ATR sensor and method for determining glucose concentration in a fluid

Abstract

This invention relates to an ATR sensor (10) for determining glucose concentration in a fluid, comprising a sensor housing (12) wherein the sensor housing (12) accommodates at least the following sensor components: an infrared radiation source (22); an ATR element (24) designed to transmit infrared radiation emitted by the infrared radiation source (22) by total internal reflection at at least one interface of the ATR element (24); at least one infrared detector (40) designed to sense the infrared radiation transmitted by the ATR element (24) and output a corresponding infrared measurement signal; and at least two infrared bandpass filters (36a, 36b) disposed between the ATR element (24) and the infrared detector (40), each infrared bandpass filter (36a, 36b) being designed such that only infrared radiation with a wavenumber within a predetermined wavenumber window (F1, F2) passes through. The first infrared bandpass filter (36a) allows a wavenumber range of 1005 cm⁻¹ at a temperature of 37°C. ‑1 Up to 1025 cm- 1 Infrared radiation at the first wavenumber window (F1) passes through. The second infrared bandpass filter (36b) allows infrared radiation with a range of 1075 cm⁻¹ at a temperature of 37°C. ‑1 Up to 1095 cm ‑1 Infrared radiation of the second wavenumber window (F2) passes through.

Description

Technical Field

[0001] This invention relates to an ATR sensor for determining the glucose concentration in a fluid. The invention also relates to a corresponding method for determining the glucose concentration in a fluid using an ATR sensor. Summary of the Invention

[0002] In a specific embodiment, an ATR sensor comprising a multi-channel sensor for multiple predetermined wavenumber windows will be used. These multiple wavenumber windows can be implemented, in particular, by multiple infrared filters having bandpass characteristics; specifically, the ATR sensor may comprise a four-channel sensor for four wavenumber windows.

[0003] ATR sensors operate based on the so-called Attenuated Total Reflection (ATR) principle. In the ATR measurement principle, the light beam is totally reflected at the interface between a reflective element (such as a prism) and a sample containing the fluid to be tested, but at the point of reflection, it penetrates into the fluid by an order of one wavelength and is then partially absorbed by the fluid.

[0004] The sensor and method according to the invention are intended for determining the concentration of certain organic molecules in a fluid, particularly in liquids (e.g., aqueous solutions containing multiple components). For example, in bioprocessing, the concentration of feed (e.g., glucose, glycerol) and / or metabolites (e.g., lactic acid, ammonium, glutamine, glutamic acid) in a fluid, particularly in liquids such as aqueous solutions containing these substances, is of particular significance for optimal process control.

[0005] Electromagnetic radiation in the mid-infrared range (MIR) has ranges from 4000 to 400 cm⁻¹. -1 The wavenumber range or wavelength range of 2.5 to 25 μm. Many vibrational and rotational bands of molecules that function in bioprocessing and therefore need to be monitored fall within this range. This is especially true for glucose.

[0006] This invention allows for the direct and high temporal resolution detection of glucose in such fluids, particularly liquids such as the aqueous solutions described above. Even though the fluid in question contains many other components, trace substances, and / or bioactive components, which, due to their structure, exhibit strong interactions with mid-infrared (MIR) radiation, making the determination of glucose concentration using MIR radiation (e.g., via an ATR sensor) difficult due to significant cross-sensitivity, this invention can be achieved with good accuracy.

[0007] The apparatus for fluid spectral analysis according to the invention comprises a process probe having a reflective element called an ATR (attenuated total internal reflection) element. MIR radiation generated by a corresponding source is coupled into the process probe in a suitable manner, for example via a light guide (e.g., silver halide fiber) or via a suitable channel such as that radiated in air, and is guided onto the reflective element. After total internal reflection of the MIR radiation in the reflective element and the resulting interaction between the MIR radiation and the fluid under test, the MIR radiation is decoupled and guided to the spectral detection device.

[0008] The ATR element (which also contacts the fluid under test) can be a prism, unclad fiber, or a special ATR crystal, in which radiation is guided by total internal reflection at the interface between the ATR element and the fluid. In total internal reflection, an evanescent electromagnetic wave is formed behind the reflective interface from the optically denser medium (ATR element) to the optically less dense medium (fluid under test). This wave typically has a range of about one wavelength, depending on the angle at which the radiation is incident on the interface. If a sample containing the fluid under test is brought close to the surface of the reflective element, molecules of the material in the MIR with pronounced and excitable vibrational / rotational transitions can interact with the evanescent electromagnetic wave, where the MIR radiation is attenuated by wavelength-dependent absorption in a manner characteristic of the respective material.

[0009] Spectroscopic detection equipment is used to examine the wavelength dependence (usually expressed as wavenumber dependence) of MIR radiation absorption and to analyze the components in a sample. Many structural units of an organic molecule always have similar intensities and absorb within a narrow range of the MIR spectrum in a manner relatively independent of the entire molecule. Because these groups are linked within the molecule, the resulting overall spectrum characterizes the corresponding molecule or a substance containing a specific combination of organic molecules. In addition to quantitative analysis, quantitative information can also be obtained via Beer-Lambert's law. However, in fluids with complex compositions (e.g., solutions, dispersions, and / or suspensions of multiple substances in a carrier fluid), the spectra of individual components overlap, often requiring additional chemometric methods (H. Mark, J. Workman Jr.: Chemometrics in Spectroscopy; 2007 Elsevier Inc., ISBN 978-0-12-374024-3), such as bandpass filters or so-called “linearly variable filters” combined with detector element arrays (e.g., see DE 10 316 514 A1) or the entire FTIR spectrometer (FTIR = Fourier Transform Infrared Spectroscopy). FTIR spectrometers are relatively large and expensive, making them unsuitable for continuous real-time process monitoring in bioprocessing technologies. On the other hand, known variants with linearly variable filters are unsatisfactory in terms of sensitivity and selectivity.

[0010] Therefore, one object of the present invention is to provide a compact ATR sensor for determining glucose concentration in a fluid and / or a corresponding method for determining glucose concentration in a fluid, by which the glucose concentration in the sample to be tested can be determined with sufficient accuracy and good temporal resolution, even in real time, even in the presence of many other substances (e.g., trace substances or metabolites) that themselves highly interact with MIR radiation, thus leading to cross-sensitivity when using infrared absorption spectroscopy-based methods (e.g., ATR spectroscopy) to determine glucose concentration. In a particularly preferred embodiment of the invention, this is achieved even if the temperature and / or pH of the fluid to be tested is not constant but varies.

[0011] This invention achieves this objective by providing an ATR sensor for determining the glucose concentration in a fluid of the type described herein, and a corresponding method for determining the glucose concentration in a fluid.

[0012] The sensor according to the present invention includes a sensor housing, wherein at least the following sensor components are housed: Infrared radiation source; An ATR element is configured to transmit infrared radiation emitted by an infrared radiation source by total internal reflection at at least one interface of the ATR element. At least one infrared detector is configured to detect infrared radiation transmitted by the ATR element and output a corresponding infrared measurement signal; and At least two infrared bandpass filters are arranged between the ATR element and the infrared detector, wherein each infrared bandpass filter is configured to be transmissible, for example, only for infrared radiation having a predetermined wavenumber window.

