EP2986970A1

EP2986970A1 - Method and device for detecting and identifying not easily volatilized substances in a gas phase by means of surface-enhanced vibration spectroscopy

Info

Publication number: EP2986970A1
Application number: EP14718398.2A
Authority: EP
Inventors: Hainer WACKERBARTH; Lars GUNDRUM; Bert UNGETHÜM; Wolf MÜNCHMEYER; Andreas Walte
Original assignee: Airsense Analytics GmbH; Laser Laboratorium Goettingen eV
Current assignee: Airsense Analytics GmbH; Laser Laboratorium Goettingen eV
Priority date: 2013-04-18
Filing date: 2014-04-16
Publication date: 2016-02-24
Also published as: WO2014170400A1; US20160041101A1; CN105393105A; DE102013103954A1

Abstract

The invention relates to the identifying of not easily volatilized substances, in particular hazardous materials, in a gas phase. A measurement cell (2) and a gas supply device (14) connected to the measurement cell (2) are heated and a plasmonic surface (1) arranged in the measurement cell (2) is temperature-controlled such that the plasmonic surface (1) has a lower temperature than the measurement cell (2) and the gas supply device (14). The gas phase is guided through the gas supply device (14) into the measurement cell (2) in such a manner that the gas phase reaches the temperature-controlled plasmonic surface (1). Substances adsorbed from the gas phase on the plasmonic surface (1) are analyzed by an optical process. Surface-enhanced Raman spectroscopy or surface-enhanced infrared spectroscopy can be used as the optical process. Selectivity can be increased by combining both methods. Selectivity can be additionally increased by using a gas detector, preferably an ion-mobility spectrometer, along with one or both optical processes, and thus the false alarm rate reduced without loss of time.

Description

METHOD AND DEVICE FOR DETECTING AND IDENTIFYING GAS-PHASE FLUID SUBSTANCES BY MEANS OF SURFACE-REINFORCED VIBRATION SPECTROSCOPY

Description

The invention relates to a method for the identification of highly volatile substances present in a gaseous phase, in particular hazardous substances. The low-volatility substances can already be present in the gas phase or can only be converted into the gas phase.

Such methods and the associated devices are used for the detection and detection of chemical substances or compounds, in particular of explosive and / or harmful substances such as toxic industrial chemicals, warfare agents or drugs.

The detection of explosive and / or very toxic chemical compounds requires measurement methods with detection limits in the ppt to ppb range (ppb = parts per billion, with 1 trillion = 1 ^* 10 ⁹ ), especially if these substances, such as plastic explosive, a very low vapor pressure exhibit. Frequently, spectrometers are used to detect and detect these chemical compounds.

If there is enough material of the substance under investigation, methods such as FTIR (Fourier Transform InfraRed Spectroscopy) or Raman spectroscopy are used for identification. The disadvantage is that in FTIR the material must be touched for analysis and transported to an analysis surface (ATR window). For some explosives, such. As peroxides, it can be triggered an explosion.

In Raman spectroscopy, the sample is irradiated with an intense laser and the reflected light is analyzed. The disadvantage is that, although the sample is no more must be touched, the intensity of the laser light may be sufficient to trigger an explosion. In Raman spectroscopy, in addition, the fluorescence of traces of fluorescent compounds can mask the Raman spectrum.

Many chemicals as well as many explosives can also be detected via the gas phase, since they have a sufficient vapor pressure.

As a method for the analysis of small amounts of a variety of substances, the surface-enhanced Raman spectroscopy (also called SERS = Surface Enhanced Raman Spectroscopy) and the surface-enhanced infrared absorption spectroscopy (also known as SEIRA = Surface Enhanced Infrared Absorption Spectroscopy called) known. Both methods are variants of the so-called Surface-Enhanced Vibrational Spectroscopy (SEVS).

