EP1269051A1

EP1269051A1 - Capillary valve that can be pulsed

Info

Publication number: EP1269051A1
Application number: EP01929397A
Authority: EP
Inventors: Egmont Rohwer; Ralf Zimmermann; Ralph Dorfner; Antonius Kettrup
Original assignee: Helmholtz Zentrum Muenchen Deutsches Forschungszentrum fuer Gesundheit und Umwelt GmbH
Current assignee: Helmholtz Zentrum Muenchen Deutsches F
Priority date: 2000-03-25
Filing date: 2001-03-03
Publication date: 2003-01-02
Also published as: JP2003529188A; CA2404338A1; US20030042458A1; WO2001073328A1; US6854712B2; JP4027096B2; DE10014962A1

Abstract

The invention relates to a capillary valve that can be pulsed and to the use thereof. The aim of the invention is to configure the capillary valve in such a way that said valve is suitable for small sample quantities, whereby said valve can be pulsed. The aim of the invention is also to provide a use for said capillary valve. A capillary (1) which has a narrowed section that is embodied as a nozzle (2), a tappet (3) that is situated in said capillary, can be moved therein and, together with the narrowed section of the capillary, can form a sealing as well as a drive for the tappet (8) are provided. The invention also relates to the use of the capillary valve as a gas supply for an ion source or as a gas supply for a UV/fluorescence cell, whereby said valve can be pulsed.

Description

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Pulsable capillary valve

The invention relates to a pulsable capillary valve and its use.

So far, it has been customary to introduce the gas to be analyzed continuously or in a pulsed manner into the ion source of the mass spectrometer. A supply line (e.g. the end of a gas chromatographic capillary) leads into the ion source, which has a closed one (e.g. many CI or EI ion sources for quadrupole or sector field mass spectrometers) or an open design (e.g. B. can have many ion sources for time-of-flight mass spectrometers). In the case of ion sources with a closed design, an area of the ion source is "flooded" with the let-in gas. H. the embedded atoms or molecules sometimes collide with the ion source wall before they are ionized and detected in the mass spectrometer. The open design of many ion sources for TOF mass spectrometers favors the use of atomic or molecular beam techniques. A relatively directed gas jet is guided through the ion source, which ideally has very little interaction with its components.

Effective molecular beams LR are used for time-of-flight mass spectrometry. Zimmermann, HJ Heger, A. Kettrup, U. Boesl, Rapid Communic. Mass Spectrom. 11 (1997) 1095-1, as well as skimmed [R. Tembreull, CH Sin, P. Li, HM Pang, DM Lubman; Anal. Chem. 57 (1985) 1186-1 _ur _d unkimmed LR. Zimmermann, HJ Heger, ER Rohwer, EW Schlag, A. Kettrup, U. Boesl, Proceedings of the 8th Resonance Ionization Spectroscopy Symposium (RIS-96), Penn State College 1996, AIP-Conference Proceeding 388, AIP-Press, Woobury, New York (1997) 119-1 supersonic molecular beams (pulsed or continuous (cw)). Supersonic molecular beam inlet systems allow the analysis gas to be cooled in a vacuum by adiabatic expansion. The disadvantage, however, is that, in conventional systems, the expansion is relative must be far from the ionization site. Since the density of the expansion gas jet (and thus the ion yield for a given ionization volume) decreases with the square of the distance from the expansion nozzle, the sensitivity that can be achieved is limited.

Effective molecular beam inlet systems do not allow cooling of the sample. However, gas inlet systems for effective molecular beams can be constructed in such a way that the gas outlet is led directly into the ionization site via a metallic needle which leads into the center of the ion source. A certain electrical potential is applied to this needle so as not to disturb the extraction fields in the ion source. The needle must be heated to relatively high temperatures in order to prevent condensate of the non-volatile analyte molecules in the needle. Please note that the coldest point should not be at the tip of the needle. The need to heat the needle is problematic because the needle must be electrically insulated from the rest of the structure (e.g. by a ceramic adapter). Electrical insulators are generally also thermal insulators and only allow a very low heat flow, e.g. B. from the heated feed line to the needle. Heating via electrical heating elements or IR radiators is also difficult because the needle protrudes between the extraction plates of the ion source.

