WO2014170384A1

WO2014170384A1 - Direct thermal desorption unit linked to gas chromatography - uv detection

Info

Publication number: WO2014170384A1
Application number: PCT/EP2014/057755
Authority: WO
Inventors: Thomas Lundeberg; Jonas FRIBERG; Erik Sparre; Lennart Torbjörn OLSSON
Original assignee: CHROMALYTICA AB
Current assignee: CHROMALYTICA AB
Priority date: 2013-04-17
Filing date: 2014-04-16
Publication date: 2014-10-23
Anticipated expiration: 2015-10-17

Abstract

A method and a solution in a gas chromatography –UV spectrometer detector to efficiently increase resolution and keep windows in the light path free from gases that can affect the window materials and thereby reduce its functionality and dilute the substances in gas phase during the passage in a light absorbing chamber to change and also increase spectral and spatial resolution of readout of the substances.

Description

DIRECT THERMAL DESORPTION UNIT LINKED TO GAS CHROMATOGRAPHY - UV DETECTION

TECHNICAL FIELD The present invention relates Thermal Desorption - Gas Chromatography, GC - Ultraviolet absorption, UV - spectroscopy, GC-UV, to detect, identify quantify and analyse unknown substances from high to very low concentrations in air and other gases. The basic technology is known and used for various purposes. Such solutions are disclosed in US 6305213 and US 4668091, Verner Lagesson et. al. The invention relates to physical, mechanical and software control solutions. The thermal desorption part of the unit is classified as a direct (one stage) desorption method. The invention solves one of the major problems to achieve in order to detect absorption of very short wavelengths (typically down to loonm) 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 e.g. stress. Substances can be such as nitric oxide, urea, acetone, isoprene, carbon disulphide coming from diseases like gastric ulcers, asthma, diabetes, psychiatric disorders, drug abuse, stress conditions and intoxications, etc.

Many of those metabolic substances in gas phase have significant high absorption of UV light in a spectrum ranging from about 100 nm wave length and longer.

BACKGROUND ART

Gas chromatography UV - spectroscopy is used for identification and quantification of various substances that can be transformed into gas. The technology is based on that substances in gas phase first passes through a heated column where the gas has a substance dependent velocity through the column and when the gas to be analysed leaves the first heated column and enters a chamber where UV light passes the gas, absorb light when the light passes the gas, in a spectral way, so the photonic spectrum relates with very high accuracy to the identity of the substance. The introduction of the sample to GC system is usually carried out by injecting a liquid sample by means of a micro litre syringe. The liquid sample is quickly vaporized in a heated injector part prior to a transport to a separation column. When the sample is in the gaseous phase injection can be performed by means of a loop injector with a certain fixed volume of the loop. However, the loop have a restricted volume of maximum of a few millilitres and the method is therefore suited only for those sample having a high concentration of compounds like concentrated tobacco smoke. In most cases the concentration of compounds in air/gas samples are so low that a pre-concentration or a trap procedure must be applied prior to the introduction to the GC system.

Collecting the compounds from a larger volume of air/gas is usually performed by drawing the air/gas sample through various types of adsorbents placed in a tubing (solid sorbent tube). The compounds in the air/gas sample are thereby trapped and adsorbed on to the sorbent particles. The procedure for the releasing of the trapped compounds and the introduction in to the separation unit (GC) is usually carried out by thermal desorption. The thermal desorption units on the market relays on a two stage procedure where the adsorbed compounds are thermally desorbed in the first stage followed by second (usually cooled) trap and a second thermal desorption. After this second desorption the released compounds goes to the GC separation. These two stage thermal desorption apparatus implies that the air/gas samples are collected at the sampling site by drawing a known volume of air/gas through a number of individual adsorbent tubes. These tubes are then transported to a laboratory where the stationary instrumentation for thermal two stage desorption, the GC and a mass spectrometer (MS) is permanently placed. The time delay before analysis is typically 24 hours. The disadvantages with this analysis procedure are that it is susceptible to

degradation and loss of instable chemical compounds and contaminations due to the considerable time delay between sampling and analysis. Furthermore the complex and expensive hyphenation of instruments are not movable from the laboratory and require highly skilled personal to be properly used. The light used for the absorption shall preferably have a wide spectral range to allow absorption over a wide spectral range.

