Determination of damage to optical surfaces used for ir spectral analysis

Abstract

An apparatus (1) for IR spectroscopic analysis and for determining damage to a surface (13, 15) exposed to measurement radiation (9) during IR spectroscopic analysis is provided, wherein the apparatus comprises: a radiation source (7) for generating measurement radiation (9); a sample container (21) for receiving a sample (16), wherein the sample container is at least partially delimited by the surface (13, 15); a detector (19) for detecting measurement radiation (17) after interaction with the sample (16), wherein the apparatus is configured to: measure an IR reference spectrum (29, 31, I V ) of a reference sample received in the sample container; evaluate the reference spectrum (29, 31, I V ) to determine an indicator (S, S 0 , S1) of damage, wherein the evaluation comprises integrating an amount based on the reference spectrum (29, 31, I V ) within a predetermined integrated spectral range (33), wherein the indicator is determined from the integrated value (S).

Description

TECHNICAL FIELD

[0001] The invention relates to a device for IR spectroscopic analysis and for determining damage to a surface exposed to measurement radiation during IR spectroscopic analysis. The invention also relates to a method of determining damage to a surface exposed to measurement radiation during IR spectroscopic analysis and also to a computer program product having program instructions which, when executed by a processor, perform the method. BACKGROUND

[0002] With an infrared spectrometer, conventional infrared-active substances can be analyzed by means of absorption / transmission measurements. Irradiation measurement radiation excites rotational or vibrational modes of the molecules contained in the sample, so that an attenuation of the irradiation radiation is observed in the characteristic wavelength state, for example in transmission or reflection. Fourier-transform infrared spectroscopy (FTIR) is a special form of infrared spectroscopy in which data in a broad spectral range can be recorded within a short period of time.

[0003] The document WO 2007 / 126612 A2 discloses a contamination monitoring which is used with an optical metrology instrument to minimize absorbing substances within the optical path of the metrology instrument and also to minimize the generation of contaminants on the surface of the optical elements. The optical metrology instrument can for example work in the ultraviolet wavelength range. A reference sample is measured before and after the measurement of the test sample and the two reference measurements are compared to determine a contamination or to determine the pollution.

[0004] The document US 2016 / 231234 A1 discloses a method for confirming cleaning or for measuring cleaning effectiveness by a near-infrared spectrophotometer. Data are recorded before and after cleaning and compared to produce a contamination signature.

[0005] The document US 9182280 B1 discloses a method for reducing frequency to record background spectra in FTIR or FTIR-ATR spectroscopy. When a previously existing reference spectrum is available, a current reference spectrum is recorded before measuring a sample. The current reference spectrum is compared to the previously existing reference spectrum to determine whether there is a non-conformity between the two. If there is a non-conformity, it is removed.

[0006] The document US 2019 / 003952 A1 discloses a particle detection method and system, in particular a flow cytometer. Furthermore, a method for determining the degree of contamination in a flow cell is disclosed. The entire construction of the flow cytometer and the physical methods and effects used are very different from an infrared spectrometer.

[0007] The document US 2010 / 277727 A1 discloses a method for detecting contamination in an optical measuring cuvette of a spectrophotometer. A measured reference spectrum is compared with a known target spectrum associated with the measuring cuvette and it is automatically determined whether there is contamination in the measuring cuvette, i.e. depending on a predetermined threshold value of a comparison parameter.

[0008] The document US 2016 / 178435 A1 discloses a method for diagnosing a spectrometer of a drilling tool. Optical data of the spectrometer of the drilling tool are recorded and based on selected data an estimation and determination of light scattering and light drift of the spectrometer are made, respectively. A quantification of baseline drift is estimated from an influence on the measurement and this influence is compared with a threshold value to diagnose a status of the spectrometer.

[0009] The document US 6028663 A discloses a photometric analysis of water suspensions, wherein light that is not absorbed and scattered back is eliminated in the spectrometer, so that un-concentrated water suspensions can be analyzed in real time without any treatment of the water.

[0010] Conventional methods for determining contamination of a relevant surface in a measurement light path are elaborate and often require at least two measurements on a reference sample. Thus, conventional methods and systems are complex and time-consuming. For example, other systems and methods of the prior art invite a user to clean the measurement unit periodically. This invitation is performed without a prior determination of the degree of contamination of the unit. Thus, cleaning can be performed too frequently or, in other cases, too seldom, with the disadvantage of increasing the time effort and reducing the measurement quality and the reliability of the measurement results, respectively. SUMMARY

[0011] It is therefore an object of the present invention to propose a device and a method, respectively, for determining a damage, in particular a contamination, of a surface exposed to measurement radiation during IR spectroscopic analysis, wherein the device and the method, respectively, are simplified with respect to the prior art and the method can be performed in a shorter time period. It is a further object of the present invention to simplify the process of determining the integrity of the measurement unit and the relevant surface, respectively, and to determine the degree of contamination of the measurement unit and the relevant optical surface, respectively, in particular by means of a simple method.

