WO1998052012A2

WO1998052012A2 - Measuring device and method for cleaning contaminated areas of a measuring device

Info

Publication number: WO1998052012A2
Application number: PCT/EP1998/002722
Authority: WO
Inventors: Horst-Henning Grotheer; Harald Oser; Reinhold Thanner
Original assignee: Deutsches Zentrum für Luft- und Raumfahrt e.V.
Priority date: 1997-05-12
Filing date: 1998-05-09
Publication date: 1998-11-19
Also published as: DE19719903A1; WO1998052012A3

Abstract

The invention relates to a measuring device comprising a measuring apparatus especially for gaseous samples and a sample input device by means of which samples can be introduced into the measuring device. To improve such a device in such a way as to ensure that the measurement and/or analysis results of the measuring apparatus are not influenced by possible contamination, the invention provides for the sample input device to be fitted with a cleaning device for cleaning contaminated areas of the sample input device by transforming impurities in said contaminated areas by a chemical reaction, and for the reaction products to be removed from the sample input device.

Description

Measuring device and method for cleaning contamination areas of a measuring device

The invention relates to a measuring device comprising a measuring device for in particular gaseous samples and a sample inlet device through which the samples can be fed to the measuring device.

The invention further relates to a method for cleaning contamination areas of a measuring device, which comprises a measuring device for in particular gaseous samples.

Measuring devices with measuring devices, which are used to analyze gaseous samples, are used, for example, in chemical analysis or in process control and process monitoring. The problem arises that, in particular if compounds of low volatility from the gas phase are to be analytically detected, they lead to contamination of the measuring device. Such contamination areas of the measuring devices can occur in particular in the area of a sample feed to the measuring device, a sample enrichment stage and a sample inlet device into the measuring device. Through such contaminations, the measuring device can deliver values that are not characteristic of the gaseous samples to be measured and analyzed, since the contamination in the contamination areas can contribute to falsification of the measurement and analysis results. The invention is therefore based on the object of improving a measuring device with the features mentioned at the outset so that the measuring and / or analysis results of the measuring device are not influenced by possible contaminations.

This object is achieved according to the invention in the measuring device with the features mentioned at the outset in that the sample inlet device is provided with a cleaning device for cleaning contamination areas of the sample inlet device by converting contaminants in the contamination areas by chemical reaction and that the reaction products can be removed.

The measuring device according to the invention makes it possible to clean contamination areas of the sample inlet device in a quick and effective manner, in particular from residues from a previous measurement, so that the measuring device does not show faulty measurement values during a sample measurement due to contamination of the measuring device.

In devices and methods known from the prior art, the cleaning process is based on the desorption of the contaminants from corresponding contaminated areas of the contamination areas. These are thermal desorption, where the contamination areas have to be heated, for example, or a hot desorbent, for example steam heated by microwave, has to be applied, or it can be solution desorption, the contamination areas then having suitable liquid Solvents must be rinsed. These desorption processes work according to the dilution principle and the degree of contamination decreases exponentially with the cleaning time. The problem arises that, in particular in the case of complex, low-volatility samples and sample mixtures, the cleaning result is not complete and residues accumulate, which in turn influence the adsorption properties of corresponding surfaces of the contamination areas. The cleaning time for cleaning the contamination areas from impurities can be several hours even with relatively lightly liquid substances, so that the measuring device has a correspondingly long measurement dead time, in which the measuring device cannot be used for sample measurements. Accordingly, the devices and methods known from the prior art cannot be used for real-time measurement and analysis applications.

In addition, there are also specific problems with the use of solvents, since, for example, the solvents have to be adapted to the impurities occurring in the contamination areas in order to achieve a solution of the impurities from the contamination areas into the solvent.

If water vapor, which is heated via microwave radiation, is used for the thermal desorption, contamination areas with a narrow cross section, such as narrow channels, cannot be cleaned with a metallic wall in this method. The measuring device according to the invention is provided with a cleaning device which ensures that the impurities are converted by chemical reaction and that the reaction products formed are removed. In this way, the contaminated surfaces of the contamination areas can be cleaned essentially completely and within a very short time, since the contaminant molecules are attacked directly and converted into corresponding gaseous compounds such as CO, CO ₂ or H ₂ O, which can then easily be removed from the sample inlet device let be led away.

The cleaning process in the measuring device according to the invention can therefore be carried out without the use of liquid solvents, no particles are generated which can absorb onto surfaces of the contamination areas again and the cleaning process itself is not a thermodynamic process, regardless of the temperature of the sample inlet device. In this way, an essentially residue-free cleaning is guaranteed. The measuring device according to the invention can thus be used in particular for fast analytical detection methods, since the cleaning process can take place within a very short time. The cleaning process is also easy to automate.

It is particularly advantageous if the cleaning device comprises a means for generating reactive ions and an application means for applying reactive ions to the contamination areas, wherein contaminations in the contamination areas can be converted into gaseous substances by chemical reaction with the reactive ions. The reactive ions, which can have kinetic energies of the order of magnitude of 1 keV in particular, destroy chemical bonds on contact with contaminants on surfaces of the contamination areas, so that chemically very stable organic compounds are also converted. The conversion of the impurities by chemical reactions with the reactive ions takes place in gaseous compounds such as CO, C0 ₂ or H ₂ 0. These gaseous compounds can then be easily removed from the sample inlet device. The chemical reaction is independent of the temperature, since the contaminating impurities are exposed to reactive ions and the breaking of the chemical bonds is caused by the kinetic impact energy of the reactive ions. Furthermore, the cleaning is residue-free, since the contamination areas can be substantially completely exposed to the reactive ions. The cleaning process depends on the surface coverage of the contaminated surfaces of the contamination areas with a constant or even increasing cleaning speed and the contaminating contaminants in the contamination area decrease essentially linearly. In contrast to thermal desorption methods, a finite cleaning time is achieved. In particular, the cleaning success can be monitored in real time, since the concentration of the gaseous substances as reaction products can be monitored directly. The cleaning process can thus also be automated in a simple manner, since the success of the cleaning can be determined by monitoring the concentration of the gaseous substances. It is particularly advantageous if the measuring device has a pump, by means of which the gaseous substances can be removed from the sample inlet device. This ensures that the gaseous substances cannot accumulate in the sample inlet device. This contributes to a high degree of cleaning.

It is particularly advantageous if a process gas can be passed through the sample inlet device. The reaction products formed by chemical reaction, which are in particular gaseous, can then be pumped off with the process gas.

The contamination areas can advantageously be acted upon by the process gas. This ensures that the gaseous substances resulting from the chemical reactions on corresponding surfaces of the contamination areas are removed directly from the process gas. The gas throughput of the process gas through the sample inlet device can be kept low, for example to a few standard ccm per minute. Due to the corresponding small amounts, the use of a process gas is significantly less expensive than the use of liquid solvents, which require a considerably larger mass throughput.