The passage, chamber, where light penetrates the gas shall be designed to have the gas absorb as much light as possible and to achieve maximum resolution in the analysis, the cross section area and the chamber volume shall be kept as small as possible. The chamber shall be heated in order to keep the substances in gas phase

The process is basically a gas chromatography apparatus where a chamber with a light path is added at the end of the column so the separated gas components eluting from the gas chromatograph_passes through the chamber and absorbs light with a spectrum that is related to the gas.

The remaining light then passes into a spectrometer and further on to a light sensitive sectioned array preferably a, Charge Coupled Device (CCD), in such a way that the spatial light components hit individual light sensitive elements enabling spatial detection of the light and thereby allows identification of the substance to be analysed.

Light is directed in to the spectrometer trough a passage that can be a window made out of a photon transparent material that allows passage of the required wavelengths.

In order to have maximum number of photons to reach the light sensitive element it is important to use windows separating the spectrometer from the gas path in material that has very high transparency, particular in the low wavelength range.

Materials used in such windows can be made of MgF2, CaF2 or material with similar optical properties. Said materials have the drawback of being sensitive to rapid degradation and consequently loss of transparency and other optical properties, if exposed to various chemical substances. Thus the spectrometer should be handled with care. Any physical window acts as a filter of passing photons in particular for short wavelength photons.

It is also important to keep the spectrometer, its dispersive element and photon sensitive array clean from contamination like particles and residuals from gases, like condensed matter from gas in order to keep the functionality of the spectrometer. A physical window has to be cleaned or replaced regularly due to contamination, if not being protected by any means. Another issue is measurements with GC-UV, as substances in gas phase enter the light absorbing chamber, is that several substances can protrude the chamber almost with the same velocity and at the same time reducing the ability of the physical separation and thereby reducing the ability to chemical identification and quantification. SUMMARY OF THE INVENTION

An object of the present invention is to eliminate at least one of the drawbacks mentioned above, which is achieved by assigning to the characteristics according to descriptions and claims. According to a first aspect of the invention, the principle of the thermal desorption is that of an one step desorption with a carrier gas flow transporting the released compounds to the injector part of a GC-UV unit. The thermal desorption takes place in a tubing 50 - 100 mm long with an internal diameter of 1 - 5 mm. The tubing contains the adsorbent materials typically in a series of three different types with different affinity for various chemical compounds. The tubing is electrically conducting either by means of a suitable metal alloy or with a metal surface applied on the outside of a glass or quartz tubing. At the fast heating a current is applied over the tubing. The temperature goes up to 300 - 350 °C in a few seconds and the trapped compounds in the adsorbents are released and carried by the carrier gas to the injector and further on to the GC separation column of the GC-UV unit.

According to a first aspect of the invention, the light entrance to the spectrometer is provided with a physical solid barrier like a physical window that has the

transparency for UV light from 100 nm wave length with a prevention of gas to be analysed to come in contact with the window by a flow over the window with gas such as nitrogen, helium, hydrogen or other gases that leave the window material unaffected.

A similar solution can be used to protect a similar window close to the light source in the light path where UV light enters a light absorbing chamber.

According to a second aspect of the invention, the arrangement of the thermal desorption is that of a loop injection employing a six way valve. The valve has two positions. At the first position, which is the air/gas sampling position, air/gas is drawn at variable rate by a pump through the thermal desorption tubing containing the adsorbents. At the second position the thermal desorption part is switched over in the carrier gas flow which has an opposite direction to the sampling flow. When switched over to the injection mode (second mode) the heating of the adsorbent tube (thermal desorption) starts immediately.

According to a second aspect of the invention, injected flush gas, to be referred to as flush gas, at the light entrance to the light absorption chamber can be used to change, increase the speed of gas to be analysed through the light absorption chamber and thereby change the separation ability of the substances better from each other and thereby change and also increase the spatial resolution.