[0012] This object is solved by a device and a method for IR spectroscopic analysis and for determining a damage of a surface exposed to measurement radiation during IR spectroscopic analysis according to the present invention.

[0013] According to embodiments of the present application, there is provided an apparatus for IR spectroscopic analysis and for determining a damage (e.g. contamination and / or deterioration) of a surface (e.g. a glass surface), which surface is exposed to (e.g. interacts with) a measurement radiation during the IR spectroscopic analysis, wherein the apparatus comprises: a radiation source generating the measurement radiation; a sample container for receiving (e.g. a reference) sample, wherein the sample container is at least partially delimited by the surface; a detector for detecting the measurement radiation after interaction with the sample (and the surface). The apparatus is configured to: measure an IR reference spectrum of a reference sample (e.g. in contact with the surface) received in the sample container; evaluate the reference spectrum (e.g. according to a pre-given algorithm) to determine an indicator of the damage, wherein the evaluation comprises integrating an amount based on the reference spectrum in a pre-determined integration spectral range, wherein the indicator is determined from the value of the integration.

[0014] The apparatus can be suitable for different types of infrared spectroscopic analysis. The apparatus can for example be suitable for a transmission IR spectroscopic analysis or an ATR-IR spectroscopic analysis. The radiation source is configured to generate and emit infrared radiation. The measurement radiation can for example comprise wavelengths in a range between 700 nm and 100 pm. Depending on the application (sample to be examined), the wavelength range of the measurement radiation emitted by the radiation source can also be reduced, for example, it can be between 1.25 pm and 50 pm. The radiation source can for example be formed by a silicon carbide element heated to a certain temperature, for example between 800 K and 1500 Kelvin, in particular approximately 1200 Kelvin. The radiation source can generate and emit radiation with wavelengths (wavenumbers) between 2 pm and 25 pm (between 5000 cm -1 -4000 cm -1 -1).

[0015] The detector can for example be configured to detect the intensity of the measurement radiation after interaction with the sample in a spectral range between 1.6 pm and 15 pm. The detector can for example be configured as a point detector or a photodiode, respectively. The detector can detect a portion of the measurement radiation with respect to the intensity, which portion is not absorbed by the sample. For example, the detector can be configured as a DTGS type detector (deuterated tri-glycine sulfate detector).

[0016] The sample to be examined and / or the reference sample can for example be a liquid. In the interaction of the IR measurement radiation with the sample, rotational or vibrational modes within the sample can be excited, for example symmetric stretching modes, asymmetric stretching modes, shear movements in a plane, rolling movements in a plane, etc.

[0017] In FTIR spectroscopy, a Fourier transform is applied to the recorded raw data to convert the interferogram into a spectrum. When the apparatus is configured as an FTIR spectrometer, the apparatus thus also comprises an interferometer. The interferometer can be configured to split the incoming light into two light portions, which are modified and produce an interference. The interference pattern is subsequently recorded as an interferogram.

[0018] If FTIR spectroscopy is applied, the interferometer can for example be configured as a known Michelson interferometer. The split measuring light and the split measuring radiation are directed to a static mirror, respectively, while the other half is for example guided to a moving mirror, which performs a motion oscillating perpendicular to its plane. The beams reflected from the two different mirrors are recombined and either guided through the sample or reflected in ATR spectroscopy under interaction with the sample by attenuated total reflection. A detector can detect the interferogram, which is converted into a spectrum (intensity depending on wavelength and wave number, respectively) by Fourier transform.

[0019] The sample container can for example be configured as a transmission measurement cell or an ATR-(attenuated total reflection) cell.

[0020] In the case of transmission IR spectroscopy, the sample container can be formed by a transmission measurement cell. The transmission cell can for example consist of a material transparent to IR radiation, for example inorganic salts (e.g. ZnSe, KBr, CaF2, NaCl, etc.) can be used. In this case, the (liquid) sample is filled into the transmission cell and thus surrounded by the IR transparent cell material. The IR measurement radiation is sent through the measurement cell. Thereby, the sample interacts with the measurement radiation and absorbs a part of the measurement radiation.

[0021] When the apparatus is configured for ATR-IR spectroscopy, the sample container can be formed by an ATR measurement cell. The IR measurement radiation propagates through a solid transparent crystal, which is for example in contact with the sample to be examined. Subsequently, the measurement radiation (from the inside of the crystal) hits the surface of the crystal, which delimits between the sample and the crystal, and is reflected, wherein, however, a part of the measurement radiation penetrates some micrometers in the sample region and thus can also interact with the sample. This part of the measurement radiation, which penetrates the sample region, is also referred to as evanescent wave. Thus, the radiation emitted or absorbed by the sample through the interaction with the sample is also detected by the detector. According to a special embodiment of the present invention, the measurement radiation is reflected multiple times within the solid transparent crystal and thus also interacts multiple times with the sample to increase the detected intensity difference (multiple bounce ATR). For example, between 10 and 15 reflections can occur within the ATR crystal. In other embodiments, between 2 and 10 reflections can occur.