It is particularly advantageous if the means for generating reactive ions is a gas discharge device for carrying out an electrical gas discharge in the process gas. In this way, the contamination areas or their contaminated surfaces can be substantially completely exposed to reactive ions and the impurities formed by chemical reactions can be directly with remove the process gas. This enables an essentially complete and thorough cleaning of the contamination areas from impurities.

So far no statements have been made about the type of process gas. It is particularly advantageous if oxygen, in particular pure oxygen, is used as the process gas. This contributes to the fact that the chemical reaction converts the impurities with the reactive ions formed in the oxygen into gaseous compounds such as CO, C0 ₂ or H ₂ 0, especially if the impurities are organic compounds. (Due to the low pressure in the sample inlet device, which is, for example, of the order of 1 mbar, the water is in vapor form.) In addition, particularly reactive molecules such as ozone or singlet oxygen are formed during an electrical gas discharge in oxygen, which are also used for Conversion of contaminants into gaseous substances can contribute.

It is also possible to use other process gases depending on the contaminants. For example, air, in particular pure air or water vapor, can be used as the process gas.

In a variant of an embodiment, the process gas is an oxygen-free gas. This prevents gaseous reaction products from being further oxidized. This is important, for example, in the detection of NO, in which the oxygen produced would further oxidize during cleaning and this would complicate the cleaning process. In this case, methane can be used as the process gas. It is advantageously provided that fluorine or fluorine compounds such as SF ₆ , CF ₆ , CF ₃ H can be mixed into the process gas. Oxygen-fluorine mixtures or air-fluorine mixtures can also be used to convert organic silicon compounds which are present as impurities in the contamination areas into gaseous reaction products. It can also be used to remove heavy metal contaminants such as tungsten or uranium contaminants by converting them into volatile compounds such as WF ₆ or UF ₆ .

Advantageously, the gas discharge device is designed as a plasma chamber so that a plasma can be formed in the sample inlet device, the contamination regions being exposed to reactive ions by the plasma in the plasma chamber. In this way, the plasma chamber acts simultaneously as a means for generating the reactive ions and as an exposure means for the exposure of the contamination areas. Due to the plasma cleaning in the plasma chamber with the reactive ions, removal rates of the order of a few μg / cm ² sec can be reached, by means of which the cleaning times for the contamination areas of the sample inlet device can be limited to a few seconds, for example.

So far, no statements have been made about how the plasma is generated by the gas discharge device. It is particularly advantageous if high-frequency power can be coupled into the process gas to form the plasma in the plasma chamber. The coupling of high-frequency power has the advantage that no arcs can form in the plasma chamber, which would lead to material removal or even destruction, especially where the Arcs touch surfaces. The coupling makes it possible, in particular, to design electrodes in such a way that an optimal cleaning process is achieved. The coupling can take place, for example, capacitively or via a transformer.

In a variant of an embodiment it is provided that high-frequency power can be inductively coupled into the process gas to form the plasma by the gas discharge device.

It can also be provided that the gas discharge device can be used to couple microwave power into the process gas to form the plasma. In this case, it is particularly advantageous if the plasma chamber is formed by a cavity resonator in order to ensure optimal coupling into the process gas for plasma formation. The microwave power can advantageously be coupled into the plasma chamber via a waveguide.

In a particularly favorable variant of an embodiment of the measuring device according to the invention, the sample inlet device is designed as a sample enrichment stage. In this way, the sample inlet device can also be used for sample enrichment and the sample enrichment stage can be cleaned efficiently and optimally.

It is expedient if the sample inlet device for sample enrichment has an enrichment element which is arranged in the plasma chamber and whose temperature can be controlled. In this way, an enrichment of gaseous or vaporous samples can be carried out on the enrichment element Carry out within the plasma chamber, since the temperature can be used to control the condensation or thermal desorption of the sample on the enrichment element. Due to the arrangement in the plasma chamber, the enrichment element can be easily cleaned of impurities.

A heat transfer medium can advantageously be applied to the enrichment element in order to control its temperature. For example, an oil or a gas can be used for temperature control. It is also conceivable that the enrichment element is cooled or heated by electrical means.

It is particularly advantageous in terms of construction if an inner electrode of the plasma chamber is designed as an enrichment element. Since the inner electrode for plasma formation is arranged within the plasma chamber, it can also be used accordingly as an enrichment element.

The walls of the plasma chamber can advantageously be heated. This contributes to the sample enrichment in the plasma chamber, since in this way it can be avoided that the walls of the plasma chamber act as condensation traps for the sample. It can also be prevented that contaminations on the inner walls of the plasma chamber contaminate it too much. The temperature at which the walls are heated is advantageously chosen so that condensation of the samples on the walls is prevented and that the samples are not thermally decomposed by the heated walls. In a particularly favorable variant of an embodiment, the sample inlet device has a monitoring device for monitoring the degree of cleaning of the contamination areas of the sample inlet device. In this way, the cleaning success can be monitored and checked, in particular in real time.

In a variant of an embodiment of the measuring device according to the invention, the sample inlet device has a viewing window for monitoring the degree of cleaning of the contamination areas. It is particularly advantageous if the monitoring device is designed and arranged in such a way that the degree of cleaning can be determined by observing the optical emission spectrum and in particular by observing individual characteristic optical emission lines of the reaction products of the chemical reaction or possible reaction products. For this purpose, the monitoring device can comprise, for example, an optical spectrometer which is aligned with corresponding characteristic emission lines, such as emission lines of CO or C0 ₂ or H ₂ 0. A decrease in the intensity of such lines or a disappearance of these lines then indicates complete cleaning of the sample inlet device.

It is also possible for the measuring device itself to be used as a monitoring device in that the process gas with the reaction products contained therein are fed to the measuring device and this is used for analyzing the gas mixtures. It is particularly advantageous if the sample inlet device has a sample inlet valve at a sample inlet into the measuring device, the closing pressure of which can be adjusted. In this way, the sample inlet device can be optimally adapted to the measuring device in order in this way to optimize the working ability of the measuring device.

It is particularly favorable if the closing pressure is infinitely adjustable in order to ensure optimal adaptation in this way.

In a variant of an exemplary embodiment, the closing pressure is adjustable according to the invention by setting a spring preload of a sample inlet valve spring. This enables adjustment in a less complex and structurally simple manner.

It is particularly expedient if an adjusting means for the closing pressure is arranged such that the closing pressure can be set without dismantling the sample inlet valve. As a result, the closing pressure can be adjusted in a simple manner without the need for expensive disassembly of the sample inlet device or ventilation of the vacuum of the measuring device. In particular, this enables adaptation to different operating conditions.

In this case, it is structurally particularly simple if the adjusting means is an adjusting element which can be rotated in a thread facing away from a valve disk and through which the sample inlet valve spring can be acted upon in order to adjust the spring preload. In order to enable simple and precise control of the sample inlet valve, it can advantageously be operated electromagnetically.