In both methods, so-called plasmonic substrates or surfaces are used, which are substrates or surfaces with a surface structure that promotes the excitation of localized plasmon. This leads to a gain in one case of Raman scattering, in the other case of infrared absorption. By these plasmonic substrates or surfaces, a detection limit is reached, which is lower by several orders of magnitude than that of pure Raman spectroscopy or infrared absorption spectroscopy. In the application of plasmonic surfaces, liquids or liquid droplets are typically applied to the surface. The use of plasmonic surfaces for the analysis of gaseous substances on the other hand is considered difficult because gaseous substances are not or only in small quantities and unevenly attached to the substrate, so that a reliable detection is difficult despite the high amplification. One known approach to solving this problem is to produce an increased effective plasmonically active surface, e.g. B. by a plurality of capillaries is used with plasmonically active surfaces. Another approach is to cool the substrate. However, this has the disadvantage that this particular to a strong Adsorption of moisture on the substrate leads, which makes it difficult to attach the substances to be measured and thus also their detection.

Further known methods for analyzing the gas phase are ion mobility spectrometry (IMS), which has also been referred to as plasma chromatography, and also other spectrometric methods, in particular mass spectrometry.

The IMS, in contrast to other spectrometric methods, such. As the mass spectrometry, no vacuum pumps for generating a vacuum needed. As a result, IMSs are small and inexpensive compared to mass spectrometers in their construction. Compared to a mass spectrometer, the lower resolution of an IMS is disadvantageous because the false alarm rate can be higher due to the poorer resolution.

A general overview of IMS and its applications can be found, for example, in: G.A. Eiceman and Z. Karpas "Ion Mobility Spectrometry" (2nd Edition, CRC, Boca Raton, 2005).

Many hazardous substances such. As the RDX-based explosives have only low vapor pressures, so that such hazardous substances, so far as they are in a gas phase, already tend to adsorb on the walls of gas guide channels, so that their transport is difficult in a measuring cell.

US Pat. No. 6,947,132 B1 discloses a thermoelectrically cooled SERS sensor system for detecting volatile organic compounds. The system includes a desorber containing an adsorbate to pre-concentrate a gas mixture. After the preconcentration, the desorber is heated to release the gas mixture into a measuring cell. In the measuring cell, a SERS structure is arranged, which is cooled by a thermoelectric cooler. The gas mixture reaches the cooled SERS structure. Choosing the temperature of the condenser allows certain analytes to condense on the SERS structure because of different analytes condense at different temperatures. Mentioned are temperatures of 15 ° C, condensed at the benzene, of 9 ° C, condensed at the toluene and from -5 ° C, condenses in the MTBE. The known system further comprises a laser and a spectrometer for performing a SERS method.

It is known from US 2007/0140900 A1 to cool a nano-structured surface for a SERS measurement with a thermoelectric cooler to a temperature in the range from 0 ° C. to 20 ° C. at which trace chemicals of interest are adsorbed on the surface.

It is known from US 2012/0133932 A1 to use a thermoelectric element on the one hand for cooling an SERS substrate in order to promote the condensation and adsorption of a selected analyte and on the other hand for heating the SERS substrate in order to maintain its surface for a subsequent one Renew analysis.

US 6,610,977 B2 describes a security system in which an ion mobility spectrometry (IMS) sensor is combined with a SERS sensor as the second sensor. Such a combination is also apparent from US 2009/0238723 A1. The SERS sensor connected downstream of the IMS sensor records spectra of ions generated in the IMS sensor instead of spectra of the starting substances.

It is the object of the invention to detect hazardous substances that are present in a gas phase or that can be converted into the gas phase in low concentrations and to identify them with high reliability.