[0022] In the case of, for example, transmission IR spectroscopy, the surfaces can be, for example, the inner and / or outer surfaces of the transmission cell and / or the inner and / or outer surfaces comprising the transmission cell, respectively. If ATR-IR spectroscopy is performed, the surfaces can also be the surfaces of the (ATR) crystal, in which the measuring radiation is coupled in and which is in contact with the sample.

[0023] Particular embodiments of the application are configured to determine, in particular, contamination of a surface, for example organic and / or inorganic molecules, such as polysaccharides, polyphenols (in particular tannins), flavonoids (in particular anthocyanins), sodium tartrate and potassium tartrate. Contaminating substances adsorbed or deposited on the surface can themselves deliver characteristic IR spectra, which can be considered, respectively, and used to determine the contamination, and in particular the degree of contamination, according to embodiments of the application.

[0024] For measuring the IR reference spectrum, the measuring radiation is directed to the sample within the sample container, and the measuring radiation transmitted and reflected, respectively, is detected and registered by the detectors, respectively, for the intensity (resolved according to the wavelength) after interaction with the sample. The reference spectrum can be stored, for example, in digital form, and can be evaluated, for example, according to a mathematical algorithm, by the evaluation unit and the processor, respectively, in order to determine, in particular, an indicator of the contamination, and in addition, in particular, an indicator of the degree of contamination.

[0025] The evaluation of the recorded spectra can be performed by the evaluation unit (for example, comprising a computer and a suitable evaluation program, respectively).

[0026] Wavelength and wave number, i.e. the reciprocal value of the wavelength, are other possibilities to define a certain point or region of the electromagnetic spectrum.

[0027] The pre-determined integral spectral range is within the IR spectral range, can have a width (expressed as wave number) between 300 cm -1 and 800 cm -1 , in particular between 400 cm -1 and 600 cm -1 , and / or can have a start between 800 cm -1 and 1000 cm -1 , and / or can have an end between 1300 cm -1 and 1700 cm -1 .

[0028] The pre-determined integral spectral range can be adapted according to the application, in particular according to the intended contaminating components or contaminating molecules, which can, for example, include characteristic absorptions within a certain wavelength range. It can be possible to perform the evaluation within this integral spectral range (or within a slightly extended spectral range, for example, up to approximately 1900 cm -1The IR reference spectrum is recorded accurately without the intensity of wavelengths not included in the integration spectral range. Thus, the IR reference spectrum can also be recorded within a short time period. The integration can be performed digitally within the evaluation unit and the computer, respectively, wherein, for example, the wavelength sampling rate of the reference spectrum can be used as a step size. Depending on the value of the integration, an indicator of damage is determined, which can indicate the degree of contamination quantitatively, in particular.

[0029] Thus, a simple method for determining an indicator of damage is provided, which can be implemented in a simple manner in a device. When indicating the indicator to a user, it is also possible to avoid performing an IR spectrum analysis by a contaminated and damaged surface, in particular a measurement unit, respectively. In other cases, depending on the determined indicator, it is possible to avoid cleaning the surface, in particular the measurement unit, unnecessarily, in order to avoid longer downtimes.

[0030] Detailed description of exemplary embodiments

[0031] According to an embodiment of the present application, the predetermined integration spectral range is between 800 cm -1 and 2000 cm -1 , in particular between 900 cm -1 and 1500 cm -1 , wherein the indicator indicates the degree of contamination of the surface quantitatively. The integration spectral range can be chosen depending on the application, in particular depending on the expected contaminating molecules and / or the expected possible damage of the surface. The damage of the surface can be given, for example, by scratches.

[0032] According to an embodiment of the present application, the reference spectrum comprises the measured intensity of the (total) reflection of the measurement radiation from the surface (including the radiation emitted from the reference sample which has dissipated due to the incidence into the sample), or the measured intensity of the transmission of the measurement radiation through the surface comprising the reference sample, respectively for different wave numbers and wavelengths, wherein the measurement radiation comprises wavelengths in the range from 2 pm to 12.5 pm. Thus, transmission IR spectrum analysis and ATR-IR spectrum analysis are supported.

[0033] According to an embodiment of the present application, the evaluation comprises normalizing the reference spectrum to obtain a normalized reference spectrum, wherein for this purpose the measured reference spectrum is divided by the intensity of a predetermined wave number and / or multiplied by a predetermined factor; and / or logarithmizing, in particular normalizing, the reference spectrum to obtain a logarithmized normalized reference spectrum.