[0013] According to the present invention, for a range of 1005 cm -1 Up to 1025 cm -1 The infrared radiation of the wavenumber within the first wavenumber window, wherein the first infrared bandpass filter in the infrared bandpass filter is transmissive, preferably at a temperature of 37°C; for a range of 1075 cm⁻¹ -1 Up to 1095 cm -1 The infrared radiation of the wavenumber within the second wavenumber window, wherein the second infrared bandpass filter in the infrared bandpass filter is transmissive, preferably at a temperature of 37°C.

[0014] The method for determining glucose concentration in a fluid using an ATR sensor according to the present invention includes: Provides a fluid containing glucose; The glucose-containing fluid interacts with infrared radiation in the mid-infrared range; The absorption of infrared radiation after interaction with a glucose-containing fluid was detected in at least two different wavenumber windows in the mid-infrared range; The first wavenumber window within the wavenumber window is preferably located at a temperature of 37°C, and includes wavenumbers around 1005 cm⁻¹. -1 Up to 1025cm -1 Infrared radiation within the range, and The second wavenumber window within the wavenumber window is preferably located at a temperature of 37°C, including wavenumbers around 1075 cm⁻¹. -1 Up to 1095cm -1 Infrared radiation within the range.

[0015] Each infrared bandpass filter has a wavenumber window in which the infrared bandpass filter is transmissive to MIR radiation. For one of the corresponding infrared bandpass filters, the relevant wavenumber window is characterized by the center wavenumber and the full width at half maximum (FWHM). At the center wavenumber, the wavenumber window has maximum transmittance. At FWHM, the bandpass filter still exhibits 50% of its maximum transmittance.

[0016] The wavenumbers specified for the first and second wavenumber windows refer to the center wavenumber. For a range of 1005 cm⁻¹ -1 Up to 1025 cm -1 The infrared radiation of the wavenumber within the first wavenumber window is transmissible, meaning that the center wavenumber of the first wavenumber window can be as low as 1005 cm⁻¹. -1 Up to 1025 cm -l Within the range. For those with a range of 1075 cm -1 Up to 1095cm -1 The infrared radiation of the wavenumber within the second wavenumber window is transmissible, meaning that the center wavenumber of the second wavenumber window can be as low as 1075 cm⁻¹. -1 Up to 1095 cm -1 Within the range. A specific value is preferably a temperature of 37°C.

[0017] Full width at half maximum (FWHM) refers to the width of the wavenumber window at half the transmittance (FWHM = full width at half the peak). Therefore, it represents the difference between the upper and lower threshold wavenumbers of the wavenumber window at 50% maximum transmittance. Effective full width at half the peak (FWHM) refers to the full width at half the peak achieved by a corresponding infrared bandpass filter under real-world environmental conditions, especially considering the incident angle and temperature divergence of the incident infrared radiation.

[0018] The first wavenumber window can be specifically at 10¹⁰ cm⁻¹. -1 and 1020 cm -1 Between, preferably 1012 cm -1 and 1018cm -1Between, the optimal value is at 1014 cm -1 and 1016 cm -1 Within the range between, in each case preferably at a temperature of 37°C.

[0019] The second wavenumber window can be specifically at 1080 cm⁻¹. -1 and 1190 cm -1 Between, preferably at 1082 cm -1 and 1087cm -1 Between, the optimal value is at 1084 cm -1 and 1086 cm -1 Within the range between, in each case preferably at a temperature of 37°C.

[0020] The corresponding effective full width at half maximum (FWHM) for the first and second wavenumber windows can be, in particular, a maximum of 20 cm for the first wavenumber window. -1 The maximum wavenumber window for the second wave is 20 cm. -1 In some embodiments, it is advantageous that the effective full width at half maximum (FWHM) is 15 cm for the first wavenumber window. -1 For the second wavenumber window, the maximum effective full width at half maximum (FWHM) is 15 cm. -1 In a further embodiment, it is advantageous that the maximum effective full width at half maximum (FWHM) is 10 cm for the first wavenumber window. -1 For the second wavenumber window, the maximum effective full width at half maximum (FWHM) is 10 cm. -1 These values ​​preferably refer to a temperature of 37°C.

[0021] Particularly preferably, the center wavenumber of the first wavenumber window is 1015 cm⁻¹. -1 The effective full width at half-peak is 20 cm. -1 It is preferably carried out at a temperature of 37°C.

[0022] Particularly preferred is that the center wavenumber of the second wavenumber window is 1085 cm⁻¹. -1 The effective full width at half-peak is 20 cm. -1 It is preferably carried out at a temperature of 37°C.

[0023] ATR sensors can be specifically configured to determine the concentration of glucose in liquids, particularly in aqueous solutions, suspensions, or dispersions. For example, glucose-containing liquids may contain CHO cell lines.

[0024] In the context of this disclosure, the term "liquid" refers to any substance whose main phase exhibits a liquid aggregate state at a temperature of 20 to 50°C and a standard pressure. The liquid in this application can be a pure liquid, as well as a single-phase or multiphase composition comprising multiple components, particularly a solution, suspension, or dispersion.

[0025] Liquids can be, in particular, cell culture media, such as liquid suspensions of cell cultures, nutrients, metabolites resulting from the interaction between cell cultures and nutrients, and other substances. Cell cultures, nutrients, metabolites, and / or other substances can exist in the liquid phase, especially in the aqueous phase, as suspensions, dispersions, or solutions. Examples of such liquids in bioprocessing technologies include feed (such as glucose, glycerol) and metabolites (such as lactic acid, ammonium, glutamine, glutamate), the quantitative monitoring and control of which are particularly important for optimal process control. In this context, monitoring and controlling glucose concentration is often especially important. For this purpose, the concentration must be reliably and rapidly determined even if the concentrations of other components and / or environmental conditions (such as temperature and / or pH) change.

[0026] Cell culture media, such as RPMI medium, are available and described in detail at the following website: https: / / www.sigmaaldrich.com / CH / en / products / cell-culture-and-analysis / cell-culture-media-and-buffers / classical-media-and-buffers.

[0027] An ATR sensor, such as the ATR sensor for determining glucose concentration according to the invention, is configured such that a sample beam generated by an infrared radiation source undergoes total internal reflection at the interface between the fluid under test and the ATR sensor, thereby allowing the evanescent field of infrared radiation to propagate into the fluid on the fluid side. The evanescent field of infrared radiation attenuates the incident infrared radiation. To determine absorption, the intensity of the total internally reflected infrared radiation is detected relative to the intensity of the infrared radiation emitted by the infrared radiation source.

[0028] This invention proposes to determine glucose concentration essentially using a specific combination of two infrared bandpass filters with corresponding beam windows. The key factor is the position of these two wavenumber windows, which are determined by the wavenumber range claimed in claim 1, with the center wavenumber range of the first wavenumber window being 1005 cm⁻¹. -1 Up to 1025 cm -1 The center wavenumber range of the second wavenumber window is 1075 cm⁻¹. -1 Up to 1095 cm -1 The infrared absorption spectra of glucose at wavenumbers within the first and second wavenumber windows do indeed show some absorption of infrared radiation. However, the known absorption maxima of glucose, caused by the vibrational and rotational processes of the functional groups in the glucose molecule, are not within either the first or second wavenumber window. The first and second wavenumber windows are chosen such that the absorption maxima of glucose lie outside these window ranges.