To improve the cleaning success, it is provided in a variant of an embodiment orm of the measuring device according to the invention that the sample inlet into the measuring device with respect to a plasma space in which the plasma is formed is arranged so that molecules and reactive ions from the plasma space near the Can get sample inlet. These molecules are, in particular, highly reactive molecules such as singlet oxygen or ozone, which are formed during the gas discharge. With the appropriate arrangement of the sample inlet with respect to the plasma space, these molecules can diffuse towards or in the vicinity of the sample inlet and thus increase the degree of purification by reacting with impurities in the vicinity of the sample inlet.

In a variant of an embodiment it is provided that the measuring device has a control unit by means of which the sample supply to the measuring device and the cleaning of the contamination areas of the sample inlet device can be controlled. As a result, the sample supply and the cleaning of the contamination areas can be coordinated with one another, in order in this way in particular to minimize the dead times of the measuring device. It is particularly advantageous if the control unit can control the sample feed to the measuring device as a function of the degree of cleaning of the sample inlet device. In a variant of an embodiment, the sample can be fed to the sample inlet device as a gaseous sample. In a further variant, the sample can be fed to the sample inlet device as a liquid sample. This makes it possible, for example, to use the measuring device as a determination device in liquid chromatography, such as high performance liquid chromatography (HPLC).

Conveniently, the feed comprises a capillary so that the sample inlet device is not excessively contaminated with liquid. It can then be provided that the sample inlet device comprises a heating element for evaporating the liquid sample so that it can be fed to the measuring device.

The measuring device according to the invention can be used particularly inexpensively if the measuring device is an on-line analytical measuring device, since the rapid cleaning of the sample inlet device only interrupts the sample measurement by the measuring device for a short time. The measuring device according to the invention can be used in particular if the measuring device comprises a REMPI device or a JET-REMPI device. (JET-REMPI is registered as a German trademark with the file number 39650736.0.) The REMPI process is a "resonance-enhanced multiphoton ionization". In the JET-REMPI method for the detection of sample molecules in a carrier gas, a divergent carrier gas jet is generated by expanding the carrier gas through a nozzle into a vacuum, the sample molecules are selectively ionized to sample molecule ions in an ionization region of the carrier gas jet by absorption of photons, and the sample molecule ions by an electric Draw field drawn into a mass spectrometer and detected in the mass spectrometer, with a continuum area of the carrier gas jet in which the temperature of the carrier gas decreases with increasing distance from an outlet opening of the nozzle, a molecular jet area of the carrier gas jet in which the temperature of the carrier gas with increasing distance from the outlet opening the nozzle substantially does not decrease further, and a boundary between the continuum region and the molecular beam region is determined, and the sample molecules are ionized in an ionization region close to the boundary between the continuum region and the molecular beam region. The JET-REMPI method is described in German Patent 44 41 972, to which reference is made.

Furthermore, the invention has for its object to provide a method for cleaning contamination areas of a measuring device with the features mentioned above, which enables effective and quick cleaning.

This object is achieved in the method with the features mentioned at the outset in that the contamination areas are acted upon by reactive ions which convert impurities into gaseous substances by chemical reaction, and in that the reaction products are removed.

The method according to the invention has the advantages already discussed in connection with the device according to the invention. Further refinements and advantageous embodiments of the method according to the invention are The subject matter of claims 42 to 82. These configurations and their advantages have already been discussed in connection with the device according to the invention.

The invention further relates to a sample inlet valve which is arranged in a sample inlet device and serves to close a sample inlet of the sample inlet device into a measuring device for the samples.

Such sample inlet valves serve to control the sample feed from the sample inlet device into the measuring device.

The invention is therefore based on the object of improving a sample inlet valve with the features mentioned at the outset such that the sample inlet device can be optimally coupled to the measuring device with respect to the sample supply from the sample inlet device into the measuring device.

This object is achieved according to the invention in the sample inlet valve with the above-mentioned features in that a closing pressure of the sample inlet valve is adjustable.

The adjustability of the closing pressure enables an optimal coupling of the sample inlet device to the measuring device. This is particularly advantageous if the sample inlet valve is clocked, since the functionality and operational reliability of the sample inlet valve can be ensured by the adjustability.

It is particularly advantageous if the closing pressure is continuously adjustable. It is particularly expedient if the sample inlet valve has an adjusting means for adjusting the closing pressure, which is arranged in such a way that dismantling of the sample inlet valve is not necessary for adjusting the closing pressure. This enables the closing pressure to be adjusted quickly and easily, without the sample inlet device having to be dismantled or a vacuum of the measuring device having to be vented. This minimizes the dead times of the measuring device during the setting of the closing pressure of the sample inlet valve.

It when the adjusting means is arranged facing away from a valve plate of the sample inlet valve is particularly advantageous.

In a structurally particularly simple embodiment, the adjusting means is formed by an adjusting element which can be rotated in a thread and through which a sample inlet valve spring can be acted upon in order to adjust a spring preload.

In order to enable cyclical operation of the sample inlet valve, it is provided in a variant of an embodiment that the sample inlet valve can be actuated electromagnetically.

The sample inlet valve according to the invention can be used particularly advantageously in the measuring device according to one of claims 1 to 25, 32 to 40.

Furthermore, the present invention relates to a measuring device comprising a measuring device in which, by means of expansion, a carrier gas containing sample molecules through a nozzle a divergent carrier gas jet can be generated in a vacuum, the sample molecules in an ionization region of the carrier gas jet can be selectively ionized to sample molecule ions by absorption of photons and the sample molecules can be drawn by an electric pulling field into a mass spectrometer and can be detected in the mass spectrometer, and a sample inlet device through which a Sample can be fed to the measuring device.

Such a method is known from German Patent 44 41 972.

However, this known device is only suitable for the detection of sample molecules present in the gas phase.

The present invention is therefore based on the object of creating a measuring device of the type mentioned above which allows analysis of sample molecules present in the liquid phase.

This object is achieved according to the invention by a measuring device according to claim 90.

Particular embodiments of this measuring device are the subject of dependent claims 91 to 93.

The present invention further relates to a method for the detection of sample molecules in a carrier gas, in which the carrier gas with the sample molecules is fed to a measuring device by means of a sample inlet device, a divergent carrier gas jet is generated by expanding the carrier gas through a nozzle into a vacuum, the sample molecules in one Ionization region of the carrier gas jet is selectively ionized to sample molecule ions by absorption of photons and the sample molecule ions are drawn into a mass spectrometer by an electric pulling field and detected in the mass spectrometer.

Such a method is known from German Patent 44 41 972, but is limited to the detection of sample molecules present in the gas phase.

The present invention is therefore based on the further object of creating a method of the type mentioned above which also allows the detection of sample molecules present in the liquid phase.

According to the invention, this object is achieved by a method according to claim 94.

Particular embodiments of the method according to the invention are the subject of claims 95 to 97.

The drawing shows:

Fig. 1 A first embodiment of the measuring device according to the invention in a schematic representation;

Fig. 2 shows a second embodiment of the measuring device according to the invention in a schematic representation; Fig. 3 shows a third embodiment of the measuring device according to the invention in a schematic representation and

Fig. 4 shows a fourth embodiment of the measuring device according to the invention in a schematic representation.

