Break-resistant electrochemical sensor containing break-resistant membrane glass, method for manufacturing a break-resistant membrane glass of a glass component of a measuring half-cell and method for manufacturing the break-resistant glass assembly of an ion-sensitive single-rod measuring chain

Abstract

Method for producing a shatter-resistant membrane glass (2) of a glass component of a measuring half-cell (1) of an analyte-sensitive sensor, comprising: - providing at least one membrane glass (2) of a sensor blown onto a shaft (3), which consists of a sodium- and lithium-containing glass, preferably sodium- and lithium silicate glass, or of a lithium-containing glass, preferably lithium silicate glass, or comprises one of these materials; - bringing the at least one membrane glass (2) blown onto a shaft (3) into contact with a pickling solution containing sodium ions, preferably a sodium acetate or sodium nitrate solution or a melt containing sodium ions; - heating the membrane glass (2) at a temperature of 200°C-500°C, preferably 300-450°C, more preferably 400-450°C for 10-20 minutes, wherein the membrane glass (2) is ion-sensitive.

Description

Determining the concentration of an analyte in a measuring medium plays a crucial role in many industrial applications, such as chemical and pharmaceutical engineering, food technology, and biotechnology, as well as in non-industrial analytical applications, for example, in environmental measurement technology. Sensors with an analyte-sensitive component are frequently used in laboratories and industrial process plants to determine ion concentrations. One example of a suitable analyte-sensitive component is an analyte-sensitive membrane. For instance, the glass membrane of the well-known pH glass electrode is sensitive to the concentration or activity of H+ or H3O+ ions in a measuring medium. For example, DE 20 2006 017 215 U1 describes measuring probes with glass electrodes for pH and redox measurements. State-of-the-art pH glass sensors consist of two half-cells (a pH half-cell and a reference half-cell). At least the pH half-cell comprises a pH-sensitive glass membrane connected to an electrically insulating glass tube, which usually terminates coaxially with the outer tube in the connector head. Despite the high theoretical strength of the glass material itself, pH glass sensors are relatively fragile in practice. Residual stresses remain, particularly in the area of ​​the pH glass membrane in contact with the medium and in the subsequent transition to the glass tube, as a result of the manufacturing process. Residual stresses parallel to the glass surface are generally undesirable and, in the case of high amplitude, microdefects, or inadequate joining of the glass components (e.g., at the membrane-glass-shaft junction), can lead to glass breakage (membrane rupture). A thermally partially prestressed pH glass membrane often exhibits better performance (lower impedance) and higher fracture strength. However, such pH glass membranes tend to splinter significantly more when their breaking point is exceeded. This serious disadvantage largely precludes the inline use of pH glass sensors in some key industries (such as the food / beverage industry) today. Shatterproof electrochemical glass sensors with a shatterproof glass component, preferably a glass shaft component, are desirable in many applications. The glass exhibits, for example, excellent corrosion resistance to acids and alkalis. The object according to the present invention is therefore to provide a sensor comprising a glass component comprising a membrane glass, wherein the membrane glass consists of a break-resistant glass which has better properties with regard to breakage resistance compared to the conventionally used lithium-containing membrane glass. The problem is solved by a method for producing a break-resistant glass component of an analyte-sensitive sensor, comprising: - providing at least one membrane glass of a sensor blown onto a shaft, which consists of a sodium- and lithium-containing glass, preferably sodium- and lithium silicate glass, or of a lithium-containing glass, preferably lithium silicate glass, or comprises one of these materials; - bringing the at least one membrane glass blown onto a shaft into contact with a pickling solution containing sodium ions, preferably a sodium acetate or sodium nitrate solution or a melt containing sodium ions; - heating the membrane glass at a temperature of 200°C-500°C, preferably 300-450°C, more preferably 400-450°C for 10-20 minutes, wherein the membrane glass is ion-sensitive. In the process described