[0029] At first glance, choosing a first and second wavenumber window to determine glucose concentration may seem paradoxical and violates the conventional rule of selecting an appropriate wavenumber range to determine the concentration of a specific substance or molecule in a fluid using absorption spectroscopy. This is because the common procedure in absorption spectroscopy for determining the concentration of a substance such as glucose is to first determine the wavenumber or wavenumber window in which the maximum absorption of the substance's infrared radiation occurs. Therefore, the absorption spectrum of the substance (e.g., glucose) in the mid-infrared range must first be determined, and this is used to determine the wavenumber window in which the substance's absorption coefficient exhibits a relative maximum. Once the wavenumber windows with the maximum absorption are known, one, or if necessary, multiple, wavenumber windows with the maximum absorption of glucose can be selected, and the glucose concentration can be determined based on this selected wavenumber window or these selected wavenumber windows respectively.

[0030] This invention employs a completely different approach. Instead of seeking the maximum absorption of glucose in the mid-infrared range (MIR radiation), this invention seeks a combination of wavenumber windows in which the absorption of glucose in the infrared range is minimally affected by the presence of other substances in the fluid under test (e.g., glycerol and / or metabolites such as lactic acid, ammonium, glutamine, or glutamate), and remains largely stable even as certain environmental parameters of the fluid under test (e.g., temperature and / or pH) change. A particular challenge lies in the complexity of all these potential factors influencing MIR radiation absorption compared to the absorption of glucose in the MIR range.

[0031] It has been found that absorption signals detected in two wavenumber windows in the mid-infrared range, specifically in the range of 1005 cm⁻¹, can be obtained by using and combining these signals. -1 Up to 1025 cm -1 Within the first wavenumber window and in the range of 1075 cm -1 Up to 1095 cm -1 The first absorption signal within the wavenumber window (preferably, each wavenumber window corresponds to a temperature of 37°C) can obtain a measurement signal that is substantially stable relative to the aforementioned influencing factors, based on which the concentration of glucose in the fluid to be tested (especially in liquids such as aqueous solutions) can be identified.

[0032] When considering the absorption of MIR radiation by glucose in the first and second wavenumber windows respectively, neither wavenumber window represents a range where the absorption of MIR radiation is particularly pronounced. (The last sentence appears to be incomplete and possibly refers to a different context.) -1 and 1025 cm -1The first wavenumber window falls within a range where the glucose uptake coefficient has a fairly moderate value, and then moves towards a very distinct maximum uptake coefficient (approximately 1035 cm⁻¹). -1 (Increases.) With a center wavenumber of 1075 cm⁻¹ -1 and 1095 cm -1 The second wavenumber window falls within a range where the glucose uptake coefficient has a fairly moderate value. Unlike the first wavenumber window, the glucose uptake coefficient in the second wavenumber window ranges from 1080 cm⁻¹. -1 The relative maximum value at a slightly lower location decreased to 1095 cm. -1 The minimum absorption coefficient at that location.

[0033] In existing technologies, the center wavenumber of 1005 cm⁻¹ has never been considered. -1 and 1025 cm -1 The first wavenumber window between the center wavenumber and the center wavenumber is at 1075 cm⁻¹ -1 and 1095 cm -1 The combination of the first and second wavenumber windows is used to determine glucose concentration. Glucose has absorption bands in the mid-infrared range due to the vibrational and rotational processes of some of its functional groups. The maxima of these absorption bands lie outside the first and second wavenumber windows. Therefore, there is no reason to believe that the first and / or second wavenumber windows used to determine glucose concentration have any particular significance. Compared to the maxima of the glucose absorption bands, the importance of these two wavenumber windows in determining glucose concentration appears to be rather small.

[0034] Therefore, surprisingly, the combination of wavenumber windows selected according to the present invention for determining glucose concentration actually has certain advantages over other wavenumber windows or combinations of wavenumber windows, and these advantages seem much more obvious at first glance. The applicant aims to understand 1005 cm⁻¹ -1 and 1025 cm -1 Between and 1075 cm -1 and 1095 cm -1Further research using a specific combination of the two wavenumber windows revealed that, particularly within these two wavenumber windows, the ratio of MIR radiation absorbed by glucose after the total internal reflection interface to that absorbed by other trace substances is very high. Therefore, by combining the absorption signals from these two wavenumber windows, an absorption signal with high robustness to cross-sensitivity caused by other trace substances can be obtained. Thus, even if the absolute intensity of the detected absorption signal is not particularly high, the signal-to-noise ratio can be significantly improved when determining glucose concentration. The combination of the two wavenumber windows appears to play a role here, as a similar effect would not be possible if only one of the two wavenumber windows were used to determine glucose concentration. The advantages recognized according to the present invention were not anticipated from the outset. The findings of the present invention did not provide prior indication that cross-sensitivity to other substances (e.g., metabolites such as lactic acid) could be suppressed in this manner, and that the measurement signal became more stable, unaffected by changes in temperature or pH of the fluid in which the glucose concentration to be determined is located.

[0035] When the temperature of the fluid changes, especially in the case of liquids (e.g., cell culture media), the temperature of the infrared bandpass filter used to determine glucose concentration also changes accordingly, because the ATR sensor is in contact with the fluid at least at its interface where total internal reflection occurs. This temperature change causes the center wavelength of the corresponding wavenumber window through which the infrared bandpass filter is transmissible to shift to a higher wavenumber as the temperature of the corresponding infrared bandpass filter increases. Therefore, the position of the corresponding wavenumber window transmitted by the infrared filter also changes relative to the absorption spectrum of glucose, since the absorption band of glucose is only slightly temperature-dependent. Furthermore, the intensity values ​​in the absorption spectrum are also temperature-dependent. The maximum intensity of the absorbed signal increases with increasing fluid temperature. The first wavenumber window (preferably 10¹⁵ cm⁻¹ at 37°C) is... -1 The absorption range is within the glucose absorption spectrum where absorption increases with increasing wavenumber. On the other hand, the second wavenumber window (preferably 1085 cm⁻¹ at 37°C) is... -1Within the glucose absorption spectrum, absorption decreases with increasing wavenumber. Therefore, these effects cancel each other out, and thus can at least largely compensate for each other. If the fluid temperature (and the temperature of the infrared bandpass filter) increases, the influence of the absorption signal obtained from the first wavenumber window increases, while the influence of the absorption signal obtained from the second wavenumber window decreases. When the fluid temperature decreases, the situation is exactly the opposite: now the influence of the absorption signal obtained from the first wavenumber window decreases, while the influence of the absorption signal obtained from the second wavenumber window increases. If the two absorption signals from the first and second wavenumber windows are combined, these effects can be approximately compensated, thus generating an absorption signal that is approximately independent of fluid temperature, at least in the range of 20°C to 45°C. Therefore, for the absorption of infrared radiation after interaction with a glucose-containing fluid, a temperature-independent measurement signal can be obtained by appropriately combining the absorption signals from the first and second wavenumber windows. "Absorption signal combination" refers to any type of combination that provides sufficient compensation for the absorption signal with temperature changes.

[0036] The ATR sensor and method for determining glucose concentration in a fluid can be specifically configured to determine the glucose concentration in a glucose-containing fluid, particularly a glucose-containing liquid, within a temperature range of 20°C to 45°C. A wavenumber window is selected such that the absorption signal, reflecting the infrared radiation absorption detected after interaction with the fluid, is almost unaffected when the temperature varies within the selected temperature range. This allows for the detection of glucose concentration largely independent of temperature changes within this range.

[0037] Further specific embodiments of the ATR sensor and / or method for determining glucose concentration according to the present invention may include at least one of the optional features listed below. It should be understood that each of these optional features can be added individually to one of the above embodiments. The features mentioned below can also be combined with each other, and combinations of features can be added to one of the above embodiments, unless it is explicitly stated that some of these features are mutually exclusive.

