DE102019103171A1 - Ion-selective electrode for an electrochemical sensor - Google Patents

Abstract

The present invention relates to an ion-selective electrode (1) for an electrochemical sensor and an electrochemical sensor. The electrode comprises an, in particular cylindrical, probe body (2), an enamel layer (4) which is arranged at least in a first partial area (T1) of the probe body (2), and an analyte-sensitive layer (5) which at least is arranged in a second partial area (T2) of the probe body such that the analyte-sensitive layer (5) is at least partially in contact with the enamel layer (4). According to the invention, the electrode (1) comprises an electrically conductive layer (8) which is arranged in a third partial area (T3) of the probe body (2).

Description

The invention relates to an ion-selective electrode for use with an electrochemical, in particular potentiometric, sensor and a potentiometric sensor.

Electrochemical sensors are used in laboratory and process measurement technology in many areas of chemistry, biochemistry, pharmacy, biotechnology, food technology, water management and environmental measurement technology for the analysis of measurement media, in particular measurement liquids. By means of electrochemical measurement techniques, the activities of chemical substances, for example ion activities, and thus correlated measured variables in liquids can be recorded. The substance whose activity or concentration is to be measured is also known as the analyte. The measured variables dependent on the activity of the analyte are, for example, an activity or a concentration of the analyte, e.g. a certain ion species, or around a pH value. The measuring medium can be a measuring liquid, for example a water-containing solution, emulsion or suspension. Electrochemical measuring probes can be designed, for example, as potentiometric or amperometric sensors.

Potentiometric sensors usually include a measuring half-cell and a reference half-cell as well as a measuring circuit. For the measurement, the measuring half-cell and the reference half-cell are brought into contact with the measuring medium. In contact with the measuring medium, the measuring half-cell forms an electrochemical potential that is dependent on the activity of the analyte in the measuring medium, while the reference half-cell provides a stable, electrochemical reference potential that is largely independent of the concentration of the analyte. The measuring circuit generates an analog or digital measuring signal which represents the electrical potential difference between the measuring half-cell and the reference half-cell and therefore the activity of the analyte in the measuring medium. If necessary, the measurement signal is output by the measurement circuit to a higher-level unit connected to the sensor, which further processes the measurement signal. This can be a transmitter or a process controller, e.g. a PLC, act. Partial or complete further processing of the measurement signal in a unit arranged in the sensor is also possible.

The reference half-cell of conventional potentiometric sensors is often used as an electrode of the second type, e.g. designed as a silver / silver chloride reference electrode and electrically connected to the measuring circuit.

The measuring half-cell comprises a potential-forming sensor element which, depending on the type of potentiometric sensor, can comprise an ion-selective membrane or layer. Examples of such measuring half-cells are ion-selective electrodes. A conventional ion-selective electrode has a housing which is closed off by the ion-selective membrane and in which an internal electrolyte in contact with the membrane is accommodated. The ion-selective electrode further comprises a discharge line that is in contact with the internal electrolyte. The lead is electrically connected to the measuring circuit. If the ion-selective membrane is in contact with the measurement medium for measurement, the membrane interacts selectively with a specific ionic species contained in the measurement medium, namely with the analyte. A change in the activity or concentration of the ion in the measuring medium brings about a relative change in the equilibrium galvanic voltage between the measuring medium and the lead in contact with the ion-selective membrane via the internal electrolyte. A special case of such an ion-selective electrode, namely an electrode that selectively detects the H ⁺ or hydronium ion activity in a measuring liquid, is the known pH glass electrode, which comprises a glass membrane as a potential-forming sensor element.

Such ion-selective glass electrodes, as well as sensors with corresponding glass electrodes, are distinguished by good measuring properties; in the case of a pH glass electrode, this concerns, for example, the slope, long-term stability, selectivity and detection limit. However, glass electrodes break easily, so they only have poor mechanical stability.

The ion-selective so-called “solid-state” electrodes represent an alternative. In this context, enamel electrodes in particular have become known, as they are for example in EP0180071B1 , EP0614694B1 or WO2018 / 069591A1 are described.

The main components of enamel are inorganic oxide components. In terms of its properties, enamel is comparable to glass. Basic components are, for example, one or more of the oxides silicon oxide, sodium oxide, potassium oxide, calcium oxide, magnesium oxide and aluminum oxide. Applied to a metal substrate, adhesive strengths of up to 100N / m ² can be achieved with an enamel coating.

Enamel electrodes usually have a metallic shaft and are accordingly characterized by high mechanical stability. In addition, they are chemically inert due to the enamel coating, and can in particular also in the case of aggressive media, in particular for chemical processes, or processes in which cleaning has to be carried out frequently, such as in the food industry, for example.