[0034] The pre-determined wave numbers can be determined depending on the expected contamination and the expected contaminating molecules, respectively. In particular, the pre-determined wave numbers can be determined such that the intensity detected in the pre-determined wave number state is only slightly influenced and changed by the contamination of the molecules actually present on the surface, respectively, or not influenced and changed at all. The pre-determined wave numbers can be between 880 cm -1 and 950 cm -1 , for example, in particular approximately 920 cm -1 . For this wavelength and wave number, the expected type of contamination that can be present on the surface does not have an influence on the intensity. The logarithmization can be performed according to the Lambert-Beer-law, thereby obtaining a logarithmized normalized reference spectrum that is proportional to the contamination concentration to be determined.

[0035] According to an embodiment of the application, the evaluation further comprises temperature compensating the (in particular logarithmized normalized) reference spectrum to obtain a temperature compensated reference spectrum; wherein the quantity of the reference spectrum is proportional to the temperature compensated reference spectrum.

[0036] The temperature compensation can be understood as a baseline correction to reduce and eliminate the dependence of the reference spectrum on the measurement temperature, respectively. Thus, the reference spectrum can be measured, for example, at different temperatures, which do not necessarily have to be explicitly adjusted and registered beforehand, respectively. By temperature compensating algorithmically, the temperature dependence of the reference spectrum can be reduced and eliminated, respectively.

[0037] According to an embodiment of the application, the temperature compensation comprises subtracting a linear function with respect to the wave number from the (in particular logarithmized normalized) reference spectrum, wherein in particular two parameters defining the linear function are defined by equalizing the (in particular logarithmized normalized) reference spectrum with the linear function in a first pre-determined wave number state and in a second pre-determined wave number state.

[0038] The linear function can comprise a positive slope, for example. The slope and the axis intercept can be determined by equalizing the reference spectrum with the linear function in the first pre-determined wave number state and in the second pre-determined wave number state. The first pre-determined wave number and the second pre-determined wave number can be selected depending on the expected contamination type and the contaminating molecules, respectively. In particular, the first pre-determined wave number and / or the second pre-determined wave number can be determined such that the (initially unknown) contamination has a small and negligible influence on the detected intensity of the measurement radiation in the first pre-determined wave number state and / or in the second pre-determined wave number state, respectively. Furthermore, the first pre-determined wave number and / or the second pre-determined wave number can be determined such that they are between the rotational bands of water vapor, thus not being influenced by atmospheric water vapor occurrence.

[0039] Generally, the IR reference spectrum to be recorded depends on the measurement temperature. However, by temperature compensation, this dependency can be compensated and eliminated, respectively. Thus, the damage of the surface can be determined at different temperatures, in particular without actually knowing and / or without separately measuring and recording the measurement temperature.

[0040] According to embodiments of the present application, the first predetermined wave number is in the range of 870 cm -1 to 970 cm -1 and / or wherein the second predetermined wave number is in the range of 1790 cm -1 to 1900 cm -1 Other values are possible, too.

[0041] According to embodiments of the present application, the evaluation comprises normalizing the value of the integral to obtain a normalized integral value, wherein the indicator is determined based on the normalized integral value. By normalizing, it can be ensured that the normalized integral value is always greater than zero. Thus, the interpretation of the indicator is simplified.

[0042] According to embodiments of the present application, the normalized integral value S 0 is calculated according to the following manner: S 0 = (S - S 最小值 ) / (S 最大值 - S 最小值 ), wherein S is the value of the integral and S 最小值 and S 最大值 are predetermined quantities.

[0043] The values S 最小值 , S 最大值 may be determined empirically, for example, S 最大值 = -60 and S 最小值 = -165 can be assumed. Other values are possible, too. The parameters S 最大值 , S 最小值 may be determined by determining the actual contamination of the surface by an independent method and adjusting the factors S 最大值 , S 最小值 correspondingly, such that the determined normalized integral value reflects the actual contamination measured by the other method.

[0044] According to embodiments of the present application, the evaluation comprises cutting (e.g., clipping and / or limiting) the normalized integral value between the values 0 and 1 to obtain the indicator. By cutting and clipping, respectively, it is ensured that the resulting indicator is between the values 0 and 1, which can enable a simple interpretation and a clear reception for the user. The higher the possible contamination, the higher the normalized integral value.

[0045] According to embodiments of the present application, the device is configured to perform ATR-IR spectroscopy, in particular ATR-FTIR spectroscopy, wherein the surface comprises a surface of at least one ATR crystal in contact with the reference sample and / or a surface of the ATR unit. The ATR crystal has a higher optical density compared to the (liquid) sample in contact with the surface. Thus, total reflection of the measurement light propagating within the ATR crystal at the inner surface of the crystal is possible.

[0046] According to embodiments of the present application, the device is configured to perform transmission IR spectroscopy, in particular transmission-FTIR spectroscopy, wherein the surface comprises an inner surface and / or an outer surface of the measurement unit having the reference sample received therein. Thus, different variants of IR spectroscopy are supported.

[0047] According to embodiments of the present application, the device further comprises a display device configured to indicate the indicator optically and / or acoustically. The display device can for example comprise a display screen which can also provide a graphical user interface for controlling the device. The indicator can comprise characters or other optical symbols, for example different colors (e.g. from green to red) or shapes. If the degree of contamination is determined to be greater than or equal to a threshold value (e.g. 1), an alarm can be output, for example by a sound whistle and / or an optical flash, inviting the user to perform cleaning and maintenance, respectively, of the surface (e.g. the measurement unit).