[0038] In a specific embodiment, the ATR sensor described herein may include a third infrared bandpass filter, which is preferably configured to filter infrared bandpass filters with a bandpass range of 945 cm⁻¹ at a temperature of 37°C. -1 Up to 965 cm -1 The infrared radiation of the wavenumbers in the third wavenumber window is transmissible. Therefore, in a specific embodiment, the method according to the invention may include a wavenumber range of 945 cm⁻¹. -1 Up to 965 cm -1 Infrared radiation is detected in the third wavenumber window.

[0039] Similarly, for the third infrared bandpass filter, the wavenumber window is characterized by the center wavenumber and the associated effective full width at half maximum (FWHM). As mentioned above, the wavenumber window has maximum transmittance at the center wavenumber, and the FWHM specifies the wavenumber range in which the bandpass filter still exhibits at least 50% of its maximum transmittance. The wavenumber specified for the third wavenumber window refers to the center wavenumber, and the FWHM specifies the width of the wavenumber window at which at least 50% transmittance is achieved. In other words: for a wavenumber window with a range of 945 cm⁻¹... -1 Up to 965 cm -1 The infrared radiation of the wavenumbers in the third wavenumber window is transmissible, meaning that the center wavenumber of the third wavenumber window can be as high as 945 cm⁻¹. -1 Up to 965 cm -1 Within the range.

[0040] The range of the third wavenumber window can be specifically 950 cm. -1 and 960 cm -1 Between, particularly preferably at 954cm -1 and 956 cm -1 between.

[0041] The full width at half maximum (FWHM) of the third wavenumber window can be specifically set to 20 cm. -1 In a specific embodiment, the full width at half maximum (FWHM) of the third wavenumber window can be 15 cm. -1 More preferably, the full width at half maximum (FWHM) of the third wavenumber window can be 10 cm. -1 .

[0042] Particularly preferred is that the center wavenumber of the third wavenumber window is 955 cm⁻¹. -1 The full width of the half-peak is 20 cm. -1 .

[0043] The absorption spectrum of glucose is in the range of 945 cm⁻¹. -1 Up to 965 cm -1In the third wavenumber window, there is no obvious structure attributable to glucose vibrations or rotation bands. Since this finding also applies to most substances that can be considered potential cross-sensitivity, the absorption signal from the third wavenumber window can still serve as a reference signal, indicating the “background” or “noise” of the absorption signal detected by the ATR sensor due to a variety of influences. To determine glucose concentration, combining the absorption signals from the first and second wavenumber windows and correlating them with the absorption signal from the third wavenumber window allows for a more precise determination of the glucose-induced absorption signal compared to determining the glucose concentration without considering the third wavenumber window. This is because the third wavenumber window is specifically chosen within a range where no obvious vibrations or rotation bands are known, at least for substances considered potentially relevant components in the fluid being tested. Therefore, the absorption signal from the third wavenumber window can be used as a reference signal, and the absorption signals derived from the first and / or second wavenumber windows can be correlated with this reference signal. In this way, the glucose concentration can be determined based on relative measurements of the absorption signals from the first and / or second wavenumber windows and the third wavenumber window, without requiring absolute calibration of the absorption signals from the first and / or second wavenumber windows.

[0044] In another embodiment, the ATR sensor may include a fourth infrared bandpass filter having a range of 1300 cm. -1 Up to 1320 cm -1 Infrared radiation within the fourth wavenumber window is transmissible. Therefore, in methods for determining glucose concentration in fluids, infrared radiation can be detected within the fourth wavenumber window in the mid-infrared range, wherein the fourth wavenumber window includes a wavenumber of 1300 cm⁻¹. -1 Up to 1320 cm -1 Infrared radiation.

[0045] Similarly, for the fourth infrared bandpass filter, the wavenumber window is characterized by the center wavenumber and the associated effective full width at half maximum (FWHM). As mentioned above, the wavenumber window has maximum transmittance at the center wavenumber, and the FWHM specifies that the bandpass filter still exhibits at least 50% of its maximum transmittance range. The wavenumber specified for the fourth wavenumber window refers to the center wavenumber, and the FWHM specifies the width of the wavenumber window at a minimum of 50% transmittance. In other words: for a range of 1300 cm⁻¹... -1 Up to 1320 cm -1 The infrared radiation of the wavenumbers in the fourth wavenumber window is transmissible, meaning that the center wavenumber of the fourth wavenumber window can be as high as 1300 cm⁻¹. -1 Up to 1320 cm -1 Within the range.

[0046] The fourth wavenumber window can be specifically located at 1305 cm⁻¹. -1 and 1315 cm -1 Between these values, a height of 1309cm is particularly preferred. -1 and 1311 cm -1 between.

[0047] The full width at half maximum (FWHM) of the fourth wavenumber window can be specifically set to 20 cm. -1 In a specific embodiment, the full width at half maximum (FWHM) of the fourth wavenumber window can be 15 cm. -1 In a further embodiment, the full width at half maximum (FWHM) of the fourth wavenumber window can be 10 cm. -1 .

[0048] Particularly preferred is that the center wavenumber of the fourth wavenumber window is 1310 cm⁻¹. -1 The full width of the half-peak is 20 cm. -1 .

[0049] At 1300 cm -1 Up to 1320 cm -1 Using a fourth wavenumber window within the range to determine glucose concentration can more effectively suppress cross-sensitivity of the absorption signal caused by other trace substances in the fluid. Therefore, the signal-to-noise ratio of the absorption signal used to determine glucose concentration can be further improved, even without noticeable vibrational / rotational bands attributable to glucose functional groups within the fourth wavenumber window. However, the additional use of the fourth wavenumber window allows for efficient correction of the absorption signal transmitted from the first, second, and (if applicable) third wavenumber windows in "raw data" form according to the proportions of substances causing cross-sensitivity (e.g., primarily lactic acid, but also including glutamine, glutamic acid, and / or asparagine, if applicable).

[0050] In particular, it has been found that if a significant amount of lactic acid is present in the fluid, the signal used to determine glucose concentration, formed by combining absorption signals from the first and second wavenumber windows, is significantly affected. By correcting for this lactic acid component's influence on the combined absorption signal from the first and second wavenumber windows, the effect can be eliminated in a very direct and clear manner.

[0051] The absorption spectrum of lactic acid is at 1300 cm⁻¹ -1 Up to 1320 cm -1 It shows a clear structure within a certain range, but at 1025cm -1 and 1100 cm -1 There are other structures at that location as well. Therefore, it is assumed that the fourth wavenumber window (at 1300 cm⁻¹) -1 Up to 1320 cm -1Within the range of the first and second wavenumber windows, conclusions about lactate concentration are primarily allowed, and the absorption of MIR radiation in the fourth wavenumber window can be used to correct the absorption signal used to determine glucose concentration based on the first and second wavenumber windows to suppress cross-sensitivity.

[0052] Expressed in wavelength, the following applies to the first, second, third, and fourth wavenumber windows:

[0053] wavenumber 955 cm -1 The full width of the half-peak is 20 cm. -1 This corresponds to a wavelength of approximately 10470 nm and a full width at half maximum (FWHM) of 220 nm.

[0054] The wave number is 1015 cm. -1 The full width of the half-peak is 20 cm. -1 This corresponds approximately to a wavelength of 9850 nm and a full width at half maximum (FWHM) of 200 nm.

