CH711093A2 - Optical detection of various substances and their concentrations in a liquid or gaseous medium. - Google Patents

Abstract

The method and the corresponding device relating to a detection device for impurities in a liquid or gaseous medium. This is based on an ATR sensor (3), to which the radiation of a radiation source (1) is supplied. The radiation may be modulated by an external modulation device (2) or internally by controlling the current. The ATR sensor (3), into which intensity-modulated radiation is coupled, consists of a predominantly 180-degree bend, a spiral, a coil or a wave structure of a multiply bent optical waveguide with curvatures (4 '' ') as shown in FIG. 4, at which liquid or solid adsorbates (8) can attach. The optical waveguide may be partially provided with a jacket (4, 4 '). A device (9 '' ') may be present, which allows to change the radius of the bend, the spiral, or the curvatures of the wave structure. This may also be a periodic change, resulting in a modulation of the radiation extraction from the optical waveguide. The expired from the ATR probe radiation is the radiation detector (7), in particular a pyroelectric detector, fed to which a monochromator (6), primarily in the form of a tunable Fabry-Perot filter, is connected upstream.

Description

introduction

The invention relates to a method and the corresponding apparatus for the optical Deterktion of mixtures and the concentrations of individual substances. These may be mixtures of substances in a pharmaceutical process, such as a bioreactor, or they may be used to determine the level of contamination of a liquid or gaseous cleaning medium. In a bioreactor process, it is of great benefit if the reactants, intermediates and / or end products can be measured in a process process. Thus, a real-time control of the process method can be carried out and thus process optimizations are carried out, which increase the product quality and / or reduce process losses and process costs. Since the infrared spectra of many substances are known and with suitable calibration also absolute concentrations can be measured, a separation of the individual substances and the determination of their concentrations can be achieved with suitable signal processing algorithms. In particular, the principle is of great use in a washing process to determine the degree of contamination of the liquid or gaseous cleaning medium, as based on this contamination of the medium, the state of the laundry can be assessed. On the one hand, this means that the washing process can be stopped prematurely, or, on the other hand, in a subsequent washing process, cleaning agents, in particular detergents, can additionally be added or reduced. The laundry may be textiles, crockery, or technical components.

In all types of process control, it is extremely helpful to know the concentrations and mixture substances, especially in process processes that take place in a bioreactor or a washing process.

Optical methods, in particular the infrared spectroscopy in the near and medium spectral range, possibly also in the far infrared, are suitable for assessing the degree of contamination of a cleaning medium, since impurities which can be absorbed very specifically absorb radiation. In addition, such methods allow in situ investigations of the liquid medium.

A problem may be the spectrum of the cleaning medium itself. The situation is very serious when water is used as the cleaning medium, since water has very strong absorptions in the near and middle infrared range. These water absorptions make it almost impossible to perform infrared measurements in aqueous environments.

It should be noted, however, that the so-called ATR technique makes it possible to detect suspended or dissolved substances in the water. ATR stands for Attenuated Total Reflection. Liquid or solid deposits (adsorbates) on a totally reflecting surface disturb the total reflection in the spectral region where the adsorbate absorbs radiation. These perturbations cause the transmission through the totally reflecting ATR probe to be reduced. The totally-reflecting ATR probe may be a crystal or an optical waveguide. By a suitable choice of the refractive index and the angle of incidence in the crystal can be achieved that the beam passes almost totally reflecting through the crystal. In this case, the transmitted radiation is very sensitive to the adsorbate. In addition to crystals, ATR probes can also be realized with optical waveguides. As is well known, an optical waveguide consists of a core surrounded by a layer of somewhat increased refractive index (ciadation). This arrangement allows the optical beam to be guided into the optical waveguide in the same for small beam incidence angles (total internal reflection). In a bend of the waveguide, the condition for the total internal reflection can be violated. There is a partial decoupling of the radiation from the waveguide. In this situation of partial violation of total internal reflection, the optical waveguide is sensitive to adsorbates. The magnitude of this total internal reflection violation depends on the local curvature of the rider and can be modeled by, for example, mechanically changing the curvature. This mechanical change may be periodic, or adjusted so that, for the specific substances and the arrangement, the most suitable curvature can be used for the measurement. Optical waveguides are usually surrounded by a protective sheath. In the ATR-sensitive region of the waveguide must be dispensed with this sheathing. Waveguide based ATR probes often have the advantage of being much cheaper in price compared to those with crystals, especially those using diamonds.

