LAGESSON HANS VERNER (SE)
OLSSON LENNART (SE)
LAGESSON HANS VERNER (SE)
| US20010010747A1 | 2001-08-02 | |||
| US20020149767A1 | 2002-10-17 | |||
| US6307204B1 | 2001-10-23 | |||
| DE3615259A1 | 1987-11-12 | |||
| US20070161876A1 | 2007-07-12 | |||
| US20090015820A1 | 2009-01-15 | |||
| EP0539021A1 | 1993-04-28 | |||
| DE10302207A1 | 2004-07-29 |
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KARL-FRIEDRICH KLEIN ET AL: "Optical fibers in instrumental UV-analytics", PROCEEDINGS OF SPIE, vol. 7173, 1 January 2009 (2009-01-01), pages 717302-1 - 717302-7, XP055009032, ISSN: 0277-786X, DOI: 10.1117/12.818663
| CLAIMS 1 . A detector arrangement for measurement of compounds eluting from a gas chromatographic separation comprising a UV lamp (3) with lamp supply (12) and housing, a spectrometer (7) with a light sensitive device comprising a light recording element to measure the UV light absorption spectra in the short UV light absorption range 140 - 400 nm wave length with a gas flow cell consisting of one UV light transparent window, inlet arrangement for the eluting compounds from a gas chromatograph, a narrow diameter tubing for the gas flow forming a light pipe through which is temperature regulated from ambient up to 300 °C characterized in that the lamp can be kept on and by dark calibration of the light recording element, the light beam will be deflected away from the light entrance to prevent the light to enter the light path to the spectrometer and the light recording element. 2. A detector arrangement according to claim 1 with a parabolic mirror acting as focusing optical element for focusing the light from the deuterium lamp into a gas flow cell of the light pipe and where the arrangement of the parabolic mirror is such that it also has a shutter function in that it can be rotated and thereby shutting of the light flow from the lamp to enter the light pipe being an essential function for recordings of the background current from a light sensitive device like a CCD detector. 3. A detector arrangement according to claim 1 or claim 2 with a gas flow channel comprised by a narrow diameter hollow tubing with an internal or external aluminium mirror coating that acts as a light guide where internal reflection of the UV light is giving a minimum of light losses. 4. A detector arrangement according to any of claim 1 - 3 where the light pipe has an internal diameter between 10 μιτι and 10m. 5. A detector arrangement according to any of claim 1 - 4 where the light pipe has a length between 0,1 mm and 10m. 6. A detector arrangement according to any of claim 1 - 5 where at an outlet of the gas flow channel the flow meets a flow of gas in the opposite direction originating from an overpressure in the spectrograph to form a combined flow. 7. A detector arrangement according to claim 6 where the combined flow leaves the system through a 0,1 mm to 10m long narrow bore tubing leading to a slit opening of the spectrograph having similar light guiding properties as the gas flow channel in the gas flow cell. 8. A detector arrangement according to any of claim 1 - 7 where a spacing between light guide tubing coming from the gas flow cell and the light guide tubing leading to the entrance slit of the spectrograph is between 0.001 and 10 mm. 9. A detector arrangement according to any of claim 1 - 8 where at the outlet of the gas flow channel the flow of gas to be analysed meets a flow of gas in the opposite direction originating from an overpressure in the spectrograph - in the light tube connected to and leading to the spectrograph. 10. A detector arrangement according to any of claim 1 - 9 where a 0,1 mm - 10m long narrow bore tubing leading to the slit opening in the spectrograph have the similar light guiding properties as for the gas flow channel in the gas flow cell. |
TECHNICAL FIELD
The present invention relates to spectrophotometric measurements of vapors and gases in vacuum, far and UVC wavelength region (120 - 400 nm)
The invention relates Gas Chromatography, GC - Ultraviolet absorption, UV - spectroscopy, GC-UV, to detect and identify, analyse of gases and liquid unknown substances from high to very low concentrations. The basic technology is known and used for various purposes. The invention relates to physical, mechanical and software control solutions. The invention solves one of the major problems in order to detect absorption of very short wavelengths (typically down to 120nm) for identification of unknown substances in gas phase. The invention is very versatile and can be used in various applications such as hand held portable and laboratory based bench top instruments.
One particular use is for detection of metabolic or other substances emanating from living cells, tissues and in particular that can be found in exhaled air, saliva, sweat, blood and urine from humans, animals, organisms and plants etc. for detection of various deceases and metabolic activities f.ex. stress. Substances can be such as nitrogen oxide, urea, acetone, isoprene, carbon disulfide coming from diseases like gastric ulcers, asthma, diabetes, psychiatric disorders, drug abuse, stress conditions and intoxications, etc.
Many of those metabolic substances have significant high absorption of UV light in a spectrum ranging from about 120 nm wave length and longer.
BACKGROUND ART
Measuring of UV light absorption in the liquid phase is widely used in various types of analyzers. The light source used is usually deuterium lamps. For continuous measurements following for example a chromatographic separation a flow cell with transparent windows, which usually consists of fused silica, are employed. The detector part in these arrangements is usually a spectrograph combined with a photo diode array element (PDA).