[0055] The wave number is 1085 cm. -1 The full width of the half-peak is 20 cm. -1 This corresponds to a wavelength of approximately 9215 nm and a full width at half maximum (FWHM) of 170 nm.

[0056] The wave number is 1310 cm. -1 The full width of the half-peak is 20 cm. -1 This corresponds to a wavelength of approximately 7635 nm and a full width at half maximum (FWHM) of 120 nm.

[0057] These wave values ​​are all preferred to refer to a standard temperature of 37°C.

[0058] In particular, one of the first, second, third, and fourth infrared bandpass filters, if applicable, can be configured to determine the center wavenumber of the corresponding wavenumber window with an accuracy of at least 5%.

[0059] In another embodiment, the ATR sensor may include a multi-channel infrared bandpass filter, each having an infrared bandpass filter for a first, second, and, if applicable, third and fourth wavenumber windows. This multi-channel infrared bandpass filter can be constructed in a particularly compact manner. In particular, the multi-channel infrared bandpass filter can be easily housed within a tubular housing with an outer diameter of 12 mm made of an inert material (e.g., stainless steel). In this way, a sensor equipped with an ATR sensor according to the invention for determining glucose concentration can be created, corresponding to the format of conventional analytical instruments used for monitoring biotechnological processes. Due to the resulting high degree of standardization, the sensor can be easily inserted into the corresponding mounting slots of conventional biotechnological devices, including those initially used to detect other parameters. In other words, the multi-channel sensor includes a housing housing at least one photodetector or infrared detector and at least two infrared bandpass filters. If the photodetector or infrared detector is configured to distinguish between two different local resolutions, then a shared photodetector is sufficient for at least two bandpass filters. Alternatively, the multi-channel sensor may be equipped with a separate photodetector or infrared detector for each infrared bandpass filter.

[0060] In another embodiment, the ATR sensor or method for determining glucose concentration in a fluid can be configured to determine the glucose concentration in a glucose-containing liquid with a pH value between 5 and 8, particularly between 6.8 and 7.4.

[0061] It is even possible to select absorption signals from the aforementioned wavenumber windows, particularly from the first and second wavenumber windows, if applicable, relative to the absorption signals from the third wavenumber window and / or the absorption signals corrected by the absorption signals from the fourth wavenumber window, such that the final combined absorption signal used varies only slightly within the selected pH range, reflecting the absorption of infrared radiation detected after interaction with the liquid. This allows for the detection of glucose concentrations independent of pH variations within this range. In some cases, the pH and / or temperature of the liquid (e.g., in nutrient solution bioprocessing techniques) may vary depending on the degree of fermentation.

[0062] The ATR sensor or method according to the invention also provides the possibility of selecting two, three, or four wavenumber windows in the cases described above, such that the detected absorption signal is largely unaffected by pH or temperature within a specified pH range and / or temperature range. In this way, glucose concentration can be reliably monitored throughout the process.

[0063] In another embodiment, the first, second, third, and fourth infrared bandpass filters, if applicable, may have a predetermined minimum quality determined by the center wavenumber of the corresponding wavenumber window that varies with temperature in the range of 20°C to 45°C by a maximum of 5 wavenumbers per 10°C.

[0064] Furthermore, the ATR sensor can be configured to detect a reference signal based on infrared radiation emitted by an infrared radiation source without being transmitted through the ATR element. In this way, the ATR sensor can detect reference infrared radiation from the corresponding wavenumber windows of the first, second, third, and, if applicable, fourth wavenumber windows. Specifically, the reference infrared radiation is not guided through the ATR element and is therefore unaffected by infrared radiation absorption in the fluid being detected. Thus, after transmission through the ATR element, the corresponding infrared radiation detected by the infrared detector can be detected in a manner related to its respective associated reference infrared radiation, thereby simplifying the calibration of the ATR sensor, since variations in the emission intensity of the infrared radiation source are excluded by referring to the reference infrared radiation and will not directly affect the detected absorption signal under any circumstances. Attached Figure Description

[0065] The present invention will now be described in more detail with reference to the accompanying drawings and exemplary embodiments.

[0066] Figure 1 A schematic longitudinal sectional view of an innovative embodiment of the ATR sensor according to this application is shown.

[0067] Figure 2 a) and Figure 2 b) shows a four-channel infrared measurement sensor with a four-channel infrared bandpass filter for an ATR sensor, viewed in front and perspective views.

[0068] Figure 3 Simplified infrared absorption spectra of glucose and lactic acid are shown, along with wavenumber windows selected for the first, second, third, and fourth infrared bandpass filters, preferably at 37°C. Detailed Implementation

[0069] exist Figure 1 In this context, embodiments of the ATR sensor according to the invention are generally designated by 10. The ATR sensor 10 includes a sensor housing 12 having a tube 13, which is preferably integrally formed. The sensor housing 12, and particularly the tube 13 of the sensor housing 12, can generally be made of plastic, but is preferably made of stainless steel in order to withstand corrosive chemical environments over time.

[0070] In the example shown, the sensor housing 12 is formed as a cylindrical housing with a cylindrical outer shell 14. The cylindrical outer shell 14 is indicated by a dashed line in the area of ​​the recess 16 that would otherwise be the cylindrical sensor housing 12. The sensor housing 12 extends along the longitudinal axis L of the sensor housing, which is imagined to be the longitudinal axis of the sensor housing 12 centered through it, and is also the cylindrical axis of the cylindrical sensor housing 12. Except for the recess 16, the cylindrical outer shell 14 coincides with the outer surface 13a of the cylindrical tube 13.

[0071] A printed circuit board 18 is arranged in the sensor housing 12 as a carrier component 20 for the infrared radiation source 22. To accommodate the printed circuit board 18, a mounting space is used within the axial extension range of the ATR element 24. This mounting space is available because the ATR element 24 (whose flat outer surface 24a serves as the measuring surface 26) must be accessible to the fluid to be measured in the external environment U of the sensor housing 12. Therefore, the ATR element 24 is arranged in the sensor housing 12 at a distance from the longitudinal axis L of the sensor housing.

[0072] The infrared radiation source 22 is soldered or welded onto the printed circuit board 18 as a surface mount device (SMD). The printed circuit board 18 is a printed circuit board with conductive paths printed in a manner known per se. It also includes a control device 27 for controlling the operation of the infrared radiation source 22.

[0073] The printed circuit board 18 and the electronic components soldered, welded or otherwise connected thereto: infrared radiation source 22 and control device 27, which can be connected via ribbon cable 28 to a power supply and / or advanced control device of the laboratory equipment using the ATR sensor 10.

[0074] The ATR sensor 10 has a connection end 10a and a head end 10b axially opposite to the longitudinal axis L of the sensor housing. At the connection end 10a, the ribbon cable 28 and the connecting assembly 30 can make electrical contact. The connecting assembly 30 is used to output measurement signals from the infrared measuring sensor 32 and the infrared reference sensor 34. At the head end 10b, the tube 13 is sealed by a plug 35.

[0075] The infrared measurement sensor 32 and the infrared reference sensor 34 can be sensor devices with essentially the same structure. They may differ at most in the corresponding infrared bandpass filters 36 and 38 arranged therein, but they do not need to be different. For simplicity, Figure 1 It is not shown but does exist in the diagram, but it does exist, with the infrared reference sensor 34 outputting a reference detection signal and routing it out of the sensor housing 12.

