WO2024194443A1

WO2024194443A1 - Method and device for measuring a gas concentration in a reaction chamber

Info

Publication number: WO2024194443A1
Application number: PCT/EP2024/057687
Authority: WO
Inventors: Sven HIESTAND; Stefan HOLENSTEIN; Dieter Zeisel
Original assignee: Trafag Ag
Priority date: 2023-03-21
Filing date: 2024-03-21
Publication date: 2024-09-26

Abstract

In order to improve the process control in reaction chambers (14), such as bioreactors for example, in particular for cell cultivation or fermentation, the invention proposes a method for measuring the concentration (cz) of a gas component (Z) to be measured of a gas mixture (12b) with a known composition in a liquid solution in a reaction chamber (for example a bioreactor) (14), having the steps of: a) providing a measuring chamber (16) which is separated from the interior of the reaction chamber (14) by a gas-permeable separating membrane (18), b) measuring the gas density (ρ), the gas pressure (p), and the temperature (T) in the measuring chamber (16), and c) determining the concentration (cz) of the gas component (Z) to be measured from the values measured in step b) and from the molar mass of the gas components (X, Y, Z) of the gas mixture.

Description

Trafag AG 10210139 P-WO Industriestrasse 11 CH-8608 Bubikon Switzerland Measuring method and measuring device for measuring a gas concentration in a reaction chamber, for example a bioreactor The invention relates to a measuring method for measuring a concentration (changing, for example, during a reaction, in particular a bioreaction, such as in particular a cell cultivation or fermentation) of a gas component to be measured of a gas mixture of known composition in a reaction chamber designed, for example, as a bioreactor or the like. In particular, the invention relates to a measuring method for measuring a CO2 concentration in a bioreactor or in a reaction chamber in the food or beverage industry or in wastewater treatment plants. The invention further relates to a reaction method, in particular a bioreaction method, in particular a cell cultivation method or fermentation method, which is carried out in a reaction chamber, such as in particular a bioreactor, using the measuring method. The invention further relates to a measuring device for measuring a concentration (changing, for example, during a reaction, in particular a bioreaction) of a gas component to be measured, in particular CO2, of a gas mixture of known composition in a reaction chamber such as a bioreactor. The invention further relates to a reaction system, in particular a bioreaction system, comprising a reaction chamber designed, for example, as a bioreactor and such a measuring device, as well as the use of a measuring device. For the technological background and the state of the art, reference is made to the following literature: [1] Wikipedia “Bioreactor”, https://de.wikipedia.org/wiki/Bioreaktor, downloaded on March 20, 2023 [2] Wikipedia “Disposable bioreactor”, https://de.wikipedia.org/wiki/Einwegbioreaktor, downloaded on March 20, 2023 [3] Wikipedia “Cell culture”, https://de.wikipedia.org/wiki/Zellkultur, downloaded on March 20, 2023 [4] Wikipedia “Severinghaus electrode, https://de.wikipedia.org/wiki/Severinghaus-Elektrode, downloaded on March 20, 2023 [5] Wikipedia “Non-dispersive infrared sensor”; https://de.wikipedia.org/wiki/Nichtdispersiver_Infrarotsensor, downloaded on 20.03.2023 [6] Wikipedia “Tunable Diode Laser Absorption Spectroscopy”, https://de.wikipedia.org/wiki/Tunable_Diode_Laser_Absorption_Spectrosc opy, downloaded on 20.03.2023 [7] Wikipedia “Photoacoustic spectroscopy”, https://de.wikipedia.org/wiki/Photoakustische_Spektrskopie, downloaded on 20.03.2023 [8] Z. Hetzler et al., “Flexible sensor patch for continuous carbon dioxide monitoring”; Front Chem.2022; 10: 983523; published online, 2022 Sep 27; doi: 10.3389/fchem.2022.983523 [9] US 9903903 B2 [10] A. Kramer, Th. A. Paul, “High-precision density sensor for concentration monitoring of binary gas mixtures, Sensors and Actuators, A202 (2013) 52-56, http://dx.doi.org/10.1016/j.sna.2013. 02.010; published on March 7, 2013; [11] Th. A. Paul et al. “SF ₆ concentration sensor for gas-insulated switchgear”, Sensors and Actuators, A206 (2014) 51-56; http://dx.doi.org/10.1016/j.sna.2013.11.024; published on November 28, 2013 [12] “Monitoring of insulating gas density”; company brochure of Trafag AG with the printing note “11/2022 H70558a”, https://media.trafag.com/literature/brochure/H70558a_DE_Gas_Density_B rochure_hires.pdf; downloaded on March 20, 2023 [13] DE 102020110349 B4 [14] US 2016/0349176 A1 The reference [13] describes a bioreaction system in which a CO ² concentration is measured using a known CO ² sensor, in particular a Severinghaus probe. The reference [14] describes a gas analysis system for analyzing the concentration of several gas components in a gas mixture for energy supply, in which hydrogen is mixed with the components of natural gas or liquefied gas. For this purpose, the proportions of those gas components that absorb infrared light are determined using infrared spectrometry, and a gas density measurement is carried out in order to determine the proportions of those gas components that do not absorb infrared light from the results of the infrared spectrometry and the gas density measurement. The method is carried out at an energy supplier in order to control the addition of hydrogen to the natural gas. Preferred embodiments of the invention relate to methods and devices for measuring a gas concentration in bioreactors or other reaction spaces for carrying out bioprocesses. In particular, the methods and devices are designed to determine the gas concentration of one or more gas components of a gas mixture contained in a liquid, in particular dissolved. The determination of gas concentrations in liquid media is particularly interesting for bioreactions, where the CO2 content in a bioreactor and in particular in a liquid contained in the bioreactor is of particular interest. Bioreactions are, for example, processes in which at least one component is transformed by a cell, a microorganism or by interactions thereof. Other areas of application for the methods and devices according to embodiments of the invention are chemical processes, processes in the food industry including beverage production, e.g. breweries, processes in energy generation and processes for packaging food. According to the literature reference [1], a bioreactor, often also referred to as a fermenter, is a container in which certain microorganisms, cells or small plants are cultivated (also: fermented) under the best possible process conditions. The operation of a bioreactor is therefore an application of biotechnology that uses or makes biological processes (bioconversion, biocatalysis) usable in technical facilities. Important factors that can be controlled or monitored in most bioreactors are the composition of the nutrient medium (also nutrient solution or substrate), the composition of the gaseous phase in the bioreactor, in particular the oxygen supply, temperature, pH value, sterility and others. The purpose of cultivation in a bioreactor can be the extraction of cells or components of the cells or the extraction of metabolic products. These can be used, for example, as active ingredients in the pharmaceutical industry or as basic chemicals in the chemical or biochemical industry. The breakdown of chemical compounds can also take place in bioreactors, for example. B. in wastewater treatment in sewage treatment plants. A wide variety of organisms are cultivated in bioreactors for different purposes. Examples of the use of bioreactors are given in [1] and [3]. Bioreactors can be made from stainless steel or glass for multiple use (in the biotech industry), for example. However, disposable bioreactors made of plastic have also been increasingly used recently, see [1] and [2] and [13]. In some embodiments of the invention, bioreactors can also be used in environmental technology and disposal technology, for example for biomass production or for the decomposition of biowaste, and can also be made from cheaper materials such as concrete. In a bioreactor there are up to three phases: solid (biomass), liquid (nutrient medium) and gaseous (for example air, oxygen, carbon dioxide, nitrogen). Their distribution is controlled in the bioreactor using various measures. One factor that influences cell cultivation is the composition of the gases dissolved in the liquid phase in the bioreactor. These usually consist of the components oxygen, nitrogen and carbon dioxide. To avoid any confusion, we then speak of dissolved oxygen, dissolved nitrogen and dissolved carbon dioxide (English: “dissolved” and correspondingly DO or DO ₂ or DCO2 or DCO ₂ ). As a rule, the composition of the desired gas mixture in the bioreactor is known and is specifically influenced, adjusted or provided in order to obtain the desired results in cell culture. In particular, the biotech industry relies on