The selectivity of resonance ionization with lasers (REMPI) depends on the inlet system used due to the different cooling properties. In addition to the effusive molecular beam inlet system (EMB), which can be used, among other things, for the detection of entire classes of substances, the use of a supersonic molecular beam inlet system (jet) enables highly selective and sometimes even isomer-selective ionization. In the usual supersonic gas nozzles developed for spectroscopic experiments, the utilization of the sample quantity (ie the achievable measuring sensitivity) is not a limiting factor. Furthermore, the existing systems are not limited to the avoidance of memory effects. The development of an improved jet inlet technique is advantageous for the use of REMPI-TOFMS spectrometers for analytical applications. It is important to ensure that the valves are made of inert materials to avoid memory effects or chemical decomposition (catalysis) of the sample molecules. Furthermore, the inlet valves for analytical applications should not have any dead volumes. It is also necessary to be able to heat the valve to temperatures of more than 200 ° C so that even non-volatile compounds from the mass range> 250 amu are accessible. In addition, the jet arrangement is said to lose as little sensitivity as possible to the effusive intake technology. Above all, this can be achieved by using the embedded sample more effectively compared to previous jet arrangements.

This increase happens e.g. B. in that each laser shot hits the largest possible proportion of the sample. Since the excitation volume is determined by the dimensions of the laser beam (an expansion of the laser beam would reduce the REMPI cross section, which, for example, scales with the square of the laser intensity in the case of two-photon ionization), an attempt must be made to achieve the spatial overlap of the molecular beam and the laser beam optimize. This can e.g. can be realized by a pulsed inlet. Boesl and Zimmermann et al. provided, for example, a heatable, pulsed jet valve for analytical applications such as B. for a gas chromatography-REMPI coupling, with minimized dead volume before TU 195 39 589. l

Pepich et al. presented a GC supersonic molecular beam coupling for laser-induced fluorescence spectroscopy (LIF), in which an increase in the duty cycle compared to the effective inlet was achieved through the pulsed inlet and sample compression l-B.V. Pepich, J.B. Callis, D.H. Burns, M. Grouterman, D.A.

Caiman, Anal. Chem. 58 (1986) 2825 All of the pulsable inlet systems described so far have the following disadvantages. Due to their geometric dimensions, they require large samples and surge gas quantities to enable adiabatic cooling. Their geometry does not allow the valve outlet to be placed near the ionization site. Due to their mechanical structure, they have long opening times and therefore form a relatively large gas pulse, which places a heavy load on the vacuum system.

The object of the invention is to design a pulsable capillary valve so that it is suitable for small amounts of sample and to indicate a use for this capillary valve.

This object is achieved by the features of claims 1 and 7. The remaining claims describe advantageous configurations of the valve.

The device has the following particular advantages over the prior art:

Due to the miniaturized structure, the supersonic molecular beam expansion can be placed directly in the ion source. In principle, the highest possible density of the gas pulse 4 is reached in the ionization site. Particular advantages of the ^" gas supply are that the sample is cooled adiabatically and the capillary can be heated well up to its lower end. The device can be designed in such a way that the sample molecules only come into contact with inert materials. By setting suitable parameters (e.g. Cooling of the gas can be achieved by an adiabatic expansion into the vacuum of the mass spectrometer (supersonic molecular beam 4), the gas flow into the ionization chamber generally being similar to that of a continuous effective inlet. The flow rates are typically with effective inlet systems in the range of 0.1-100 ml / min (1 bar). Compared to an effusive capillary inlet, the stronger orientation of the supersonic molecule in the gas inlet according to the invention is larstrahls 4 advantageous, so that a better overlap of laser and gas jet can be achieved (higher sensitivity). The pulsed inlet also enables better utilization of the sample, since the sample pulse length can be correlated with the laser pulse length. As a result, more effective sample utilization increases sensitivity (improved duty cycle) and reduces the load on the vacuum system. Above all, a cooled jet gas jet can be generated with the gas inlet of the type mentioned at the beginning, even at low gas flows (<10 ml / min). As shown in FIG. 5, this succeeds very well, for example, with the capillary constriction version A shown in FIG. 1. Cooling the admitted gas is advantageous for many mass spectrometric questions. The lower internal energy of cooled molecules often has an effect on the degree of fragmentation in the mass spectrum. Cooling is particularly advantageous for the use of resonance ionization with lasers (REMPI). When using a so-called supersonic molecular jet inlet system (jet) to cool the gas jet, REMPI can be used to selectively ionize (sometimes even isomer-selectively) [R. Zimmermann, Ch. Lermer, KW Schramm, A. Kettrup, U. Boesl; Europ. Mass Spectrom. 1 (1995) 341-351]. Since the cooling takes place through the expansion, the sample gas feed line, the capillary 1, the expansion nozzle 2 and the plunger 3 can be heated without the cooling properties deteriorating. This is important for analytical applications. Without sufficient heating, sample components in the supply line or in the gas inlet could condense out. An important application for the invention is the transfer of a chromatographic eluent or a continuous sample gas flow from an online sampling (probe) into a cooled supersonic molecular beam 4. The inlet system described here allows the expansion site to be placed in the ion source of the mass spectrometer. The ions can thus be generated directly or close to under the expansion nozzle 2, which is very advantageous for the detection sensitivity that can be achieved. - 6 -

The invention is explained in more detail below on the basis of exemplary embodiments with the aid of the figures.

The shows

Figure 1 three different nozzle shapes, the

Figure 2 shows a possible arrangement of the pulsed capillary valve in a time-of-flight mass spectrometer. The

Figure 3 shows valves with two different plunger variants, the

Figure 4 examples of a direct and indirect ram drive.

FIG. 5 shows a REMPI spectrum of benzene recorded with a gas inlet according to the invention.

Detailed description of the pictures:

Figure 1

Different shapes A to C of the nozzle 2 for the capillary 1. The nozzle shape A can be produced by melting and careful re-grinding. The nozzle shape B corresponds to a Laval nozzle and can be produced by careful local melting.

Figure 2

Possible arrangement of the gas inlet according to the invention in an ion source of a mass spectrometer with REMPI ionization by means of laser pulses 6. The capillary 1 protrudes between the fume hoods 5 of the ion source. The supersonic molecular beam 4 that is formed is detected as close as possible to the nozzle 2 by the ionization laser pulse 6. The ions formed are accelerated by electrical fields along the trajectory 7 into the mass spectrometer for mass analysis. The supersonic molecular beam 4 falls directly into a vacuum pump. Heating elements are not shown - - elements and the conductive coating / covering of the capillaries 1 and the transition to vacuum with a seal.

Figure 3

Different possible plunger shapes: A) A ball as a plunger prevents possible tilting when opening and closing. The lower dead weight of the ball (lower inertia) enables a high opening frequency. B) Rod-shaped tappets are particularly well suited for melting magnetic or easily magnetizable materials as the drive component of a simple tappet direct drive. Long rod-shaped tappets reduce the risk of tilting, while short tappet shapes allow higher opening frequencies due to their lower mass.

Figure 4

Direct and indirect plunger drive: A) Direct drive of the plunger through a coil surrounding the capillary. The plunger is actively lifted by electromagnetic fields due to the melted-in wire (magnetic or easily magnetizable) and possibly also actively lowered again by reversing the current direction in the electromagnet. B) Indirect tappet drive. Jerky movements of the capillary up or down cause the internal plunger to move due to a momentum transfer or because of its inertia, thus opening the nozzle for the sample gas.