In order to achieve a sufficient service life of the respective sensors, however, it is necessary that the analyte-sensitive layer, which is applied in the enamelled area, is made comparatively thick. The consequence of this is the presence of a comparatively high electrical impedance and the associated poorer signal quality.

An alternative to using comparatively thick analyte-sensitive layers is to enlarge the geometry of the respective electrode, in particular to enlarge the area of the potential-forming sensor element. However, this has the consequence that corresponding electrodes can generally not be used in standard process fittings due to the sizes that arise. In this context, standard process fittings are understood to mean process fittings that are suitable for installing sensors with a diameter of 12 mm. Typical installation lengths of the respective electrodes are, for example, in a range between 120-225 mm. Enamel electrodes according to the prior art often cannot be integrated into customary process fittings. This disadvantageously leads to a high level of installation effort and also to comparatively complex calibrations and / or adjustments.

The present invention is based on the object of providing an ion-selective electrode for an electrochemical sensor which overcomes the disadvantages described.

This object is achieved by the ion-selective electrode for an electrochemical sensor according to claim 1, as well as by the electrochemical sensor according to claim 15.

The ion-selective electrode according to the invention for an electrochemical sensor comprises a, in particular cylindrical, probe body, an enamel layer, which is arranged at least in a first sub-area of the probe body, and an analyte-sensitive layer, which is arranged at least in a second sub-area of the probe body that the analyte-sensitive layer is at least partially in contact with the enamel layer. The enamel layer is designed such that the enamel is formed in particular on the side facing away from the probe body. The analyte-sensitive layer is in turn preferably arranged and / or configured in such a way that it is in at least temporary and / or partial contact with a measurement medium during the operation of a corresponding electrochemical sensor.

The enamel layer can be built up from a single layer or from a plurality of partial layers, in particular one above the other. The enamel layer thus comprises at least one partial layer. In the event that at least two partial layers are present, at least one partial layer facing away from the surface of the probe body is an enamel. In addition, different sub-layers can consist of differently composed enamels. In addition to said enamel layer and said analyte-sensitive layer, the electrode can also comprise at least one intermediate layer, in particular an intermediate layer can be arranged between the enamel layer and the analyte-sensitive layer, in particular if they are at least partially arranged one above the other.

According to the invention, the electrode comprises an electrically conductive layer which is arranged in a third partial area of the probe body. The arrangement can take place directly and / or indirectly on the probe body. The third partial area can be located both in an inwardly and in an outwardly facing area of the probe body.

Both the enamel layer and the analyte-sensitive layer are preferably at least partially arranged in a first section of the electrode which comes into contact with the medium during continuous operation of a respective sensor, that is, in a first section which is connected to a process fitting by a the container containing the medium is introduced.

The electrically conductive layer serves for electromagnetic shielding and / or can be used to use the electrode as a redox-active element, as an electrical potential equalization element (PAL) and / or to derive the electrochemical potential of the analyte-sensitive layer. The use of an electrically conductive layer advantageously leads to an improved signal-to-noise ratio. This makes it possible to arrange the analyte-sensitive layer with a smaller thickness and / or along a reduced sub-area compared to the prior art. Much more compact electrodes with a constant signal-to-noise ratio or signal / interference ratio can therefore be produced.

In one embodiment, the third partial area is arranged in an inwardly facing area of the probe body. In this case, the third sub-area preferably extends along and encompasses the entire probe body in particular a second section of the electrode which does not come into contact with the medium during continuous operation of a corresponding sensor, that is to say in particular a section which is arranged outside a container containing the medium.

In a further embodiment, the third sub-area is arranged in an outward-facing area of the probe body, the second sub-area being separated from the third sub-area. In this case, the electrically conductive layer can partially also include the second section of the electrode, which comes into contact with the medium. It can thus also include a section of the first partial area in which the enamel layer is arranged; however, it does not include the second sub-area. Rather, in this case it is not in contact with the analyte-sensitive layer.

In the context of the present invention, it is conceivable, on the one hand, for the electrode to have a single analyte-sensitive layer. However, it is also possible that the electrode also has at least two, in particular separate, analyte-sensitive layers, which are arranged in different partial areas.

In one embodiment, the analyte-sensitive layer contains lithium.

