-specific sensor and the conductivity sensor to be connected via measuring electronics, so that the difference of the signals from the first and second signal transmission elements can be calculated for the purpose of compensating the cross-sensitivity by the fluid conductivity.

The invention will be explained in more detail below with reference to embodiments, which are not intended to limit the invention, with reference to the drawings. Show

Fig. La is a schematic representation of the ion-specific sensor and the conductivity sensor in one

Measuring fluid;

FIG. 1b shows a partial perspective view of a first embodiment of an ion-specific sensor; FIG.

Figure lc is a partial schematic representation of a first substrate having a surface functionalization;

2 shows schematic partial sectional representations of first substrates in whose surface nanostructures are introduced (FIG.2a: conical nanochannel, FIG.2b: cylindrical nanochannel, FIG.2c: a nanopore);

3 is a schematic sectional view of a first substrate, in the surface of which nanostructures are introduced;

4 is a schematic sectional view of a first substrate whose surface has a surface functionalization;

5 shows a schematic partial sectional view of a first substrate with a conically shaped nanochannel without surface modification; and FIG. 6 shows a schematic partial sectional view of a first substrate with a conically shaped nanochannel with surface modification.

1 a shows an ion-specific sensor 11 and a conductivity sensor 21, which may be part of a device or arrangement according to the invention. The sensors 11, 21 are spaced from each other with one of its ends inserted into a measuring fluid 31, which is located in a sample container 32.

The ion-specific sensor 11 has a first substrate 12 with a substrate surface 13, to which a first signal transmission element 14 is applied. It can be seen in FIG. 1 that the first signal transmission element 14 is designed in the form of an IDES. The first signal transmission element 14 has a positive pole (+) and a negative pole (-), which are formed at the end of the ion-specific sensor 11 which is not in the measuring fluid 31 is introduced. The ion-specific sensor 11 is electrically connected via the positive pole and the negative pole of the first signal transmission element 14 to a transmitter (not shown) with microelectronics, so that the measurement signal, which is received by the first signal transmission element 14 and transmitted to the transmitter, can be evaluated.

The conductivity sensor 21 has a second substrate 22 with a substrate surface 23, to which a second signal transmission element 24 is applied. It can be seen in FIG. 1 that the second signal transmission element 24 is designed in the form of an IDES. The second signal transmission element 24 has a positive pole (+) and a negative pole (-), which are formed at the end of the ion-specific sensor 11, which is not introduced into the measuring fluid 31. The conductivity sensor 21 is connected via the positive pole and the negative pole of the second signal transmission element 24 as well as the ion-specific sensor 11 to the transmitter, so that the measurement signal, which is received by the second signal transmission element 24 and transmitted to the transmitter, can be evaluated. The substrate surface 13 of the ion-specific sensor 11 has a nanostructure of nanochannels 16 and nanopores 17, which extend from the substrate surface 13 into the first substrate 12 (FIG. 1b). The substrate surface 13 additionally has a surface functionalization (FIG. 1c). These are ligands 15, which are formed as coupling elements on the substrate surface 13. Analyte ions 33, which are in the measurement fluid 31, can attach to the ligand 15 to form chemical complexes 34.

The second substrate 22 of the conductivity sensor 21 consists of an inert material to which no analyte ions 33 can bind.

In FIGS. 2a-c, the nanostructure on the substrate surface 13 is further illustrated. In FIGS. 2a-c, the first substrate 12 is shown in each case as a partial section, wherein the sectional area is shown hatched. FIGS. 2 a and 2 b each show a nanochannel 16 which forms an attachment site for an analyte ion 33. In Fig. 2a, the nanochannel 16 is a conical nanochannel 16 ', in Fig. 2b a cylindrical nanochannel 16 ".Figure 2c shows a nanopore 17 which forms an attachment site for an analyte ion 33. The nanochannels 16 and Nanopores 17 together form the nanostructure of the substrate surface 13. Analyte ions 33, which are located in the measurement fluid 31, can enter the nanostructure and attach to the substrate surface 13 there.

3 shows a section through a first substrate 12, on whose substrate surface 13 attachment sites in the form of conical nanochannels 16 ', cylindrical nanochannels 16 "and nanopores 17 are formed Nanostructures surface functionalization in the form of Lig- anden 15 is formed on the substrate surface 13.