The emerging from the optical waveguide radiation is fed to an optical detector. In principle it does not matter which type of detector is used; Thermopiles based on the Seebeck effect are used, pyroelectric detectors, which rely on the thermal sensitivity of crystal structures (a charge shift and thus generate an electrical voltage), or galvanomagnetic sensors, which work with semiconductor band gaps. Pyroelectric detectors are suitable for detecting near and mid IR radiation, where most chemical substances absorb very selectively and strongly. While many of the known IR sensors are only cooled (below -20 ° C) to reduce noise, pyroelectric detectors can be operated at room temperature. The detection by means of pyroelectric detectors is based on a purely thermal process. As a result, the sensitivity to light - for example compared to cooled IR diodes - is low and the elements can only be operated at low frequency. But since the cost of cooling is eliminated, can be realized with pyroelectric detectors, a very low-cost IR spectrometer.

The selectivity of detection of the adsorbate can be achieved by using monochromatic radiation at application specific frequencies. Of course, broadband and / or specially polarized radiation may also be used to allow parallel measurements. Also, an interferometer could be used for spectral determination but has the commercial disadvantage of a much higher price than monochromators. Monochromators may be interference filters, crystals, optical gratings or Fabry-Perot filters. In the case of crystals and gratings, the tuning to a desired optical frequency can be achieved by twisting the crystal or the grating relative to the incoming beam, in the case of the Fabry-Perot filter by changing the spacing of the filter plates. Recently exist pyroelectric detectors, which are provided with a Fabry-Perot filter, which latter can be electrostatically matched.

In order to determine absolute concentrations or to compensate for aging processes of the sensor, a differential measurement can be performed. In this case one can generate reference spectra with one or more reference solutions of a desired substance mixture. A calibration can be achieved with signal-analytical algorithms. In a washing process, a differential measurement, for example, take place at the beginning of the washing process, in which only the actual washing medium is passed through the sensor without additives, and you can get a reference spectrum. Depending on the arrangement, such reference measurements can also be made with additives (e.g., detergent detergents) or during the washing process by incorporating a special sensor scavenging cycle. Thus, creeping sensor deviations and sensor aging or other sensor compensations can be easily performed.

task

The object of the invention is to describe a method and a corresponding device to determine mixtures and the concentrations of these substances, in particular for concentrations of substances in mixtures in a bioreactor and for the detection of the degree of contamination of a liquid or gaseous cleaning medium ,

The object is achieved by the method presented in claim 1 and the corresponding device according to claim 5.

Detailed description of the invention

The invention will be explained with reference to the following drawings: <Tb> FIG. 1 <SEP> is a representation of a detection device for impurities in a liquid or gaseous medium, consisting of a radiation source (1), a modulation device (2), as an ATR probe (3) optical waveguide with critically curved bends (4) at least in the bend (4) is not surrounded by a jacket (5, 5), a tunable monochromator (6) and a radiation sensor (7). The radius of the bend (4), where Adsorbate (8) can attach, is periodically changed by a mechanical device (9) or it can be brought into a fixed position. <Tb> FIG. 2 <SEP> shows an analogous representation to FIG. 1, wherein the ATR probe (3) is designed as a spiral (4) and the radius of the spiral is changed periodically by a mechanical device (9) or into a fixed position can be brought. <Tb> FIG. 3 <SEP> illustrates the structure of the ATR probe (3), which is formed as a coil (4) and wound on a bobbin (10) and the radius of the coil (4) by a mechanical device (9) can be changed periodically or brought into a fixed position. <Tb> FIG. 4 shows an ATR probe (3) with a pantograph-like parallel displacement device with drive (9), hinges (11, 11), pantograph mount (13) and waveguide mounts (12 ), which causes the critical radii of curvature of the waveguide to be periodically changed or brought into a fixed position.

Fig. 1 shows the basic structure of a detection device for contaminants in a liquid or gaseous medium, based on an ATR probe. A radiation source 1 is in communication with a modulation device 2. The radiation source 1 can be, for example, a UV source, an LED, or a thermal radiator. Thus, ultraviolet, visible, near-infrared, medium-infrared or far-infrared radiation is available, but the near and mid-infrared regions are the most important. The periodic modulation of the radiation intensity can be carried out with an external modulation device 2, for example in the form of a rotating sector disk, an electronic shutter, et cetera, or inside the radiation source via the modulation of the current which operates the radiation source 1.

The intensity-modulated radiation of the radiation source 1 is coupled into an ATR probe 3. This consists in the present case of a - mainly 180-degree bend 4 in a part of an optical waveguide, which may be partially surrounded by a jacket 5, 5. In at least part of the optical waveguide with the bend 4, no cladding 5, 5 is present. There is a sensitivity to liquid or solid adsorbed adsorbent 8. A device 9 is provided, which allows to change the radius of the bend 4 of the optical waveguide periodically, resulting in a modulation of the radiation extraction from the optical waveguide and thus to a modulation The sensitivity to adsorbates 8. The device 9 can also serve to bring the radius of curvature of the bend 4 in a suitable fixed position.