In a further embodiment, the first and / or third outer diameter of the first and / or third partial area is approximately, in particular at most, 12 mm. In the case that the third sub-area is arranged in an inwardly facing area of the probe body, the first outer diameter is approximately, in particular a maximum of 12 mm, and in the case that the third sub-area is arranged in an outward-facing area of the probe body, the third outside diameter is approximately, in particular, a maximum of 12 mm. The electrode can therefore not only be detachably introduced into any process fitting, but in particular into a standard fitting.

Another embodiment includes that an installation length from a first end area of the electrode to an electrode head arranged in a second end area of the electrode or to an area in which the electrode can be attached to or in a container via a process connection, for example a PG13, 5-process screw connection, in the range between 120-500 mm.

In a further embodiment, a second outer diameter of the second partial area is at most as large as a first outer diameter of the first partial area. The outer diameter in the first or second partial area is composed at least of a first diameter of the probe body and a first thickness of the enamel layer and / or a second thickness of the analyte-sensitive layer. The enamel layer and the analyte-sensitive layer can be arranged both next to one another or at least partially one above the other.

The fact that the second outer diameter of the second sub-area is at most as large as the first outer diameter of the first sub-area ensures that the electrode can be introduced, in particular detachably, into a standard fitting. The electrode can thus be easily introduced into and removed from the container through an opening in a container or through a process fitting, in particular from the outside. In particular, there is no increase in the outer diameter of the electrode in the second sub-area compared to the first sub-area.

Both the enamel layer and the analyte-sensitive layer are preferably arranged at least partially in a section of the electrode which comes into contact with the medium during continuous operation of a respective sensor, i.e. in a section which is introduced into the medium through a process fitting containing container is introduced.

Such a configuration of the electrode is also advantageous with regard to the sealing and / or hygienic properties if the electrode is tightly and / or hygienically introduced into a container containing the process medium.

It is an advantage if the probe body is completely enamelled. In this case, the probe body is enamelled in that section of the electrode which comes into contact with the respective measuring medium during continuous operation of a corresponding sensor. In addition, the probe body is also enameled up to a second end area, that is to say in that section which does not usually come into contact with the medium during continuous operation. Complete enamelling of the probe body is easy to implement in terms of production technology.

In an alternative embodiment, the first sub-area is again selected in such a way that it comprises a section of the electrode that comes into contact with the medium. This section extends from a first end region of the electrode, for example, to a sealing region, which can in particular comprise a sealing surface. When the electrode is attached to or in a container, this sealing area is usually arranged in an area of a process connection, in particular a standard fitting, which is used to introduce the electrode into the container. The section may also include one Sealing area of the electrode. The enamelling thus extends beyond the section that comes into contact with the medium. For this embodiment, at least that portion of the electrode which protrudes into the container during continuous operation of the respective sensor is completely enamelled. In the section which does not come into contact with the medium during continuous operation, ie which remains outside the container, enamelling is not necessary. Such a choice of the first sub-area, on the other hand, can be implemented cost-effectively.

In an advantageous embodiment, the electrode has a circular cross-sectional area, particularly in the area of a sealing surface. In particular, a roundness of the electrode according to FIG DIN ISO 1101 standard less than or equal to 0.1 mm.

It is also advantageous if a concentricity and / or a cylindrical shape of the electrode, in particular in the area of the sealing surface, according to FIG DIN ISO 1101 Norm is / are less than 0.1 mm, preferably less than 0.05 mm.

Another embodiment of the electrode includes that a thickness of the analyte-sensitive layer and / or a thickness of the enamel layer is / are less than 1 mm, preferably less than 0.5 mm, particularly preferably less than 0.3 mm. In this way, a comparatively low impedance of the respective measuring chain of the respective sensor can be guaranteed. This leads to a significantly improved signal-to-noise ratio or signal / interference ratio.

A preferred embodiment includes that the enamel layer and / or the analyte-sensitive layer is / are each applied directly to the probe body. If both layers are applied directly to the probe body, the enamel layer and the analyte-sensitive layer can be arranged adjacent to one another, for example. Alternatively, it is also conceivable that the analyte-sensitive layer is arranged between two enameled cutouts of the first partial area.

In a further preferred embodiment, the analyte-sensitive layer is at least partially applied to the enamel layer. In this regard, it is conceivable on the one hand for the analyte-sensitive layer to be arranged on the enamel layer only in at least one overlapping area. It is also conceivable, however, that the analyte-sensitive layer is applied completely to the enamel layer.

In order to ensure that the second outer diameter of the second sub-area is at most as large as the first outer diameter of the first sub-area, a wide variety of measures are conceivable, of which a few particularly preferred variants are given below.