According to the invention, it may be provided that a surface modification is formed on the surfaces of the nanostructures 16, 17. The surface modification may correspond to the surface functionalization of the substrate surface 13. The surfaces of the nanostructures 16, 17 are also referred to as inner surfaces due to their position. However, they are part of the substrate surface 13. FIG. 5 shows a nanochannel 16 '. its inner surface has no surface modification. Into the nanochannel 16 'an analyte ion 33 is incorporated.

Fig. 6 corresponds to Fig. 5, except that the substrate surface 13 has a surface functionalization and the inner surface of the nanochannel 16 'has a surface modification. Both surface functionalization and surface modification are ligands 15 formed as coupling elements on the substrate surface 13 and the inner surface of the nanochannel 16 '. Analyte ions 33 located in the measurement fluid 31 may attach to the ligand 15 forming chemical complexes 34 (see also FIG. 1c) at the substrate surface 13 and the inner surface of the nanochannel 16 '.

example 1

In this embodiment of the invention, the first substrate 12 is a substrate made of a polymer having nanochannels 16 and nanopores 17. The first substrate 12 has a thickness of 0.2 mm. The nanochannels 16 and the nanopores 17 have a dimension between 2 and 100 nm. The first substrate 12 has a surface functionalization formed by ligands 15. The first substrate 12 is thus a surface-modified substrate, i. H. a nanostructured and ligand-functionalized polymer substrate.

On the first substrate 12, the first signal transmission element 14 is applied in the form of an IDES. The IDES is an interdigital thin-film metal electrode structure made of Ni, Pt or Au. The IDES is fabricated on the nanostructured ligand-functionalized polymer substrate.

An identical IDES is applied as a second signal transmission element 24 to an inert polymer substrate. The inert polymer substrate is the second substrate 22, which in turn is part of the conductivity sensor 21. The IDES is made on the inert polymer substrate.

The first substrate together with the first signal transmission element 14 forms a nanochannel electrode. The nanochannel electrode consists of the first substrate 12, interspersed with nanopores 17 and nanochannels 16 and therefore being a nanostructured substrate, and the first signal transmission element 14. In addition, the first substrate may have surface functionalization. For this purpose, the nanostructured substrate with ligands 15 can be functionalized for the specific incorporation and addition of analyte ions 33. On the first substrate 12, the first signal transmission element 14 is applied in the form of an IDES. The nanochannel electrode can be manufactured rationally and reproducibly together with IDES.

A preferred construction of the ion-specific sensor 11 is based on the use of microelectronic chips with the required number of interdigital electrodes forming the first signal transmission element 14 on the first substrate 12. If the analyte ion 33 is a cation, the first substrate 12 is a cation-specific substrate , A preferred construction of the conductivity sensor 21 is based on the use of microelectromic chips with the required number of interdigital electrodes forming the second signal transmission element 24 on the second substrate 22. Thus both sensors can be based on the use of microelectromic chips with the required number of interdigital electrodes that the respective signal transmission element form, on the respective substrate. Such a design has the advantage of technological compatibility with microelectronic chip technologies as well as the simplicity of miniaturization.

The nanopores 17 and nanochannels 16 in the first, analyte-specific substrate 12 can be produced with the aid of production technology, the so-called ion tracking and etching ion trace. Optionally, the inner surfaces of the nanopores 17 and nanochannels 16 may have a surface modification in the form of coupling elements. The coupling elements can be ligands 15 which can form a chemical complex 34 with analyte ions 33. The ligands 15 are therefore chemical complexing agents. If the analyte 33 is a cation, then the ligand is a cation recognizing ligand.

For determining the analyte ion concentration in a measurement fluid 31, the ion-specific sensor 11 and the conductivity sensor 21 are introduced into the measurement fluid 31. The measurement fluid 31 in this example is a measurement solution containing cations as analyte ions 33. The cations to be detected contained in the measurement solution enter the first cation-specific sensitive substrate 12 and form complexes with the nanostructure, i. H. the nanochannels 16 and the nanopores 17, and, if present, the functionalized chemical groups, d. H. ligand 15. Due to the described ionic processes, the bulkelektrischen properties of the first substrate 12 change, which can be detected by means of the first substrate 12 in contact with the first signal transmission element 14, which has the shape of an electrode structure.

Example 2

Example 2 corresponds to Example 1, except that the first, analyte-specific substrate 12 has no nanopores and nanochannels and thus no nanostructure, but only a surface functionalization. The surface functionalization is a surface functionalization of coupling elements, for example ligands 15, on the substrate surface 13. In this variant, the substrate does not contain nanopores and nanochannels.