In a first exemplary embodiment of the measuring device according to the invention, which is designated as a whole by 10 in FIG. 1, it comprises a sample inlet device 12 and a measuring device 14. The sample inlet device 12 is held on the measuring device 14 via holding elements 16.

The measuring device 14, which is used in particular for the analysis or for the detection of gaseous samples, has a sample inlet 18 through which the in particular gaseous samples can be fed from the sample inlet device 12 to the measuring device 14.

The sample inlet device includes a cylindrical housing 20 with walls 22, a lid 24 and a bottom 26. The bottom 26 has an opening 28 which communicates with the sample inlet 18 of the measuring device 14 so that the samples are taken from the sample inlet device 12 to the measuring device are feedable.

In the cover 24, a cup-shaped element 30 is inserted, which is made of an insulator and in particular glass. The cup-shaped element 30 has a cavity 31 coaxial to an axis 32 of the cylindrical housing 20 so that walls 34 of the cup-shaped element 30 are parallel to the walls 22 of the housing 20.

The cup-shaped element 30 is open towards the opening 28. A valve holder 36 is inserted into this opening. The valve holder has a cylindrical opening 38, coaxial with the axis 32, in which a sample inlet valve 40 is guided.

The sample inlet valve comprises a valve spindle 42 and a valve plate 44 which is non-positively connected to the valve spindle 42 and by means of which the opening 28 of the sample inlet 18 can be opened or closed depending on the position of the sample inlet valve 40. For this purpose, a needle-shaped element 46 sits on the valve plate 44 coaxially to the axis 32, through which the opening 28 can be closed.

The sample inlet valve spindle 42 is displaceably mounted in a guide 48, so that the sample inlet valve 40 is movable in the axial direction along the axis 32.

The valve spindle 42 has an inner cavity 50 which is in fluid communication with the cavity 31 of the cup-shaped element 30. Valve stem 42 has lateral openings 52 near its lower end so that fluid can flow from cavity 31 through cavity 50 via openings 52 into an access space 54 in front of sample inlet 18.

At its upper end facing away from the valve plate 44, the valve holder 36 has an internal thread 56 coaxial with the axis 32, into which an annular nut 58 engages. The ring nut 58 has at its lower end facing the sample inlet valve plate 44 an annular recess 60 which serves as a contact surface for a valve spring 62.

The valve spring 62 sits between this contact surface of the ring nut 58 and the valve plate 44 in the cavity 50 of the valve spindle 42.

The spring preload of the sample inlet valve spring 62 can be adjusted by rotating the ring nut 58 in the internal thread 56, so that the closing pressure of the sample inlet valve 40 and in particular of the needle-shaped element 56 on the opening 28 can be adjusted in this way.

The sample inlet valve 40 can be actuated by means of an electromagnet 64, by means of which the valve spindle 42 can be held in an open position with respect to the opening 28. For this purpose, the sample inlet valve spindle 42 is advantageously made of a magnetic material. When the electromagnet 64 is switched off, the needle-shaped element 46 of the valve plate 44 is pressed onto the opening 52 by the spring force of the sample inlet valve spring 40.

In a variant of an embodiment, the sample inlet valve can be actuated by means of a piezo element (not shown in the figure).

The connection between the walls 34 of the cup-shaped element 30 and the valve holder 36 is designed to be fluid-tight, so that a fluid can flow from the cavity 31 into the access space 54 only via the cavity 50. The valve holder 36 is held on the inside of the walls 22 of the housing 20 via holding elements 66. An annular flow space 68 is formed between the inside of the walls 22 and the outside of the cup-shaped element 30 and an outside of the valve holder 36. An inlet / outlet 70 leads into this flow space via an orifice 72 for process gas. At the mouth 72 there is a valve 74, which is particularly controllable in order to make the supply or discharge of process gas to the flow space 68 controllable. The feed / discharge 70 is connected to a pump, in particular for pumping out process gas from the flow space 68. The flow space 68 is connected to the access space 54.

The cross section of an access from the flow space 68 into the access space 54 is reduced by a corresponding shaping of the valve holder 36 at its lower end as a truncated cone 76, the access space 54 being formed by a recess in this frustoconical section 76 of the valve holder 36 coaxial to the axis 32. The reduction in the cross-section due to this frustoconical shape increases the speed of the process gas at the opening 28, in order in this way to prevent contaminants from accumulating in the vicinity of the sample inlet 18 in the measuring device 14 and to make it more difficult for samples to penetrate into the flow space 68 .

The flow space 68 has a mouth 78, at which a controllable valve 79 is located, a further feed / discharge 80 for the process gas, which is connected to a pump (not shown in FIG. 1), so that process gas through the Flow space 68 is feasible and the sample inlet device 12 can be evacuated when the sample inlet valve 40 is closed. The mouth 78 is arranged, for example, diametrically to the mouth 72. Coaxial to the axis 32 sits in the cavity 31 of the cup-shaped element 30, an inner electrode 82 which is electrically insulated from the housing 20 via the cup-shaped element 30.

An alternating electrical field can be applied between the inner electrode 82 and the housing 20. For this purpose, the electrode 82 is provided with an electrical connection 84 which is connected to a high-frequency generator 90 via a line 86. The housing is also connected to the high-frequency generator 90 via a connection 92 and a line 94.

The housing 20 is made of metal, so that an electric field can be generated between the inner electrode 82 and the housing 20. In a variant of an embodiment, the valve holder 36 is also made of metal, in order to make it possible, in particular, to form the end facing the inner electrode 42.

A feed line 96 leads through the inner electrode 82 into the cavity 31, through which fluids can be introduced into the latter. For this purpose, the electrode 82 has outlet openings 98 for the fluids at its lower end.

The feed line 96 leads to an outlet of a fluid control 100, which is, for example, a four-way valve. A line 102 for process gas opens into a first input of the fluid control 100, so that process gas can be conducted into the access space 54 via the line 96 and via the cavity 31. A feed line 104 for gaseous samples leads into a second input of the fluid control 100, so that the sample gas can be fed through the cavity 96 to the sample inlet 18 of the measuring device 14 through the line 96.

The fluid controller 100 has a second output, to which an outlet 103 is coupled, which is connected to a pump (not shown in the figure), so that when a passage between the line 96 and the outlet 103 is activated by the fluid controller 100 in particular the cavity 31 can be evacuated.

The fluid controller 100 is designed such that the sample gas supply can be blocked when the process gas is supplied or the process gas supply can be blocked when the sample gas is supplied. For this purpose, a control unit 106 is provided according to the invention, through which the sample inlet valve 74 for the process gas supply to the flow space 68 can also be controlled. It can also be provided according to the invention that the valve 74 can be controlled via the control unit 106.

In a variant of an embodiment (not shown in FIG. 1) it is provided that the feed lines for the process gas and for the sample gas lead separately into the inner electrode 82.

A feed 108 for a heat transfer medium leads into a flow channel and an outlet 110 through the inner electrode 82, so that the heat transfer medium can be passed through the inner electrode 82 in order in this way to control the temperature of the inner electrode 82. The walls 22 of the housing 20 can be heated, for example via resistance heating of wire loops arranged on the walls (not shown in the figure).