precise control of the CO 2 content in bioreactors such as incubators, fermentation vessels and other equipment in order to support the growth and development of cells, tissues and organisms. Reasons for measuring CO ₂ in a bioreactor during cell cultivation are in particular: ^ high CO ₂ accumulation changes cells and product quality and productivity ^ low CO 2 concentration also affects productivity ^ a correlation has been found between biomass growth and CO ₂ evolution rate (CER) CO ₂ accumulation can be reduced by stripping. Dissolved CO ₂ can easily penetrate the cell membrane and affect the intracellular pH value, which has a direct influence on cell mechanisms. By determining CO 2 in bioreactors online (process measurement), the processes in bioreactors can be significantly improved and/or optimized. It is therefore desirable that the measurement results are available immediately, with very short response times. Furthermore, the measurements should be economical and easy to carry out and as accurate as possible. However, the CO ₂ sensors currently on the market are often expensive, prone to drift and inaccuracy and must be calibrated frequently. This can lead to costly downtime and fluctuations in the test results. In addition, the known sensors are susceptible to reactive gases and have a slow response time. The methods used to measure CO2 in connection with bioreactions are in particular: Severinghaus, see [4] and [13], NDIR (non-dispersive infrared), see [5], TDL (tunable diode laser), see [6], PAS (photo acoustic), see [7], TC (thermal conductivity) and BGA (blood gas analysis with Severinghaus); see also [8]. According to [13], a sensor can also be used to measure dissolved _CO2 optochemically, whereby the sensor should have a _CO2 -sensitive chromophore. Tunable diode laser (TDL) or tubable diode laser absorption spectroscopy (TDLAS) are methods with which the concentration or density of the gas or gas component to be examined is deduced from a measured absorption. TDLs are only accurate to about 2%, require relatively long path lengths (>50mm), achieve a maximum repeatability of 0.75% and are comparatively large and expensive. However, the measurement is very fast (<10 seconds response time). Another possibility is to excite the gas or gas component CO ₂ in the infrared range. This creates a noise that can be measured. However, this photo-acoustic measurement is significantly slower than a TDL. Response times of two minutes can only be achieved without a sterilizable separation membrane. The measurement technology reaches its limits, especially in the area of high humidity. Response times of three minutes are realistic. Sensor technology for the traditional area is based on NDIR (non-dispersive infrared), for example. Tests with first-generation devices showed response times of around 10 minutes (time: end of 2021). Other suppliers of bio-process containers (BPC Bio Process Containers), which the SUB also offers including sensors, rely on fluorophore-based technology. Similar to the following «Severinghaus» electrodes, the pH value of an electrolyte (bicabonate) is actually measured here. This means that CO2 must first diffuse through a separating membrane, then "influence" a fluorophore in order to then move a buffer, ultimately enabling a pH measurement. The accuracy of the devices is stated as 3% in the 0-10% CO2 range. A measurement of up to 15% is probably possible. Users' experiences report a response time of over 5 minutes. The devices are based on PDMS-based (polydimethylsiloxane) measurements and scientific publications even mention 10 minutes. The most common measurement method is the sensor in the form of the Severinghaus electrode. The Severinghaus principle is based on a pH probe that is immersed in a bicarbonate electrolyte solution that is housed in a _CO2 -permeable membrane. When _CO2 reaches equilibrium with the bicarbonate buffer, the pH is lowered by the formation of carbonic acid, and the pH change is then correlated with a CO2 concentration. Probes based on the Severinghaus principle are used in the biopharmaceutical industry as inline sensors for real-time detection and have become a gold standard in analytics. The reference [13] aims to use the commercially available sensors for oxygen and CO2 in a disposable bioreactor. These established systems are based on processes in which the gas components present or dissolved in the medium (M) are dissolved out, then bound in a polymer and then determined therein or released again into a defined fluid (for example bicarbonate buffer or special electrolytes). Costs, handling and maintenance effort were probably one reason why _CO2 measurement took so long to adapt. Blood gas analysis is also a form of the Severinghaus principle and is always offline and therefore outside the bioprocess. Measurement using thermal conductivity (TC) is of little practical importance. It is used primarily in the food industry and only in processes where the gas or gas mix is precisely known, such as packaging under protective gas or bottling drinks - especially beer. Despite the critical importance of the CO2 content in culture media, little attention was paid to this measurement in the past. One reason for this was the lack of reliable sensors and measuring methods. The object of the invention is to provide measuring methods and measuring devices for determining concentrations of critical gases in processes that can be carried out quickly and reliably using relatively simple means. To solve this problem, the invention creates a measuring method according to claim 1 and a measuring device according to the auxiliary claim. Advantageous uses are the subject of the further auxiliary claims. Advantageous embodiments of the invention are the subject of the subclaims. According to a first aspect, the invention provides a measuring method for measuring a concentration of a gas component to be measured of a gas mixture of known composition in a liquid solution in a reaction space, comprising the steps: a) providing a measuring chamber which is separated from the reaction space by a liquid-impermeable and gas-permeable separating membrane, b) measuring the gas density ρ, the gas pressure p and the temperature T in the measuring chamber and c) determining the concentration of the gas component to be measured from the values measured in step b) and from the molar masses of the gas components of the gas mixture. The measuring chamber is preferably very small. This results in particularly fast reaction times and short measuring times. Changes in the concentration in the solution are transferred very quickly to the very small measuring chamber volume. In some embodiments, the measuring chamber volume V is less than 5000 mm ³ . In particular, V is less than 3000 mm ³ or less than 1000 mm ³ or significantly less than 100 mm ³ . The lower limit of the measuring chamber volume depends on the miniaturization of the available sensors for gas density, pressure and temperature. The lower limit is, for example, 0.5 mm ³ , or 1 mm ³ or 2 mm ³ depending on the sensor used. It is particularly preferred that step a) comprises the step: a1) providing the measuring chamber (16) with a measuring chamber volume V, where 0.5 mm ³ ≤ V ≤ 15 mm ³ , in particular 1 mm ³ ≤ V ≤ 10 mm ³ , and preferably 2 mm ³ ≤ V ≤ 5 mm ³ . The physical quantities gas density, pressure and temperature are determined. Thus, no chemical conversions are necessary for the measurement, which also contributes to reliability and rapid measurement. The sensors used are in particular sensors that can be manufactured in small dimensions. In particular, quartz oscillators or tuning fork sensors are used for gas density measurement. Tuning fork gas density sensors are known for other technical fields, in particular for monitoring insulating gases in electrical switchgear, and are available on the market. It is preferred that step b) comprises the step: b1) measuring the gas density by means of a tuning fork gas density sensor and/or a quartz oscillator. In particular, a quartz tuning fork is used. In particular, this is miniaturized as much as possible. In some embodiments, the measuring method for measuring a concentration of a gas component to be measured in a gas mixture of known composition - preferably changing during a bioreaction - is designed in a bioreactor and comprises the steps: a) providing a measuring chamber which is separated from the interior of the bioreactor by a gas-permeable separating membrane, b) measuring the gas density ρ, the gas pressure p and/or the temperature T in the measuring chamber and c) determining the concentration of the gas component to be measured from the values measured in step b) and/or from the molar masses of the gas components of the gas mixture (known due to the known composition). In particular, the gas component to be measured is CO2. The impetus for developing embodiments of the invention was and is the interest in the concentration of the dissolved gas component sought in the liquid