Figure 5

REMPI spectrum of the ^v 6 in the first excited singlet state of benzene recorded with a gas inlet according to the invention, as shown in FIG. 2. Argon with some 10 o / oo parts of benzene (1 bar) was expanded through the capillary 1 and nozzle 2 of the nozzle shapes A (FIG. 1) into the ion source of a REMPI-TOFMS mass spectrometer. The free nozzle diameter was about 65 μm with a capillary diameter of 530 μm. The gas flow rate was about 8 ml / min, the pressure in the ion source was about 5 * 10-4 mbar. The spectrum shows the rotation contour of ^v 6. From the rotation contour, the rotation temperature can be determined determine to approx. 3 K [R. Zimmermann, Ch. Lermer, KW Schramm, A. Kettrup, U. Boesl; Europ. Mass Spectrom. 1 (1995) 341-351]. This excellent rotary cooling shows that the gas inlet according to the invention allows the generation of a pulsed supersonic molecular beam 4 with good properties for analytical applications.

The capillary 1 is used for gas supply and has a typical inner diameter of 0.05-10 mm. At the end, the capillary 1 has a constriction with a typical minimum inside diameter of 1-50% of the inside diameter of the capillary, which is called nozzle 2 in the following. The capillary 1 is connected with the side facing away from the nozzle 2 in a gas-tight manner to a sample gas supply which is led into the mass spectrometer via a vacuum seal. Alternatively, the side of the capillary 1 facing away from the nozzle 2 can also be used, for. B. via an O-ring seal

(e.g. with Kalrez -0 rings) directly from the vacuum chamber of the mass spectrometer. The nozzle 2 is located in or near the ion source of the mass spectrometer and has the following task: it acts as a restrictor and a supersonic molecular beam 4 is formed as a result of the expansion of the gas into a vacuum, the molecules being cooled adiabatically. FIG. 1 shows three different configurations of this nozzle 2. The nozzle shape can either be purely convergent or initially convergent and then divergent

(Laval nozzle).

The embodiments A, B and C are nozzles 2, which are obtained by melting or melting and possible mechanical reworking of one end of the capillaries 1. Capillary 1 and nozzle 2 are made of the same material, for example quartz or glass. In the case of capillaries 1 made of metal or ceramic, if a nozzle 2 of the embodiments A, B or C is used, a piece of quartz or glass must be used to produce the nozzle. The capillary and nozzle can be connected, for example, using mineral glue or a clamping ring. Alternatively, the nozzle 2 can be melted onto the capillary 1 - - the. The production of embodiment A is in EJ Gurthrie, HE Schwartz; J. Chromatograph. Be. 24 (1986) 236-241. The versions B and C can be produced, for example, by carefully melting the capillary 1 made of glass or quartz with a micro-nozzle burner. The smooth inner surface in versions A, B and C is probably responsible for the high quality (ie cooling properties) of the observed molecular beams 4. It is important that the pressure drop, in contrast to effusive inlet techniques via capillary restrictors, occurs essentially via the nozzle 2.

For use in an ion source, the capillary 1 will generally be coated with conductive material from the outside or be guided into the ion source in a thin metal tube. A certain electrical potential can thus be applied via a contact. The use of deactivated steel (Silicosteel ^) is also advantageous for this purpose. Furthermore, a steel capillary 1 can be directly electrically heated (resistance heating). A narrow design of the capillary 1 is advantageous for this application since the withdrawal fields of the ion optics are less disturbed. Furthermore, an electrically conductive coating / covering of the capillary 1 is necessary in order to adapt the electrical potential of the capillary 1 to the potential profile in the ion source.

For analytical purposes, the capillary should preferably consist of quartz glass, which is deactivated on the inside, in order to avoid memory effects. Ceramics and glass are also suitable for this. The clear width of the nozzle opening should not exceed 50% of the inner diameter of the capillary. Capillaries with a nozzle opening of less than 20% of the inner capillary diameter are more suitable. For example, the nozzle can be produced by melting or also by melting and then grinding the capillary end. It is also important that the capillary 1 is sufficiently well heated up to the tip. Due to the small opening of the nozzle 2, there is a risk of blockage when sample components are condensed out. In addition to the possibilities to realize a resistance heating by means of an electrically conductive coating / covering or an optical heating by means of IR radiation, the capillary 1 can also be surrounded by a thermally highly conductive covering which is heated outside the confined ion source and via thermal heat conduction for sufficient heating of the nozzle 2 provides.

