Gas chromatographic device for autonomously measuring the concentration of a volatile marker in a liquid sample - Patents.com

Abstract

The present invention relates to a gas chromatography device 2 for autonomously determining the concentration of a volatile marker in a liquid sample. The device 2 comprises a sampling device 8 configured to autonomously sample the liquid to be analyzed, a gas sensor 14 and a conversion device 12 connected to the sampling device 8 and to the gas sensor 14. By utilizing the conversion device 12 configured to autonomously convert the sampled liquid into a gas that is analyzed by the gas sensor 14, automatic continuous monitoring of the relevant marker in the liquid sample is achieved.

Description

[Technical field]

[0001] The present invention relates to a gas chromatography device, a method and a computer program for autonomously measuring the concentration of a volatile marker in a liquid sample. [Background technology]

[0002] A gas chromatography instrument is a known device for detecting and measuring the concentration of gaseous compounds. It consists of a chromatography column capable of separating a mixture of gases into its individual components, and a detector that outputs a signal depending on the concentration and / or type of gas passing through it.

[0003] From the prior art, chromatographic devices are known which make it possible to monitor a gas sample continuously or semi-continuously by means of a so-called sample loop. However, the sample loop only allows the analysis of the gas sample. Therefore, such devices cannot be used satisfactorily in applications where a continuous or semi-continuous monitoring of a liquid is required.

[0004] Other devices known from the prior art allow the analysis of liquid samples, but are not autonomous and require the manual provision of a single liquid dose. Such devices are known from US 9 435 772 B2 and EP 2 924 429 A1. Summary of the Invention [Problem to be solved by the invention]

[0005] It is an object of the present invention to provide a gas chromatography device, a method and a computer program for autonomously measuring the concentration of a volatile marker in a liquid sample. [Means for solving the problem]

[0006] In a first aspect, a gas chromatography apparatus for autonomously measuring the concentration of a volatile marker in a liquid sample is presented, the apparatus comprising a sampling apparatus configured to autonomously sample the liquid to be analyzed, a gas sensor and a conversion device connected to the sampling apparatus and the gas sensor, the conversion device configured to autonomously convert the sampled liquid into a gas to be analyzed by the gas sensor.

[0007] It has been found that several types of gas sensors are available that have superior performance in terms of reusability, reliability and affordability compared to liquid sensors known from the prior art for analyzing liquid samples by automatically and continuously sampling the liquid to be analyzed and converting this liquid into a gas that can be analyzed by a gas sensor.

[0008] The term "autonomously" is to be understood within this application as continuous or semi-continuous operation without requiring manual activity from a human operator in the steps between the liquid sampling input step and the sensor output step. Semi-continuous operation can be performed, for example, at least hourly.

[0009] The proposed gas chromatography device can be utilized in agricultural environments for monitoring relevant substances in plant substrate or soil water, milk or urine collected on the floor of livestock pens. Another field of application is in human healthcare where relevant biomarkers such as creatinine, glucose and cortisol levels can be monitored from a patient's blood line or urinary catheter at the hospital bedside or at home.

[0010] In a preferred embodiment, the sampling device is connected to a fluid sampling inlet and a fluid sampling outlet, and the fluid to be analyzed is provided continuously or semi-continuously via the fluid sampling inlet. The gas sensor preferably includes a chromatography column connected to a detector. In this way, conventional chromatography columns and detectors can be utilized with superior performance in terms of reusability, reliability and affordability.

[0011] Alternatively, the gas sensor comprises a detector, which comprises a plurality of non-identical sensors. In this embodiment, it is not necessary to provide a chromatography column. Instead, the functionality of the chromatography column is provided by a detector comprising a plurality of non-identical sensors. In particular, an array of sensors can be utilized. The sensors can detect gases based on known techniques such as chemoresistance, electrochemical and optical absorption. This embodiment offers the advantage of a higher measurement speed compared to solutions comprising a chromatography column and a detector. Preferably, the plurality of non-identical sensors comprises different sensor materials and / or operating conditions.