phase. The measuring method according to the invention is thus designed to determine the concentration of the dissolved gas component sought in the liquid phase. However, the measuring method also works for measurements in the gas supply and exhaust gas measurement in bioreactors, fermenters or reactors for e.g. gas synthesis. In particularly preferred embodiments, the concentration of a gas component to be measured in a gas mixture of known composition dissolved in the liquid phase in the reaction chamber, such as in particular the bioreactor, is measured. Preferably, the separation membrane is in contact with the liquid phase in the reaction chamber, e.g. the bioreactor. Particularly preferably, the entire surface of the measuring membrane facing the interior of the reaction chamber is in the liquid phase. Particularly preferably, the measuring membrane is attached or provided in an area of the lower half or the lower third of the reaction chamber. Examples of the reaction space are a bioreactor, a disposable bioreactor, a bioreactor with a diameter of less than 10 mm, a reaction space in the food industry, a reaction space for beverage production, a reaction space in a brewery, a reaction space in a sewage treatment plant, a reaction space in a wastewater treatment plant, a reaction space in a CO2 extraction plant, a reaction space in process analytics, a pipeline, a water pipeline. The term “gas-permeable separation membrane” means that the separation membrane is permeable to the gas components of the gas mixture. In the methods according to embodiments of the invention, not one analyte or one of the gas components is measured, but all analytes or gas components in the medium are measured together. At least two of the physical or chemical properties of the gas mixture are determined (e.g. density, pressure, thermal conductivity, electrical conductivity and/or temperature, or others). In particular, the density is determined together with one of the other physical properties mentioned. In some embodiments, the gas components contained in or dissolved in the medium contained in the bioreactor are extracted and then directly determined in a measuring chamber. Measurements are taken in the fluid phase. For this purpose, in some embodiments, the separation membrane is a composite material that contains, among other things, a polymer that is not flexible. The rigidity of this separation membrane ensures stable measurement in the event of fluctuations in the process pressure (cf. today's conventional membranes). In some embodiments, the membrane is stiffened and/or reinforced. While in sensors for gas analysis in bioreactors according to the prior art, the analyte is bound in a polymer or the like, in embodiments of the invention all gas components are displaced into the measuring chamber by diffusion. In embodiments of the invention, it is provided that not one analyte is determined, but rather all dissolved gases in the measuring chamber are measured and then a of these components can be determined. In a CO2 determination, for example, one is not restricted to determining CO2 in an air mixture, but one could also determine the CO ₂ content in a hydrogen-methane mixture. Gases other than CO2 can also be determined. Preferably, the separation membrane contains a stiffener and/or a reinforcement. Preferably, the separation membrane is not stretchable. Preferably, the separation membrane is stiff and not flexible. In some embodiments, a fluid is characterized in the measuring chamber. In some embodiments, the reaction system has a gas-tight construction so that no gas can escape from the measuring chamber to the outside. In some embodiments, the measuring chamber is gas-tight to the outside and is only connected to the interior of the bioreactor via the gas-permeable separation membrane. In some embodiments, the measuring chamber is designed such that gas can only pass from the medium in the reaction space into the measuring chamber through the gas-permeable membrane, which is designed such that it is sealed from the environment. It is preferred that the gas mixture contains at least one further gas component from the group comprising air, technical air, dried air and a mixture of O2 and N2. Bioreactors or other reaction chambers are usually operated with a liquid phase in which a predetermined gas mixture is introduced. In particular, the reaction chamber, designed as a bioreactor, for example, is operated with air, or with a specifically introduced mixture of O2, N2, CO2 and/or other gases. Preferably, the measuring method comprises: measuring a further physical parameter of the gas mixture. In particular, a further physical property or a further gas component is measured. By further measuring a further physical property or a gas component, for example, another gas component can be determined precisely. The measuring method preferably comprises: measuring the relative humidity. The concentration of the gas component to be measured, in particular CO ₂ , is determined as a function of the measured humidity value. Within the liquid phase, the humidity and thus the partial pressure is a function of the temperature, although the gas component to be measured on the opposite side of the separating membrane in the measuring chamber does not have to be 100%. The measuring method preferably comprises: measuring the content of another gas in the gas mixture, such as the O ₂ content. In particular, this allows the average molar mass of the gas mixture to be determined more precisely, which improves the measurement result. This applies to all components of the gas mixture. It is preferred that the gas mixture is grouped into the gas component to be measured and a component group with the other components of the gas mixture, that the average molar mass of the component group weighted according to the concentration of the components is determined and that in step c) the concentration of the gas component to be measured is determined from the molar mass of the gas component to be measured and the weighted average molar mass. The corresponding step is known, for example, in a completely different technical field - the determination of the electrical breakdown strength of an insulating gas present as a gas mixture in electrical switchgear - for example from [9]. It is preferred that in step b) the gas density is measured by means of a quartz oscillator and more preferably by means of a tuning fork. For example, a quartz oscillator known from [12] can be used. Measurements of the gas density using a quartz oscillator sensor are also known from [9] to [11] in the field of Gas density measurement of insulating gases in electrical switching and distribution systems (high-voltage technology) is known. According to a further aspect, the invention creates a reaction method for carrying out a reaction in a reaction chamber, comprising measuring a concentration of a gas component of the gas mixture in the reaction chamber by carrying out the measuring method according to one of the preceding embodiments and carrying out further steps of the reaction method depending on the measurement. In some embodiments, the reaction method is a bioreaction method for carrying out a bioreaction in a bioreactor, comprising measuring a concentration of a gas component of the gas mixture in the bioreactor by carrying out the measuring method according to one of the preceding embodiments and carrying out further steps of the bioreaction method depending on the measurement. In particular, cell cultivation is carried out in the bioreactor and controlled by measuring the concentration of CO ₂ , particularly preferably by measuring the concentration of DCO2, using the measuring methods presented here. According to a further aspect, the invention provides a measuring device for measuring a concentration of a gas component to be measured of a gas mixture of known composition in a reaction space, comprising: a measuring chamber with a gas-permeable separating membrane for separating the measuring chamber from the interior of the reaction space, a measuring device for measuring the gas density ρ, the gas pressure p and the temperature T in the measuring chamber and an evaluation device which is set up to determine the concentration of the gas component to be measured from the values measured by the measuring device and from the molar masses of the gas components of the gas mixture. In some embodiments, the measuring device is designed to measure a concentration of a gas component to be measured in a gas mixture of known composition in a bioreactor, which concentration preferably changes during a bioreaction, and comprises: a measuring chamber with a gas-permeable separating membrane for separating the measuring chamber from the interior of the bioreactor, a measuring device for measuring the gas density ρ, the gas pressure p and the temperature T in the measuring chamber and an evaluation device which is designed to determine the concentration of the gas component to be measured