In a variant of an exemplary embodiment according to the invention, it is provided that the cavity 31 of the cup-shaped element 30 can be monitored by a monitoring device 112. In particular, this can be a spectrometer or optical filter, by means of which the intensity of characteristic optical emission lines of substances in the sample inlet device 12 according to the invention are monitored. For this purpose, the cup-shaped element 30 has a see-through window 131 at its upper end.

The sample inlet device according to the invention works as follows:

For the detection or analysis of gaseous samples, the samples are fed through the feed line 104 through the fluid controller 100 via the feed line 96 and the outlet openings 98 into the sample inlet device 12 and through the cavity 31 and via the openings 52 into the access space 54, from where they reaches the sample inlet 18 of the measuring device 14 via the opening 28. For this, the sample inlet valve 40 is open, i.e. the valve plate 44 with the needle-shaped element 46 does not close the opening 28.

The valve 74 for the process gas supply is closed and the flow space 68 of process gas is evacuated by means of the pump, so that essentially only the sample is supplied to the measuring device 14. The measuring device is, in particular, an on-line analytical measuring device such as, for example, a JET-REMPI device for rapid analytical detection of sample molecules. (JET-REMPI is registered as a German brand with the file number 39 650 736.0.)

A JET-REMPI device, which is described in DE-PS 44 41 972, to which reference is hereby expressly made, serves for the detection of sample molecules in a carrier gas. In this case, the term sample gas introduced above means the carrier gas with sample molecules contained therein.

It can be provided according to the invention that the sample inlet valve 40 is clocked in order to clock the sample supply to the measuring device 14.

In order to exclude the possibility of errors in the measurements of the measuring device 14 due to impurities which are formed, for example, by residues from previous measurements, it is necessary to clean the contamination areas 113 of the sample inlet device from such impurities. The contamination areas 113 are formed by inner surfaces 113 of the sample inlet device 12.

For this purpose, the opening 28 is closed by the needle-shaped element 46 of the sample inlet valve 40 in the method according to the invention. The flow space 68 is then flushed with process gas via the feed / discharge 70 and the feed / discharge 80, and the cavity 31 is also flushed with process gas via the line 102 and the feed line 96. An alternating voltage is applied between the inner electrode 82 and the housing 20 via the high-frequency generator 90, so that an electric field is formed. A gas is formed by gas discharge in a plasma space 114, which in particular comprises a substantial portion of the flow space 68 and the cavity 31. In this way, reactive ions are generated which act on the contamination regions 113 of the sample inlet device 12.

A plasma chamber 116 is formed by the inner electrode 82 and the housing 20. An electrical field for plasma formation can also be generated between the upper end of the valve holder 36 and the inner electrode 82 via the holding elements 66, which provide an electrical connection and short-circuit the valve holder 36 with the housing 20.

The plasma space 114 includes substantially all of the inner surfaces in the sample inlet device 12 so that substantially all of the inner surfaces are exposed to reactive ions.

The reactive ions from the plasma have high kinetic energies of up to 1 keV, so that they are destroyed with adsorbed surface contaminants, which consist, for example, of residues of low-volatility compounds from a previous measurement process, and in gaseous compounds such as CO, CO ₂ or H ₂ 0 are transferred regardless of the temperature. As a result, particularly chemically stable organic compounds can be implemented. Pure oxygen or pure air is used as the process gas. Around the sample inlet device 12 of silicon To clean organic compounds, it is advantageous if fluorine or fluorine compounds such as CF ₄ or CF ₃ H are added to the process gas.

The cleaning process of the contaminated surfaces proceeds at a constant or even increasing cleaning speed, since with a fixed process gas pressure in the sample inlet device the plasma generation rate is essentially constant, but the surface coverage of contaminants in the contamination areas 113 decreases. The decrease in surface coverage is essentially linearly dependent on the cleaning time or the degree of cleaning of the contamination areas increases linearly with the cleaning time. In this way, the contamination areas can be substantially completely cleaned with a corresponding cleaning time.

Such a plasma cleaning of the contamination areas with the aid of reactive ions has typical removal rates of a few μg / cm ² sec. Since the sample quantities that are introduced into the sample inlet device 12 are usually relatively small, cleaning times of at most a few seconds can then be achieved.

The flow space 68 and the cavity 31 are flushed with process gas so that the gaseous substances formed as reaction products by the chemical reaction with the plasma are discharged through the discharge gas 80 through the process gas. With a volume of the plasma chamber 116 of the order of 150 ml, a good cleaning of the sample inlet device can be carried out, which increases the plasma generation in the process gas and the Removal of the gaseous reaction products includes, for example, by reaching a process gas throughput of the order of a few standard ccm / min.

In one variant of an embodiment, the process gas throughput through the sample inlet device is regulated via the pressure in the plasma chamber 116. In another variant, the gas throughput is fixed.

The walls 34 of the cup-shaped element 30 serve to seal the cavity 31 with respect to the flow space 68. However, a plasma is also generated in the flow space 68, since the electric field lines between the inner electrode 82 and the walls 22 can penetrate through the walls 34.

The sample inlet 18 or the opening 28 and the sample inlet valve 40 are preferably arranged opposite the plasma space 114, in which the plasma is generated, in such a way that highly reactive molecules such as ozone or singlet oxygen formed in the process gas by means of diffusion in the vicinity of the sample inlet 18 or the opening 28 can get there to react chemically with impurities and thus contribute to cleaning. Areas within the plasma chamber 116 that are shadowed with respect to the plasma formation can also be cleaned by means of a chemical reaction.

The degree of cleaning of the contamination areas in the plasma chamber 116 is monitored by the monitoring device 112. For this purpose, certain characteristic optical spectral lines of the reaction products such as CO, C0 ₂ or H ₂ 0 are determined. The intensity of these spectral lines is a measure for the number of impurities contained in the purge gas which is formed by the process gas. The degree of coverage of the contaminated surfaces decreases as a result of the cleaning process. Since the gaseous substances are removed by the process gas, the intensity of the corresponding spectral lines has to drop substantially to zero when the sample inlet device 12 is completely cleaned, since then no further reaction products can then be produced.

It can also be provided according to the invention that the measuring device 14 itself is used to determine the degree of purification of the plasma chamber 116, in that the process gas with gaseous substances contained therein is supplied to the measuring device 14 by opening the sample inlet valve 40 and the measuring device 14 the type and / or amount of these substances. This has the additional advantage that in particular a tip of the needle-shaped element 46 of the sample inlet valve 40 is also cleaned while the sample inlet valve is open.

The cleaning process can be automated by the control unit 106. For this purpose, when the cleaning process is started, the sample inlet valve 40 is closed and the sample supply via the fluid control 100 is interrupted. The valve 74 is opened and the flow space 68 is flushed with process gas.