[0012] According to one embodiment, the conversion device has a droplet dispenser connected to a sampling device and a pyrolysis well configured to convert the droplets provided by the droplet dispenser into a gas, in particular by heating. The pyrolysis well can advantageously convert non-volatile metabolites into a number of volatile fragments that can be detected by gas chromatography. Preferably, the carrier gas supplied to the pyrolysis well does not contain oxygen, to avoid complete conversion to CO2. Pyrolysis in the pyrolysis well can be carried out by rapidly heating the walls of the pyrolysis well, resistively or with an RF coil, in particular by utilizing the Curie effect. The droplets can be transported by pressure, for example piezoelectric, gravity or electrowetting. Furthermore, the pyrolysis well can utilize split injection / splitless injection of liquids heated well above the boiling point. In the case of pyrolysis, the temperature can be lower than the boiling point, since rapid heating in the absence of oxygen breaks down the molecules into volatile fragments. Preferably, the fragmentation may be temperature dependent, which allows the optional advantage to achieve additional selectivity of marker detection by performing sequential analyses at different pyrolysis temperatures.

[0013] According to one embodiment, the sampling device has a liquid filter connected to the fluid inlet, which liquid filter provides a retentate stream and a permeate stream, either the retentate stream or the permeate stream being connected to a conversion device, in particular a droplet dispenser. The additional liquid filter increases the selectivity of the sample liquid containing the mixture of markers. According to an alternative embodiment, the liquid filter can be configured as a liquid chromatography column into which the sample fluid is injected. The output of the liquid chromatography column is fed to a droplet dispenser or any alternative liquid-gas converter. In this embodiment, it is beneficial to repeat the liquid-gas conversion multiple times, since different compounds reach the output of the liquid chromatography column at different times.

[0014] According to one embodiment, the conversion device comprises a liquid-gas converter configured to convert the liquid sampled by the sampling device to a gas, and a valve device configured to provide the following modes of operation: a supply mode in which the sampling device is connected to the liquid-gas converter to fill the liquid-gas converter with a liquid sample, a wash mode in which a carrier gas source is connected to the liquid-gas converter to wash excess fluid using a carrier gas, and an analysis mode in which the liquid-gas converter is connected to a gas sensor. The liquid-gas converter can be configured as a pyrolysis well or a solid phase microextraction device (SPME).

[0015] The conversion device can have a six-port valve connected to a sampling device, a carrier gas source, and a gas sensor.

[0016] The gas chromatography device may further comprise a valve disposed between the liquid-gas converter and the gas sensor, the valve having at least three ports, a first port connected to the liquid-gas converter, a second port connected to the gas sensor, and a third port connected to the outlet. In one embodiment, the liquid-gas converter comprises a six-port valve. In this embodiment, the advantage of high robustness is achieved, since non-volatile ash that may remain in the pyrolysis well is washed away in the next sampling step. Preferably, the surface area next to the pyrolysis well is covered with a hydrophobic coating to facilitate the washing step. In an embodiment in which a solid phase microextraction device (SPME) is utilized, the SPME is preferably heated gradually or stepwise to achieve desorption of selective volatile species to facilitate selective detection. Preferably, ambient air is used as the carrier gas. Due to the SPME sampling, the analyte is concentrated, resulting in high sensitivity detection.

[0017] In one embodiment, the conversion device has a membrane connected to the sampling device and the gas sensor, the membrane being configured to release volatile compounds from the liquid sample. This gas release is also called pervaporation. Preferably, the conversion device has a three-way valve that closes the gas chamber below the membrane to concentrate the volatile compounds and allow them to be injected collectively into the gas sensor. The liquid above the membrane can be heated to increase the gas release rate, allowing the detection of less volatile compounds. This embodiment utilizes a simple structure. Preferably, the membrane is connected to a carrier gas source, with ambient air being supplied as carrier gas. A volatile organic compound (VOC) filter is preferably used to filter the ambient air before supplying it to the conversion device. The VOC filter removes VOCs present in the ambient air to be sampled as a clean reference. This approach is beneficial compared to a carrier gas from a pressurized cylinder, because this embodiment allows to have an additional negative pressure in the gas chamber below the membrane. In one embodiment, the chromatography device has a processor, the processor being configured to perform the steps of the method described in claim 15.