from the values measured by the measuring device and from the molar masses of the gas components of the gas mixture. The term "gas-permeable separating membrane" means that the separating membrane is permeable to all gas components of the gas mixture. The separating membrane is designed in such a way that it allows convection of the gas mixture into the measuring chamber. In some embodiments, the separating membrane has a stiffening or reinforcement and/or is not flexible and also not stretchable. Particularly when the measuring chamber volume is very small, very short reaction times can be achieved, e.g. less than 60 s in the liquid phase. It is therefore preferred that the measuring chamber has a measuring chamber volume of less than 5000 mm ³ , in particular less than 3000 mm ³ , preferably less than 1000 mm ³ , preferably less than 100 mm ³ . The lower limit for the measuring chamber volume depends on the miniaturizability of the sensors, in particular the gas density sensor, and is, for example, 0.5 mm ³ , 1 mm ³ or 2 mm ³ . In some embodiments, the measuring chamber has a measuring chamber volume V with 0.5 mm ³ ≤ V ≤ 15 mm ³ , in particular 1 mm ³ ≤ V ≤ 10 mm ³ , and preferably 2 mm ³ ≤ V ≤ 5 mm ³ . In some embodiments, the measuring device has a quartz oscillator and/or a tuning fork sensor for measuring the gas density. In particular, a quartz oscillator fork is used. In some embodiments, the measuring device has a further measuring device for measuring a further physical property or a further physical parameter of the gas mixture. Preferably, the measuring device has a humidity measuring device for measuring the relative humidity. Preferably, the measuring device has a gas content measuring device for measuring the content of at least one further gas in the gas mixture. Preferably, the evaluation device is designed to determine the concentration depending on the measurement of the further physical property, the measurement of the humidity measuring device and/or the measurement of the gas content measuring device. It is preferred that the evaluation device is designed to determine the concentration of CO2 in an atmosphere containing O2 and N2 in the reaction chamber designed, for example, as a bioreactor. The evaluation device is particularly preferably designed to use the concentrations of CO ₂ in an atmosphere containing O ₂ and N ₂ within the measuring chamber to determine the partial pressure and thus the concentration of dissolved CO 2 in the liquid phase of the reaction chamber. Preferably, the measuring device according to one of the above embodiments is designed to carry out a measuring method according to one of the above embodiments. According to a further aspect, the invention provides a reaction system for carrying out a reaction, comprising a reaction chamber and a measuring device according to one of the above embodiments, wherein the measuring chamber is separated from the interior of the reaction chamber by the separating membrane. Examples of the reaction space are: a bioreactor, a disposable bioreactor, a bioreactor with a diameter of less than 10 mm, a reaction space in the food industry, a reaction space for beverage production, a reaction space in a brewery, a reaction space in a sewage treatment plant, a reaction space in a wastewater treatment plant, a reaction space in a CO2 extraction plant, a reaction space in process analytics, a pipeline and a water pipeline. In some embodiments, the reaction system is a bioreaction system for carrying out a bioreaction, such as in particular cell cultivation or fermentation, comprising: a bioreactor and a measuring device according to one of the preceding embodiments, wherein the measuring chamber is separated from the interior of the bioreactor by the separation membrane. It is preferred that the bioreactor is a disposable reactor. According to a further aspect, the invention provides a use of a measuring device which has a measuring chamber delimited by a gas-permeable separating membrane and a measuring device for measuring the gas density ρ, the gas pressure p and the temperature T in the measuring chamber, for measuring a concentration of a gas component to be measured of a gas mixture in a reaction chamber separated from the measuring chamber by the separating membrane, such as in particular a bioreactor. The measuring device is particularly preferably used to measure a concentration of a gas component to be measured of a gas mixture dissolved in the liquid medium of the reaction chamber (e.g. bioreactor). In the embodiments of the methods and devices and systems of the invention, a temperature measurement is also carried out. The measuring chamber is preferably designed in such a way that its temperature can rise faster than the temperature gradient of the reaction in the reaction chamber. This is also supported by a small measuring chamber volume. Preferred embodiments of the invention relate to the measurement of the concentration of a gas component, in particular the dissolved CO ₂ in the liquid phase, in a reaction chamber designed, for example, as a bioreactor, preferably by means of a combination sensor. The relationships between the influencing variables density, pressure/partial pressure, gas density and their dependence on temperature and relative humidity are known. In preferred embodiments of the invention, Henry's law is applied with the aid of a gas-permeable separation membrane, according to which the partial pressure of a gas above and in a liquid is equal and directly proportional to the concentration of the gas in the liquid. Density, temperature, (optional) relative humidity and absolute pressure of the gas mixture between the separation membrane and the measuring device are determined. With sufficiently precise determination, the partial pressure of individual gas components can be deduced, in particular if they differ significantly in their molar mass and/or can be divided into two groups. For example, a difference of just 12 g/mol is significant - the literature reference [9] speaks of MA-MB >20 g/mol. With preferred embodiments, a factory-calibrated measuring device can be designed which is calibration-free for the end user. Some embodiments provide the possibility of coupling the electrical device (the measuring device) with an oxygen sensor. This makes it possible to increase the accuracy due to a more precise determination of the effective molar mass of a component group of the gas mixture. Preferably, a concentration of DCO ₂ is measured due to the great economic importance for cell cultivation or similar bioreactions carried out in bioreactors. The measurement of the concentration of DCO ₂ is also possible in other reactions, such as in the food industry, beverage production, environmental technology, Waste water treatment, etc. is interesting and can be carried out using the methods and devices presented here. Of course, other gas concentrations can also be measured using the same principle. For example, the measuring method would also be possible for dissolved ammonia and acetone in the liquid phase, provided the separation membrane is compatible. Applications in the field of biogas production (methane and carbon dioxide with traces of nitrogen, oxygen, hydrogen sulphide, hydrogen and ammonia) and biofuel production, in which CO2 and methane CH4 play a key role, are also possible. The principle and structure are explained in more detail below using the example of a CO2 measurement. Although a bioreactor is used in particular as an example for the reaction chamber, it should be clear that the reaction chamber is also constructed differently in other embodiments of the invention. Examples of possible reaction chambers are listed above. Exemplary embodiments are explained in more detail below using the attached drawings. These show: Fig. 1 a schematic block diagram of embodiments of a measuring device for measuring the concentration of a dissolved gas component in a reaction chamber designed, for example, as a bioreactor; Fig.2 is a schematic diagram illustrating a grouping of gas components of a gas mixture with the gas component to be measured in component groups during the evaluation of measurement signals from a sensor of the measuring device; Fig.3 is a block diagram of a bioreactor system with a bioreactor and the measuring device; Fig.4 is a schematic diagram of a disposable bioreactor with a coupling for coupling the measuring device; Fig.5 is a sectional view through the coupling of Fig.4; Fig.6 is a sectional view of an embodiment of the coupling together with a separation membrane module; and Fig.7 is a further schematic block diagram with a basic representation of the measuring principle according to further embodiments of the invention; and Fig.8 is a microscopic photograph of an embodiment of a measuring device of the measuring device designed as a combination sensor. Fig.1 shows an embodiment of a measuring device 10, with further optional components of further possible embodiments of the measuring