[0048] According to embodiments of the present application, the device is further configured to indicate to the user by means of the display device that maintenance should be performed if the value of the indicator exceeds a threshold value. The maintenance can for example be specified as performing cleaning. Depending on the particular degree of contamination, additional hints can also be given for the type of cleaning and the type of maintenance, respectively, for example to perform the cleaning program several times or to apply a special cleaning agent or method if the indicator is above a particular threshold value. For example, only one cleaning is recommended if the indicator is below another threshold value.

[0049] According to embodiments of the present application, the reference sample comprises water, in particular high-purity water, or is high-purity water. True, water also comprises a characteristic IR spectrum. However, within a predetermined integral wave range, no significant absorption peaks are observed. In other embodiments, another substance can be used as the reference sample.

[0050] According to embodiments of the present application, the device is configured to determine the indicator without performing a measurement and / or without comparing to a previous reference spectrum. Thus, the determination and thus the complexity of the device can be simplified.

[0051] According to embodiments of the present application, the device further comprises a processor and an electronic memory (e.g. RAM, hard disk, memory stick, CD) which is accessible to the processor and in which a computer program product with program instructions is stored, wherein the processor is configured to execute the program instructions for evaluating the reference spectrum (in particular measuring and) to determine the indicator of damage. Thus, the device can be implemented by conventional available components.

[0052] It is to be understood that features mentioned, described, explained and provided respectively or in any combination according to embodiments of the present application in the context of a device for IR spectral analysis and for determining damage of a surface are also applicable to a method of determining damage of a surface exposed to measuring radiation during IR spectral analysis, alone or in any combination, and vice versa.

[0053] According to embodiments of the present application, a method for determining damage of a surface exposed to measuring radiation during IR spectral analysis is provided. The method comprises: measuring an IR reference spectrum of a reference sample; evaluating the reference spectrum to determine an indicator of damage, wherein the evaluation comprises integrating an amount based on the reference spectrum in a pre-determined integral spectral range, wherein the indicator is determined from the value of the integration.

[0054] The above-mentioned device can be configured to perform the method.

[0055] According to embodiments of the present application, a computer program product with program instructions is also provided, which, when executed by a processor, controls or carries out the method according to the previous statement. The computer program product can be stored, for example, on a storage medium such as a CD, DVD, memory stick, or on a computer server which is accessible via a communication network (e.g. the Internet). BRIEF DESCRIPTION OF DRAWINGS

[0056] Embodiments of the present application are described below with reference to the accompanying drawings. The present application is not limited to the illustrated or described embodiments.

[0057] Figure 1 A device for IR spectral analysis and for determining damage of a surface according to embodiments of the present application is schematically shown, with an enlarged view of the scheme of the IR measurement;

[0058] Figure 2A and 2B A measurement process for measuring a sample in an ATR-IR spectral analysis and a measurement process for measuring an IR reference spectrum are schematically shown, respectively;

[0059] Figure 3 Reference spectra of a surface exposed to measuring radiation at different degrees of contamination are schematically shown.

[0060] Figure 4 A method for determining an indicator of damage of a surface exposed to measurement radiation during IR spectroscopic analysis according to an embodiment of the application is schematically shown; and

[0061] Figures 5 to 7 An indicator of contamination of a surface determined according to an embodiment of the application is shown. DETAILED DESCRIPTION

[0062] In Figure 1 A device 1 for IR spectroscopic analysis schematically shown in Fig. 1 shows a device housing 3 with a graphical user interface on a display device 5 to enable a user to operate and control the device 1, respectively. In a zoomed view Figure 6 In Fig. 2, a part of the interior of the device 1 is schematically shown. The device 1 comprises a radiation source 7 to generate measurement radiation 9. In Figure 1 The shown embodiment is configured as an ATR-FTIR spectrometer. The device 1 comprises an ATR crystal 11 comprising surfaces 13, 15 in contact with a sample 16. The measurement radiation 9 is coupled into the ATR crystal 11 and totally reflected at the surfaces 13, 15, wherein evanescent electromagnetic waves also penetrate a certain depth into the sample 16 and can interact with the sample. After a total of 12 reflections at the surfaces 13, 15, the measurement radiation 17 that has interacted with the sample 16 is coupled out of the ATR crystal 11 and guided to a detector 19 that registers the intensity of the measurement radiation 17 after interaction with the sample 16.