Otherwise, the capillary 1 can be heated using special resistance coatings. An elegant variant is the irradiation of the capillaries 1 with IR radiation z. B. via a heating element or a laser diode. This allows the particularly critical nozzle region to be heated very well.

The operation of the generic gas inlet in an ion source of a time-of-flight mass spectrometer is described below. The narrowed end (nozzle 2) of the capillary 1 projects into the vacuum of the ion source of a mass spectrometer. The capillary 1 consists of quartz glass with an inner diameter of 530 μm and has a nozzle 2 with the embodiment A according to FIG. 1 with an inner diameter of 65-10 μm. The end of the capillary 1 with the nozzle 2 is guided in an approximately 3 cm long thin steel hollow needle (e.g. sawn-off injection needle), so that the tip of the nozzle 2 protrudes just a few 10 μm beyond the end edge of the hollow steel needle. The steel needle is connected to a metal block that can be heated by heating cartridges. In addition, the needle can be placed on a defined electrical potential. The analysis gas can be added through the end of the capillary 1 protruding from the vacuum housing, which is sealed with a graphite pinch seal against the atmospheric pressure. A gas jet forms behind the nozzle in a vacuum. The nozzle acts as a restrictor, so that the flow through the capillary is only about 1 ml / min at 1 bar and there are good vacuum conditions of about 10-4 mbar in the ion source. The expansion via the restriction into a vacuum leads to the formation of a supersonic molecular beam 4 with adiabatic cooling of the sample molecules. This adiabatic cooling is significant e.g. B. for applications to increase selectivity sonically amplified multiphoton ionization mass spectrometry (REMPI-TOFMS). The capillary 1 projects between the diaphragms 5 of the ion source of the mass spectrometer. The capillary 1 with the nozzle 2 can end in the center of the ion source of the mass spectrometer. This is advantageous because the ionization z. B. with a laser beam 6 directly below or very close (z. B. 1 - 30 mm) below the nozzle opening 2. The ions 7 that are formed are then drawn off through trigger plates 5 into the time-of-flight mass spectrometer for mass analysis. Since the density of the supersonic molecular beam 4 decreases in vacuum with the square of the distance to the nozzle opening, the ionization directly under the nozzle 2 achieves a significantly higher sensitivity. The degree of cooling also depends on the distance to the nozzle 2. The optimum cooling 20 nozzle diameter below the nozzle opening 2 is typically achieved. In addition, ion-molecule reactions can be expected directly below nozzle 2. Since the nozzle diameter of nozzle 2 is very small (typically 0.1 - 200 μm), optimal cooling can be achieved at a distance of 2 - 4000 μm. From this distance, a bumpless regime can also be assumed to exist (ie no ion-molecule reactions take place which could reduce the selectivity). The ionization near the nozzle 2 allows the full width of the supersonic molecular beam 4 to be detected with the laser. 2 shows schematically ^', the arrangement of the capillaries 1 with the nozzle 2 between the aperture 5 of the flight mass spectrometer. The plunger is not shown in Figure 2. FIG. 5 shows a REMPI spectrum, recorded with the arrangement shown in FIG. 2. The REMPI spectrum in FIG. 5 shows a rotational contour of the benzene. A rotation temperature of 3 K can be derived from the spectrum. This shows that very good properties of the supersonic molecular beam 4 can be achieved even with gas flows of less than 10 ml / min. The REMPI-TOFMS laser mass spectrometer with the gas inlet according to the invention can, for. B. for field applications, e.g. B. for the analysis of process gases. Compared to the prior art for this application [HJ Heger, R. Zimmermann, R. Dorfner, M. Beckmann, H. Griebel, A. Kettrup, - -

U. Boesl; Anal. Chem. 71 (1999) 46-57], the gas inlet according to the invention has the advantage of increased selectivity due to the cooling of the gas jet with at the same time a small amount of sample required and a reduced load for the vacuum system due to pulsed inlet.