device 10 being shown with dashed lines. Fig.1 is a purely schematic block diagram to illustrate the principle of the measuring device 10, with the size relationships not actually shown. The measuring device 10 is designed to measure a concentration of a dissolved gas component Z to be measured of a dissolved gas mixture 12, 12b of known composition in a reaction chamber 14 designed, for example, as a bioreactor. For example, in the reaction chamber 14 there is a predetermined or regulated atmosphere (gaseous phase - gas mixture 12a -) with the components X, Y and Z. For example, in the reaction chamber, which is designed as a bioreactor, there is air with an increased proportion of CO2 or another, e.g. technically produced mixture of O2, N2 and CO2. Accordingly, for example, a gas mixture 12b dissolved in the liquid phase with the components X=O ₂ , Y=N ₂ and Z=CO ₂ is contained in the reaction chamber 14. The measuring device 10 is designed to measure the concentration of one of the gas components in a liquid solution in the reaction chamber. In some embodiments, the measuring device 10 is designed to measure the concentration of CO ₂ , more particularly CO2 dissolved in the liquid phase, i.e. DCO2, is formed in the reaction chamber 14. In the example shown, the measuring device 10 is designed as an electrical device with a combination sensor 22 for determining the concentration of CO2. The reaction chamber 14 is a container with process medium (liquid and gaseous). Examples of the reaction chamber 14 are explained in more detail below. In particular, a bioreaction, namely cell cultivation or fermentation, is carried out in the reaction chamber 14, which in some embodiments is designed as a bioreactor, wherein the content of DCO2 is to be determined and used to control/monitor the bioreaction. The measuring device 10 has a measuring chamber 16 with a gas-permeable separating membrane 18 for separating the measuring chamber 16 from the interior of the reaction chamber 14. During operation, the separation membrane 18 is in full contact with the liquid phase in the reaction chamber 14. The dissolved gas components of the gas mixture 12b in the liquid phase are allowed to pass through the separation membrane 18, so that a gas mixture 12c corresponding to the gas mixture 12b dissolved in the liquid phase is located in the measuring chamber 16. The separation membrane 18 is permeable to all gas components of the gas mixture and enables convection. In some designs, the separation membrane 18 is neither flexible nor stretchable and for this purpose has reinforcement and/or stiffening (not shown). The measuring chamber 16 is designed with the smallest possible measuring chamber volume V. In particular, the measuring chamber volume V is less than 5000 mm ³ , preferably less than 4000 mm ³ , less than 3000 mm ³ and more, in particular less than 500 mm ³ , in particular less than 100 mm ³ . The measuring chamber 16 is in particular as small as a miniaturization of the measuring device 20 explained in more detail below allows. For example, lower limits for the measuring chamber volume V are 0.5 mm ³ to 2 mm ³ , depending on the degree of miniaturization. The measuring device 10 has a measuring device 20 for measuring the gas density ρ, the gas pressure p and the temperature T in the measuring chamber. In particular, the measuring device 20 is designed as a combination sensor 22. The combination sensor 22 has a known temperature sensor 24, a known pressure sensor 26 and a gas density sensor 28. The gas density sensor 28 is, as is known in particular from [12], to which reference is made for further details, a quartz oscillator sensor, preferably designed as a tuning fork, in which the gas density is determined via the difference in the oscillation frequencies of a quartz oscillator fork exposed to the measuring medium and a quartz oscillator fork oscillating in a reference volume. For further details on this measuring principle, reference is made to the literature references [9] to [12]. The different sensors 24, 26, 28 can be provided in a sensor housing or separately; they are designed in such a way that they measure the temperature T, the pressure p and the gas density ρ of the gas mixture 12c located within the measuring chamber 16. The measuring device 10 also has an evaluation device 30 which is set up to determine the concentration of the gas component Z to be measured from the values measured by the measuring device 20 and from the molar masses of the gas components X, Y, Z of the gas mixture 12c. The evaluation device 30 is, for example, part of an analysis and control unit 32 which has a processor 34 and a memory 36. The evaluation device 30 is programmed with appropriate computer programs in order to carry out the evaluations described in more detail below for determining the concentration of CO ₂ from the measured values T, p and ρ. The measurement results depend on the influencing variables temperature and humidity. In order to reduce this influence, some embodiments of the measuring device 10 optionally have one or more additional filters 38 and/or a heater 40. In some embodiments of the measuring device 10, a humidity sensor 42 is optionally provided for measuring the relative humidity φ in the measuring chamber 16. Some embodiments of the measuring device 10 can have an optional external sensor 44 for detecting a further gas component Y, in particular DO2, in the reaction chamber 14. During operation of the reaction chamber 14, a measuring method for measuring a concentration of a gas component Z to be measured of a gas mixture 12b of known composition in a liquid solution is carried out in the reaction chamber 14, comprising: a) providing a measuring chamber 16 which is separated from the interior of the reaction chamber 14 by a gas-permeable separating membrane 18, b) measuring the gas density ρ, the gas pressure p and the temperature T in the measuring chamber 16 and c) determining the concentration of the gas component Z to be measured from the values measured in step b) and from the molar masses of the gas components X, Y, Z of the gas mixture 12c (= 12b). The physical relationships of the measurements carried out in preferred embodiments are explained in more detail below. Carbon dioxide is typically encountered as a gas. Therefore, the measurement of carbon dioxide in processes is a measurement of the pressure exerted by the carbon dioxide either in the gas or in the liquid in which it is dissolved. The relevant physico-chemical laws are: ^ Dalton's law (law of partial pressures) and ^ Henry's law (Henry's law) ^ Mass balance (law of conservation of mass) Dalton's law (law of partial pressures):

The total pressure is made up of the partial pressures of the individual gas components. The sum of all partial pressures gives the total pressure. The partial pressure corresponds to the pressure that the individual gas component would exert if it were present alone in the volume under consideration. The extent to which gases react with other substances, diffuse and dissolve in liquids is determined by their partial pressure and not by their concentration in gas mixtures or liquids. Therefore, for dry air (pwater=0): P _{total air} = p _nitrogen + p _oxygen + p _{carbon dioxide} + p _argon + p _{trace gases} At an air pressure of 1013 mbar (hPa), 0.038% of this pressure is contributed by carbon dioxide. According to Dalton, p _{carbon dioxide} is therefore 0.385 mbar. Due to the low volume percentage of carbon dioxide in air, and the increased expected concentration of carbon dioxide in the process application, air is not recommended as a gas for calibration. A gas mixture consisting of 5% carbon dioxide, 20% oxygen and 75% nitrogen is more advantageous in both respects. According to Dalton, under normal conditions (1013 mbar and 25°C) for a dry gas, the following results: p _carbon of 50.65 mbar, p _oxygen of 202.60 mbar and p _nitrogen of 759.75 mbar Henry's Law: According to Henry's Law, each individual gas dissolves in a liquid according to its partial pressure in the gas phase. After the distribution equilibrium has been reached, each individual gas has the same partial pressure in the gas phase and in the liquid. With the help of the gas-permeable separation membrane 18, Henry's Law is applied to the bioreactor 14, according to which the partial pressure of a gas above and in a liquid is equal and directly proportional to the concentration of the gas in the liquid. Gas density ρ, temperature T, optionally relative humidity φ and absolute pressure p of the gas mixture 12c between the separation membrane 18 and measuring device 20 are determined. With sufficiently accurate determination, the partial pressure of individual gas components pX, pY, pZ can be determined, provided that they differ significantly in their molar mass. In particular, the gas components X, Y and Z of the gas mixture are divided into two groups A, B, as indicated in Fig.2. For example, the components X and Y, in this case oxygen and nitrogen, are