Furthermore, the cavity 31 is flushed with process gas via the opening of the line 96. By applying the high-frequency AC voltage, the plasma is generated in the process gas in the plasma chamber 116. The monitoring device 112 monitors the cleaning process. When cleaning success is achieved, the valves 72 and 79 are closed again, the fluid control switches off the process gas supply. The interior of the plasma chamber 116 is evacuated from the process gas by the pump or pumps.

The fluid control 100 then switches over to sample gas supply, which reaches the access space 54 via the line 96 and the cavity 31. The sample inlet valve 40 is opened so that the sample can be fed to the measuring device 14 via the sample inlet 18.

It is provided that the high-frequency power supply to the plasma chamber 116 is interrupted during the sample supply to the measuring device.

The sample inlet device according to the invention can also be used according to the invention as a sample enrichment stage. This is done by controlling the temperature of the inner electrode 82 by supplying and removing a heat transfer medium. This heat transfer medium can be, for example, a gas or an oil such as silicone oil.

By correspondingly lowering the temperature, when sample gas is fed via the lines 104 and 96 into the cavity 31, this can condense on the inner electrode 82 and thus accumulate on the latter. By increasing the temperature above a critical value, a desorption of the condensed sample gas and thus impoverishment ¹¹ "is effected. In order to prevent the inner walls of the housing 20 from acting as a condensation trap, they are heated. The sample enrichment is thus limited to the cavity 31 and contamination of the flow space 68 by impurities can be reduced.

In a second variant of an exemplary embodiment according to the invention, the sample inlet device designated 118 in FIG. 2 comprises a plasma chamber 120, which is formed by a cavity resonator 122. A waveguide 124 opens into the cavity resonator 122, by means of which microwave power can be coupled into the cavity resonator 122 from a microwave generator (not shown in FIG. 2). At a mouth 126 of the waveguide 124 into the cavity resonator 122, a protective window 128 is arranged, which serves to prevent the penetration of fluid into the waveguide 124.

The housing 20 has a see-through window 131, so that an interior of the cavity resonator 122 can be monitored optically, for example by means of the monitoring device 112.

An enrichment element 130, which serves for sample enrichment, is arranged in the cavity resonator 122. This element is basically of the same construction as described above and also works accordingly, although in this variant, since the AC power is coupled into the process gas via microwave power, there is of course no internal electrode as in the first exemplary embodiment. With regard to the cleaning method, the second variant of an exemplary embodiment basically works exactly as described above. The difference essentially consists in that the alternating current power for forming the plasma is not coupled capacitively, as in the exemplary embodiment according to FIG. 1, but in the cavity resonator 122 by means of microwave power.

In a third variant of an embodiment of the measuring device according to the invention, which is shown in FIG. 3, the sample inlet device 132 comprises an induction coil 134 which is arranged in the housing walls of a plasma chamber 136 and is coaxial to the axis 32. The induction coil 134 has electrical connections 138 and 140. The plasma in the plasma chamber 136 is generated inductively by high-frequency heating by the induction coil. The induction coil 134 is arranged in a dielectric medium and, for example, encapsulated therein. It is also provided according to the invention that the device also has an electromagnetic shield (not shown in the figure).

Otherwise, the sample inlet device is constructed and functions as described above.

In a fourth variant of an embodiment, which is shown in FIG. 4, a sample inlet device 142 comprises a housing 144 in which a cavity 146 is formed. The housing 144 has a cover 148 made of an electrically insulating material and in particular made of glass. An inner electrode 150 is held in the cover 148 and extends into the cavity 146.

The housing 144 is seated on a housing carrier 152. The measuring device 14 is seated at a lower end of the housing carrier 152 and the sample inlet 18 of the measuring device 14 is connected to the housing carrier 152.

In the housing support 152 sits the sample inlet valve 40, which is otherwise constructed and functions as described above.

A flow space 154 is formed in the housing 144 and continues in a flow space 156 formed in the housing support 152. Connected to this flow space is an access space 158 which is coaxial with the housing axis 32 and is arranged in front of the sample inlet 18 of the measuring device 14. An opening 116, which is coaxial to the axis 32, leads from the access space 158 to the sample inlet 18.

A feed 164 for a liquid sample opens into the access space 158 via a capillary 162. In one variant of an embodiment, a heating element 166 is provided at the mouth, by means of which the liquid sample supplied can be evaporated.

According to the invention, it can also be provided that the housing 144 / or the housing carrier 152 are heated. The heat radiation to the mouth or the heat of the capillary 162 transferred to the mouth by heat conduction can be sufficient to vaporize the liquid sample. The process gas is fed into the flow space 154 and the flow space 156 via feeds 168 and discharged via discharges 170. It can be provided according to the invention that a valve 172, which is particularly controllable, is arranged at an opening of the feed 168 into the flow space 154.

The inner electrode 150 has a process gas supply 174 in the cavity 146. The process gas can reach the access space 158 from the cavity 146 via the cavity 50 of the valve spindle 42.

This variant of an exemplary embodiment according to the invention works as follows:

To supply the sample via the sample inlet 18 to the measuring device 14, the liquid is introduced into the access space 158 via the feed 164 and the capillary 162, the sample inlet valve in particular being closed. There the liquid evaporates so that a gaseous sample is formed. This gaseous sample reaches the cavity 146 through openings 10 in the valve plate 44 and the openings 52 of the valve spindle 42.

After the liquid sample supply has been switched off, the sample inlet valve 40 is opened in order to supply the measuring device with gaseous sample from the cavity 146.

During the cleaning process, the sample supply is switched off via the capillary 162 into the access space 158 and the flow spaces 154 and 156 are flushed with process gas and the Cavity 146 is purged with process gas. A plasma is formed by coupling the power into the process gas and, as already described above, the reactive ions thus formed lead to a chemical conversion of the impurities.

In the variant of an exemplary embodiment shown in FIG. 4, the high-frequency power is capacitively coupled into the process gas. It is also possible to couple the high-frequency power inductively or via microwaves.

In this way, the cavity 146 can be cleaned of impurities such as samples evaporated into the cavity 146.

In principle, this variant of one embodiment works exactly as described above for the other variants.

Claims

PATENT CLAIMS

1. Measuring device comprising a measuring device for in particular gaseous samples and a sample inlet device, through which the samples can be fed to the measuring device, characterized in that the sample inlet device (12) with a cleaning device (116) for cleaning contamination areas (113) of the sample inlet device (12) is provided by means of conversion of impurities in the contamination areas (113) by chemical reaction and that the reaction products can be removed from the sample inlet device (12).

2. Measuring device according to claim 1, characterized in that the cleaning device (116) comprises a means for generating reactive ions and an exposure means for the exposure of the contamination areas with reactive ions, wherein impurities in the contamination areas (113) by chemical reaction with the reactive ions in gaseous substances are convertible.

3. MeßVorric device according to claim 2, characterized in that the measuring device (10) has a pump, by means of which the gaseous substances from the sample inlet device (12) can be removed.

4. Measuring device according to claim 2 or 3, characterized in that a process gas can be guided through the sample inlet device (12).

5. Measuring device according to claim 4, characterized in that the contamination areas (113) can be acted upon by the process gas.