[0076] Infrared measurement sensor 32 in Figure 2As shown in the image. Figure 2 a) The infrared measurement sensor 32 is shown in a front view, with four infrared bandpass filters 36a, 36b, 36c, and 36d visible through its entrance window. Figure 2 b) shows a perspective view of the four-channel measurement sensor 32.

[0077] It should be understood that the infrared reference sensor 24 can be constructed in the same manner as the infrared measurement sensor 32, such that... Figure 2 The illustrations in the diagrams also apply to the infrared reference sensor 34.

[0078] In the illustrated example, both the infrared measurement sensor 32 and the infrared reference sensor 34 have four detectors 40a, 40b, 40c, and 40d (in... Figure 1 In simplified form, they are represented by reference numerals 40) and 42a, 42b, 42c, and 42d (in the attached figures). Figure 1 (Simplified representation by reference numeral 42) In the optical path from the infrared radiation source 22, infrared bandpass filters 36a, 36b, 36c, 36d or 38a, 38b, 38c, 38d are arranged in front of the detector. Infrared bandpass filter 36 includes four infrared bandpass filters 36a, 36b, 36c, and 36d. Correspondingly, infrared bandpass filter 38 also includes four infrared bandpass filters 38a, 38b, 38c, and 38d.

[0079] The infrared measurement sensor 32 comprises a total of four detectors 40a, 40b, 40c, and 40d. Only two detectors, 40a and 40c, located behind the longitudinal section containing the longitudinal axis L of the sensor housing, are... Figure 1 As can be seen, and is simplified by reference numeral 40 in the accompanying drawings. The other two detectors 40b and 40d are... Figure 1 The drawing plane is orthogonal to and located in front of the two detectors 40 shown. The same applies to the infrared bandpass filters 36a, 36b, 36c, 36d, which are arranged in front of the incident side of the detectors 40 to allow only infrared radiation with wavelengths defined by the respective infrared bandpass filters 36a, 36b, 36c, 36d to be incident on the detectors 40a, 40b, 40c, 40d.

[0080] Infrared bandpass filters 36a, 36b, 36c, and 36d each have different wavenumber windows, within which they are effective for radiation in the mid-infrared range (MIR radiation, 4000 to 400 cm⁻¹). -1 The wavelengths (wavenumbers within the range or wavelengths in the range of 2.5 to 25 μm) are transmissible. Each infrared bandpass filter 36 is impermeable to MIR radiation outside its corresponding wavenumber window.

[0081] The individual infrared bandpass filters 36a, 36b, 36c, 36d and 38a, 38b, 38c, 38d are transmittable for the following bandwidths (also known as wavenumber windows) of MIR radiation, specified by the corresponding center wavenumber and full width at half maximum (FWHM):

[0082] First infrared bandpass filter 36a or 38a: center wavenumber 1015 cm⁻¹ -1 The effective full width at half-peak is 20 cm. -1 It is preferably carried out at a temperature of 37°C.

[0083] Second infrared bandpass filter 36b or 38b: center wavenumber 1085 cm⁻¹ -1 The effective full width at half-peak is 20 cm. -1 It is preferably carried out at a temperature of 37°C.

[0084] Third infrared bandpass filter 36c or 38c: center wavenumber 955 cm⁻¹ -1 The full width of the half-peak is 20 cm. -1 .

[0085] Fourth infrared bandpass filter 36d or 38d: center wavenumber 1310 cm⁻¹ -1 The full width of the half-peak is 20 cm. -1 .

[0086] Therefore, the infrared measurement sensor 32 is a four-channel measurement sensor. The infrared reference sensor 34 can have the same construction, so the description provided for the infrared measurement sensor 32 in this example can also be used to explain the infrared reference sensor 34.

[0087] The infrared measurement sensor 32 includes a housing 44, which is cylindrical for at least 75% of its longitudinal extension along the longitudinal axis L of the sensor housing, with its cylindrical axis Z32 coaxial with the longitudinal axis L of the sensor housing. Therefore, the housing 44 of the infrared measurement sensor 32 also has a cylindrical shape for at least 75% of its axial extension along the cylindrical axis Z32. This also applies to the housing 46 of the infrared reference sensor 34 and its cylindrical axis Z34 with necessary modifications to the details.

[0088] The sensor housing 12 includes an axial measuring portion 48, which is defined as a cylindrical measuring portion 48 by the axial portion of the cylindrical outer surface 13a of the tube 13 of the sensor housing 12. An infrared measuring sensor 32 is housed within the measuring portion 48.

[0089] At the axial distance of the measuring portion 48, the sensor housing 12 includes an axial reference portion 50. This is also a cylindrical reference portion 50, defined by the axial portion of the cylindrical outer surface 13a of the tube 13 of the sensor housing 12. An infrared reference sensor 34 is housed within the reference portion 50.

[0090] In the corresponding measuring section 48 and reference section 50, the corresponding infrared measuring sensors, infrared measuring sensor 32 and infrared reference sensor 34, are housed by positioning elements 52 of substantially the same design. Positioning element 52 is an annular element, preferably including a groove formed on its radially outer surface for through which the ribbon cable 28 passes. In the illustration, the groove on the positioning element 52 of the reference section 50 is empty. The ribbon cable 28 is guided through the groove of the positioning element 52 of the measuring section 48. However, the conductor used to lead the measuring signal from the infrared reference sensor 34 out of the sensor housing 12 ( Figure 1 (Not shown) can pass through the groove of the positioning element 52 of the reference portion 50 and further through the groove of the positioning element 52 of the measuring portion 48.

[0091] The annular positioning elements 52 can be arranged within the tube 13 by friction engagement, and can also hold the corresponding infrared measuring sensors 32 or 34 held by them by friction engagement. However, the positioning elements 52 can also be adhesively fixed to the appropriate position on the tube 13 by an adhesive 25 applied between them, and can similarly be adhesively attached to the corresponding infrared measuring sensors 32 or 34 to which they are to be positioned.

[0092] A carrier component 20 with an infrared radiation source 22 and an ATR element 24 are axially arranged between infrared measurement sensors 32 and 34, which are positioned such that the detector surfaces of detectors 40 and 42 face each other. Furthermore, an infrared measurement radiation reflector 54 is axially arranged between the infrared radiation source 22 and the ATR element 24. This reflector 54, through its reflective surface 54a, deflects the portion 56 of infrared measurement radiation emitted by the infrared radiation source 22 and reflected by the ATR element 24 at its parallel interfaces 24a and 24b toward the bandpass filter 36 of the infrared measurement sensor 32 and the detector 40.

[0093] The printed circuit board 18 includes a recess 58 in which an infrared radiation source 22 is disposed. The infrared radiation source 22 is disposed above the recess 58 such that it can not only emit infrared radiation toward the inclined surface of the ATR element 24 as an infrared measurement radiation portion 56, but also, in the example shown, simultaneously emit an infrared reference radiation portion 60 in the opposite direction through the recess 58 in the printed circuit board 18.

[0094] The infrared reference radiation portion 60 reaches the infrared reference sensor 34 via the infrared reference radiation reflector 62. The reflective surface 62a of the infrared reference radiation reflector 62 deflects the infrared reference radiation portion 60 emitted by the infrared radiation source 22 toward the bandpass filter 38 and the detector 42.

[0095] An infrared reference radiation reflector 62 is axially positioned between a carrier component 20 on one side, on which an infrared radiation source 22 and an ATR element 24 are mounted, and an infrared reference sensor 34 on the other side. The infrared reference radiation reflector 62 supports the carrier component 20. This carrier component is located between... Figure 1 The support member 64 is located behind the cross-section. The additional support member 64 can be parallel to the shown support member 64. Figure 1 The front of the cross-section.