[0018] In another aspect of the invention, a method is presented for autonomously measuring the concentration of a volatile marker in a liquid sample using gas chromatography, the method including autonomously providing a sample fluid to be analyzed, autonomously converting at least a portion of the sample fluid into a gas sample, and autonomously measuring the marker concentration in the gas sample.

[0019] In a further aspect of the present invention, a computer program for autonomously determining the concentration of a marker in a sample is presented, which comprises program code means for causing an apparatus as defined in any of claims 1 to 13 to perform the steps of the method as defined in claim 14, when the computer program is executed on a computer controlling the apparatus.

[0020] It is to be understood that the gas chromatography device of claim 1, the method of claim 14 and the computer program of claim 15 have similar and / or identical preferred embodiments, in particular as set out in the dependent claims.

[0021] It is to be understood that a preferred embodiment of the invention can be any combination of the dependent claims or the above embodiments with the respective independent claim.

[0022] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. [Brief description of the drawings]

[0023] [Figure 1] 1A and 1B are schematic and exemplary diagrams illustrating embodiments of a gas chromatography apparatus for measuring the concentration of a volatile marker in a liquid sample; [Diagram 2] 1A and 1B show schematic and exemplary embodiments of a gas chromatography device for measuring the concentration of a volatile marker in a liquid sample; [Diagram 3] 1A and 1B show schematic and exemplary embodiments of a gas chromatography device for measuring the concentration of a volatile marker in a liquid sample; [Figure 4] FIG. 2 shows, in a schematic and exemplary manner, yet another alternative embodiment of a gas chromatography apparatus for measuring the concentration of a volatile marker in a liquid sample. [Diagram 5] FIG. 2 shows a schematic and exemplary diagram of a further alternative embodiment of a gas chromatography device for measuring the concentration of a volatile marker in a liquid sample; [Figure 6] 1A and 1B show schematic and exemplary embodiments of a gas chromatography device for measuring the concentration of a volatile marker in a liquid sample; [Figure 7] FIG. 2 shows, in a schematic and exemplary manner, another alternative embodiment of a gas chromatography apparatus for measuring the concentration of a volatile marker in a liquid sample. [Figure 8]FIG. 2 shows a schematic and exemplary diagram of a further alternative embodiment of a gas chromatography device for measuring the concentration of a volatile marker in a liquid sample; [Figure 9] FIG. 1 illustrates an embodiment of a method for autonomously measuring the concentration of a volatile marker in a liquid sample using a gas chromatography device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] FIG. 1 shows a first embodiment of a gas chromatography device 2 for measuring the concentration of a volatile marker in a liquid sample. The gas chromatography device 2 comprises a sampling device 8. The sampling device 8 is configured to automatically sample a liquid provided via a fluid sampling inlet 4. The sampling device 8 is further connected to a fluid sampling outlet 6. The sampling device 8 is fluidly connected to a conversion device 12. The conversion device 12 is configured to convert the liquid provided by the sampling device 8 into a gas. With the help of a carrier gas provided by a carrier gas source 10, the gas generated in the conversion device is supplied to a gas sensor 14. The gas sensor 14 is configured to analyze the concentration of a volatile marker in the supplied gas sample. The gas sensor 14 is connected to a gas outlet 16. The gas chromatography device 2 according to the invention allows an automated, in particular semi-continuous, monitoring of relevant markers in liquid samples. The gas sensor 14 can comprise conventional sensing means. These conventional sensing means have superior performances in terms of reusability, reliability and affordability compared to the liquid sensors typically used in the prior art.