In order to determine the analyte ion concentration of a measurement fluid 31, the ion-specific sensor 11 and the conductivity sensor 21 are introduced into the measurement fluid 31. The measurement fluid 31 in this example is a measurement solution containing cations as analyte ions 33. The cations to be detected contained in the measurement solution enter the first cation-specific sensitive substrate 12 and form complexes with the functionalized chemical groups, i. H. ligand 15. Due to the described ionic processes, the bulkelektrischen properties of the first substrate 12 change, which can be detected by means of the first substrate 12 in contact with the first signal transmission element 14, which has the shape of an electrode structure.

LIST OF REFERENCE NUMBERS

11 ion-specific sensor; 12 first substrate; 13 substrate surface; 14 first signal transmission element; 15 ligand; 16 nanochannel; 17 nanopores; 21 conductivity sensor; 22 second substrate; 23 substrate surface; 24 second signal transmission element; 31 measuring fluid; 32 sample containers; 33 Analytion; 34 Complex of ligand and analyte ion.

Claims

claims

Apparatus for quantitatively and / or qualitatively determining an ionic analyte (33), in particular ions of a species, in a fluid (31), the apparatus comprising: an ion-specific sensor (11) comprising a first substrate (12) and a first Signal transmission element (14), wherein at least the first substrate (12) is brought into contact with the fluid (31) and wherein the first substrate (12) attachment sites (15, 16, 17) for the analyte (33); and a conductivity sensor (21) having a second substrate (22) and a second signal transmission element (24) and brought into contact with the fluid (31).

Device according to claim 1, characterized in that the attachment sites (15, 16, 17) are selected from the group comprising pores (17), channels (16), surface functionalization (15) or combinations thereof.

Apparatus according to claim 1 or claim 2, characterized in that the attachment sites of pores (17), channels (16) and a surface functionalization (15) are formed.

Device according to one of the preceding claims, characterized in that it further comprises a transmitter, which is connected via electrical conduction means to the ion-specific sensor (11) and the conductivity sensor (21).

Device according to one of the preceding claims, characterized in that it further comprises an evaluation device for evaluating the signals that are supplied by the ion-specific sensor (11) and the conductivity sensor (21).

Ion-specific sensor for the quantitative and / or qualitative determination of an ionic analyte (33) in a fluid (31), wherein the ion-specific sensor (11) has a first substrate (12) and a first signal transmission element (14), wherein at least the first substrate ( 12) is brought into contact with the fluid (31) and wherein the first substrate (12) has attachment sites (15, 16, 17) for the analyte (33).

Sensor according to claim 6, characterized in that the attachment sites (15, 16, 17) are selected from the group comprising pores (17), channels (16), surface functionalization (15) or combinations thereof.

8. Sensor according to claim 6 or claim 7, characterized in that the pores (17) and / or the channels (16) have a surface modification (15).

9. Sensor according to one of claims 6 to 8, characterized in that the first signal transmission element (14) is an inter-digital electrode or an inter-digital electrode structure.

10. Sensor according to one of claims 6 to 9, characterized in that the first signal transmission element (14) applied to the first substrate (12) or embedded in the first substrate (12).

11. Arrangement for the quantitative and / or qualitative determination of an ionic analyte (33) in a fluid (31), comprising an ion-specific sensor (11) according to one of claims 6 to 9 and a conductivity sensor (21) for determining the conductivity of the fluid (31 ).

12. Arrangement according to claim 11, characterized in that the conductivity sensor (21) has a second substrate (22) and a second signal transmission element (24) and is brought into contact with the fluid (31).

13. Method for the quantitative and / or qualitative determination of an ionic analyte (33), in particular of ions of a species, in a fluid (31) by means of a device according to one of claims 1 to 5 or an arrangement according to claim 11 or 12, full

(a) contacting the first substrate (12) of the ion-specific sensor (11) with the fluid (31);

(b) contacting the conductivity sensor (21) with the fluid (31);

(C) quantitative and / or qualitative determination of the analyte (33) in the fluid (31) from signals of the ion-specific sensor and the conductivity sensor.

14. The method according to claim 13, characterized in that step (c) comprises the substeps of: (c1) determining an electrical property of the first substrate (12); and

(c2) determining the electrical conductivity of the fluid (31) by means of the conductivity sensor (21).

15. The method according to claim 14, characterized in that the electrical property is selected from the group comprising the resistance, the electrical conductivity, the capacitance, the admittance and the impedance.