above, stresses parallel to the surface in the pH glass / shaft interface are relieved, and the pH glass membrane is chemically strengthened / hardened. This increases the fracture resistance of the glass membrane by a factor of 4-5. The planned residence time in the heat treatment step is sufficient because, due to the good mobility of the Li+ ions in the lithium silicate pH membrane glass, the Li / Na ion exchange between the pickling solution and the membrane glass, as well as between the membrane glass and the shaft glass, occurs sufficiently quickly. The heat treatment step is short enough to prevent devitrification of the pH glass. In one embodiment of the process, the pickling solution containing sodium ions, preferably a sodium acetate or sodium nitrate solution or a melt containing sodium ions, further contains potassium ions. In an alternative embodiment of the process, after the heating step, the membrane glass is subsequently brought into contact with a pickling solution containing potassium ions, preferably a potassium acetate or potassium nitrate solution or a melt containing potassium ions. This step is also carried out at a temperature of 200°C-500°C, preferably 300-450°C, more preferably 400-450°C for 10-20 minutes. In one embodiment of the above-mentioned method, contact with a pickling solution includes immersion in the pickling solution or spraying with the pickling solution. In one embodiment, after immersion in the pickling solution or spraying with the pickling solution, the glass is heated with a laser. In one embodiment, at least the membrane glass is immersed in the melt. In one embodiment of the method, the ion-sensitive sensor is an analyte-sensitive sensor, preferably a cation-sensitive or anion-sensitive sensor. In one embodiment of the method, the cation-sensitive sensor is a Na+, K+ sensor or a pH-sensitive or hydronium ion-sensitive sensor. In one embodiment of the method, the shaft consists of sodium silicate glass hardened with potassium ions or the shaft contains sodium silicate glass hardened with potassium ions. The term "shaft" refers to the shaft of the glass component of the measuring half-cell. In one embodiment, the method comprises the process steps according to the invention or an embodiment thereof, followed by the steps of: cooling the glass component comprising a shaft and shatter-resistant membrane glass blown onto the shaft and materially bonded to the glass component to room temperature. Cleaning of the glass component, wherein the cleaning is preferably automated and preferably carried out with deionized water. The invention further relates to a method for manufacturing the shatter-resistant glass assembly of a single-rod measuring chain comprising a tempered ion-sensitive membrane glass, comprising providing a glass body containing an inner shaft tube having a cylindrical cavity and an outer shaft tube surrounding the inner shaft tube and being materially connected to the inner shaft tube and closed at the bottom, inserting a cylindrical diaphragm into a receptacle of the inner shaft tube, wherein the diaphragm has an O-ring on its outer surface for sealing with the inner shaft tube, and shatter-resistant membrane glass of a glass component of a measuring half-cell according to the invention or an embodiment thereof, followed by the steps Insertion of the glass component of a measuring cell, containing a shaft tube and a pH-sensitive glass membrane bonded to the shaft tube, into the cylindrical cavity. The inner and outer shaft tubes are arranged coaxially. The material bond is achieved through fusion. The material bond and the ion-sensitive membrane glass are located on the side of the single-rod measuring chain that faces the medium during operation. In a preferred embodiment, the glass body consists of or comprises a sodium-containing glass tempered with K+ ions, preferably a sodium-containing silicate glass. Alternatively, the invention comprises a method for manufacturing the break-resistant glass assembly of a single-rod measuring chain comprising a break-resistant ion-sensitive membrane, comprising: providing a glass body of a single-rod measuring chain comprising an inner shaft tube having a cylindrical cavity and an outer shaft tube surrounding the inner shaft tube and being materially bonded to the inner shaft tube and closed at the bottom; blowing or melting a lithium-containing membrane glass onto the cylindrical cavity of the inner shaft tube, wherein the membrane glass consists of a sodium- and lithium-containing glass, preferably sodium- and lithium silicate glass, or of a lithium-containing glass, preferably