In one embodiment, a diameter of the probe body is variable, a second diameter of the probe body in the second partial area being smaller than a first diameter of the probe body in the first partial area. In particular, the diameter is varied in such a way that the second outer diameter of the second sub-area is at most as large as the first outer diameter of the first sub-area. For this purpose, the probe body can, for example, have at least one groove, a shoulder and / or a tapering of the diameter.

In a further embodiment, the thickness of the enamel layer is variable, a second thickness of the enamel layer in the second partial area being less than a first thickness of the enamel layer in the first partial area. In this case, the diameter of the enamel layer in particular is varied in such a way that the second outer diameter of the second sub-area is at most as large as the first outer diameter of the first sub-area.

It is also conceivable to vary the diameter and / or thickness of several components of the electrode, in particular the diameter of the probe electrode, the thickness of the enamel layer and / or the thickness of the analyte-sensitive layer.

Another particularly preferred embodiment provides that the second sub-area has a disk-shaped, ring-shaped, cap-shaped and / or at least partially spherical, in particular hemispherical or almost spherical, geometry. The second partial area can be arranged in the area of a jacket surface and / or a base surface of the probe body. The probe body is preferably of cylindrical design, an end region of the probe body which comes into contact with the medium during operation of a respective sensor being planar or rounded, in particular spherical.

In one embodiment, the electrode comprises a sealing surface, by means of which the electrode can be inserted into a container, in particular into a process fitting, in a sealing manner. For example, the process fitting or an opening in the container comprises a sealing ring which surrounds and thus seals the sealing surface. The sealing surface is preferably arranged within the first partial area, that is to say in the enameled partial area of the electrode.

In a further particularly preferred embodiment, the third sub-area at least partially surrounds the first sub-area, the second outer diameter of the second Sub-area is at most as large as a third outer diameter of the third sub-area. For this configuration, the electrically conductive layer is therefore arranged in an outwardly facing region of the probe body. Furthermore, the outer diameter of the second sub-area in which the analyte-sensitive layer is arranged is at most as large as an outer diameter of the third sub-area, which for this configuration is the sum of the diameter of the probe body and the thicknesses of the enamel layer and the electrical conductive layer composed. This allows the detachable fastening in a process fitting.

One embodiment includes that the electrically conductive layer comprises at least one noble metal, in particular gold or platinum.

Another embodiment includes that the electrode comprises at least one electrical line, by means of which the conductive layer is electrically contacted. In this case, both active electromagnetic shielding and passive electromagnetic shielding are conceivable.

The electrical line is used in particular to make electrical contact between the electrically conductive layer and a measuring circuit of a corresponding sensor (active) or with a reference electrode of a corresponding sensor (passive).

In a preferred embodiment, the electrode comprises a flexible, in particular shielded, printed circuit card for making electrical contact with the analyte-sensitive layer.

In another preferred embodiment, the electrode comprises a preamplifier which is arranged in an inner volume of the probe body. The preamplifier leads to a further improvement in the signal-to-noise ratio.

In one configuration, the electrode comprises a mechanically stabilizing, in particular electrically insulating, layer which is arranged in a fourth partial area of the probe body. The use of an additional mechanically stabilizing layer increases the mechanical stability of the electrode. This measure makes the electrode essentially splinter-free.

It is advantageous if the fourth sub-area at least partially surrounds at least the first sub-area. The mechanically stabilizing layer is then applied at least to a section of the first partial area and thus at least partially surrounds the enamel layer. However, it does not include the second sub-area. The analyte-sensitive layer is therefore not surrounded by the mechanically stabilizing layer.

It is also advantageous if the second outer diameter of the second sub-area is at most as large as a fourth outer diameter of the fourth sub-area. In this way, even when using a mechanically stabilizing layer, it can be ensured that the electrode can be introduced into the respective container and removed from the respective container in a simple manner.

The object on which the invention is based is further achieved by an electrochemical sensor for measuring an ion activity in a measuring medium, comprising an analyte-sensitive electrode according to one of the embodiments described and a reference electrode. In particular, it is a potentiometric sensor with which a potential difference between the ion-selective electrode and the reference electrode can be detected via a measuring circuit that is also present. The sensor can be used to determine a measured variable that is dependent on the concentration or activity of an analyte, in particular an analyte ion, in a measuring medium. The measuring medium can be a measuring liquid, for example a water-containing solution, emulsion or suspension.