[0063] The device comprises a processor not explicitly shown in Fig. 1 and an electronic memory having a computer program stored. The processor is configured to execute the computer program while measuring an IR reference spectrum of a reference sample, in particular high-purity water received in a sample container 21. Further, the processor is configured to evaluate the reference spectrum to determine an indicator of damage. The evaluation of the reference spectrum comprises integrating an amount of the reference spectrum within a predetermined indicator range, as explained in detail below. Figure 1

[0064] Figure 2A And 2B Again, the measurement process is shown for two different embodiments. Figure 2A A measurement with single reflection (single bounce) is shown, whereas Figure 2B ​A measurement with multiple reflections (multiple bounces) is shown. The incident measurement radiation 9 is coupled into the ATR crystal 11 and is guided to the sample 16 contained in the sample container 21, which is in contact with the surface 13 of the ATR crystal 11. Although a total reflection takes place at the surface 13, evanescent electromagnetic waves 23 penetrate some micrometers into the sample container 21 and thus also interact with the sample 16. The measurement radiation 17 is measured by the detector 19 after interaction with the sample 16.

[0065] Figure 3 Different reference spectra recorded according to the method of the apparatus shown in Figure 1 , Figure 2A , Figure 2B are illustrated in order to determine an indicator for the damage of the surface (e.g. surface 13, 15). In a coordinate system with an abscissa 25 representing the wave number and an ordinate 27 representing the intensity, the spectra 29 and 31 of high-purity water are shown, respectively, as they have been measured by the apparatus 1 for different degrees of contamination of the surface 13, 15. The surface 13 and / or 15 is more contaminated when recording the spectrum 31 than when recording the spectrum 29, wherein in particular the surface is completely clean.

[0066] In Figure 3 , a predetermined integral spectral range 33 is shown, in which the normalized, logarithmized and temperature-compensated reference spectra 31, 29, respectively, are integrated, wherein an indicator for the damage of the surface is determined from the value of the integral. It can be seen from Figure 3 that the spectra 31, 29 differ greatly from each other, in particular in the predetermined integral spectral range 33, while they are hardly distinguishable in other spectral ranges and respectively for other wavelengths and respectively for other wave numbers. Thus, the intensity in this predetermined integral spectral range 33 indicates the presence of contamination at the surface 13, 15.

[0067] In Figure 3 , a first predetermined wave number 34, namely 920 cm -1 , and a second predetermined wave number 36, namely 1844 cm -1 , are also indicated. In addition, the course of the linear function is represented as a straight line, which passes through the point I (920 cm -1 ) and the point I (1844 cm -1 ), respectively.

[0068] It is to be understood that the predetermined wave numbers 34, 36 and / or the predetermined integral spectral range 33 can depend on the specific application and can illustratively be applied, for example, to alcoholic beverage samples, such as beer, wine. For other substances (e.g. fuel, oil), other values can be applied.

[0069] Figure 4An exemplary method 50 for determining an indicator for damage of a surface exposed to measuring radiation during IR-spectroscopic analysis or spectroscopic analysis is shown schematically. First, in a method step 51, an IR reference spectrum I V of high-purity water as an example of a reference sample is measured. V In a further method step 53, the reference spectrum I N is normalized to calculate a normalized reference spectrum I V . The reference spectrum is divided by the intensity in the wave number range 920 cm -1 - 1844 cm N -1 and then multiplied by a factor 107. In a further method step 55, the normalized reference spectrum I V is logarithmized to obtain a logarithmized reference spectrum E V . In a further method step 57, a temperature compensation of the logarithmized normalized reference spectrum is performed to obtain a temperature-compensated reference spectrum E V T . A baseline correction with a linear function B V is performed by subtracting this linear function B V from the logarithmized normalized reference spectrum E V . It is assumed that B V = k * v + d, where B V = E V is set to v = 920 and 1844 cm -1 -1 to determine the parameters k and d in the linear function.

[0070] In a further method step 59, the integration already mentioned above, i.e. the integration of the temperature-compensated logarithmized normalized reference spectrum E V T , is performed within a predetermined integration range 33.

[0071] In a further method step 61, the value of the integration S from step 59 is normalized to obtain a normalized integration value S 0 . S 最大值 may for example be set to -60, while S 最小值 may be set to -165 to obtain S 0 . In a further optional method step 63, the normalized integration value S 0 is further cut to a range relevant to practice to obtain a cut normalized integration value S1. According to an embodiment of the present invention, the result S1 in method step 65 constitutes an indicator for contamination of the surface 13 and / or 15 of the ATR crystal 11.

[0072] Figure 1 The display device 5 shown is configured to indicate the indicator, e.g. the indicator S1, acoustically or optically to a user.

[0073] Method step 51 shows the measurement of the IR reference spectrum, and method steps 53, 55, 57, 59, 61, and 63 show the evaluation of the reference spectrum captured in method step 51 to determine indicators of damage to surfaces 13 and / or 15.