Such separation can be made nonlinear to the velocity of the gas to be analysed entering the light absorption chamber and can vary over time by change of pressure and flow of this, the flush gas.

According to a third aspect of the invention, two loop desorption units are working in parallel. With this arrangement two sampling sites can be collected simultaneously. For example compounds from ambient air can be collected at the same time as the air from the sampling site (e.g. exhaled breath). According to a third aspect of the invention, the gas that is used for protecting the windows can simultaneously also be used for diluting and increasing the speed of the gas through the light absorbing chamber, in relation to the source of the gas, to shorten the time in the light absorption chamber for the gas to be analysed and thereby increase spectral - spatial resolution of the readout in the spectrometer. This can be referred to as flush gas.

According to a fourth aspect of the invention, the gas used for protecting the window of the light source can simultaneously also be used for flushing through the spectrometer to produce a gas flow of the same flush gas or other with similar properties, in opposite direction to the gas to be analysed approaching the

spectrometer trough the light pipe, to eliminate the flow of gas to be analysed to enter the spectrometer or reach the window to the spectrometer.

The same type of gas can be simultaneously used for all the above functions or different types of gas can be used for the different aspects of the invention.

Different pressure at the different locations directs the flow of gas in a desired way from locations with higher pressure to locations with lower pressure.

Protection by a gas that flushes the windows prevents the substances to be analysed in gas phase to reach the surfaces of the windows facing light absorbing chamber in GC-UV applications. BRIEF DESCRIPTION OF THE DRAWINGS

In order to explain the invention, a number of embodiments of the invention will be described below with reference to the drawings, in which: 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.

Fig l shows Adsorption/desorption tubing

1) Metal alloy or glass or quartz tubing with metal deposition on the outside.

Electrically conducting for fast heating.

2) Adsorbent layers a,b,c (example 3 various adsorbents) physically isolated from each other with for example glass wool.

3) Glass wool or glass down plugs.

4) a/ gas flow at sampling b/ gas flow at injection

5) Lens of synthetic fused silica alternative sapphire - window

6) Light source, deuterium lamp

7) Gas flow in "make up" (0.5 - 10 ml/min)

8) Gas flow in from GC

9) Heated body (50 - 280 °C)

10) Gas flow out

11) Gas flow to Spectrometer

12) Gas flow regulators

13) Gas chromatograph (GC)

Figurei shows schematically a set up comprising GC (13), UV-light source (6), light pipe (3), spectrometer (1) without a protective window, gas distribution control and gas flow regulator (12) with a gas flow from GC colon (13) through light pipe (3) enclosed in an heated body (9) where the gas to be analysed is prevented to enter the spectrometer (1) by a flow of another gas (11) through the spectrometer (1) that has an opposite direction of flow relative the gas to be analysed and a flow of gas not being the gas to be analysed that is injected through a pipe (8) in close proximity to the light source (6) between the light source (6) and the inlet (7) to the light pipe (3) through an optical fibre (4) of the gas to be analysed in order to prevent the gas to be analysed to reach the window (5) of the light source (6).

Fig 2a shows

The invention relates to a method of increasing the long term transparency of light windows of very and increase spatial resolution of read out of short wavelength I30nm wave length and up photons in GC-UV applications comprising:

1) Spectrometer

2) Optical fiber "hollow core" type

3) "Light pipe" "hollow core" type (Al reflective mirror on the inside) alternative quarts, alternative Safire

4) Optical fiber "hollow core" type

5) Lens of synthetic fused silica alternative sapphire

6) Light source, deuterium lamp

7) Gas flow in "make up" (0.5 - 10 ml/min)

8) Gas flow in from GC

9) Heated body (50 - 280 °C)

10) Gas flow out

11) Gas flow to Spectrometer

12) Gas flow regulators

13) Gas chromatograph (GC)