classified in a component group A with the partial pressure pA=pX+pY and the at least one gas component Z to be measured, such as carbon dioxide, is classified in a component group B. For component group A, the average molar mass weighted according to the concentration of components X, Y is determined. The molar mass of component Z is known. From this, as explained in more detail in [9], the partial pressure of component group B and thus the partial pressure of component Z (in this case carbon dioxide) and thus the concentration can be determined. The schematic diagram in Fig. 1 shows a schematic representation of an example of an electrical device for implementing the measuring device 10. The design of the container with the process medium (liquid or gaseous) is irrelevant. This makes it possible to determine a gas concentration of a gas component of a gas mixture in a liquid solution. The electrical device is connected to the container with the process medium (=bioreactor 14) via a process connection provided with the gas-permeable separation membrane 18. The process connection with the gas-permeable separating membrane 18 forms a coupling 48 between the container with the medium to be characterized and the measuring device 10. The gas mixture 12b of the process medium diffuses through the gas-permeable separating membrane 18 into the measuring chamber 16. Due to the influencing factors of temperature and humidity, it may be advantageous or, for certain applications, also necessary to equip the measuring device 10 with the additional filters 38 and the heater 40, in particular to avoid condensation within the measuring chamber 16 and on the surfaces of the sensors 22, 24, 26, 28. The measuring device 20, designed as a sensor package or combination sensor 22, for example, determines the density ρ, the absolute pressure p, the temperature T and here also the relative humidity φ of the gas mixture 12c. The signals are temporarily stored in the evaluation device 30 of the measuring device 10 and processed in the processor 34. The components X, Y, Z of the gas mixture, their proportions and the accuracy of the sensors 24, 26, 28, 42 in the sensor package are the influencing variables for the precise determination of the partial pressure p _B of component B. In some versions, the measuring device 20 is designed as a Rho-pT sensor with the gas components CO ₂ , O ₂ and N ₂ for determination and component analysis. The molar masses of the gas components are: CO2: 44g/mol O ₂ : 32g/mol N228 g/mol. The three components are assigned to two component groups A and B to be defined. The molar masses M _A and M _B are taken into account as the average molar mass weighted with respect to their relative concentrations, as was done in [9] for O ₂ , N ₂ and «C5» to determine the dielectric breakdown strength. A bioreactor 14 has a higher concentration of CO2. CO2 is assigned here, for example, to component group B, and N2 and O2 to component group A. Examples of determining the concentration of CO2 in a gas mixture 12 in the form of air are explained below. Example 1: A container connected to the measuring device 10 with the measuring chamber 16 by means of the separating membrane 18 is filled with dry air. A gas mixer adds Carbon dioxide is added until it contains 5% carbon dioxide by volume. The measurement is then carried out. The conditions are: ^^ _^^^ =1013.25 mbar T=30°C rH = φ = 0% The sensors ideally deliver the following signals: Density sensor: 1194.085354 g/m ³ Pressure sensor: 1013.25 mbar Temperature sensor: 30°C Humidity sensor: 0% The concentration is determined using the general gas equation: ^ _{^ ൌ} ^{^^ ⋅ ^^} ^ _{^ ⋅ ^^} where R is the universal gas constant (R= 8.31446 ^{^} ^ _^^⋅^ and M is the molar mass of the gas mixture. This equation can be solved for the molar mass. In the processor, the molar mass M is therefore determined by ^ _{^ ൌ} ^{^^ ⋅ ^^ ⋅ ^^} ^ _^^^^ This results in a value of M= 29.70204501 g/mol. For the CO ₂ of the molar mass of CO ₂ is: ^^ ^^ _^ _ைమ ൌ ^^ െ ^^ _^௨^௧ For dry air, an average molar mass M _air =28.949 g/mol was determined. This gives the molar mass portion attributable to CO2: ΔMCO2=0.753045011g/mol. From this, the concentration of _CO2 can be determined using a corresponding factor k, which indicates the increase in the molar mass of the gas mixture per addition of 1% CO2. This calibration factor k can be determined according to the following table: O ^{2 31.998 g/mol Air 28.949 g/mol k} N2 28.0134 g/mol 5 vol-% CO2 29.702045 g/mol 0.150609 CO2 44.0099 g/mol 10 vol-% CO2 30.45509 g/mol 0.150609 Ar 40 g/mol 15 vol-% CO2 31.208135 g/mol 0.150609 20 vol-% CO2 31.96118 g/mol 0.150609 _{Table 1:} For air, the molar mass is M _Air = 28.949 g/mol. If the proportion of CO2 is increased to 10 vol-%, the total molar mass is M=90%*Mair+10%*MCO2=30.45509 g/mol, which is a difference of 1.50609g/mol to M _air . For each percent of _CO2, this results in an increase of 0.150609 g/mol. With the factor k=0.150609 g/(mol*vol-%), the concentration of _CO2 thus results from the determined proportion of the molar mass: c _CO2 = ΔM _CO2 : k= 0.753045011g/mol : 0.150609 g/(mol*vol-%)= 5.00000007 vol-%. If you want to specify the partial pressure p _CO2 , this results in pCO2=p*cco2=1013.25 mbar*0.05=50.6625007 mbar. With an accuracy (based on the measured value) of 0.50% for the density sensor 28, 0.50% for the pressure sensor 26, 0.15°C for the temperature sensor 24 and 3% for the humidity sensor 42, it can be estimated that the measuring device 10 delivers values between 2.94% and 7.08% at a concentration of 5% CO ₂ and delivers partial pressure values between 29.8 mbar and 71.7 mbar. Example 2: A gas measurement is carried out as in example 1. The container is filled with dry air. The gas mixer adds CO2 until 20 vol.% CO2 is contained. The conditions are: pAbs=1013.25 mbar T=30°C rH = φ = 0% The sensors ideally deliver the following signals: Density sensor: 1284.90738 g/m ³ Pressure sensor: 1013.25 mbar Temperature sensor: 30°C Humidity sensor: 0% In the processor, the molar mass M is again determined by

This gives a value of M = 31.96118 g/mol. The following applies to the portion of the molar mass of CO2 that is attributable to CO2: ^^ ^^ _^ைమ ൌ ^^ െ ^^ _^௨^௧ For dry air, the average molar mass M _air = 28.949 g/mol. This gives the portion of the molar mass that is attributable to CO2: ΔM _CO2 = 3.01218g/mol. With the factor k = 0.150609 g/(mol*Vol-%), the measured concentration of CO ₂ results from the determined portion of the molar mass: cCO2 = ΔMCO2 : k = 3.01218g/mol : 0.150609 g/(mol*Vol-%) = 20 Vol-%. If you want to specify the partial pressure p _CO2 , this results in p _CO2 =p*c _co2 =1013.25 mbar*0.2= 202.65 mbar. Taking into account the above-mentioned accuracies of the sensors 24, 26, 28, 42, real measured values for the concentration in the range of 17.78% to 22.24% and real measured values for the partial pressure between 180.2 mbar and 225.3 mbar are to be expected. Example 3: Example 3 shows how the value of the humidity sensor can be taken into account. A gas measurement is carried out as in Example 1. The container is filled with moist air with rH= φ=50%. The gas mixer adds CO ₂ until 5 vol.% CO ₂ is contained. The conditions are: p=1034.34 mbar T=35°C rH = φ = 50% The sensors ideally deliver the following signals: Density sensor: 1174.710287 g/m ³ Pressure sensor: 1034.34 mbar Temperature sensor: 35°C Humidity sensor: 50% From the relative humidity and the known values for the temperature-dependent saturation pressure pm(T), the partial pressure of the water vapor pw can be calculated with pw=pm(T)* φ. In the processor, the pressure of the dry air is first calculated with pAbs=p-pw=1013.25 mbar. Then the molar mass of the gas mixture is again calculated. _{^^ ൌ} ^{^^ ⋅ ^^ ⋅ ^^} ^ _{^ ൌ 27.702045 ^^/ ^^ ^^ ^^} _^^^ was calculated. The following applies to the portion of the molar mass of CO2 that is due to CO2: ^^ ^^ _^ைమ ൌ ^^ െ ^^ _^௨^௧ For dry air, an average molar mass Mair=28.949 g/mol was determined. This gives the portion of the molar mass of ΔM _CO2 =0.753045011g/mol that is due to CO ₂ . With the factor k=0.150609 g/(mol*Vol-%), the concentration of CO ₂ is calculated from the determined molar mass fraction: cCO2= ΔMCO2 : k= 0.753045g/mol : 0.150609 g/(mol*Vol-%)= 5.00000 Vol-%. If you want to specify the partial pressure p _CO2 , this results in pCO2=p*cco2=1034.34 mbar*0.05=51.717 mbar. With an accuracy (based on the measured value) of 0.50% for the density sensor 28, 0.50% for the pressure sensor 26, 0.15°C for the temperature sensor 24 and 3% for the humidity sensor 42, it can be estimated that the measuring device 10 delivers values between 2.68% and 7.35% at a concentration of 5% CO ₂ and 50% air humidity and delivers partial pressure values between 27.7 mbar and 76.0 mbar. The deviation from the actual values is directly dependent on the accuracy with which the measurements for gas density ρ, temperature T, optionally relative humidity φ and absolute pressure p can be