This object is achieved by a method having the features of independent patent claim 1 and a device having the features of independent claim 19. Preferred embodiments of the method and apparatus are defined in the dependent claims. A concrete embodiment of the method according to the invention comprises the steps:

Heating a measuring cell and a gas supply device connected to the measuring cell,

- Temperieren a arranged in the measuring cell plasmonic surface such that the plasmonic surface has a lower temperature than the measuring cell and the gas supply means,

Feeding a gas phase into the measuring cell such that the gas phase reaches the tempered plasmonic surface,

- Application of a SEVS method, comprising irradiation of the plasmonic surface with electromagnetic radiation, for the detection of hazardous substances contained in the gas phase.

The tempering may require active cooling of the plasmonic surface. The detection of the hazardous substances contained in the gas phase takes place on the basis of adsorbed from the gas phase on the cooler surface portions of the substance. In addition to the gas supply device, the heating can detect the entire gas supply system connected to the measuring cell. It prevents the adsorption of substances on the inner surfaces of the measuring cell and the gas supply system. This prevents contamination of the inner walls by adsorbed substances. This prevents in particular that such substances are carried off into a subsequent measurement. In addition, the detection sensitivity of the method according to the invention is optimized because the substances of interest can adsorb exclusively on the plasmonic surface.

In the case of SERS as an analysis method, the electromagnetic radiation used is preferably laser light. Both SERS and SEIRA use wavelengths outside the visible spectral range commonly used for SERS and SEIRA, respectively. These are known to the person skilled in the art as well as in the case of SEIRA suitable sources of electromagnetic radiation. The safety of the measurement can be increased if the method according to the invention is combined with an independent further measuring method. A combination of SERS and SEIRA analysis can be carried out in the measuring cell.

Furthermore, a combination of the SEVS analysis with a non-optical gas detection method can advantageously be carried out.

In this case, it is generally advantageous if the gas phase is first conducted into the SEVS measuring cell and is first conducted into the further analysis modules in a subsequent step. This advantage results from the fact that the substances to be detected are generally not chemically or physically changed in the SEVS measuring cell.

As a downstream analysis method, the IMS is advantageous. In particular, in the analysis of mixtures of substances may be the case that a separation of the spectra belonging to individual substances is only unreliable and it is unclear from what number in the sample of existing substances, the composite spectrum is generated. By contrast, IMS reliably separates the mixtures into individual fractions so that the number of substances contained in the sample can be reliably determined from the I MS data. This knowledge can then be advantageously incorporated in the chemometric analysis of the SEVS data.

Particularly in the case of the IMS, it is advantageous to pass the gas phase into the SEVS measuring cell, since ionization of the sample substance takes place in the IMS, so that in the reverse order, ie when the gas phase is first introduced into the IMS device and then into the SEVS cell, in the latter only ions of the starting substance and optionally ionized derivatives of the starting substance can be detected. The set of measured values is fed to an evaluation unit. The SEVS spectra are advantageously analyzed using methods of chemometrics. If the SEVS measuring method is combined with other measuring methods, the data is evaluated as a whole, ie when evaluating the measurement results of a method, the knowledge obtained from the evaluation of the other measuring method (s) is taken into account, or but alternatively there is first a fusion of the data and then a uniform chemometric analysis of the data set obtained during the fusion or in the evaluation a combination of mutual analysis of measurement results and a data fusion of data of several measurement methods is performed.

In this case, the plasmonic surface can be heated successively, and analysis data of the gas detector and optionally also of the SEVS method can be assigned to the respective temperature of the plasmonic surface. In this way, the analysis data of the gas detector and also of the SEVS method can be assigned to individual substances which differ by their vapor pressure or their boiling point.

With the method according to the invention, substances with vapor pressures at 30 ° C, which are less than or equal to 6,46 Pa, d. i. the vapor pressure of triacetontriperoxide (TATP) can be detected.

The Applicant Laser-Laboratorium Göttingen carried out measurements with TATP. For this purpose, a container with TATP was heated in the gas phase to 45 ° C, air was saturated in this way with TATP, this air was fed to a measuring cell. In the measuring cell, a SERS substrate with the plasmonic surface was set to a fixed temperature. Values of 25 ° C, 20 ° C, 15 ° C, 10 ° C and 5 ° C were used within the series of measurements.