lithium silicate glass, or comprises one of these materials;Bringing the at least one membrane glass, blown onto a shaft, into contact with a pickling solution or a melt containing sodium ions, preferably a sodium acetate or sodium nitrate solution or a melt containing sodium ions, heating the membrane glass at a temperature of 200°C-500°C, preferably 300-450°C, more preferably 400-450°C for 10-20 minutes, wherein the membrane glass is ion-sensitive. The inner and outer shaft tubes are arranged coaxially. The metallurgical bond between the inner and outer shaft tubes is achieved through fusion. This metallurgical bond and the ion-sensitive membrane glass are located on the side of the glass body of the single-rod measuring chain that faces the medium during operation. In a preferred embodiment of the above-mentioned method, the glass body of the single-rod measuring chain consists of a sodium-containing glass tempered with K+ ions, preferably sodium silicate glass, or it comprises this material. In one embodiment of the above-mentioned methods for manufacturing the shatterproof glass assembly comprising an ion-sensitive membrane, the method further comprises the inventive method for manufacturing a shatter-resistant ion-sensitive membrane glass or an embodiment thereof. The invention further relates to a glass assembly of a single-rod measuring chain comprising an inner shaft tube having a cylindrical cavity and an outer shaft tube surrounding the inner shaft tube and being materially connected to the inner shaft tube and closed at the bottom, and a shatter-resistant ion-sensitive membrane glass blown onto the shaft tube, wherein the shatter-resistant ion-sensitive membrane glass comprises or consists of lithium ion silicate glass, wherein at least some of the lithium ions are replaced by sodium ions. In one embodiment of the glass assembly, the shatter-resistant ion-sensitive membrane glass is obtainable by the method according to the inventive method for producing a shatter-resistant membrane glass or an embodiment thereof. The material-bonded connection and the ion-sensitive membrane glass are arranged on the side of the glass assembly of the single-rod measuring chain that faces the medium during operation. The invention further relates to a break-resistant electrochemical sensor comprising: - a glass assembly according to the invention or an embodiment thereof, - a measuring half-cell and a reference half-cell, each comprising a lead and an electrolyte, - an electronic unit which is electrically connected to the lead of the measuring half-cell and the lead of the reference half-cell. All the above-described embodiments of the modular system and the measuring system can each be combined with each other, provided this is technically possible. The invention is explained in more detail in the following description with reference to the exemplary embodiments shown in the drawing. Figure 1 shows an embodiment of a glass component of a measuring half-cell obtainable by the method according to the invention. Figure 2 shows an embodiment of a glass assembly obtainable by the method according to the invention. Fig. 1 shows a glass component (1) of a measuring half-cell comprising a shatter-resistant ion-sensitive membrane glass (2) and a shaft (3) of the glass component. Fig. 2 shows a glass assembly (4) comprising a shatter-resistant, ion-sensitive membrane glass (2), a glass body (5) comprising an inner shaft tube (6) and an outer shaft tube (7), which are made of shatter-resistant glass or non-shatter-resistant glass. The shatter-resistant glass of the shaft tubes comprises a sodium ion-containing glass, preferably a sodium silicate glass in which at least some of the sodium ions have been replaced by potassium ions, or the shatter-resistant glass consists of this material. The outer shaft tube (7) has a diaphragm (8). The inner shaft tube (6) is metallurgically bonded, preferably by fusion, to the shatter-resistant, ion-sensitive, lithium-containing membrane glass (2) in which at least some of the lithium ions have been replaced by sodium ions. The tempered, ion-sensitive glass is obtained by a method according to the invention or an embodiment thereof. Reference symbol list (1) Glass component of a measuring half-cell (2) Break-resistant ion-sensitive membrane glass made of tempered lithium-containing glass (3) Shaft of the glass component of the measuring half-cell (4) Glass assembly (5) Glass body (6) Inner shaft tube (7) Outer shaft tube (8) Diaphragm QUOTES INCLUDED IN THE DESCRIPTION This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature DE 20 2006 017 215 U1

