MEASURING DEVICE AND METHOD FOR DETERMINING A SUBSTANCE CONCENTRATION

Abstract

A measuring device for determining a substance concentration of a fluid arranged in a measurement volume includes a source emitting a source spectrum, a wavelength-selective means arranged before the measurement volume, a measurement space limiting the measurement volume at least in a beam path, and a detector for measuring a wavelength-related absorption of a measurement spectrum having passes through the measurement volume. A fluorescence-reducing element is arranged in the beam path between the detector and the measurement volume. A beam splitter is arranged between the source and the measurement volume.

Claims

1.-8. (canceled)

9. A measuring device for determining a substance concentration of a fluid arranged in a measurement volume, comprising: a source emitting a source spectrum; a wavelength-selective means arranged before the measurement volume; a measurement space limiting the measurement volume at least in a beam path; and a detector for measuring a wavelength-related absorption of a measurement spectrum having passed through the measurement volume, wherein a fluorescence-reducing element is arranged in the beam path between the detector and the measurement volume, and wherein a beam splitter is arranged between the source and the measurement volume.

10. The measuring device according to claim 9, wherein the fluorescence-reducing element is designed to at least predominately absorb fluorescence.

11. The measuring device according to claim 9, wherein the fluorescence-reducing element is configured to reduce an intensity of a measurement wavelength radiation in a measurement wavelength range by at most a factor of 10.

12. The measuring device according to claim 9, wherein the fluorescence-reducing element comprises one or more filters, a monochromator, or a combination thereof.

13. The measuring device according to claim 9, wherein the source is a narrow-band light source or a broadband-light source with a downstream wavelength-selective optical element.

14. The measuring device according to claim 9, wherein the measuring device is designed to measure a measurement spectrum between 200 nm and 15 μm.

15. The measuring device according to claim 9, wherein the detector is designed to measure a measurement wavelength between 200 nm and 15 μm.

16. The measuring device according to claim 9, wherein the fluorescence-reducing element is designed to almost completely absorb fluorescence.

17. The measuring device according to claim 9, wherein he fluorescence-reducing element is designed to reduce the intensity of the measurement wavelength radiation in the measurement wavelength range by at most a factor of 5.

18. The measuring device according to claim 12, wherein the filters are arranged on a filter wheel.

19. The measuring device according to claim 9, wherein the measuring device is designed to measure a measurement spectrum between 250 nm and 320 nm.

20. The measuring device according to claim 9, wherein the measuring device is designed to measure a measurement spectrum of 280 nm +/−5 nm, 260 nm +/−5 nm, 254 nm +/−5 nm, or one more combinations thereof.

21. The measuring device according to claim 9, wherein the detector is designed to measure a measurement wavelength between 250 nm and 320 nm.

22. The measuring device according to claim 9, wherein the detector is designed to measure a measurement spectrum of 280 nm +/−5 nm, 260 nm +/−5 nm, 254 nm +/−5 nm, or one more combinations thereof.

23. A method for determining a substance concentration of a fluid arranged in a measurement volume, comprising: outputting a source spectrum with a beam path running at least partially through the measurement volume; and measurement of a wavelength-related absorption of a measurement spectrum having passed through the measurement volume by means of a detector, wherein wavelength-selective means are provided before the measurement volume, wherein fluorescence in the beam path is reduced between the detector and the measurement volume, and wherein a beam splitter is arranged between the source and the measurement volume.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0063] FIG. 1 shows a diagrammatic, perspective representation of a first embodiment of a measuring device according to the invention; and

[0064] FIG. 2 shows a diagrammatic, perspective representation of a second embodiment of the measuring device according to the invention.

[0065] Identical and identically functioning components/features are denoted in the figures with the same reference numbers.

DETAILED DESCRIPTION OF THE INVENTION

[0066] A source 1 is represented in FIG. 1, which is formed from a light source 2 and a wavelength-selective optical element 3. Light source 2 is constituted as a broadband light source, which emits a broadband source spectrum with a beam path 7, which runs in particular linearly up to a detector 6.