carried out. Fig. 3 shows an example of a reaction system 50 designed, for example, as a bioreactor system, in which the measuring device 10 is used. The reactor system has the reaction chamber 14 designed, for example, as a bioreactor or the like, and the measuring device 10. In the reaction chamber 14, a stirrer 52 with drive 54, a pH sensor 56 and a DO sensor 58 are Detection of dissolved oxygen (example of external sensor 44) is provided. Inlets for steam 62, water 64, acidic medium 66, alkaline medium 68, nutrient solution 70 and air 72 that can be controlled via valves are also provided, as is an exhaust for exhaust gas 74 that is controlled via a valve. Measuring signal lines that transmit values to transmitters and controllers 78 are shown with dash-dotted lines, while control signal lines from these transmitters and controllers 78 to the corresponding valves or other actuators (e.g. the drive 54) are shown with dashed lines. For example, a specific cell cultivation with predetermined process parameters is carried out in the reaction chamber 14 designed as a bioreactor. As can be seen from Fig.3, the value of the CO2 concentration provided by the measuring device 20 can be used directly, for example, to regulate the addition of nutrients - nutrient solution 70. The value of the oxygen sensor 58 can be fed to the evaluation device 30 in order to incorporate possible changes in the molar mass of component group A (here air with a correspondingly changing oxygen content). Examples of the reaction chamber are a bioreactor, a disposable bioreactor 80, a bioreactor with a diameter of less than 10 mm, a reaction chamber in the food industry, a reaction chamber for beverage production, a reaction chamber in a brewery, a reaction chamber in a sewage treatment plant, a reaction chamber in a wastewater treatment plant, a reaction chamber in a CO2 extraction plant, a reaction chamber in process analytics, a pipeline, a water pipeline. A switch to disposable bioreactors (SUBs) and bio process containers (BPC) is explained below. Traditional biopharmaceutical and biotechnology processes have long used stainless steel or glass bioreactors for the majority of batch production, such as the bioreactor shown in Fig.3. However, the use of single-use bioreactors 80 has increased, mainly due to the advantages they bring for scalability, flexibility and cost. Although the use of SUBs 80 brings some significant advantages for certain batch productions, it also brings unique challenges - especially with regard to measuring the environment inside the SUB during production. One parameter that is particularly affected by this is CO2 measurement. A look at the catalogs of the Who's Who of process analytics shows: There are solutions for determining the CO2 content for the traditional processes, but not for the SUBs. Since SUBs are usually delivered to pharmaceutical companies and biotech companies pre-sterilized and ready for production, it is necessary that the sensors have either been installed in the bioreactor 80 before delivery or can be inserted into the reactor without affecting the sterilized internal environment. There are currently no viable solutions for the installation before delivery of the SUB 80. Installing measurement technology on site without affecting the sterilized internal environment can currently only be achieved with major losses in terms of costs and measurement performance. Preferred embodiments of the measurement method and the measuring device 10 address both paths and in particular the possibility of installing a separation membrane 18 in the SUB 80 before the SUB 80 is delivered to the end user. Fig.4 shows a highly schematic view of a disposable bioreactor 80 with a coupling 48 already attached. Fig.5 shows a section through the coupling 48 and Fig.6 shows a view of the coupling with a separation membrane module 82 attached. Two of the most critical parameters in a bioreactor, DO and pH, can be supplemented by the use of CO2 measurement technology - as is done in traditional processes. The shown designs of the coupling 48 with separation membrane 18 are by no means the only possible design. In some embodiments, a needle-sized design is sufficient. As described above, the components X, Y, Z of the gas 12c are grouped into groups A, B in preferred embodiments. From this, and with the description of the measurement principle, it can be concluded that knowledge about individual components X, Y, Z of the gas 12a, 12b and 12c can have an enormous effect on the accuracy of the measurement. For example, there are niche applications that have pure oxygen or an increased oxygen concentration. The signal from the measurement technology - DO sensor 58 or other external sensor 44 - which measures and monitors oxygen concentration can be fed into the combination sensor 22 via an interface. This increases the accuracy. A similar scenario is interesting when particularly heavy VOCs (volatile organic compounds) are present in the process and are monitored. To improve the process control in bioreactors (14), in particular in cell cultivation or fermentation, some embodiments of the invention provide a measuring method for measuring a concentration (cz) of a gas component (Z) to be measured of a gas mixture (12, 12a, 12b and 12c) of known composition in a solution in a bioreactor (14), comprising: a) providing a measuring chamber (16) which is separated from the interior of the bioreactor (18) by a gas-permeable separating membrane (18), b) measuring the gas density ρ, the gas pressure p and the temperature T in the measuring chamber (16) and c) Determining the concentration (cz) of the gas component (Z) to be measured from the values measured in step b) and molar masses of the gas components (X, Y, Z) of the gas mixture. Dissolved CO2 (dCO2) is an important parameter for understanding the course of any biotechnological process. Solutions for determining the proportion of CO2 in liquid solutions are therefore proposed in particular. However, the methods and devices are also suitable for determining the concentration of other gas components and, in some embodiments, are also set up for this purpose. The determination of dissolved gas components in liquid samples has so far been particularly difficult. Previous determinations were generally made indirectly, e.g. via the pH value. The sensors had to be calibrated frequently, were relatively inaccurate and had very long response times and were susceptible to interference from other gases that influenced the pH value. Fig.7 illustrates the measuring principle of some preferred embodiments of the measuring device. The liquid sample is separated from the measuring chamber 16 by the liquid-impermeable and gas-permeable separation membrane 18, where the density of the gas components in the gas phase is measured. The gas density GD is measured by a Quartz Crystal Microbalance Density Measurement (QCM). As shown in the graph on the right in Fig.7, the obtained signal difference in frequency (difference frequency) df is proportional to the density of the gas, which in this case is proportional to the amount of CO2 in the solution. The measuring principle does not require any intermediate chemical steps, it is only measured in the gas phase through a separation membrane 18 in equilibrium with the solution. This results in a very small measurement error (e.g. +/- 5 mbar for a non-optimized system). Tests have shown response times of only 4s plus the time for diffusion through the separation membrane 18. The measuring device 20 can also be greatly miniaturized as a combination sensor 22. Fig.8 shows a microscopic image of an embodiment of the measuring device designed as a combination sensor 22 with the quartz oscillator (in the form of a tuning fork) as a gas density sensor 28, and a combined pressure and temperature sensor 24, 26 as well as an optional humidity sensor 42 on its side. Diameters of the sensor head of less than 1 mm are achievable, so that the measuring chamber volume V can be made very small. The sensors 28, 24, 26, 42 are arranged on a circuit board (PCB) 84, on the back of which a chip with the evaluation device 30 or parts thereof can be arranged. This sensor head shown in Fig.8 sits on a holder with which the combination sensor 22 can be arranged on the disposable bioreactor 80 or another reaction chamber with the separation membrane 18 in between. After the initial calibration in the manufacturing plant, the measurement does not require any further calibration. The construction is simple and can be built using industrially available components on the market. The separation membrane 18 is attached so that it can be removed. Only physical measurements are taken, and no wet chemical processes are necessary. The signal is linear and available with fast response times in the range of a few seconds. Other gas components that react acidically or alkaline have no influence on the measurement. The gas density sensor 28 has a quartz crystal tuning fork that oscillates. An increase in