[0025] In the embodiment of Fig. 2, the arrangement of the sampling device 8, the conversion device 12 and the gas sensor 14 is shown in detail. The sampling device 8 has a fluid pump 18 for pumping the sampling fluid from the fluid sampling inlet 4 to the fluid sampling outlet 6 and towards the conversion device 12. The conversion device 12 has a droplet dispenser fluidly connected to the sampling device 8. The droplet dispenser 26 generates droplets of sample liquid that are dispensed into a pyrolysis well 28. The pyrolysis well 28 is heated to convert the sample droplets into a volatile marker that is transported to the gas sensor 14. The gas sensor 14 has a chromatography column 22 and a detector 24 connected to the chromatography column 22.

[0026] The gas containing the volatile markers produced in the pyrolysis well 28 is fed to the chromatography column together with the carrier gas supplied by the carrier gas source 10. The detector 24 records the output of the chromatography column 22 as a function of time to establish a chromatogram. Different temperatures can be used in the pyrolysis well 28 to improve the selectivity and the measurement process can be repeated for different temperatures. The carrier gas source 10 is preferably oxygen-free to avoid complete conversion to CO2. The pyrolysis well 28 can include walls that can be rapidly heated, the heating can be performed with an RF coil or resistively. In the droplet dispenser 26, the droplets can be transported by pressure, for example using the piezoelectric effect, gravity or electrowetting. In the presented embodiment, the pyrolysis well 28 includes the widely used split injection / splitless injection of a liquid heated in the well above its boiling point. In the case of pyrolysis, the temperature can be lower than the boiling point, since the rapid heating in the absence of oxygen breaks down the molecules into volatile fragments.

[0027] FIG. 3 shows an alternative embodiment of a gas chromatography device 2. Compared to the embodiment of FIG. 2, FIG. 3 proposes an alternative design of the gas sensor 14. The gas sensor 14 of FIG. 3 only comprises a detector 24. The detector 24 is preferably composed of a plurality of non-identical sensors, e.g. an array of sensors composed of different sensor materials and / or operating conditions. This improves the selectivity of the device 2. The individual sensors can detect gases based on known techniques such as chemiresistive, electrochemical and optical absorption. Overall, compared to the embodiment of FIG. 2, the measurement speed can be improved by the configuration of FIG. 3.

[0028] FIG. 4 shows yet another alternative embodiment of the gas chromatography apparatus 2. In this embodiment, the conversion device 12 has a liquid-gas converter 30 configured to convert the liquid sampled by the sampling device 8 into gas. The liquid-gas converter 30 is configured as a pyrolysis well 28 connected to a valve device 31 configured as a six-port valve 32. The valve device 31 can be switched between a supply mode in which the sampling device 8 is fluidly connected to the liquid-gas converter 30 to fill the liquid-gas converter 30 with a liquid sample, a wash mode in which a carrier gas source 10 is fluidly connected to the liquid-gas converter 30 to wash excess fluid with a carrier gas, and an analysis mode in which the liquid-gas converter 30 is fluidly connected to a gas sensor 14. The switching between the above-mentioned modes is performed by the six-port valve 32. The conversion device 12 further has a valve 34 arranged between the six-port valve 32 and the gas sensor 14. The valve 34 has three ports 36, 38, 40. The first port 36 is connected to the six-port valve 32. The second port 38 is connected to the gas sensor 14 and the third port 40 is connected to the outlet 42. Similar to the embodiment of FIG.

[0029] During the supply mode operation, the pyrolysis well 28 is filled with sample liquid when the six-port valve 32 is in the dotted position. Then, in the wash mode, the excess fluid is washed dry using carrier gas provided by the carrier gas source 10 and discharged via the outlet 42. The six-port valve 32 is therefore switched to the position shown by the black dashed line. Then, in the analysis mode, the pyrolysis well 28 is heated. The resulting volatile pyrolysis products are transported to the gas sensor 14 with the help of the carrier gas. Optionally, the surface area next to the pyrolysis well 28 is covered with a hydrophobic coating to facilitate the washing step. This embodiment has been found to be robust, since any non-volatile ash that may remain in the pyrolysis well 28 is washed away in the next sampling stage.