[0074] By using Figure 4 The algorithm shown applies to spectrum 31 (see Figure 3 An assessment can be conducted to determine the extent of surface contamination. Cleaning parameters were determined based on the measured reference spectrum of high-purity water. At these values, the user can determine whether cleaning is necessary. Measurements of the reference sample yielded an IR reference spectrum (i.e., intensity as a function of wavenumber and wavelength, respectively). A 920cm² sample can be used... -1 The intensity values ​​under the given conditions are normalized. Inclusions within the radiation source can be removed through calculation and compensation, respectively. In temperature compensation, the baseline, which is located at a point 920 cm below the baseline, is subtracted. -1 and 1844cm -1 Set a straight line. Select a wavenumber such that it is not in the rotation band of the water vapor spectrum. Then, within a predetermined spectral integration range (i.e., 920 cm⁻¹), -1 Up to 1484cm -1 Integrate it. Empirically, this wavelength interval can characterize the spectral range where the spectrum varies significantly due to pollution. The result of the integration can be positive or negative. Furthermore, it is obtained through two empirically determined values ​​S... 最小值 and S 最大值 Normalize the result and apply a capping. A result of 0 indicates a clean surface, a result of 1 indicates a highly contaminated surface, and values ​​in between indicate the degree of contamination. Therefore, the degree of contamination can also be quantified to enable the output of cleaning recommendations in an improved manner.

[0075] IR spectrometers and their sample containers can become contaminated by samples, which can negatively impact measurement results. However, issuing permanent cleaning requests to users can be annoying and not mandatory, but may lead to increased workload and unnecessary wear and tear on components.

[0076] According to embodiments of the invention, the user is invited to clean only when actually needed. Therefore, unnecessary cleaning can be avoided, and signs of wear, such as those that might appear on the relevant surfaces with chemical cleaners, are also reduced.

[0077] On the other hand, by quantitatively indicating the contamination, it can also be avoided that, despite the contamination, further samples are still measured, with the result that the measurement results are respectively unreliable and false. Furthermore, in the conventional method, the properties of the sample to be examined are not sufficiently taken into account, and the necessary number of cleanings can be over- or underestimated. This can lead to a considerable additional effort, respectively, and to damage to the components when using aggressive cleaning agents.

[0078] Embodiments of the present application display the degree of contamination as a simple number between 0 and 1, for example in steps of 0.1. This number can be displayed, for example, in color or otherwise. In this way, a clear and simple message can be sent to the user. To determine this degree of contamination or indicator, the measurement of the water spectrum, i.e. the IR reference spectrum, is converted into the desired display by means of mathematical operations. Basically, the estimate of the contamination is based on the interpretation of the recorded water spectrum. A synchronous reference measurement of the cleaning system is not necessary, nor is an initial state of the measurement system. By calculating the information contained in the spectrum, trends that occur over time, which are not caused by contamination, can be eliminated.

[0079] According to embodiments of the present application, the cleaning is suggested such that the range of the indicator does not remain between 0 and 1. For example, a sufficient, but not unnecessary, cleaning should be suggested. For example, a quantification of the degree of contamination can be performed, whereas, for example, a reference measurement of the "clean channel" is not necessary at the same time. A single-coded display, for example in color, can be provided to quantify the contamination of the ATR unit, thus proving the necessity of cleaning. A gentle and targeted cleaning recommendation based on the indicator can be output to the user.

[0080] Figure 5 、 6 , 7 exemplary shows the normalized integral value S 0 as a single measurement point (as ordinate 71), wherein the abscissa 73 respectively represents the measurement number. In Figure 5 , the measurement points 72 in successive measurements without effective cleaning are shown. It can be seen that the normalized indicator S 0 increases with increasing measurement number (on the abscissa 70), as expected when respectively using the measurement unit and the associated surface successively.

[0081] Figure 6 The normalized contamination parameter S 0 is shown as points 73, wherein cleaning was respectively performed at position 74, so that the indicator 73 rapidly decreases, as expected due to the cleaning.

[0082] In Figure 7In this case, the surface was initially in a contaminated state and was cleaned at position 76. The contamination indicator 75 calculated therefrom decreases as expected after each cleaning.

Claims

1. An apparatus (1) for IR spectral analysis and for determining damage to surfaces (13, 15) exposed to measuring radiation during IR spectral analysis, wherein, The device includes: Radiation source (7), the radiation source being used to generate the measured radiation; A sample container (21) for receiving a liquid sample (16), wherein the sample container is at least partially bounded by the surfaces (13, 15); Detector (19), the detector being used to detect measured radiation after interaction with the sample (16); The device is configured to: The IR reference spectrum of the reference sample contained in the sample container is measured; The reference spectrum is evaluated to determine indicators of the damage. The assessment includes: Integrate the quantity of the reference spectrum within a predetermined integral spectral range (33), wherein the indicator is determined based on the value S of the integral; and The reference spectrum is normalized to obtain the normalized reference spectrum I. N V For this purpose, the measured reference spectrum is divided by the intensity at a predetermined wavenumber state and / or the measured reference spectrum is multiplied by a predetermined factor; and / or the normalized reference spectrum I is... N V Logarithmic transformation to obtain a logarithmically normalized reference spectrum E V .