The measuring circuit can further be configured to generate a measuring signal based on the detected potential difference. It can be combined with a higher-level data processing electronics, e.g. a measuring transducer or transmitter, connected or connectable and be set up to output the measurement signal to the higher-level data processing electronics. The data processing electronics can be set up to convert a measured value of the measured variable to be determined by means of the potentiometric sensor, e.g. an analyte activity or concentration or the pH value, to determine and output and / or display. Likewise, the data processing electronics can be integrated in the sensor and in particular comprise a data memory, in particular for the at least temporary storage of calibration, sensor and / or measurement data.

The higher-level data processing electronics are preferably arranged in a sensor head, with data exchange between the measuring circuit and the higher-level data processing electronics inductively via a connection path which is used for galvanic decoupling.

The sensor also preferably has a PG13.5 thread for the detachable connection of the sensor to the container, in particular a standard process fitting

It should be noted that in connection with the electrode according to the invention The embodiments described can also be applied mutatis mutandis to the sensor according to the invention and vice versa.

• 1: eine emaillierte ionenselektive Elektrode gemäß Stand der Technik;
• 2: zwei Ausgestaltungen einer erfindungsgemäßen Elektrode mit einer elektrisch leitfähigen Schicht;
• 3: zwei Ausgestaltungen einer erfindungsgemäßen Elektrode mit einer mechanisch stabilisierenden Schicht;
• 4: verschiedene Ausgestaltungen einer erfindungsgemäßen Elektrode, bei welchen die Emaille-Schicht und die Analyt-sensitive Schicht direkt auf den Sondenkörper aufgebracht sind; und
• 5: verschiedene Ausgestaltungen einer erfindungsgemäßen Elektrode, wobei (a,b,c) ein Durchmesser des Sondenkörpers entlang seiner Längsachse, und (d,e) eine Dicke der Emaille-Schicht entlang ihrer Längsachse variabel ausgestaltet sind;

The invention is illustrated by the following figures 1 - 5 explained in more detail. It shows

• 1 : an enameled ion-selective electrode according to the prior art;
• 2 : two configurations of an electrode according to the invention with an electrically conductive layer;
• 3 : two configurations of an electrode according to the invention with a mechanically stabilizing layer;
• 4th : various configurations of an electrode according to the invention, in which the enamel layer and the analyte-sensitive layer are applied directly to the probe body; and
• 5 : different configurations of an electrode according to the invention, wherein (a, b, c) a diameter of the probe body along its longitudinal axis, and (d, e) a thickness of the enamel layer along its longitudinal axis are designed to be variable;

In the figures, the same elements are provided with the same reference numerals.

In 1 is an enamelled ion-selective electrode 1 shown according to the prior art. The electrode 1 has a cylindrical probe body 2 on, which is in an end area 2a is rounded. In the continuous operation of a corresponding sensor [not shown here] the electrode comes 1 in a first section A , which is the end area 2a includes and which for the embodiment shown here up to a sealing area of the electrode 1 ranges in which the electrode 1 by means of a process connection 3 is attached in a container not shown separately here, with a measuring medium [also not shown] in contact.

On the probe body 2 is facing outwards at least in a first sub-area T1, which is composed of the two sub-areas T1a and T1b, an enamel layer 4th applied, which the probe body 2 surrounds. For the embodiment shown here, the probe body is 2 even completely enamelled. In a second sub-area T2 within section A there is also an analyte-sensitive layer 5 upset. The enamel layer 4th ensures that the electrode has high mechanical stability and is chemically inert. However, for various reasons described in the introduction, the analyte-sensitive layer must 5 are usually made comparatively thick in order to be able to guarantee good measurement accuracy. Since an outer diameter d2 of the second sub-area T2 is greater than a first outer diameter d1 outside this sub-area T2, the electrode is 1 however not suitable for use with standard process fittings. In particular, it usually has to be firmly attached to the respective container [not shown] or process connection 3 are connected, which means in particular a high installation effort.

The present invention counteracts this problem in that the electrode according to the invention 1 an electrically conductive layer 8th includes, which in a third sub-area T3 of the probe body 2 arranged as in 2 shown by way of example for two possible, different configurations.

According to the design 2a is the electrically conductive layer 8th and consequently the third sub-area T3 in an inwardly facing area of the probe body 2 arranged. The third sub-area T3 extends along the entire probe body 2 , so both in a first section A1 of the electrode 1 , which comes into contact with the medium when a corresponding sensor is in operation, as well as in a second section A2, which is outside a container [represented by the process connection 3 ] remains.

The enamel layer 4th is arranged in a first sub-area T1, which extends partially along the first section A1, and which also has a sealing surface 7th , which when a corresponding sensor [not shown] is attached in the area of the process connection 3 is arranged, and includes an overlying tolerance range T, which ensures that the first section A1 of the electrode is completely enamelled. The analyte-sensitive layer 5 includes an end area 2a of the probe body 2 and is also arranged in the first section A1 and designed in the shape of a cap. In the transition area 6 are the enamel layer 4th and the analyte-sensitive layer 5 in contact with each other.