The measurement results show clear SERS intensity signals even at 25 C. At a temperature of 5 ° C, the signal level is about a factor of about. 2.5 enlarged. The signal quality, determined from edge steepness and half width of the Raman Bands, as an indicator of the signal-to-noise ratio is even increased by a factor of about 2.8.

From preliminary experiments it was known that further cooling down to freezing point or below leads to adsorption of moisture on the SERS substrate.

It is known from common work of the Applicants that effective suppression of adsorption in the gas delivery system also applies to less volatile substances such as e.g. TNT and / or RDX-based explosives are achieved when gas supply system and measuring cell are heated to temperatures of 160 ° C and higher. It should be noted that the preferred temperatures to use depending on the exact measurement task. Thus, for hazardous substances such as TATP and EDN (ethylene glycol dinitrate = nitroglycol) with the class of substances of comparatively high vapor pressures to be detected according to the invention, less heating will be sufficient, whereas in particular for RDX-based explosives and for PETN (other names: nitropenta, pentritol, pentaerythrityl tetranitrate) comparatively higher temperatures are needed. For all substances, a higher temperature reduces the tendency to be adsorbed in the gas delivery system. Temperature limits may result, for example, from the ignition temperature and / or decomposition temperature of the substances to be detected. Typically, the gas supply system and the measuring cell are heated to temperatures in the range of 150 C to 200 C.

In Applicant's work, it has also been demonstrated that when a SERS surface is cooled to 80 ° C., reliably evaluable TNT spectra are obtained. Since TNT has a lower vapor pressure than RDX, it can be assumed that cooling to 80 ° C will suffice even for RDX detection.

That cooling of the plasmonic surface to such comparatively high temperatures above room temperature is sufficient, proves in the comparatively high temperature to which the gas supply system and the measuring cell are to be heated, as advantageous because it limits the amount of heat to be dissipated.

Preferably, however, the plasmonic surface is more strongly cooled, for example up to 5 ° C.

Unless it can be excluded that the gas phase contains moisture, cooling should only take place at a temperature above the freezing point of water. There may also be a stepwise cooling of the plasmonic surface with analysis of the adsorbed substances in each step.

If a liquid or solid substance to be examined for whether it contains a hazardous substance that passes only to a very limited extent in a surrounding gas phase, z. B. because the hazardous substance has only a very low vapor pressure and / or because in the substance to be examined only little hazardous substance is contained or because there are restrictions on the time in which can be enriched in a gas volume of the hazardous substance, so the invention, that a Thermodesorptions- method or a corresponding device is applied.

From the work of the applicant Airsense Analytics GmbH it is known that for the thermal desorption of RDX-based hazardous substances preferably temperatures of 200 ° C and above are to be used. Also, the temperature at which the desorption occurs can be gradually increased, with analysis of the substances adsorbed on the plasmonic surface in each step.

It is advantageous in the application of the new method for the identification of gases that the substances can be enriched without contact on a suitable surface by sampling from the gas phase. This surface can z. B. by means of a Peltier element or a Stirling cooler (pulse tube cooler) to be cooled. Advantageous developments of the invention will become apparent from the claims, the description and the drawings. The advantages of features and of combinations of several features mentioned in the description are merely exemplary and can take effect alternatively or cumulatively, without the advantages having to be achieved by embodiments according to the invention. Without altering the subject matter of the appended claims, as regards the disclosure of the original application documents and the patent, the following applies: Further features can be found in the drawings. The combination of features of different embodiments of the invention or of features of different claims is also possible deviating from the chosen relationships of the claims and is hereby stimulated. This also applies to those features which are shown in separate drawings or are mentioned in their description. These features can also be combined with features of different claims. Likewise, in the claims listed features for further embodiments of the invention can be omitted.