2. The apparatus according to claim 1, wherein, The predetermined integral spectral range (33) is between 800 cm⁻¹ -1 With 2000cm -1 Between, wherein the indicator quantitatively indicates the degree of contamination of the surface.

3. The apparatus according to claim 1, wherein, The predetermined integral spectral range (33) is between 900 cm⁻¹ -1 With 1500cm -1 Between, wherein the indicator quantitatively indicates the degree of contamination of the surface.

4. The apparatus according to claim 1, wherein, The reference spectrum includes: An indication of the intensity of the reflected radiation from the measured surfaces (13, 15), or An indication of the intensity of the transmitted radiation through the surface including the reference sample, measured for different wavenumbers and wavelengths, wherein the measured radiation includes wavelengths in the range of 2µm to 12.5µm.

5. The apparatus according to claim 1, wherein, The assessment includes: The logarithmically normalized reference spectrum E V Temperature compensation is performed to obtain a temperature-compensated reference spectrum E. V T , The amount based on the reference spectrum is proportional to the temperature-compensated reference spectrum.

6. The apparatus according to claim 5, in, Temperature compensation includes adjusting the normalized reference spectrum E from the logarithmically normalized spectrum. V Subtract the linear function B from the middle V , The two parameters defining the linear function are defined as follows: the logarithmically normalized reference spectrum is equalized using the linear function under a first predetermined wavenumber (34) state and a second predetermined wavenumber (36) state.

7. The apparatus according to claim 6, in, The first predetermined wavenumber (34) is between 870 cm⁻¹ -1 With 970cm -1 Between, and / or The second predetermined wavenumber (36) is between 1790 cm⁻¹. -1 With 1900cm -1 between.

8. The apparatus according to claim 1, wherein, The assessment includes: The integral value S is normalized to obtain the normalized integral value S0. 0 , The indicator is determined based on the normalized integral value.

9. The apparatus according to claim 8, wherein, The normalized integral value S 0 It is calculated according to the following formula: S 0 = (S – S 最小值 ) / (S 最大值 - S 最小值 ), Among them, S 0 S is the normalized integral value, and S is the value of the integral. 最小值 and S 最大值 It is a predetermined quantity.

10. The apparatus according to claim 8, wherein, The assessment includes: The normalized integral value S is divided between the values ​​of zero and one. 0 To obtain the indicator.

11. The apparatus according to claim 1, in, The device (1) is configured to perform ATR-IR spectral analysis. The surface includes the surface of at least one ATR crystal and / or the surface of an ATR unit that is in contact with the reference sample.

12. The apparatus according to claim 1, in, The device (1) is configured to perform ATR-FTIR spectral analysis. The surface includes the surface of at least one ATR crystal and / or the surface of an ATR unit that is in contact with the reference sample.

13. The apparatus according to claim 1, in, The device is configured to perform transmission IR spectroscopy analysis. The surface includes the inner and / or outer surface of the measuring unit that receives the reference sample.

14. The apparatus according to claim 1, in, The device is configured to perform transmission FTIR spectroscopy analysis. The surface includes the inner and / or outer surface of the measuring unit that receives the reference sample.

15. The apparatus according to claim 1, further comprising: Display device (5), the display device being configured to indicate the indicator in an optical and / or acoustic manner.

16. The apparatus according to claim 15, further configured to: if the value of the indicator exceeds a threshold, indicate to the user by means of the display device (5) that maintenance should be performed.

17. The apparatus according to claim 1, wherein, The reference sample contains water.

18. The apparatus according to claim 1, wherein, The reference sample contained high-purity water.

19. The apparatus according to claim 1, further comprising: processor; as well as An electronic memory, accessible by the processor, stores a computer program product with program instructions. The processor is configured to execute the program instructions to evaluate the reference spectrum to determine the indicator of the damage.

20. The apparatus of claim 1, further comprising: processor; as well as An electronic memory, accessible by the processor, stores a computer program product with program instructions. The processor is configured to execute the program instructions to measure and evaluate the reference spectrum to determine the indicator of the damage.

21. A method for determining damage to surfaces (13, 15) exposed to measuring radiation during IR spectral analysis, wherein, The method includes: The IR reference spectrum of a reference sample is measured, the reference sample being received in a sample container (21) for receiving a liquid sample (16), wherein the sample container is at least partially bounded by the surfaces (13, 15). The reference spectrum is evaluated to determine indicators of the damage. The assessment includes: Integrate the quantity of the reference spectrum within a predetermined integral spectral range (33), wherein the indicator is determined based on the value of the integral; and The reference spectrum is normalized to obtain the normalized reference spectrum I. N V For this purpose, the measured reference spectrum is divided by the intensity at a predetermined wavenumber state and / or the measured reference spectrum is multiplied by a predetermined factor; and / or the normalized reference spectrum I is... N V Logarithmic transformation to obtain a logarithmically normalized reference spectrum E V .

22. A computer program product having program instructions configured to control or perform the method of claim 21 when executed by a processor.

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