[0030] In the embodiment of Fig. 5, the conversion device 12 and the gas sensor 14 are equal to the embodiment of Fig. 2. However, the configuration of the sampling device 8 is different. In the embodiment of Fig. 5, the sampling device 8 has a fluid pump 18 which pumps the sampling fluid from the fluid sampling inlet 4 to a liquid filter 44. The liquid filter 44 provides a retentate flow 46 and a permeate flow 48. The permeate flow 48 is connected to the conversion device 12, in particular to the droplet dispenser 26. In this embodiment, the advantage of a higher selectivity is achieved by the liquid filter 44, in particular for sample liquids containing a mixture of markers.

[0031] In the embodiment of FIG. 6, a membrane 54 is utilized to release volatile compounds from the liquid sample provided by the sampling device 8. This is also called pervaporation. Valves 50, 52 close the gas volume defined by the lower part of the membrane 54 (in the dashed black position) to concentrate the volatile compounds and allow them to be injected collectively into the chromatography column 22 of the gas sensor 14. As carrier gas, ambient air is supplied via the ambient air inlet 56. The ambient air is filtered by a VOC filter 58 before reaching the membrane 54. A pressure controller 20 is arranged downstream of the gas sensor 14. With the help of a pump 60, the carrier gas containing the volatile markers is guided towards the gas outlet 16. The use of ambient air filtered by the VOC filter 58 is beneficial compared to the use of carrier gas from a pressurized cylinder, since this embodiment allows to have an additional negative pressure especially below the membrane 54. Optionally, the liquid provided by the sampling device 8 above the membrane 54 can be heated to increase the outgassing rate, allowing the detection of less volatile compounds. In all, the embodiment shown in FIG. 6 is simpler and ambient air can be used as the carrier gas.

[0032] FIG. 7 shows an alternative embodiment that also utilizes a membrane 54. Compared to the embodiment of FIG. 6, the gas sensor 14 only has a detector 24. By removing the chromatography column 22 (see FIG. 6) from the gas sensor 14, the valves 50, 52 can be removed, allowing continuous detection of the gas permeating the membrane 54. Using an array of non-identical detectors 24, for example an array of chemiresistive or electrochemical sensors made of different sensor materials and / or operating conditions, is preferred to increase selectivity. This allows further selectivity compared to the embodiment of FIG. 6, compensating for the removal of the chromatography column 22.

[0033] Figure 8 shows yet another alternative embodiment of a gas chromatography device 2 similar to the embodiment of Figure 4, with the difference being, however, that the pyrolysis well 28 is replaced by a solid phase microextraction device (SPME) 62. The device 2 according to the embodiment of Figure 8 operates as follows:

[0034] A solid phase microextraction (SPME) sorbent is used to extract analytes from the sampled liquid when the six-port valve 32 is switched to the dotted position. The sorbent of the SPME 62 is then washed and dried using a carrier gas in the dashed position of the six-port valve 32. Excess fluid is exhausted via the outlet 42. After being washed and dried, the SPME 62 is heated so that the desorbed VOCs are transported to the gas sensor 14 and analyzed. The SPME 62 can be heated gradually or in stages to achieve selective desorption of volatile species to facilitate selective detection. The embodiment of FIG. 8 is beneficial because ambient air is used as a carrier gas and is analyzed or concentrated during SPME sampling, resulting in high detection sensitivity.

[0035] 9 illustrates an embodiment of a method 100 for autonomously determining the concentration of a volatile marker in a liquid sample using gas chromatography. The method 100 includes autonomously providing 102 a sample fluid to be analyzed, autonomously converting 104 at least a portion of the sample fluid into a gas sample, and autonomously determining 106 the marker concentration in the gas sample.

[0036] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

[0037] In the claims, the word "comprise" does not exclude other elements or steps and the indefinite article "a" or "an" does not exclude a plurality.

[0038] A single unit or device may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0039] The computer program may be stored / distributed on a suitable medium, such as an optical storage medium or a solid-state medium, supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems.