The features mentioned in the patent claims and the description are to be understood in terms of their number so that exactly this number or a larger number than the genan nte Anzah l is present, oh ne that an explicit use of the adverb "at least" required. For example, when talking about an element, it should be understood that there is exactly one element, two elements or more elements. These features may be supplemented by other features or be the only characteristics that make up the product in question.

The reference numerals contained in the claims do not limit the scope of the protected by the claims objects. They only serve the purpose of making the claims easier to understand.

The invention will be explained and described in more detail below with reference to the accompanying drawings. Fig. 1 shows the basic structure of an embodiment of the device according to the invention.

FIG. 2 is a longitudinal section through a measuring cell and a gas guiding system connected to the measuring cell of a further embodiment of the device according to the invention; FIG. and

FIG. 3 is a front view of the measuring cell and the gas guiding system of the embodiment of the device according to the invention according to FIG. 2. FIG.

A sample, if present in gaseous form, is sucked directly into a measuring cell 2 of the device according to FIG. Otherwise, it is given by means of an absorbent fleece in a thermal desorber 12 or thermal desorber. In the thermal desorber 12, the substances contained in the sample are heated and desorbed, with desorption temperatures of> 200 ° C. being produced in the case of RDX-based explosives. From the thermal desorber 12, the gas phase, which contains the desorbed sample in air, which is sucked in through an inlet 3, is then forwarded to a plasmonic surface 1 arranged in the measuring cell 2. The suction is controlled by means of a gas pump 4.

The measuring cell 2 and connected to the measuring cell 2 Gaszuführungs- and gas discharge devices 14, 15 are heated by in Fig. 1 only schematically indicated heating elements 8. For the airborne transport of heavy explosives such as RDX, the heating is carried out at temperatures of about 1 60 ° C and more, to prevent the deposition of the molecules le ellen walls of the measuring cell 2 and the gas supply and gas discharge devices 14, 1 5. In order to minimize the adsorption of explosives and the like to any inner walls, small volumes are preferred and all parts are made heatable.

The plasmonic surface 1 is a specially structured surface of a plasmonic substrate, with which the laser light 6 interacts, so that it becomes a Reinforcement of a signal excited by the laser light 6 comes. The plasmonic substrate is cooled by a Peltier element 23 provided as a cooling element 7. Thus, a temperature difference is generated, whereby the molecules, which come into contact with the plasmonic surface 1, are deposited. For example, the plasmonic surface 1 has a temperature which is 80K lower than the measuring cell 2. The molecules deposited on the plasmonic substrate are detected by means of the laser light 6 by an SEVS method, for example by SERS or SEIRA spectroscopy, or by both SERS and SEIRA spectroscopy. For this purpose, a Raman spectrometer 9 and an IR spectrometer 10 are provided. The laser light 6 is irradiated by the respective spectrometer 9 or 1 0 via a window 5 in the measuring cell 2.

In the apparatus according to FIG. 1, the measuring cell 2 is followed by a gas detector 1 1 for carrying out a further analysis method. For this purpose, the molecules are desorbed from the plasmonic surface 1 by heating the plasmonic substrate. The heating can be done by switching off the cooling element 7 and / or the use of additional, not shown here, heating elements for the plasmonic substrate.

The gas pump 4 sucks in all the time. If the gas detector 1 1 is coupled, can be dispensed with an external gas pump usually because the gas detectors have internal gas pump. With an IMS as a gas detector 11, the molecules which do not adsorb on the plasmonic substrate can already be ionized and analyzed. Also during the heating of the plasmonic substrate 1 1 is measured by means of the gas detector. This ensures that two gas packages with different loading reach the Gasdetektorl 1 during a measurement process, once without and once with desorbed substances. FIG. 1 shows the combination SEVS (SERS and / or SEIRA) -IMS.