Furthermore, in 2a for example a preamplifier 9 in an internal volume of the probe body 2 arranged next to the shield by the electrically conductive layer 8th a further improvement in the signal-to-noise ratio of the electrode 1 causes. The preamplifier 9 can for example have a conductive connection 9 ' with the analyte-sensitive layer 5 be connected. The integration of a preamplifier 9 however, it is not absolutely necessary. In the embodiments shown below, a preamplifier was also used 9 waived. However, it should be noted that the configurations shown below also have a preamplifier 9 can include.

In contrast to the design 2a is for 2 B the electrically conductive layer 8th in an outward-facing area of the probe body 2 arranged. Here the third sub-area T3 extends over the second section A2 and furthermore comprises a section of the first sub-area T1. The electrically conductive layer 8th but is not in contact with the analyte-sensitive layer 5 which is analogous to the in 2a analyte-sensitive layer shown 5 is designed and arranged.

In 2 B the third sub-area T3 partially surrounds the first sub-area T1. The electrode 1 is such that an outer diameter d2 of the second sub-area T2 is smaller than an outer diameter d3 in the third sub-area T3. In other configurations, the outer diameter d2 of the second partial area T2 can also be larger than in FIG 2a embodiment shown, but it should correspond at most to the third outer diameter d3 of the third sub-area T3.

The electrode further comprises 1 according to 2 B an electrical line 10 for making electrical contact with the electrically conductive layer 8th , for example with electronics [not shown]. The type of contact depends on the type of shielding required - active or passive. There is also a flexible, shielded printed circuit board 11 for electrical contacting of the analyte-sensitive layer 5 intended. Also the electrical wiring 10 as well as the circuit board 11 are not absolutely necessary. In the embodiments shown below, an electrical line was also shown 10 and a circuit board 11 waived. It should be noted, however, that the configurations shown above and those shown below also have an electrical line 10 and / or a circuit board 11 can include.

In the two in 3 The variant shown is the electrode 1 analogous to 2 designed. In addition to those related to 2 components described includes the electrode 1 a mechanically stabilizing layer 12th , which is applied to the probe body in a fourth sub-area T4. The use of an additional mechanically stabilizing layer 12th increases the mechanical stability of the electrode 1 . The electrode 1 becomes essentially splinter-free through this measure.

For the design according to 3a the fourth sub-area T4 completely surrounds the first sub-area T1. In 3b on the other hand, is only a section of the third sub-area T3 of the mechanically stabilizing layer 12th surround. In both configurations, the second outer diameter d2 of the second sub-area T2 is smaller than a fourth outer diameter d4 of the fourth sub-area T4. In other configurations, the second diameter can also be larger than for the exemplary configurations shown here, but the second diameter d2 should be at most as large as the fourth diameter d4.

It is also advantageous if the second outer diameter d2 of the second sub-area T2 is at most as large as the first outer diameter d1 of the first sub-area T1 in which the enamel layer 4th on the probe body 2 is upset. This is without restriction of the generality for the configurations according to 2 and 3 the case. In addition to the configurations shown there, however, a wide variety of other possibilities are conceivable, some of which are particularly preferred variants given by way of example in the following figures.

4th shows four different configurations of an electrode according to the invention 1 in which the enamel layer 4th and the analyte-sensitive layer 5 each directly on the probe body 2 are upset. According to 4a is the analyte-sensitive layer 5 arranged in a second sub-area T2, which is arranged between two sub-areas T1a and T1b of the first sub-area T1. The second sub-area T2 is configured in an annular manner and in the area of a lateral surface of the probe body 2 arranged. In the transition area 6 are the analyte-sensitive layer 5 and the enamel layer in contact with each other. For the in 4a The embodiment shown, the first d1a and the second outer diameter d1b of the two sub-areas T1a and T1b of the first sub-area T1 are essentially the same size (d1a = d1b = d1). Furthermore, the second outer diameter d2 of the first sub-area T1 is as large as the outer diameter d1 of the first sub-area T1 [d1 = d2]. In this way the electrode 1 can be used for a standard fitting.

The electrode 1 further comprises a sealing surface 7th , which is located in the first sub-area T1a of the first sub-area T1. In the area of the sealing surface 7th can the electrode 1 be sealingly attached to or in a container.