14) Gas pipe leading to the outside of a window (15) to spectrometer

15) Window to spectrometer

Figure 2b shows schematically a set up comprising GC (13), UV-light source (6), light pipe (3), spectrometer (1) without a protective window, gas distribution control and gas flow regulator (12) with a gas flow from GC colon (13) through light pipe (3) enclosed in an heated body (9) where the gas to be analysed is prevented to reach the window (15) to the spectrometer (1) by a flow of another gas through the a pipe (14) connected to an extension by an optical fibre (2) of the light pipe between the light pipe (3) and the spectrometer (1) that has an opposite direction of flow relative the gas to be analysed and a gas flow of gas not being the gas to be analysed that is injected through a pipe (8) in close proximity to the light source (6) between the light source (6) and the inlet (7) to the light pipe (3) of the gas to be analysed in order to prevent the gas to be analysed to reach the window (5) of the light source (6). As long as the pressure is higher at the point where the gas enters the spectrometer than the point where it leaves the spectrometer there will be a gas flow where the gas has a velocity preventing gas or particles to enter the spectrometer.

Definitions: A spectrometer (l) is consisting of a slit where light enters, a dispersive element that reflects the fractioned light. The spectrometer 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 Collecting Device.

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. Examples:

Example l

Breast cancer

Two normal healthy women attending for a screening mammogram, aged 32 and 46 were included. They donated a breath sample prior to screening mammography. Subjects were excluded if they had a previous history of breast cancer, cancer at any other site, breast biopsy, abnormal mammogram or palpable breast mass. One abnormal (BIRADS 5) screening mammogram referred for breast biopsy due to a massive tumor mass was included.

The BreathLink system has been described previously. In summary, subjects wore a nose-clip and respired normally for 2.0 min, inspiring room air from a valved mouthpiece, and expiring into a breath reservoir. Alveolar breath VOCs were pumped from the breath reservoir through a sorbent trap where they were captured and concentrated. VOCs in a similar volume of room air were separately collected and concentrated in the same fashion. Breath VOCs were analyzed with a portable gas chromatograph (GC) coupled to a deep UV spectrometer. The GC-UV was calibrated with an external standard. In the patient with a highly malignant form of breast cancer the concentrations of pentane, decene, naphthalene, trichloroethylene, acetophenone, was higher as analysed with the GC-UV as compared to the breath samples of the two healthy women (in whom the concentrations of the corresponding VOCs were lower or not even detected). See Fig 3

Example 2 Lung cancer

Early detection of lung cancer is a key factor for increasing the survival rates of lung cancer patients. The analysis of exhaled breath is promising as a noninvasive diagnostic tool for diagnosis of lung cancer. One compound with a suggested key role is 2-butanone.

Air and exhaled breath samples were collected in i-L Tedlar bags (Sigma-Aldrich, St. Louis, MO) from a non- smoker, a smoker and a patient with non-small cell lung cancer (NSCLS) stage IV.

For the collection of exhaled breath samples, subjects would directly breathe into Tedlar bags through the Teflon tube, thus providing a noninvasive collection technique. A i-L breath sample was collected from a single exhaled breath; thus, a mixture of tidal and alveolar breath was collected. After collection of exhaled breath, the Tedlar bags were connected to the inlet port of the GC-UV through one fused silica tube.

After the exhaled breath sample had been pulled through the silica tube the samples were analysed usign the GC-UV. In the healthy individual 2-butanone was not detected whereas it was detected at a very low concentration in smoker ant at a three- fold concentration in the patient with non-small cell lung cancer (NSCLS) stage IV. See Fig 4 Example 3

Schizophrenia

It has been suggested that increased contractions of pentane and carbon disulfide is found in the in the breath of patients with schizophrenia.

J Clin Pathol. 1993 Sep;46(9):86i-4.

In the present single-case study one patient with a newly discovered schizophrenia. Air and exhaled breath samples were collected in 2-L Tedlar bags (Sigma-Aldrich, St. Louis, MO) from a non- smoker, a smoker and a patient with non-small cell lung cancer (NSCLS) stage IV.