The thermal desorber 12 can give a start signal, whereby the SERS spectrometer, as a combination of the Raman spectrometer 9 and the plasmonic surface 1, and the SEIRA spectrometer, as a combination of the IR spectrometer 10 and the plasmonic surface 1, and the gas detector 1 1, z. As an IMS, begin to detect. Data is read from the SERS spectrometer, the SEIRA spectrometer and the IMS and forwarded to a computer 13 with an evaluation software. The data are processed there and analyzed using mathematical chemometric methods. All data is analyzed and weighted. Before and during the heating of the plasmonic surface I, the signals of the I MS or SERS or SEI RA spectrometer are recorded. The data fusion takes place on the computer 13, the measurement results being compared during the enrichment and during the heating. The comparison helps in the interpretation of the data as z. For example, volatile compounds can not accumulate on the substrate, while sparingly volatile compounds can accumulate on the substrate. In addition, the results of the individual optical detectors should be compared with the results of the gas detector 1 1. The quality of the result of the spectra compared to database spectra of each individual spectroscope or spectrometer is to be determined. Subsequently, the results of the individual detectors are weighted in order to arrive at an overall result. Depending on the identification, exclusion criteria should be defined. If z. For example, if a substance can only be identified as "A or B" via SERS, but the IMS reacts differently to the substances A and B, an exclusion criterion for the result "substance A" or "substance B" can be defined via additional weight factors. These criteria are to be determined experimentally.

The result of the evaluation is output according to the situation. When inspecting the airport, an alarm signal can be triggered when detecting explosives. For use with police or fire brigade, the name of the substance or its composition can be given.

The device according to FIG. 1 has a modular structure, ie the thermal desorber 12, the spectrometers 9 and 10, the measuring cell 2 and the gas detector 11 are individual modules. The Raman spectrometer 9 can, for example, only with the thermal Desorber 12 are operated. The thermal desorber 12 can be omitted if you want to integrate the device in locks or air conditioners. This means the modularity allows a high degree of flexibility to adapt the device to different conditions.

Specifically, with the device according to FIG. 1, an identification of volatile substances present in a gaseous phase, in particular of hazardous substances, can be carried out as follows: In the thermal desorber 12, an analyte, eg. As an explosive, desorbed at a temperature greater than or equal to 200 ° C in the otherwise consisting of air gas phase. The gas phase is introduced into the measuring cell 2. In this case, the gas supply device 14 and the measuring cell to temperatures, for. B. between 150 ° C and 200 ° C, which prevent condensation of the analyte. In the measuring cell, the analyte deposits on the plasmonic surface 1 due to the cooling of the plasmonic substrate. For many explosives cooling to about 50 ° C is sufficient. The spectrometers 9 and 10 are then used to record spectra of the analyte. After recording the spectra, the plasmonic substrate is heated to desorb the analyte. The desorbed analyte is sucked in by the gas detector 1 1 and detected there. During the whole time (about 30 s.) The gas detector records 1 1 data (one spectrum per second). As a result, in addition to the data of the gas detector, z. As an I MS, metadata on the dynamics of the release of the analyte in the thermal desorber and the plasmonic surface 1 and its transport generated. Among other things, the metadata describes the time course of the spectra recording by the I MS and records the temperatures of various components as a function of time. As a result, the kinetics of the analysis process, in particular the adsorption and desorption process on the plasmonic surface 1 can be described. The kinetics of these processes are specific for various substances, as determined inter alia by the vapor pressure and the adsorption energy of the analyte at the surfaces of the desorber 12 and the plasmonic substrate. In short, by the temporal change of the signals in the spectra of the gas detector 1 1 in Combined with the recorded temperatures generates additional information that can be used for substance detection.