[0096] An ATR element 24 capable of transmitting infrared radiation is connected to the tube 13 via a circumferential weld joint 66. The measuring surface 26 is covered by a membrane 68, which is in direct contact with the measuring surface 26. This membrane 68 is transmissible to the fluid being measured in the external environment U of the ATR sensor 10, but not to suspended particles (e.g., cells, cell debris, etc.) contained in the fluid. This prevents measurement results from being distorted by interference from solid particles. The membrane 68 is attached to the measuring surface 26 via a frame 70, which is anchored within the tube 13 or the sensor housing 12 by form-fitting. A seal 72 between the frame 70 and the weld joint 66 prevents fluid from the external environment U from entering the interior A of the ATR sensor 10 or its sensor housing 12. The membrane 68 is made accessible to fluid from the external environment U by completely penetrating the recess 71 of the frame 70 in the thickness direction.

[0097] The above-described structure has components arranged sequentially along the axial direction, wherein the majority of the ATR element 24, the infrared radiation source 22, and the carrier component 20 overlap axially in the axially extending region of the ATR element 24, allowing the ATR sensor 20 to be very slim. The ATR sensor 20 has a dimension D orthogonal to the longitudinal axis L of the sensor housing in its cylindrical and therefore rotationally symmetrical portions 48 and 50 relative to the longitudinal axis L of the sensor housing, which does not exceed 12 mm.

[0098] In the region between the measuring portion 48 and the reference portion 50, i.e. in the region of the recess 16, the sensor housing 12 is formed as a partial cylinder and has a radial dimension starting from the longitudinal axis L of the sensor housing, which does not exceed 6 mm at least in the partially cylindrical region of the tube 13 of the sensor housing 12.

[0099] Figure 3Simplified infrared absorption spectra of glucose and lactic acid in the mid-infrared (MIR) range are shown, along with wavenumber windows F1, F2, F3, and F4 (preferably at a temperature of 37°C) selected for the first (36a, 38a), second (36b, 38b), third (36c, 38c), and fourth (36d, 38d) infrared bandpass filters of the infrared measurement sensor 32 and infrared reference sensor 34, respectively. The relationship between the glucose absorption coefficient and wavenumber is shown in the figure. Figure 3 As shown, this relationship curve is indicated by reference numeral 50 in the attached figure. The relationship curve between the lactic acid absorption coefficient and the wavenumber is as follows. Figure 3 As shown, the relationship curve is indicated by reference numeral 70 in the attached figure.

[0100] Figure 3 The absorption coefficient of glucose 50 is shown at a wavenumber of 1035 cm⁻¹. -1 (52) 1080 cm -1 (54) 1110 cm -1 (54) and 1150 cm -1 The maximum absorbance is observed at (58). The absorption coefficient of lactic acid is 70 at a wavenumber of 1040 cm⁻¹. -1 (72) 1125cm -1 (74) and 1315 cm -1 The maximum absorption value is observed at (76).

[0101] The first infrared bandpass filter 36a or 38a includes a first wavenumber window F1 with a center wavenumber of 10¹⁵ cm⁻¹. -1 The effective full width at half-peak is 20 cm. -1 .

[0102] The second infrared bandpass filter 36b or 38b includes a second wavenumber window F2 with a center wavenumber of 1085 cm⁻¹. -1 The effective full width at half-peak is 20 cm. -1 .

[0103] The third infrared bandpass filter, 36c or 38c, includes a third wavenumber window with a center wavenumber of 955 cm⁻¹. -1 The full width of the half-peak is 20 cm. -1 .

[0104] The fourth infrared bandpass filter, 36d or 38d, includes a fourth wavenumber window with a center wavenumber of 1310 cm⁻¹. -1 The full width of the half-peak is 20 cm. -1 .

[0105] The absorption coefficient curves for glucose at 50 were observed in the first wavenumber window F1 and the second wavenumber window F2, respectively. Neither of these wavenumber windows represents a region where MIR radiation absorption is particularly significant. The center wavenumber is 10¹⁵ cm⁻¹. -1 The first wavenumber window F1 is located in a region where the glucose uptake coefficient 50 has a fairly moderate value and increases significantly towards the maximum uptake coefficient 52 (approximately 1035 cm⁻¹). The central wavenumber is 1085 cm⁻¹. -1 The second wavenumber window F2 is located in a region where the glucose uptake coefficient 50 also has a fairly moderate value. Unlike the first wavenumber window F1, the glucose uptake coefficient 50 in the second wavenumber window F2 ranges from 1080 cm⁻¹. -1 The relative maximum value of 54 at a slightly lower location decreased to 1095 cm. -1 The minimum absorption coefficient at that location.

[0106] However, a common feature of the first wavenumber window F1 and the second wavenumber window F2 is, particularly within these two window ranges, an unusually high ratio of the absorption coefficient 50 for glucose to the absorption coefficient 70 for lactate. Similar phenomena have been found to apply to the absorption coefficients of other trace substances, such as glutamine, glutamic acid, or asparagine. Therefore, by combining the absorption signals from these two wavenumber windows F1 and F2, a glucose absorption signal with high robustness to cross-sensitivity to other trace substances can be obtained. This significantly improves the signal-to-noise ratio when determining glucose concentration, even if the absolute intensity of the detected glucose absorption signal is not particularly high.

[0107] Another significant characteristic of the selected combination of absorption signals from the first wavenumber window F1 and the second wavenumber window F2 stems from the fact that the absorption coefficient 50 of glucose in the first wavenumber window F1 increases with increasing wavenumber, while the absorption coefficient 50 of glucose in the second wavenumber window F2 decreases with increasing wavenumber. When the temperature of the fluid under test changes, the temperature of the infrared bandpass filters 36a, 36b, 38a, 38b used to determine the glucose concentration also changes, because the ATR sensor 10 is in contact with the fluid under test at least at its totally reflective interface. As the temperature of each infrared bandpass filter 36a, 36b, 38a, 38b increases, this temperature change causes the center wavenumber of the corresponding wavenumber windows F1, F2 (in which infrared bandpass filters 36a, 36b, 38a, 38b are transmissive) to shift to a higher wavenumber. Therefore, the positions of the corresponding wavenumber windows F1 and F2, in which the infrared bandpass filters are transmissible, also vary relative to the glucose absorption spectrum 50, since the glucose absorption bands 52, 54, 56, and 58 depend only to a certain extent on temperature. Since the first wavenumber window F1 lies within the range where the absorption coefficient 50 in the glucose absorption spectrum increases with increasing wavenumber, while the second wavenumber window F2 lies within the range where the absorption coefficient 50 in the glucose absorption spectrum decreases with increasing wavenumber, these effects counteract each other and can therefore at least largely compensate for each other. If the temperature of the fluid under test (and the temperatures of the infrared bandpass filters 36a, 36b, 38a, and 38b) increases, the influence of the absorption signal obtained from the first wavenumber window F1 increases, while the influence of the absorption signal obtained from the second wavenumber window F2 decreases. When the fluid temperature decreases, the situation is exactly the opposite: now the influence of the absorption signal obtained from the first wavenumber window F1 decreases, while the influence of the absorption signal obtained from the second wavenumber window F2 increases. These effects can be approximately compensated by combining the two absorption signals from the first and second wavenumber windows F1 and F2, thereby generating an absorption signal that is approximately independent of fluid temperature, at least in the range of 20°C to 45°C. Therefore, by appropriately combining the absorption signals from the first and second wavenumber windows F1 and F2, a measurement signal that absorbs infrared radiation after interacting with a glucose-containing fluid and is highly independent of temperature can be obtained.