[0067] A beam splitter 9 is arranged between source 1 and measurement volume 4, wherein beam splitter 9 is arranged between optical element 3 of source 1 and measurement volume 4. Beam splitter 4 splits the incoming light beam into a first partial beam, which continues to run along beam path 7, and a second partial beam (not represented), which continues to run in another direction. This second partial beam can run at right angles to beam path 7 and in particular strike a reference detector (not represented), by means of which the second partial beam is evaluated.

[0068] The broadband source spectrum of light source 2 strikes wavelength-selective optical element 3 and, when it passes through wavelength-selective optical element 3, radiant power is markedly reduced in shortwave to a measurement wavelength of 280 nm. Wavelength-selective element 3 leaves a narrow-band source spectrum with a predominant power density in a wavelength range of over 250 nm. Over 90% of the irradiated power density is preferably in this range.

[0069] The narrow-band source spectrum limited at least below the measurement wavelength strikes a measurement volume 4 along beam path 7. Measurement volume 4 is limited by a measurement space, which at least in the direction of beam path 7 comprises windows 8, 8′ arranged transversely to beam path 7. Windows 8, 8′ are preferably arranged orthogonal to beam path 7 and preferably have a defined distance along beam path 7. The distance corresponds to the layer thickness through which the narrow-band spectrum passes along beam path 7 through a fluid arranged in the measurement volume.

[0070] The fluid is arranged either statically in measurement volume 4 or flowing transversely to beam path 7.

[0071] The fluid has a substance concentration of a substance (target substance) to be determined, preferably tryptophan, which gives rise to a change measurable by detector 6 in the narrow-band source spectrum in the measurement wavelength range passing through measurement volume 4.

[0072] The narrow-band source spectrum can produce fluorescence generated in particular by the target substance, which fluorescence can lead, amongst other things along beam path 7, to a falsification of the signals to be measured by detector 6, in particular in a spectrum with a wavelength above the measurement wavelength.

[0073] For this reason, a further wavelength-selective optical element in the form of a fluorescence-reducing element 5 is arranged in the beam path behind measurement volume 4 in the beam path direction. During the passage of the narrow-band source spectrum passing through measurement volume 4, any fluorescence radiation generated in measurement volume 4 is at least predominantly, preferably largely, still more preferably completely absorbed. The narrow-band spectrum, in particular limited in shortwave and longwave and provided for the measurement of the substance concentration, thus at least predominantly, preferably virtually exclusively strikes detector 6, said spectrum having its power density at least predominantly in the measurement wavelength range. The measurement spectrum preferably has a maximum of the power density at the measurement wavelength.

[0074] Fluorescence-reducing element 5 is preferably selective at 280 nm +/−5 nm and/or 260 nm +/−5 nm and/or 254 nm +/−5 nm.

[0075] Detector 6 measures the light having passed out of measurement volume 4 and through fluorescence-reducing element 5 by conversion into a photoflow by means of an electrical current measurement, in particular a photomultiplier. Conclusions can be drawn from this regarding the substance concentration of the target substance.

[0076] The embodiment shown in FIG. 2 differs from the embodiment described in FIG. 1 in that a narrow-band light source 2′ is provided as source 1, so that a wavelength-selective optical element 3 can be dispensed with in this embodiment. Light source 2′ already emits a source spectrum at least predominantly radiating in the measurement wavelength range and thus comprises wavelength-selective means arranged before measurement volume 4.

[0077] A beam splitter 9′ is arranged between source 1 and measurement volume 4, wherein beam splitter 9′ is arranged between light source 2′ and measurement volume 4. Beam splitter 4 splits the incoming light beam into a first partial beam, which continues to run along beam path 7, and a second partial beam (not represented), which continues to run in another direction. This second partial beam can run at right angles to beam path 7 and in particular strike a reference detector (not represented), by means of which the second partial beam is evaluated.

[0078] Fluorescence-reducing element 5′ in this embodiment is preferably at least predominantly, preferably virtually exclusively selective for longwave to the measurement wavelength.

LIST OF REFERENCE NUMBERS

[0079] 1 source [0080] 2, 2′ light source [0081] 3 wavelength-selective optical element [0082] 4 measurement volume [0083] 5, 5′ fluorescence-reducing element [0084] 6 detector [0085] 7 beam path [0086] 8, 8′ window [0087] 9, 9′ beam splitter