The measuring cell 2 shown in FIGS. 2 and 3, together with the adjoining gas supply and gas discharge means 14 and 15, has a shaped body 16 made of stainless steel. A gas channel 17 extends through the molded body 16. In the region of the measuring cell 2, the diameter of the gas channel 17 is only a few millimeters in order to keep the volume of the measuring cell 2 small. Parallel to the gas channel 17, the heating elements 8 are provided in the molded body 16, with the adjacent gas supply and gas discharge means 14 and 15 being heated by means of the same. The temperature of the molded body 16 is monitored by a temperature sensor 29. The plasmonic substrate 18 with the plasmonic surface 1 adjoins the gas channel 17 in the measuring cell 2. In this case, the plasmonic substrate 18 is thermally decoupled from the shaped body 16 with the aid of an O-ring 19, and it is held by substrate holder 20 made of thermally insulating polyetherketone. The substrate holders 20 also hold a substrate carrier 21 which adjoins the substrate 18 at the rear and has a channel for a temperature sensor 22 and a Peltier element 23 serving as a cooling element 7 on the rear side of the substrate carrier 21. At the back of the Peltier element 23, a fin heat sink 24 is arranged made of aluminum, the cooling effect is increased by a fan 25. The finned heat sink and the substrate holder 20 are laterally surrounded by thermal insulators 26, which are also formed of polyether ketone. The plasmonic surface 1 across the gas channel 17 across is the Raman spectrometer 9, 9 between the molded body 16 and the Raman spectrometer 9 further thermal insulators 27 made of polyether ketone and an O-ring 28 are provided.

Between the Raman spectrometer 9 and the gas channel 17, a not shown in Fig. 2 window for delimiting the measuring cell may be provided which is then preferably heated as well as the adjacent molded body 1 6, to prevent adsorption of substances to be identified by condensation , List of reference numbers

1 plasmonic surface

2 measuring cell

3 inlet

4 gas pump

5 windows

6 laser light

7 cooling element

8 heating element

9 Raman spectrometer

10 IR spectrometers

1 1 gas detector

12 Thermal desorber

13 computers

14 gas supply device

15 Gas discharge device

16 moldings

17 gas channel

18 Plasmonic substrate

19 O-ring

20 substrate holder

21 substrate carrier

22 temperature sensor

23 Peltier element

24 finned heat sink

25 fans

26 Thermal insulator

27 Thermal insulator

28 O-ring

29 temperature sensor

Claims

P ate n t nsp sk t

1 . Method for the identification of highly volatile substances, in particular hazardous substances, which are present in a gaseous phase, with the following steps:

Heating a measuring cell (2) and a gas supply device (14) connected to the measuring cell (2),

- tempering a in the measuring cell (2) arranged plasmonic surface (1) such that the plasmonic surface (1) has a lower temperature than the measuring cell (2) and the gas supply means (14),

- Passing the gas phase through the gas supply device in the measuring cell (2) such that the gas phase reaches the tempered plasmonic surface (1),

- Applying a SEVS method, which comprises the irradiation of the plasmonic surface (1) with electromagnetic radiation, to identify substances adsorbed from the gas phase at the plasmonic surface (1).

2. The method according to claim 1, characterized in that the measuring cell (2) and the gas supply means (14) are heated to a temperature of at least 160 ° C.

3. The method according to claim 1 or 2, characterized in that the plasmonic surface (1) is cooled to a temperature of less than or equal to 80 ° C.

4. The method according to any one of the preceding claims, characterized in that on the plasmonic surface (1) adsorbed substances are optically analyzed by surface-enhanced Raman spectroscopy.

5. The method according to any one of the preceding claims, characterized in that at the plasmonic surface (1) adsorbed substances are optically analyzed by surface-enhanced infrared spectroscopy.

6. The method according to any one of the preceding claims, characterized in that substances which are passed in the gas phase over the plasmonic surface (1) and are not adsorbed on the plasmonic surface (1) are continued in the gas phase and by means of a gas detector (1 1) are analyzed.

7. The method according to any one of the preceding claims, characterized in that the substances which have been adsorbed on the plasmonic surface (1), after the application of the SEVS process by heating the plasmonic surface (1) are converted back into the gas phase, in the gas phase are continued and analyzed by means of a gas detector (1 1).