6. Measuring device according to claim 4 or 5, characterized in that the means for generating reactive ions comprises a gas discharge device (116) for performing an electrical gas discharge in the process gas.

7. Measuring device according to one of claims 4 to 6, characterized in that the process gas is oxygen.

8. Measuring device according to one of claims 4 to 6, characterized in that the process gas is air.

9. Measuring device according to one of claims 4 to 6, characterized in that the process gas is an oxygen-free gas.

10. Measuring device according to one of claims 7 to 9, characterized in that fluorine or fluorine compounds can be admixed to the process gas.

11. Measuring device according to one of claims 6 to 10, characterized in that the gas discharge device is designed as a plasma chamber (116), so that a plasma can be formed in the sample inlet device (12), the contamination areas being caused by the plasma in the plasma chamber (116) can be acted upon with reactive ions.

12. Measuring device according to claim 11, characterized in that high-frequency power can be coupled into the process gas to form the plasma in the plasma chamber (116) by the gas discharge device.

13. Measuring device according to claim 11, characterized in that by the gas discharge device (136) high-frequency power can be inductively coupled into the process gas to form the plasma.

14. Measuring device according to claim 11, characterized in that through the gas discharge device (120) microwave power can be coupled into the process gas to form the plasma.

15. Measuring device according to claim 14, characterized in that the plasma chamber (120) is formed by a cavity resonator (122).

16. Measuring device according to claim 14 or 15, characterized in that the microwave power can be coupled into the plasma chamber (120) via a waveguide (124).

17. Measuring device according to one of the preceding claims, characterized in that the sample inlet device (12) is designed as a sample enrichment stage.

18. Measuring device according to claim 17, characterized in that the sample inlet device (118) has an enrichment element (130) which is arranged in the plasma chamber (136) and whose temperature is controllable.

19. Measuring device according to claim 18, characterized in that the enrichment element (130) can be acted upon with a heat transfer medium in order to control its temperature.

20. Measuring device according to claim 18 or 19, characterized in that an inner electrode (82) of the plasma chamber (120) is designed as an enrichment element.

21. Measuring device according to one of claims 11 to 20, characterized in that the walls (22) of the plasma chamber (116) are heatable.

22. Measuring device according to one of the preceding claims, characterized in that the sample inlet device (12) has a monitoring device (112) for monitoring the degree of cleaning of the contamination areas (113) of the sample inlet device (12).

23. Measuring device according to claim 22, characterized in that the sample inlet device (118) has a viewing window (131) for monitoring the degree of cleaning of the contamination areas.

24. Measuring device according to claim 22 or 23, characterized in that the monitoring device (112) is designed and arranged such that the degree of cleaning can be determined by observing the optical emission spectrum and in particular by observing individual characteristic optical emission lines of the reaction products of the chemical reaction or possible reaction products .

25. Measuring device according to one of claims 22 to 24, characterized in that the measuring device (14) is itself used as a monitoring device.

26. Measuring device according to one of the preceding claims, characterized in that ^' the sample inlet device (12) at a sample inlet (18) in the measuring device (14) has a sample inlet valve (40) whose closing pressure is adjustable.

27. Measuring device according to claim 26, characterized in that the closing pressure is infinitely adjustable.

28. Measuring device according to claim 26 or 27, characterized in that the closing pressure is adjustable by setting a spring preload of a valve spring (62).

29. Measuring device according to one of claims 26 to 28, characterized in that an adjusting means (58) for the closing pressure is arranged so that the closing pressure is adjustable without dismantling the sample inlet valve (40).

30. Measuring device according to claim 29, characterized in that the adjusting means comprises an adjusting element (58) which in a valve plate (44) facing away from the thread (56) is rotatable and through which the valve spring can be acted upon to adjust the spring preload.

31. Measuring device according to one of claims 26 to 30, characterized in that the sample inlet valve (40) can be actuated electromagnetically.

32. Measuring device according to one of claims 26 to 31, characterized in that the sample inlet (18) with respect to a plasma space (114) in which the plasma is formed is arranged so that molecules and reactive ions from the plasma space (114) in can get close to the sample inlet (18).

33. Measuring device according to one of the preceding claims, characterized in that the measuring device (10) has a control unit (106) through which the sample supply to the measuring device (14) and the cleaning of the contamination areas (113) of the sample inlet device (12) can be controlled.

34. Measuring device according to claim 33, characterized in that the sample supply to the measuring device (14) can be controlled by the control unit (106) depending on the degree of cleaning of the sample inlet device (12).

35. Measuring device according to one of the preceding claims, characterized in that the sample of the sample inlet device (12) can be supplied as a gaseous sample.

36. Measuring device according to one of claims 1 to 34, characterized in that the sample of the sample inlet device (142) can be supplied as a liquid sample.

37. Measuring device according to claim 36, characterized in that the feed comprises a capillary (162).

38. Measuring device according to one of claims 36 or 37, characterized in that the sample inlet device (142) comprises a heating element (166) for evaporating the liquid sample in order to make the evaporated sample feedable to the measuring device (14).

39. Measuring device according to one of the preceding claims, characterized in that the measuring device (14) is an on-line analytical measuring device.

40. Measuring device according to one of the preceding claims, characterized in that the measuring device (14) comprises a REMPI device or a JET-REMPI device.

41. A method for cleaning contamination areas of a measuring device, which comprises a measuring device for in particular gaseous samples, characterized in that the contamination areas are acted upon by reactive ions which convert impurities into gaseous substances by chemical reaction and that the reaction products are removed.

42. The method according to claim 41, characterized in that the contamination areas are flushed with a process gas.

43. The method according to claim 41 or 42, characterized in that the reactive ions are generated by electrical gas discharge.

44. The method according to claim 43, characterized in that the reactive ions are generated by electrical gas discharge in the process gas with which the contamination areas are applied.

45. The method according to any one of claims 42 to 44, characterized in that oxygen is used as the process gas.

46. The method according to any one of claims 42 to 44, characterized in that air is used as the process gas.

47. The method according to any one of claims 42 to 44, characterized in that an oxygen-free gas is used as the process gas.

48. The method according to any one of claims 42 to 47, characterized in that fluorine is added to the process gas.

49. The method according to any one of claims 41 to 48, characterized in that the contamination areas of a sample inlet device of the measuring device, by means of which the samples are fed to the measuring device, are acted upon by reactive ions.

50. The method according to claim 49, characterized in that the reactive ions essentially act on the inner surfaces of the sample inlet device, which are contaminable by impurities.

51. The method according to any one of claims 44 to 50, characterized in that a plasma is formed in the sample inlet device in a plasma space for generating the reactive ions, wherein the plasma essentially acts on the contamination areas of the sample inlet device.

52. The method according to claim 51, characterized in that the sample inlet device comprises a plasma chamber, the plasma being formed in an interior of the plasma chamber which essentially comprises the contamination areas.

53. The method according to claim 51 or 52, characterized in that the power for forming the plasma of the sample inlet device is supplied as an AC power.