For the collection of exhaled breath samples, subjects would directly breathe into Tedlar bags through the Teflon tube, thus providing a noninvasive collection technique. A 2-L breath sample was collected from a single exhaled breath; thus, a mixture of tidal and alveolar breath was collected. After collection of exhaled breath, the Tedlar bags were connected to the inlet port of the GC-UV through one fused silica tube.

After the exhaled breath sample had been pulled through the dedicated silica

+ asbest tube the samples were analysed using the GC-UV.

Carbon-disulfide could be detected suggesting that GC-UV can be used for the screening of schizophrenia. See Fig 5.

Example 4 Diabetes

It is well known that known human breath contains clues to many diseases. It has been demonstrated that the odor of acetone is a sign of increasing ketoacidosis in diabetes. However, breath from healthy humans also contains a number of short chain hydrocarbons like isoprene (2-methyl-i,3-butadiene), which may due to exhalation of previously inhaled air pollutants and/or derive from metabolic processes in human body. One problem with several reports dealing with the analysis of exhaled volatile hydrocarbons is the failure to distinguish between isoprene and pentane. We here demonstrate a new highly sensitive and specific method for the analysis of isoprene in human breath, based on gas chromatography with deep UV detection. With this method, unequivocal identification of isoprene is possible by matching the UV absorption spectrum of the biologic sample with an authentic isoprene standard. Moreover, with this method of analysis, breath isoprene cannot be confused with breath pentane, because saturated hydrocarbons such as pentane and ethane do not absorb UV radiation in the same range of wavelengths as does isoprene. The 4 children participating in the investigation were two school children (8-, 14- years old) and two school children with diabetes (io-,i2- years old). The diabetic children had had insulin-dependent diabetes mellitus for 4-7 y and were 3-15 y of age at the time of diagnosis. In all of the subjects exhaled air was collected when the patients were fasting (catabolic state with increased acetone production). The breath collection procedure was as follows: After holding the breath for 2 s, each subject exhaled into a 5-L Teflon (PTFE) bag. Each child exhaled only once into the PTFE bag, producing a gas volume between 500 and 1000 mL, depending on the size of the child. In a second stage, the compounds to be analyzed (isoprene and acetone) were collected from the exhaled breath air sample onto a solid sorbent tube. Aliquots of breath air (250 mL) were drawn from the collecting bag, and compounds in the breath were trapped on an adsorbent tube containing two different adsorbent materials, Tenax TA and Anasorb CMS. To prevent acetone loss due to dissolution in condensed water, the bag was kept at 37°C during this procedure. The adsorbent tubes were then transferred to the laboratory for immediate analysis. The chemical determination of isoprene and acetone was made with a recently developed technique the deep GC-UV technique. In brief, this technique involves gas chromatographic separation and deep UV detection and identification by way of a diode array spectrophotometer. The equipment used was a Chromalytica AB

(Malmoe Sweden). The adsorbent tubes were connected to the carrier gas line and placed in the thermal desorption oven of the instrument. The temperature of the oven was kept at 200°C. After a time delay of 1 min, the desorbed compounds were flushed onto the separation column of the instrument by means of opening the valve for the carrier gas flow. The carrier gas flow rate was kept at 25 mL/min, whereas the temperature program was a linear ramp starting at 50°C with an increment of io°C/min. The overall separation time was 6 min; during that time deep UV spectra were recorded every 4th s. A typical three-dimensional chromatogram of breath isoprene and acetone is shown in Fig. 6. The three-dimensional plot shows l) the deep UV-spectral wavelength (in nanometers) along the x axis, 2) the absorbance of the two compounds(proportional to concentration) along the y axis, and 3) the retention time (in seconds) of the separated compounds along the z axis. Quantifications were made from the chromatograms formed at 214.5 ^nm (isoprene) and 193.9 ^nm (acetone). The integrated values from the sample analysis were compared with those of standards injected directly into the instrument. Acetone and isoprene air vapor standards were prepared from stock solutions containing 0.2% (vol/vol) acetone and 0.02% (vol/vol) isoprene in hexane. Standard curves were obtained by injecting exactly measured volumes (1, 2 and 4 μL) of this solution into the gas chromatograph for analysis by diode array deep UV detection. The detection response was linear over the concentration range encountered in breath samples. Moreover, when ambient room air (250 mL) was analyzed in control experiments, acetone and isoprene could not be detected. Repeated analysis of the same breath sample showed a variation coefficient of 9% both for isoprene and acetone.