The expiring from the ATR probe 3 radiation is the radiation detector 7, in particular a pyroelectric detector supplied, which optionally a monochromator 6 is connected upstream, which leads to a monochromatization of the radiation. In principle, the monochromator 6 can also be inserted in front of the ATR probe 3 into the beam. Particular attention is paid to the combination of a pyroelectric detector 7 with an electrostatically tunable Fabry-Perot filter 6.

Fig. 2 also shows the basic structure of a detection device for impurities in a liquid or gaseous medium, wherein the ATR probe 3 but not from a bend 4 of an optical waveguide, but consists of a spiral 4 with at least one turn. The supply lines to the spiral can be surrounded by at least one jacket 5, 5. At least a part of the spiral is not provided with a jacket, so that an adsorbate 8, in solid or liquid form, can be detected. A device 9 may be provided which allows the radius of the spiral 3 of the optical waveguide to be changed periodically, resulting in a modulation of the radiation extraction from the optical waveguide. The device 9 can also serve to bring the radius of curvature of the bend 4 in a suitable fixed position.

Fig. 3 further shows the basic structure of a detection device for impurities in a liquid medium, wherein the ATR probe but not from a bend 4 of an optical waveguide or a spiral 4, but from a coil 4 with at least one turn consists. The supply lines to the spiral can be surrounded by a jacket 5, 5. At least a part of the coil is not provided with a jacket, so Adsorbate 8 can be detected. The coil-shaped optical waveguide can be wound on a bobbin 10. A device 9 may be provided which allows the radius of the optical waveguide to be changed periodically resulting in a modulation of the radiation output from the optical waveguide or to bring the radius of the bend 4 into a desired fixed position.

Fig. 4 shows an ATR probe 3 in the form of a wavy curved and curvature modulatable waveguide, by means of waveguide holders (12) which are part of the pantographic parallel guide, consisting of pantograph holder (13) and the movable and fixed hinges (11, 11). This form is characterized by simplicity of manufacture, good cleaning possibilities and simple measurements in several places. Depending on the application, the number of rhombic elements of the pantographic parallel guidance can be chosen to obtain 2 (2N-1) critical areas of curvature. Adsorbates (8) at critical points of curvature influence the light extraction according to the ATR measurement principle. The device 9 can also serve to bring the radii of curvature of the bends in a suitable fixed position.

Claims (10)

1. A method for the selective analysis of liquid or solid-state contaminants (adsorbates) in a liquid or possibly also gaseous medium, characterized in that used with an ultraviolet, visible, near-infrared, medium-infrared or far-infrared radiation ATR probe used and whose emitted radiation is optionally selectively detected, wherein the radiation is guided in an optical waveguide whose total reflection properties can be periodically modulated or optimally adjusted for the detection of adsorbates. 2. The method according to claim 1, characterized in that the applied radiation generated by a thermal source and the emitted radiation is detected pyroelectrically. 3. The method according to claim 2, characterized in that before or after the ATR probe, the radiation is spectrally decomposed by a tunable monochromator element. 4. The method according to claims 3, characterized in that the monochromatization is carried out according to the Fabry-Perot principle. 5. An apparatus for the selective analysis of liquid or solid contaminants in a liquid or possibly gaseous medium, characterized in that in the ultraviolet, in the visible, in the near, middle or far infrared emitting radiation source (1) is used and their radiation by a modulation device (2) is modulated in intensity and the radiation source (1) in conjunction with an ATR probe (3), the latter reflects the incoming radiation internally and partially by liquid, solid or gaseous adsorbates (8) in a bend (4 ) of the optical waveguide at the surface of the ATR probe (3), said optical waveguide may be partially provided with at least one sheath (5, 5), wherein the sheath is not present in at least a portion of the bend (4) and the radiation emanating from the ATR probe (3) communicates with a radiation detector (7) and communicates in the Beam path is an optionally tunable monochromator (6), and optionally the radius of the bend (4) by a mechanical device (9) can be changed periodically or brought into a suitable fixed position. 6. The device according to claim 5, characterized in that the radiation source (1) is a thermal radiator and its radiation intensity via the modulation of the current which operates the radiation source (1) is periodically modulated. 7. The device according to claim 5, characterized in that the ATR probe (3) has a predominantly 180-degree bend (4) of an optical waveguide and at least in the bend (4) surrounded by any sheath (4, 4) is. 8. The device according to claim 5, characterized in that the ATR probe (3, 3, 3) a spiral (4), a coil (4), which optionally on a bobbin (10 ) or a wave structure (4), the latter being realized by a pantograph-like sliding device with hinges (11, 11), pantograph holder (13) and waveguide holders (12) and optionally by means of a mechanical device (9, 9, 9) the radius of the spiral, the coil or the curvatures (4) of the wave structure changed periodically, or the curvatures can be set fixed. 9. Device according to claim 5, characterized in that the radiation detector (7) is a pyroelectric element. 10. The device according to claim 5, characterized in that the radiation detector is provided with a tunable monochromator (6) in the form of a Fabry-Perot filter.