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Claims

Method for producing a shatter-resistant membrane glass (2) of a glass component of a measuring half-cell (1) of an analyte-sensitive sensor, comprising: - providing at least one membrane glass (2) of a sensor blown onto a shaft (3), which consists of a sodium- and lithium-containing glass, preferably sodium- and lithium silicate glass, or of a lithium-containing glass, preferably lithium silicate glass, or comprises one of these materials; - bringing the at least one membrane glass (2) blown onto a shaft (3) into contact with a pickling solution containing sodium ions, preferably a sodium acetate or sodium nitrate solution or a melt containing sodium ions; - heating the membrane glass (2) at a temperature of 200°C-500°C, preferably 300-450°C, more preferably 400-450°C for 10-20 minutes, wherein the membrane glass (2) is ion-sensitive. The method of claim 1, wherein the pickling solution contains sodium ions, preferably a sodium acetate or sodium nitrate solution, or a melt containing sodium ions, further contains potassium ions. Method according to claim 1 or 2, wherein bringing into contact with a pickling solution comprises immersion in the pickling solution or spraying with the pickling solution. Method according to claim 3, wherein after immersion in the pickling solution or spraying with the pickling solution the glass is heated with a laser. Method according to claim 1 or 2, wherein at least the membrane glass (2) is immersed in the melt. Method according to one of claims 1 to 5, wherein the membrane glass (2) is subsequently brought into contact with a pickling solution, preferably a potassium acetate or potassium nitrate solution or with a melt containing potassium ions. Method according to one of claims 1-6, wherein the ion-sensitive sensor is an analyte-sensitive sensor, preferably a cation-sensitive or anion-sensitive sensor. Method according to claim 7, wherein the cation-sensitive sensor is a Na+, K+ sensor or a pH-sensitive or hydronium ion-sensitive sensor. Method according to any one of claims 1 to 8, wherein the shaft (3) consists of or contains potassium ion-tempered sodium silicate glass. A method comprising the process steps according to any one of claims 1 to 9, followed by the steps: Cooling the glass component (1) comprising a shaft (3) and shatter-resistant membrane glass (2) blown onto the shaft (3) and materially bonded to the glass component (1) to room temperature; Cleaning the glass component (1), wherein the cleaning is preferably automated and preferably carried out with deionized water. Method for manufacturing the shatter-resistant glass assembly (4) of an ion-sensitive single-rod measuring chain comprising tempered ion-sensitive membrane glass (2), comprising providing a glass body (5) containing an inner shaft tube (6) having a cylindrical cavity and an outer shaft tube (7) surrounding the inner shaft tube (6) and being materially bonded to the inner shaft tube (6) and closed at the bottom, inserting a cylindrical diaphragm (8) into a receptacle of the inner shaft tube (6), wherein the diaphragm (8) has an O-ring on its outer surface for sealing with the inner shaft tube (6), and the method for manufacturing a shatter-resistant membrane glass (2) of a glass component of a measuring half-cell (1) according to any one of claims 1-10, followed by the steps of inserting the glass component of a measuring cell (1), comprising a shaft tube and a pH-sensitive glass membrane (2) materially bonded to the shaft tube, into the cylindrical cavity. Glass assembly (4) of a single-rod measuring chain for an analyte-sensitive sensor comprising an inner shaft tube (6) having a cylindrical cavity and an outer shaft tube (7) surrounding the inner shaft tube (6) and being materially connected to the inner shaft tube (6) and closed at the bottom, and a shatter-resistant ion-sensitive membrane glass (2) blown onto the shaft tube, wherein the shatter-resistant ion-sensitive membrane glass (2) comprises or consists of lithium ion silicate glass, wherein at least some of the lithium ions are replaced by sodium ions. Glass assembly (4) of a single-rod measuring chain according to claim 12, wherein the shatter-resistant ion-sensitive membrane glass (2) is obtained by the method according to any one of claims 1 to 10. Break-resistant electrochemical sensor comprising: - a glass assembly (4) according to claim 12 or 13, - a measuring half-cell and a reference half-cell, each comprising a lead and an electrolyte, - an electronic unit which is electrically connected to the lead of the measuring half-cell and the lead of the reference half-cell.

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