Concentrations of isoprene and acetone in the Teflon bag were stable for 1 d but decreased thereafter; adsorption of the compounds onto the adsorbent tubes was therefore performed within 1 d after the breath sampling. All chemicals and solvents used throughout the investigation were of analytical grade and were supplied by Merck (Darmstadt, Germany). Isoprene (99% purity) was purchased from Sigma Chemical Co. (St. Louis, MO).

The concentration of isoprene in expired air from the two healthy children were and from the two diabetic children were:

Healthy 28 and 43 ng/L Diabetes 59 and 111 ng/L

The concentration of acetone in expired air from the two healthy fasting children were and from the two fasting diabetic children were:

Healthy 0.4 and 0.5 ug/L

Diabetes 3.4 and 5.2 ug/L The result is illustrated in Fig 6 Example 5

Head and neck cancer

Recently an electronic nose has been applied in the diagnosis of head and

neck cancer (Laryngoscope, 2013 Oct 19). Characteristically the electronic nose does not detect which compounds that are characteristic of the cancer but determine the general electric pattern as a marker of head and neck cancer. To allow for an optimal treatment of the type of cancer the type and stage of the cancer needs to be

determined and this may be done by assessing specific VOCs. One VOC which has been suggested to be of major importance in cancer diagnosis is toluene. In the present trial we set out to determine the concentration of toloune in exhaled breath in a patient with a severe head and neck tumor before and after treatment. The breath collection procedure was as follows: After holding the breath for 2 s, the patient exhaled into a 5-L Teflon (PTFE) bag, producing a gas volume of 755 - 82omL before and after treatment. In a second stage, the toluene was collected from the exhaled breath air sample onto a solid sorbent tube. Aliquots of breath air (250 mL) were drawn from the collecting bag, and compounds in the breath were trapped on an adsorbent tube containing two different adsorbent materials, Tenax TA and Anasorb CMS. To prevent toluene, the bag was kept at 37°C during this procedure. The adsorbent tubes were then transferred to the laboratory for analysis within 12 hours. The chemical determination of toluene was made with a recently developed technique the deep GC-UV technique, Chromalytica AB (Malmoe Sweden). The adsorbent tubes were connected to the carrier gas line and placed in the thermal desorption oven of the instrument. The temperature of the oven was kept at 200°C. After a time delay of 1 min, the desorbed compounds were flushed onto the

separation column of the instrument by means of opening the valve for the carrier gas flow. The carrier gas flow rate was kept at 25 mL/min, whereas the temperature program was a linear ramp starting at 50°C with an increment of io°C/min. The overall separation time was 10 min; during that time deep UV spectra were recorded every 8th s. A typical three-dimensional chromatogram of breath tolouene is shown in Fig. 7. The three-dimensional plot shows 1) the deep UV-spectral wavelength (in nanometers) along the x axis, 2) the absorbance along the y axis, and 3) the retention time (in seconds) along the z axis.

Quantifications were made from the chromatograms. The integrated values from the sample analysis were compared with a standard injected directly into the instrument. Tolouene air vapor standards were prepared from stock solutions containing 0.02% (vol/vol) tolouene in hexane. Standard curves were obtained by injecting exactly measured volumes (l and 10 μί,) of this solution into the gas chromatograph for analysis by diode array deep UV detection. The detection response was linear over the concentration range encountered in breath samples. Moreover, when ambient room air (250 mL) was analyzed in control experiments, toluene could not be detected. Repeated analysis of the same breath sample showed a variation coefficient of 3% for toluene. Concentrations of toluene in the Teflon bag were stable for 2 d but decreased thereafter; adsorption of the compounds onto the adsorbent tubes was therefore performed within 12 hrs after the breath sampling. All chemicals and solvents used throughout the investigation were of analytical grade and were supplied by Merck (Darmstadt, Germany). Toluene (99% purity) was purchased from Sigma Chemical Co. (St. Louis, MO).