[0040] Any reference signs in the claims should not be construed as limiting the scope.

[0041] The present invention relates to a gas chromatography apparatus for autonomously determining the concentration of a volatile marker in a liquid sample, the apparatus comprising a sampling device configured to autonomously sample the liquid to be analyzed, a gas sensor and a conversion device connected to the sampling device and the gas sensor. By utilizing a conversion device configured to autonomously convert the sampled liquid into a gas that is analyzed by the gas sensor, automatic continuous monitoring of the relevant marker in the liquid sample is achieved.

Claims

1. 1. A gas chromatography apparatus for autonomously measuring the concentration of a volatile marker in a liquid sample, comprising: a sampling device configured to autonomously sample the liquid to be analyzed; A gas sensor; a conversion device connected to the sampling device and the gas sensor; wherein the conversion device is configured to autonomously convert the sampled liquid into a gas to be analyzed by the gas sensor.

2. 10. The gas chromatography apparatus of claim 1, wherein the sampling device is connected to a fluid sampling inlet and a fluid sampling outlet, and the fluid to be analyzed is provided continuously or semi-continuously via the fluid sampling inlet.

3. 3. The gas chromatography apparatus according to claim 1, wherein the gas sensor comprises a chromatography column connected to a detector.

4. 3. The gas chromatography apparatus of claim 1, wherein the gas sensor comprises a detector, the detector comprising a plurality of non-identical sensors.

5. The gas chromatography apparatus of claim 4 , wherein the plurality of non-identical sensors have different sensor materials and / or operating conditions.

6. 3. A gas chromatography apparatus according to claim 1 or 2, wherein the conversion device comprises a droplet dispenser connected to the sampling device and a pyrolysis well configured to convert droplets provided by the droplet dispenser into a gas, in particular by heating.

7. 3. The gas chromatography apparatus of claim 1, wherein the sampling device has a liquid filter connected to the fluid sampling inlet, the liquid filter providing a retentate stream and a permeate stream, and either the retentate stream or the permeate stream is connected to the conversion device.

8. the conversion device includes a liquid-gas converter configured to convert the liquid sampled by the sampling device into gas, and a valve device; The valve device has the following operating modes: a supply mode in which the sampling device is fluidly connected to the liquid-gas converter to fill the liquid-gas converter with the liquid sample; a cleaning mode in which a carrier gas source is fluidly connected to the liquid-gas converter to clean excess fluid using a carrier gas; and an analytical mode in which the liquid-gas converter is fluidly connected to the gas sensor; 3. The gas chromatography apparatus of claim 1, configured to provide:

9. 9. The gas chromatography device of claim 8, wherein the liquid-to-gas converter is configured as a pyrolysis well or a solid phase microextraction device (SPME).

10. 9. The gas chromatography system of claim 8, wherein the conversion device comprises a six-port valve connected to the sampling device, the carrier gas source, and the gas sensor.

11. 9. The gas chromatography apparatus of claim 8, further comprising a valve disposed between the liquid-gas converter and the gas sensor, the valve having at least three ports, a first port connected to the liquid-gas converter, a second port connected to the gas sensor, and a third port connected to an outlet.

12. 3. The gas chromatography device of claim 1, wherein the conversion device comprises a membrane connected to the sampling device and the gas sensor, the membrane being configured to release volatile compounds from the liquid sample.

13. 15. A gas chromatography apparatus according to claim 1 or 2, comprising a processor configured to carry out the method of claim 14.

14. 1. A method for autonomously measuring the concentration of a volatile marker in a liquid sample using gas chromatography, comprising: autonomously providing a sample fluid to be analyzed; autonomously converting at least a portion of the sample fluid into a gas sample; autonomously measuring a marker concentration in the gas sample; A method having the following.

15. A computer program for autonomously measuring the concentration of a marker in a sample, the computer program being executed by a computer that controls a gas chromatography apparatus according to claim 1 or 2, and causing the gas chromatography apparatus to carry out the method according to claim 14.

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