54. The method according to claim 53, characterized in that in the process gas for plasma formation electrical high-frequency power is coupled capacitively or via a transformer.

55. The method according to claim 53, characterized in that high-frequency electrical power is inductively coupled into the process gas.

56. The method according to claim 53, characterized in that microwave power is coupled into the process gas to form the plasma, the plasma chamber being designed as a cavity resonator.

57. The method according to claim 54, characterized in that the plasma is generated in a plasma space between an inner electrode and inner surfaces of the plasma chamber.

58. The method according to any one of claims 41 to 57, characterized in that a degree of cleaning of the contamination areas is monitored or checked.

59. The method according to claim 58, characterized in that the monitoring of the degree of cleaning is carried out as real-time monitoring.

60. The method according to claim 58 or 59, characterized in that the optical emission spectrum and in particular characteristic optical emission lines of reaction products or possible reaction products are monitored.

61. The method according to any one of claims 58 to 60, characterized in that the measuring device itself is used for monitoring or checking the degree of cleaning of the contamination areas.

62. The method according to any one of claims 41 to 61, characterized in that the cleaning process of the contamination areas is time-controlled.

63. The method according to any one of claims 49 to 62, characterized in that the sample feed to the sample inlet device is blocked while the cleaning process is being carried out.

64. The method according to any one of claims 49 to 63, characterized in that process gas is passed through the sample inlet device during the execution of the cleaning process and this process gas flow is blocked when the cleaning process is ended.

65. The method according to claim 44, characterized in that the process gas is pumped out of the sample inlet device at the end of the cleaning process.

66. The method according to any one of claims 62 to 65, characterized in that the generation of the reactive ions is controlled in time.

67. The method according to claim 66, characterized in that at the end of the cleaning process, the coupling of power into the process gas for generating reactive ions is switched off.

68. The method according to any one of claims 58 to 67, characterized in that a termination of the cleaning process is controlled by the degree of cleaning of the contamination areas, which is monitored.

69. The method according to any one of claims 49 to 68, characterized in that a sample inlet of the sample inlet device into the measuring device is timed by a sample inlet valve.

70. The method according to claim 69, characterized in that during the cleaning process of the contamination areas of the sample inlet into the measuring device is closed by the sample inlet valve.

71. The method according to claim 69 or 70, characterized in that the closing pressure of the sample inlet valve is adjustable and in particular continuously adjustable.

72. The method according to any one of claims 69 to 71, characterized in that the sample inlet is arranged with respect to the plasma space so that molecules and reactive ions formed in the plasma can get close to the sample inlet.

73. The method according to any one of claims 49 to 72, characterized in that the sample inlet device is designed as a sample enrichment stage.

74. The method according to any one of claims 42 to 73, characterized in that an enrichment element, which is arranged in the plasma space, is acted upon by a heat transfer medium in order to control the temperature of the enrichment element, so that samples of the enrichment element depending on the temperature can condense or desorb.

75. The method according to claim 74, characterized in that with capacitive coupling of high-frequency power into the process gas for plasma formation, the enrichment element is formed by the inner electrode of the plasma chamber.

76. The method according to any one of claims 51 to 75, characterized in that the plasma chamber and in particular walls of the plasma chamber are heated.

77. The method according to any one of claims 49 to 76, characterized in that the sample which is fed to the sample inlet device is gaseous.

78. The method according to any one of claims 49 to 77, characterized in that the sample which is fed to the sample inlet device is liquid.

79. The method according to claim 78, that the liquid sample is supplied in a capillary.

80. The method according to claim 78 or 79, characterized in that the liquid is evaporated in the sample inlet device.

81. The method according to any one of claims 41 to 80, characterized in that the measuring device is an on-line analytical measuring device.

82. The method according to any one of claims 41 to 81, characterized in that the measuring device comprises a REMPI device or a JET-REMPI device.

83. Sample inlet valve, which is arranged in a sample inlet device and serves to close a sample inlet of the sample inlet device into a measuring device for the samples, characterized in that a closing pressure of the sample inlet valve (60) is adjustable.

84. Sample inlet valve according to claim 83, characterized in that the closing pressure is infinitely adjustable.

85. Sample inlet valve according to claim 83 or 84, characterized in that the sample inlet valve (40) has an adjusting means (58) for adjusting the closing pressure, which is arranged such that a dismantling of the sample inlet valve (40) is not necessary for adjusting the closing pressure.

86. Sample inlet valve according to claim 85, characterized in that the adjusting means (58) is arranged facing away from a valve plate (44) of the sample inlet valve (40).

87. Sample inlet valve according to claim 86, characterized in that the adjusting means (58) is formed by an adjusting element which is rotatable in a thread (56) and through which a valve spring (62) can be acted upon for adjusting a valve spring preload.

88. Sample inlet valve according to one of claims 83 to 87, characterized in that the sample inlet valve (40) can be actuated electromagnetically.

89. Sample inlet valve according to one of claims 83 to 88, characterized by its use in a measuring device according to one of claims 1 to 25, 32 to 40.

90. Measuring device, comprising a measuring device in which a divergent carrier gas jet can be generated by expanding a carrier gas containing sample molecules through a nozzle into a vacuum, the sample molecules in one Ionization range of the carrier gas jet are selectively ionizable to sample molecule ions by absorption of photons and the sample molecules can be drawn into a mass spectrometer by means of an electric pulling field and can be detected in the mass spectrometer, and a sample inlet device through which a sample can be fed to the measuring device, characterized in that the sample of the Sample inlet device (142) can be supplied as a liquid sample.

91. Measuring device according to claim 90, characterized in that the sample can be supplied by means of a capillary (162).

92. Measuring device according to one of claims 90 or 91, characterized in that the sample inlet device (142) comprises a heating element (166) for evaporating the liquid sample in order to make the liquid sample feedable to the measuring device (14).

93. Measuring device according to one of claims 90 to 92, characterized in that the sample inlet device (142) at a sample inlet (160) in the measuring device (14) has a sample inlet valve (40) and that the liquid sample of the sample inlet device (142) when the Sample inlet valve (40) can be supplied.

94. A method for the detection of sample molecules in a carrier gas, in which the carrier gas with the sample molecules is fed to a measuring device by means of a sample inlet device, by means of expansion of the carrier gas through a nozzle into a vacuum, a divergent carrier gas jet is generated, the sample molecules are ionized selectively to sample molecule ions in an ionization region of the carrier gas jet by absorption of photons, and the sample molecule ions are drawn through an electric pulling field into a mass spectrometer and detected in the mass spectrometer, characterized in that the sample is fed to the sample inlet device as a liquid sample.

95. The method according to claim 94, characterized in that the liquid sample is supplied by means of a capillary.

96. The method according to any one of claims 94 or 95, characterized in that the liquid sample is evaporated in the sample inlet device.

97. The method according to any one of claims 94 to 96, characterized in that a sample inlet of the sample inlet device into the measuring device is timed by a sample inlet valve and that the liquid sample is supplied to the sample inlet device when the sample inlet valve is closed.