Both sub-areas T1a and T1b of the first sub-area are arranged in such a way that they are at least partially connected to a section A of the electrode that comes into contact with the medium 1 include. The first sub-area T1b includes the first end section 2a the electrode 1 ; the second sub-area T1a extends from the second sub-area T2 over the sealing surface 7th and comprises, beyond the sealing surface, a tolerance range T to ensure complete enamelling of section A of the electrode, which is from the first end section 2a up to the sealing surface 7th runs.

Also for the design according to 4b is the probe body 2 enamelled in area T1. Here, however, the first sub-area T1 is not divided into two sub-areas. The second sub-area T2, in which the analyte-sensitive layer 5 is arranged, is cap-shaped and includes the end region 2a of the probe body 2 . The first sub-area T1 and the second sub-area T2 are accordingly adjacent to one another and are also in the transition area 6 in contact with each other. As in the case of the design according to 4a the first outer diameter d1 of the first sub-area T1 is equal to the second outer diameter d2 of the second sub-area T2.

It should be pointed out that the second outer diameter d2 of the second sub-area T2 does not necessarily have to correspond to the first outer diameter d1 of the first sub-area T1. Rather, the second outside diameter d2 can also be smaller than the first outside diameter d1.

While for the configurations according to 4a and 4b the probe body 2 in the end area 2a ends with a surface of a spherical section, closes the probe body for the configurations according to the figures 4c and 4d with a concave base G from. In the area of the base area G there is the second sub-area T2 and, associated therewith, the analyte-sensitive layer 5 arranged. For the design according to 4c the second sub-area T2 is configured circular, while for the configuration according to FIG 4d is designed ring-shaped. In both cases, the second outside diameter d2 is smaller than the first outside diameter d1.

It is also conceivable that the probe body terminates with a planar base area G. In this case too, the second outside diameter d2 would be smaller than the first outside diameter d1.

In order to ensure that the second outer diameter d2 of the second sub-area T2 is at most as large as the first outer diameter d1 of the first sub-area T1, a diameter D of the probe body can also be used, for example 2 be variable, as in 5a-5c shown. Alternatively or additionally, a thickness δ of the enamel layer can also be used 4th be designed to be variable (cf. 5d and 5e) .

In 5a points the probe body 2 in the first sub-area T1 a first diameter D1 which is larger than a second diameter D2 in the second sub-area T2. The probe body 2 is completely enamelled, for example, and the analyte-sensitive layer is in the second sub-area T2, which is covered by the first sub-area T1 5 arranged. The difference between the first D1 and the second diameter D2 corresponds, for example, in the case of a constant thickness δE of the enamel layer 4th maximum of the thickness δA of the analyte-sensitive layer 5 so that the outer diameter d2 of the second sub-area T2 is as large as the first outer diameter d1 of the first sub-area T1. The outer diameter d2 of the second sub-area T2 can, however, also be smaller than the first outer diameter d1 of the first sub-area, as in FIG 5b shown.

In addition to a cap-shaped configuration of the second sub-area T2, the second sub-area T2 can, for example, also be configured in an annular manner, as in FIG 5c shown. The first sub-area T1 is again subdivided into two sub-areas T1a and T1b with the outer diameters d1a and d1b, which are the same size for the embodiment shown (d1a = d1b = d1). Also the diameter D1a and D1b of the probe body 1 are the same size in both sub-areas T1a and T1b (D1a = D1b = D1). In the second partial area T2, on the other hand, the probe body has a groove such that the first diameter D1 of the probe body, or the diameters D1a and D1b of the probe body 2 are larger than the second diameter D2 of the probe body 2 in the second sub-area T2. In this case too, the difference between the first D1 and the second diameter D2 corresponds, for example, in the case of a constant thickness δE of the enamel layer 4th maximum of the thickness δA of the analyte-sensitive layer 5 so that the outer diameter T2 of the second sub-area T2 is at most as large as the outer diameter d1 of the first sub-area T1.

In the configurations according to 5d and 5e which regarding the configurations of the analyte-sensitive layer 5 , or with regard to the configuration of the second sub-area T2, the configurations in each case 5a and 5c correspond to the probe body 2 a constant diameter D. However, the enamel layer has 4th in the first sub-area T1 of 5d or in the two sub-areas T1a, T1b in 5e a first thickness δE1, which is greater than a second thickness δE2 in the second partial area T2. Again, it is assumed for the embodiment shown that the probe body 2 is completely enamelled.