8. The method according to claim 7, characterized in that the plasmonic surface (1) is heated successively and that analysis data of the gas detector (1 1) and optionally also the SEVS method of the respective temperature of the plasmonic surface (1) are assigned.

9. The method according to any one of claims 6 to 8, characterized in that the gases are analyzed with an ion mobility spectrometer as a gas detector (1 1).

10. The method according to any one of the preceding claims, characterized in that the plasmonic surface (1) is cleaned after each identification of a poorly volatile substance.

1 1. A method according to claim 10, characterized in that the plasmonic surface (1) is heated for cleaning for a defined period of time to a cleaning temperature.

12. The method according to claim 10 or 1 1, characterized in that the plasmonic surface (1) is exposed for cleaning for a defined period of at least one chemical cleaning compounds.

13. The method according to claim 12, characterized in that the plasmonic surface (1) is exposed for cleaning ozone as the at least one chemical cleaning compound.

14. The method according to claim 12 or 13, characterized in that the plasmonic surface (1) for cleaning after exposure to the at least one chemical cleaning compounds is rinsed with clean air.

15. The method according to any one of the preceding claims, characterized in that the low-volatile substances are transferred with a thermal desorber (12) in the gas phase in order to guide them through the gas supply means in the measuring cell (2).

16. The method according to claim 15, characterized in that the low-volatile substances in the thermal desorber (12) are heated to a desorption temperature of at least 200 C.

17. The method according to any one of the preceding claims, characterized in that results of the SEVS process during the adsorption on the plasmonic surface (1) are compared with results of the SEVS process during heating of the plasmonic surface (1).

18. The method of claim 4 and 5 or any one of claims 6 to 9, characterized in that the various analyzes are evaluated individually and their results are weighted in summary to form an overall result.

19. An apparatus for the identification of highly volatile substances present in a gaseous phase, in particular of hazardous substances, with

a measuring cell (2),

a plasmonic surface (1) arranged in the measuring cell (2),

a gas supply device (14) connected to the measuring cell (2),

at least one connection for a radiation source for irradiation of the plasmonic surface (1) with electromagnetic radiation and an optical detection device for application of a SEVS method,

a heating device for heating the measuring cell (2) and the gas supply device (14) connected thereto,

- A tempering device for controlling the temperature of the plasmonic surface (1) such that the plasmonic surface (1) has a lower temperature than the measuring cell (2) and the gas supply means (14), and

- Gas guiding means for guiding the gas phase through the gas supply means (14) in the measuring cell (2) such that the gas phase reaches the tempered plasmonic surface (1).

20. Device according to claim 19, characterized in that a gas supply system comprising the gas supply device (14) comprises a gas pump (4).

21. Apparatus according to claim 19 or 20, characterized in that the measuring cell (2) has a window (5) which is permeable to the electromagnetic radiation.

22. Device according to one of claims 19 to 21, characterized in that the tempering device has a cooling element (7).

23. Device according to one of claims 19 to 22, characterized in that at the at least one connection, a radiation source for irradiating the plasmonic surface (1) with electromagnetic radiation and an optical detection device for the application of a SEVS method are connected.

24. The device according to claim 23, characterized in that the optical detection device comprises a Raman spectrometer (9) which generates SERS spectra with the plasmonic surface (1).

25. Device according to claim 23 or 24, characterized in that the optical detection device has an infrared spectrometer (10) which generates SEIRA spectra with the plasmonic surface (1).

26. The device according to claim 25, characterized in that the infrared spectrometer (10) is a Fourier transform infrared spectrometer.

27. Device according to one of claims 19 to 26, characterized in that at an output of the measuring cell (2) with the plasmonic surface (1), a gas detector (1 1) is connected.

28. Device according to claim 27, characterized in that the gas detector (1 1) is an ion mobility spectrometer.

29. Device according to one of claims 19 to 28, characterized in that the gas supply means (14) is connected to a thermal desorber (12) for the thermal desorption of samples.