Measurements of UV light absorption in the vapour/gas phase in combination with gas chromatographic separation (GC-UV) are only described in a few cases. The principal is of these measurements is similar to those in the liquid phase but there are a number important and significant differences. The wavelength range accessible in the vapour/gas is not limited by any solvent cut off which opens up for recordings at short wavelengths in the vacuum to far UV region 140 - 200 were very important and conclusive spectral information is present. The optical elements suitable for measuring in this wavelength regions are window materials consisting of magnesium fluoride (MgF2) with transmittance of 50 - 95 % from 120 - 400 nm, sapphire with transmittance of 70 - 83 % from 150 - 400 nm and synthetic fused silica with transmittance of 70 - 80 % from 165 - 400 nm. The mirror suitable for these measurements are Al mirrors which have a reflectance of 80 - 90 from 145 - 400 nm. The measurements in this wavelength region also implies that recordings are performed in an inert atmosphere were water vapour and oxygen are carefully removed. This atmosphere could be nitrogen (which absorbs light at wavelengths below 120 nm) or permanent / noble gases like helium, argon or hydrogen.
The detector part in this arrangement is a spectrograph combined with preferably a back thinned type of CCD element. This type of detector ship has a considerably more favourable quantum efficiency and response at shorter wavelengths.
BRIEF DESCRIPTION OF THE DRAWINGS
In order to explain the invention, one embodiment of the invention will be described below with reference to the drawing which is a schematic side view of the detector arrangement. SUMMARY OF THE INVENTION
The characteristics of the invention are illustrated in the enclosed figure. The embodiment shown comprises a lamp emitting the light beam to a parabolic mirror which guides and focus the light into a gas flow cell where the flow of compounds eluting from an external gas chromatograph passes through. The light output from the gas flow cell is collected at the outlet and further guided to the entrance slit of a spectrometer to measure spectra appearing in the light beam. The conventional carrier gases for gas chromatography are nitrogen, helium and hydrogen which are all transparent in the wavelength range of interest. The lamp compartment including the parabolic mirror and the spectrograph compartment are all flushed with dry nitrogen in order to prevent any absorption from water vapour and oxygen. The parabolic mirror can be tilted, so that the focus that normally by measurement of a substance is at the light entrance to the spectrograph, is moved to eliminate the ability for the light to enter the spectrograph enabling dark calibration of the light sensitive elements like CCD.
In order to have the resolution and accuracy of analyse of a substance it is vital to keep the dimensions i.e. volume of the gas flow cell, such as quartz capillary light pipe, so that the length of the penetration of light is maximized in relation to its internal volume.
The objects of the present invention are to achieve functionality by assigning to the characteristics according to claim 1- 10.
According to a first aspect of the invention it is a device that has the capability to analyse and identify substances in gas phase by absorption of UV light penetrating the gas with a spectral distribution of the light energy that corresponds to, identifies and quantifies the substance.
According to a second aspect of the invention, the absorption of UV light takes place in a tubular shaped arrangement where light penetrates along the axis of the device. According to a third aspect of the invention the light that penetrates the substance in gas phase is focused to the light pipe by identification and can be switched on and off by moving the focus from the light pipe.
According to a forth aspect of the invention it allows spectral resolution down to below 120nm wave length to be analysed.
According to a fifth aspect of the invention it allows the light to be in reverse direction relative the gas flow.
DETAILED DESCRIPTION
The embodiment shown in Figure 1 comprises:
A body (1 ) being temperature regulated up to 300 °C,
A preferably quartz capillary (2), typically, but not limited to10 - 300 mm length with aluminum or other high UV reflective coating at inside or the outside and having an internal diameter of 0.1 - 10 mm ("light pipe").
A UV preferably, deuterium lamp (3) with magnesium fluoride (MGF2) window powered by a lamp power supply (12).
a parabolic Al mirror (4) (freshly MGF2 coated), serving by measurement of a substance, by directing the light from the lamp (3) to the quartz capillary (2) through a window (5) and also serving as a shutter by dark calibration of the spectrometer by redirecting the light by rotation so that the focus will be away from the window (5) and the quarts capillary (2) comprising such as;, a MGF2 (5) alternatively a sapphire window
a 1 mm - 10m long hollow core optical fiber (6) with an internal Al mirror coating a spectrograph (7) including a CCD element and nitrogen flushed trough or over from outside spectrograph slit (8)
a flow inlet (9) from the gas chromatographic (GC) separation flow outlet (10), flow of inert gas from the spectrograph through the slit (1 1 ) and a typically 1 mm - 10m long hollow core optical fiber (6) meeting the outlet from quartz capillary (2) with a distance enough to thermally insulate between hollow fiber and spectrograph. The hyphenation between gas chromatography and the present innovation utilizing the vacuum-, far-, and UVC UV wavelength range from120 is denoted GC-VUV.
Same reference numerals have been used to indicate the same parts in the figures to increase the readability of the description and for the sake of clarity. The figures are not made to scale, and the relative dimensions of the illustrated objects may be disproportional. The magnesium fluoride (MGF2) can be other materials like sapphire or other material with sufficient optical transparency at wavelengths down below 120nm.
Additionally, although individual features may be included in different embodiments, these may possibly be combined in other ways, and the inclusion in different embodiments does not imply that a combination of features is not feasible. In addition, singular references do not exclude a plurality. The terms "a", "an" does not preclude a plurality. Reference signs in the claims are provided merely as a clarifying example and shall not be construed as limiting the scope of the claims in any way.
Definition:
A light pipe is a tubular shaped device where substances in gas phase passes, penetrated by light and where the light is fully or partially absorbed by the gas molecules with a spectrum that relates to the substance.
Definitions: A spectrograph is consisting of a slit where light enters, a dispersive element that reflects the fractioned light.
A spectrometer is a spectrograph that has a photon collecting device to collect the fractioned light for read out and measurement of spectra. The Photon collecting device can be a CCD - Charge 5 Collecting Device.
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