The analyte-sensitive layer is also in the second sub-area T2, which is covered by the first sub-area T1, T1a, T1b 5 arranged. The difference between the first δE1 and second thickness δE2 of the enamel layer 4th corresponds at most to the thickness δA of the analyte-sensitive layer 5 so that the outer diameter T2 of the second sub-area T2 is at most as large as the outer diameter d1 of the first sub-area T1, T1a, T1b. In case of 5e is also the first for simplicity Thickness δE1 of the enamel layer 4th the same size in both sub-areas.

It goes without saying that in other configurations, both the thickness D of the probe body 2 , as well as the thickness δA of the analyte-sensitive layer 5 can be variable.

Finally, it should be noted that in connection with the figures 4th and 5 Considerations made mutatis mutandis also apply to the electrically conductive layer 8th in the third sub-area T3 and on the mechanically stabilizing layer 12th have T4 applied in the fourth sub-area.

List of reference symbols

1

electrode

2

Probe body

3

Sealing of a process connection

4th

Enamel layer

5

Analyte-sensitive layer

6

Transition area

7th

Sealing surface

8th

Electrically conductive layer

9

Preamplifier

9 '

Line between preamplifier and analyte-sensitive layer

10

Electrical line

11

Circuit board

12th

Mechanically stabilizing layer

T, T1-T4, T1a, T1b

Sub-areas

A, A1, A2

Sections

d1-d4, d1a, d1b

Outside diameter of the sub-areas

D1-D2

Diameter of the probe body

δE, δE1, δE2

Thickness of the enamel layer

δA

Thickness of the analyte-sensitive layer

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• EP 0180071 B1 [0007]
• EP 0614694 B1 [0007]
• WO 2018/069591 A1 [0007]

Non-patent literature cited

• DIN ISO 1101 standard [0031]
• DIN ISO 1101 [0032]

Claims (15)

Ion-selective electrode (1) for an electrochemical sensor comprising an, in particular cylindrical, probe body (2), an enamel layer (4) which is arranged at least in a first partial area (T1) of the probe body (2), and an analyte-sensitive one Layer (5) which is arranged at least in a second partial area (T2) of the probe body in such a way that the analyte-sensitive layer (5) is at least partially in contact with the enamel layer (4), characterized in that the electrode ( 1) comprises an electrically conductive layer (8) which is arranged in a third partial area (T3) of the probe body (2). Electrode (1) Claim 1 , wherein the third partial area (T3) is arranged in an inwardly facing area of the probe body (2). Electrode (1) Claim 1 wherein the third partial area (T3) is arranged in an outwardly facing area of the probe body (2), and wherein the second partial area (T2) is separated from the third partial area (T3). Electrode (1) according to at least one of the preceding claims, wherein a first (d1) and / or third outside diameter (d3) of the first (T1) and / or third partial area (T3) is approximately, in particular at most, 12 mm. Electrode (1) according to at least one of the preceding claims, wherein an installation length from a first end region (2a) of the electrode (1) to an electrode head arranged in a second end region of the electrode (1) or to a process connection for fastening the electrode ( 1) on or in a container in the range between 120-500 mm. Electrode (1) according to at least one of the preceding claims, wherein a second outer diameter (d2) of the second partial area (T2) is at most as large as a first outer diameter (d1) of the first partial area (T1). Electrode (1) according to at least one of the preceding claims, wherein the third sub-area (T3) at least partially surrounds at least the first sub-area (T1), and wherein the second outer diameter (d2) of the second sub-area (T2) is at most as large as a third (d3) Outside diameter of the third sub-area (T3). Electrode (1) according to at least one of the preceding claims, wherein the electrically conductive layer (8) comprises at least one noble metal, in particular gold or platinum. Electrode (1) according to at least one of the preceding claims, comprising at least one electrical line (10), by means of which the electrically conductive layer (8) is electrically contacted. Electrode (1) according to at least one of the preceding claims, comprising a flexible, in particular shielded, printed circuit card (11) for making electrical contact with the analyte-sensitive layer (5). Electrode (1) according to at least one of the preceding claims, wherein a preamplifier (9) is arranged in an inner volume of the probe body (2). Electrode (1) according to at least one of the preceding claims, comprising a mechanically stabilizing layer (12) which is arranged in a fourth partial area (T4) of the probe body (2). Electrode (1) Claim 12 wherein the fourth sub-area (T4) at least partially surrounds the first sub-area (T1). Electrode (1) Claim 12 or 13th , wherein the second outer diameter (d2) of the second sub-area (T2) is at most as large as a fourth outer diameter (d4) of the fourth sub-area (T4). Electrochemical sensor for measuring ion activity in a measuring medium, comprising an analyte-sensitive electrode (1) according to one of the preceding claims and a reference electrode.

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