[0108] The absorption spectrum of glucose at a wavenumber of 955 cm⁻¹ -1 There are no specific structures attributable to glucose vibrations or rotational bands in the third wavenumber window F3. Since this finding also applies to most substances that can be considered as potential cross-sensitivity, the absorption signal from the third wavenumber window F3 can be used as a reference signal to indicate the “background” or “noise” caused by various effects in the absorption signal detected by the ATR sensor 10.

[0109] At 1310 cm-1 Using a fourth wavenumber window (F4) at the specified wavenumber to determine glucose concentration more effectively suppresses cross-sensitivity in the absorption signal caused by other trace substances in the fluid. Therefore, even without a significant vibrational / rotational band attributable to glucose functional groups in the fourth wavenumber window (F4), the signal-to-noise ratio of the absorption signal used to determine glucose concentration can be further improved. However, the additional use of the fourth wavenumber window (F4) allows for efficient correction of the absorption signal, as "raw data," from the first, second, and, if applicable, third wavenumber windows based on important cross-sensitive components (e.g., primarily lactic acid, but also including glutamine, glutamic acid, and / or asparagine, if applicable).

[0110] In particular, it has been found that if a significant amount of lactic acid is present in the fluid, the signal formed by combining the absorption signals from the first and second wavenumber windows F1 and F2 to determine the glucose concentration will be significantly affected. By correcting for this by using the absorption signal from the fourth wavenumber window F4, the effect of this lactic acid component on the combined absorption signal from the first and second wavenumber windows F1 and F2 can be eliminated in a very direct and clear manner.

[0111] The absorption coefficient of lactic acid is 70 at 1315 cm⁻¹. -1 It shows a significant maximum value of 76 at the wavenumber, but at the wavenumber of 1040 cm⁻¹ -1 and 1125 cm -1 Additional maximum values ​​of 72 and 74 are also observed. Therefore, it can be assumed that the absorption signal provided by the fourth wavenumber window F4 primarily allows for conclusions regarding lactate concentration, and that this absorption signal from the fourth wavenumber window F4 can be used to correct the absorption signal used to determine glucose concentration based on the first and second wavenumber windows F1 and F2 to suppress cross-sensitivity.

Claims

1. An ATR sensor (10) for determining the glucose concentration in a fluid, comprising a sensor housing (12), wherein The sensor housing (12) contains at least the following sensor components: Infrared radiation source (22); ATR element (24), the ATR element (24) being configured to transmit infrared radiation emitted by the infrared radiation source (22) by total internal reflection at at least one interface of the ATR element (24); At least one infrared detector (40) is configured to detect the infrared radiation transmitted by the ATR element (24) and output a corresponding infrared measurement signal; as well as At least two infrared bandpass filters (36a, 36b) are arranged between the ATR element (24) and the infrared detector (40), wherein each infrared bandpass filter (36a, 36b) is configured to be transmissible only to infrared radiation having a predetermined wavenumber window (F1, F2); characterized in that The first of the infrared bandpass filters (36a) in the infrared bandpass filter is transmissive for infrared radiation having a wave number in a first wave number window (F1) ranging from 1005 cm -1 to 1025 cm -1 -1 The second of the infrared bandpass filters (36b) in the infrared bandpass filter is transmissive for infrared radiation having a wave number in a second wave number window (F2) ranging from 1075 cm -1 to 1095 cm -1 .

2. The ATR sensor (10) according to claim 1, wherein the ATR sensor (10) is configured to determine the concentration of glucose in a liquid.

3. The ATR sensor (10) according to claim 1 or 2, wherein the ATR sensor (10) is configured to determine the concentration of glucose in an aqueous solution, suspension or dispersion.

4. The ATR sensor (10) according to claim 2 or 3, wherein, Glucose-containing liquids include the CHO cell line.

5. The ATR sensor (10) according to any one of claims 1 to 4, comprising a third infrared bandpass filter (36c) which is transmissive for infrared radiation having a wave number in a third wave number window (F3) ranging from 945 cm -1 to 965 cm -1 .

6. The ATR sensor (10) according to any one of claims 1 to 5, comprising a fourth infrared bandpass filter (36d) which is transmissive for infrared radiation having a wave number in a fourth wave number window (F4) ranging from 1300 cm -1 to 1320 cm -1 .

7. The ATR sensor (10) according to any one of claims 1 to 6, wherein, The first, second, third, and fourth infrared bandpass filters (36a, 36b, 36c, 36d) are configured such that the center wavenumber of the corresponding wavenumber window (F1, F2, F3, F4) is determined with an accuracy of at least 5%.

8. The ATR sensor (10) according to any one of claims 1 to 7, comprising a multi-channel infrared bandpass filter (36) having an infrared bandpass filter for each of the first wavenumber window (F1), the second wavenumber window (F2), the third wavenumber window (F3) if applicable, and the fourth wavenumber window (F4) if applicable.

9. The ATR sensor (10) according to any one of claims 2 to 8, wherein the ATR sensor (10) is configured to determine the glucose concentration in a glucose-containing liquid with a pH value in the range of 5 to 8, particularly in the range of 6.8 to 7.

4.

10. The ATR sensor (10) according to any one of claims 1 to 9, wherein, The first, second, third, and fourth infrared bandpass filters (36a, 36b, 36c, 36d) have a predetermined minimum quality, which is determined by the center wavenumber of the corresponding wavenumber windows (F1, F2, F3, F4) that are offset by a maximum of 5 wavenumbers per 10 degrees Celsius in the temperature range of 20°C to 45°C.

11. The ATR sensor (10) according to any one of claims 1 to 10, wherein the ATR sensor (10) is configured to detect a reference signal based on infrared radiation emitted by the infrared radiation source (22) that is not transmitted through the ATR element (24).

12. A method for determining glucose concentration in a fluid using an ATR sensor (10), comprising: Provide glucose-containing fluids; The glucose-containing fluid interacts with infrared radiation in the mid-infrared range; The absorption of infrared radiation after interaction with the glucose-containing fluid was detected in at least two different wavenumber windows (F1, F2) in the mid-infrared range; wherein a first wave number window (F1) of the wave number window comprises infrared radiation having a wave number in a range from 1005 cm -1 to 1025 cm -1 and wherein a second wave number window (F2) of the wave number window comprises infrared radiation having a wave number in a range from 1025 cm -1 to 1055 cm -1 and wherein wherein a second of the wave number windows (F2) includes infrared radiation having a wave number in a range of 1075 cm -1 to 1095 cm -1 -1.

13. The method according to claim 12, wherein, infrared radiation in a third wavenumber window (F3) in the mid-infrared range, wherein the third wavenumber window (F3) comprises infrared radiation with a wavenumber of 945 cm -1 to 965 cm -1 .

14. The method according to claim 12 or 13, wherein, infrared radiation is detected in a fourth wavenumber window (F4) in the mid-infrared range, wherein the fourth wavenumber window (F4) comprises infrared radiation having a wavenumber of 1300 cm -1 to 1320 cm -1 .

15. The method according to any one of claims 12 to 14, wherein, Determine the glucose content of aqueous solutions containing CHO cell lines.

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