The concentration of toluene in expired air from patient before and after surgery 38 and 22 ng/L suggesting that tolouene may be used as a marker of treatment efficacy. See Fig 7.

Claims

CLAIMS l. A method to obtain photonic signal levels and spatial resolution from samples in gas phase of substances by a first step selection by time by gas chromatography and by a second step by absorption of photons by UV light down toioonm of wavelength that passes a light absorbing chamber for identification and quantification of substances ch ara cte ri z e d in that by entrance to the light absorbing chamber another additional gas, being not the gas to be analysed, is fed in to the light absorbing chamber to protect and prevent light source windows from being in contact with the gas to be analysed.

2. A method according to claim ι to obtain photonic signal levels and spatial resolution from samples in gas phase of substances by a first step selection by time by gas chromatography and by a second step by absorption of photons by UV light down toioonm of wavelength that passes a light absorbing chamber for identification and quantification of substances ch ara cteri z e d in that by entrance to the light absorbing chamber additional gas, being not the gas to be analysed, is fed in to the light absorbing chamber in close proximity to the light entrance and window between the light source and the light absorbing chamber to dilute the gas to be analysed and thereby increase the velocity of the gas through the light absorbing chamber and thereby increase spatial UV resolution of a following spectrometer.

3. A method according to claims 1-2 to obtain photonic signal levels and spatial resolution from samples in gas phase of substances by a first step selection by time by gas chromatography and by a second step by absorption of photons by UV light down toioonm of wavelength that passes a light absorbing chamber for identification and quantification of substances ch ar act eri z e d in that by the exit from the light absorbing chamber another additional gas, being not the gas to be analysed, is fed in to the light absorbing chamber to protect and prevent the spectrometer windows from being in contact with the gas to be analysed.

4. A method according to claims 1 and 3 to obtain photonic signal levels and spatial resolution from samples in gas phase of substances by a first step selection by time by gas chromatography and by a second step by absorption of photons by UV light down toioonm of wavelength that passes a light absorbing chamber for identification and quantification of substances ch ar act eri z e d by that the pressure of the additional other gas is higher than the pressure of the gas to be analysed.

5. A method according to claims 1 to 4 to obtain photonic signal levels and spatial resolution from samples in gas phase of substances by a first step selection by time by gas chromatography and by a second step by absorption of photons by UV light that passes a light absorbing chamber for identification and quantification of substances ch ara cte ri z e d by that the additional other gas is preferably, H ₂, He, N₂ or other low molecular weight, inert gas.

6. An apparatus to be used in the method according to claims 1-5 to obtain photonic signal levels and spatial resolution from samples in gas phase of substances by absorption of photons by UV light that passes a chamber with the gas for

identification and quantification of substances ch ar act eri z e d by that the entrance of a following spectrometer there is a physical window

7. An apparatus according to claim 6 to obtain photonic signal levels and spatial resolution from samples in gas phase of substances by a first step selection by time by gas chromatography and by a second step by absorption of photons by UV light that passes a chamber with the gas for identification and quantification of substances ch ara cte ri z e d by that the entrance of the following spectrometer has a physical window or windows in the light path.

8. Device for use in the method according to any of the above claims 1-5,

ch ara cte ri z e d in its use for detection and diagnose of diseases by analyse of metabolic gases emanating from exhaled air, urine and sweat.

9. Device according to claim 8, ch ar a cte ri z e d in its use for detection and diagnose of diseases by analyse of metabolic gases emanating from exhaled air, urine and sweat comprises a light pipe embedded in a heated body with a temperature range between 50 and 280 °C.

10. Device according to any of the above claims 8-9, ch ara cte ri z e d in the same type of gas can be simultaneously used for all the above functions or different types of gas can be used for the different aspects of the invention.