the gas density reduces the oscillation frequency. Possible applications are CO ₂ measurements in biochemical processes, in particular in bioreactors, especially in disposable bioreactors 80. Other possible applications are the food and beverage industry, water management (wastewater disposal and drinking water supply), CO ₂ capture and CO2 storage, as well as direct measurement of CO2 emissions in industry. Applications in energy supply are also possible, e.g. in applications where methane or other hydrocarbon gases are produced from excess renewable energy for later energy generation, or in the production of fuel from algae cultures. List of reference symbols: 10 Measuring device Gas mixture a Gas mixture in the gaseous phase of the bioreactor b Gas mixture dissolved in the liquid phase of the bioreactor c Gas mixture in the measuring chamber Reaction chamber (e.g. bioreactor or similar) Measuring chamber Separating membrane Measuring device Combined sensor Temperature sensor Pressure sensor Gas density sensor Evaluation device Analysis and control unit Processor Storage Filter Heating Humidity sensor External sensor Coupling Reaction system (e.g. bioreactor system or similar) Stirrer Drive pH sensor DO sensor Steam Water Acidic medium Alkaline medium Nutrient solution Air Exhaust gas Transmitter and controller 80 Disposable bioreactor 82 Separation membrane module 84 Circuit board X, Y, Z Gas components A, B Gas component groups c _X Concentration of gas component X cY Concentration of gas component Y cZ Concentration of gas component Z c _A Concentration of gas component group A c _B Concentration of gas component group B pB Partial pressure of gas component group B GD Gas density df Difference frequency QCM

Claims

Trafag AG 10210139 P-WO Industriestrasse 11 CH-8608 Bubikon Switzerland Claims: 1. Measuring method for measuring a concentration (cz) of a gas component (Z) to be measured of a gas mixture (12b) of known composition in a liquid solution in a reaction space (14), comprising the steps: a) providing a measuring chamber (16) which is separated from the reaction space (18) by a liquid-impermeable and gas-permeable separating membrane (18), b) measuring the gas density ρ, the gas pressure p and the temperature T in the measuring chamber (16) and c) determining the concentration (c _z ) of the gas component (Z) to be measured from the values measured in step b) and from the molar masses of the gas components (X, Y, Z) of the gas mixture. 2. Measuring method according to claim 1, characterized in that step a) comprises the step: a1) providing the measuring chamber (16) with a measuring chamber volume V of less than 5000 mm ³ , preferably less than 1000 mm ³ , and preferably with 5 mm ³ ≤ V ≤ 15 mm ³ , in particular 1 mm ³ ≤ V ≤ 10 mm ³ , and preferably 2 mm ³ ≤ V ≤ 5 mm ³ . 3. Measuring method according to one of the preceding claims, characterized in that step b) comprises the step: b1) measuring the gas density by means of a tuning fork gas density sensor. 4. Measuring method according to one of the preceding claims, characterized in that the reaction space is selected from a group comprising a bioreactor, a disposable bioreactor, a bioreactor with a diameter of less than 10 mm, a reaction chamber in the food industry, a reaction chamber for beverage production, a reaction chamber in a brewery, a reaction chamber of a sewage treatment plant, a reaction chamber of a wastewater treatment plant, a reaction chamber of a CO2 extraction plant, a reaction chamber in process analytics, a pipeline and a water pipeline. 5. Measuring method according to one of the preceding claims, characterized in that the gas component (Z) to be measured is 5.1 a gas component of the gas mixture (12b) which changes during the reaction in the reaction chamber (14), in particular a bioreaction in the reaction chamber (14) designed as a bioreactor and/or 5.2 CO2. 6. Measuring method according to one of the preceding claims, characterized in that the gas mixture (12b) contains at least one further gas component (X, Y) from the group comprising air, technical air, dried air and/or a mixture of O2 and N2. 7. Measuring method according to one of the preceding claims, characterized by at least one of the steps: 7.1 measuring the relative humidity and/or 7.2 measuring the content of a further gas in the gas mixture, wherein step c) is determined depending on the value measured in step 7.1 or 7.2. 8. Measuring method according to one of the preceding claims, characterized in that the gas mixture (12b) is grouped into the gas component (Z) to be measured and a component group (A) with the further components (X, Y) of the gas mixture (12b), that the concentration of the components (X, Y) weighted average molar mass of the component group (A) is determined and in step c) the concentration of the gas component (Z) to be measured is determined from the molar mass of the gas component (Z) to be measured and the weighted average molar mass. 9. Measuring method according to one of the preceding claims, characterized in that in step b) the gas density is measured by means of a quartz crystal. 10. Reaction method for carrying out a reaction in a reaction chamber (14), comprising measuring a concentration of a gas component of the gas mixture (12b) in the reaction chamber (14) by carrying out the measuring method according to one of the preceding claims and carrying out further steps of the reaction method depending on the measurement. 11. Reaction method according to claim 10, characterized in that the reaction method is a bioreaction method carried out in the reaction chamber designed as a bioreactor for carrying out a bioreaction. 12. Bioreaction method according to claim 11, wherein the bioreaction includes cell cultivation in the bioreactor (14). 13. Measuring device (10) for measuring a concentration (cZ) of a gas component (Z) to be measured of a gas mixture (12b) of known composition in a reaction chamber (14), comprising: a measuring chamber (16) with a gas-permeable separating membrane (18) for separating the measuring chamber (16) from the interior of the reaction chamber (14), a measuring device (20) for measuring the gas density ρ, the gas pressure p and the temperature T in the measuring chamber (16) and an evaluation device (30) for determining the concentration of the gas component to be measured from the values measured by the measuring device (20). measured values and from the molar masses of the gas components of the gas mixture (12b). 14. Measuring device according to claim 13, characterized in that the measuring chamber (16) has a measuring chamber volume V, where 0.5 mm ³ ≤ V ≤ 15 mm ³ , in particular 1 mm ³ ≤ V ≤ 10 mm ³ , and preferably 2 mm ³ ≤ V ≤ 5 mm ³ . 15. Measuring device according to one of claims 13 or 14, characterized in that the measuring device (20) has a quartz oscillator and/or a tuning fork sensor for measuring the gas density. 16. Measuring device (10) according to one of claims 13 to 15, characterized by 16.1 a humidity measuring device (42) for measuring the relative humidity and/or 16.2 a gas content measuring device (44, 58) for measuring the content of at least one further gas in the gas mixture; wherein the evaluation device (30) is designed to determine the concentration depending on the measurement of the humidity measuring device and/or the gas content measuring device. 17. Measuring device (10) according to one of claims 13 to 16, characterized in that the evaluation device (30) is designed to determine the concentration of CO2 in an O2 and N2-containing atmosphere in the reaction chamber (14). 18. Measuring device (10) according to one of the preceding claims, designed to carry out a measuring method according to one of claims 1 to 10. 19. Reaction system (50) for carrying out a reaction, comprising a reaction chamber (14) and a measuring device (20) according to one of claims 13 to 18, wherein the measuring chamber (16) is separated from the interior of the reaction chamber (14) by the separating membrane (18). 20. Reaction system (50) according to claim 19, characterized in that the reaction chamber is selected from the group comprising a bioreactor, a disposable bioreactor (80), a bioreactor with a diameter of less than 10 mm, a reaction chamber in the food industry, a reaction chamber for beverage production, a reaction chamber in a brewery, a reaction chamber of a sewage treatment plant, a reaction chamber of a wastewater treatment plant, a reaction chamber of a CO2 extraction plant, a reaction chamber in process analytics, a pipeline and a water pipeline. 21. Use of a measuring device (10) which has a measuring chamber (16) delimited by a gas-permeable separating membrane (18) and a measuring device (10) for measuring the gas density ρ, the gas pressure p and the temperature T in the measuring chamber (16), for measuring a concentration (c _Z ) of a gas component (Z) to be measured of a gas mixture (12b) in a reaction space (14) separated from the measuring chamber (16) by the separating membrane (18).