FIG. 3A shows a capillary with a nozzle, the nozzle being able to be designed in any way, for. B. as shown in Figure 1. The plunger is a glass ball. This plunger shape has the following advantages. It does not tilt when opening and closing the valve. It has a small mass so that a high valve opening frequency can be achieved. The ball diameter should be at least 50 μm smaller than the capillary inner diameter, so that enough gas can flow past the tappet through the nozzle. In FIG. 3B, the capillary contains an elongated plunger, which can consist, for example, of a capillary which is melted at the top and bottom. The length of this tappet can be between 5 mm and 20 cm, the long tappet tilting less and the short tappet allowing higher valve opening frequencies due to its lower inert mass. The outside diameter of the plunger and the inside diameter of the capillary should differ by at least 50 μm. With long plunger shapes, the outer diameter of the plunger can be much smaller than with the short form. For a secure seal, it should only be 50 μm larger than the clear width of the nozzle opening. Due to the smaller clear width of the tappet, a larger amount of gas can be made available to the nozzle. As a result, the high pressure difference between the vacuum chamber and the sample feed is maintained for longer and consequently better cooling properties can be achieved.

FIG. 4A shows a magnetic drive of the plunger as an example of a direct drive for the plunger. The winding of an electromagnet 8 is indicated above the upper part of the capillary. The plunger 3 contains an elongated wire 9 made of soft iron or a rod-shaped permanent magnet 9. In the case of a permanent magnet 9, the current direction can be reversed - - An active drive of the ice cream up and down can be achieved, while with a soft iron wire 9 only an active upward stroke is possible. The wire or permanent magnet are melted into the plunger without play.

FIG. 4B shows an example of an indirect drive of the ice cream, which takes place by means of jerky movements on the capillary 1. The force coupling takes place via a sleeve with a flange 10 which is on the outside of the capillary wall, for. B. is fixed by gluing. The mechanics and electrics of a pulse valve can be used as the drive, and a pulse valve can be used to force the capillary up or down. In the event of a force surge upward, an impulse is transmitted upward to the tappet, so that the tappet briefly opens the nozzle in accordance with the impulse and its own inertia. In the event of a power surge downwards, the tappet only temporarily releases the nozzle opening due to its own inertia. The capillary is sealed against the atmosphere by a graphite pinch seal. The sealing point should ideally be at least approx. 5 cm, but better 10 cm from the vibrating mechanism. At shorter distances, the capillary may break due to mechanical stress on the capillary due to the vibrating mechanism.

The operation of a gas inlet according to the invention in a fluorescence cell is even simpler, since no consideration has to be given to the requirements of ion optics, as in the case of the ion source for the mass spectrometer. The capillary 1 can therefore be easily provided with heating elements here. For example, wrapping with heating wire is possible. Furthermore, the requirement for the vacuum system is lower, so that a very compact and inexpensive vacuum cell z. B. for field use of laser-induced fluorescence detection (LIF) can be built. The fluorescence can be dispersed in a wavelength (e.g. with an Echelle spectrograph and CCD detector) or recorded integrally. If the excitation wavelength is tuned, excitation spectra can be recorded. A dispersed The excitation spectra recorded is a two-dimensional spectrum (fluorescence signal as a function of the excitation and emission wavelength). The decay time of the fluorescence can be used as a further analytical dimension, since different compounds have different fluorescence lifetimes. The combination of a small vacuum chamber with a gas inlet according to the invention, an excitation laser and a fluorescence detector represents an ideal (mobile) gas analysis system for gas samples that are not too complex. The supersonic molecular beam 4 allows a significant increase in the selectivity compared to an effective inlet. By moving to characteristic absorption lines with a tunable, narrow-band laser (e.g. a compact optical parametric oscillator, OPO), an online individual substance analysis can be carried out. Here, for. For example, the laser is first tuned to the absorption band (“on resonance”) and the LIF signal. Then the LIF signal is determined at one or more wavelength positions at which the target substance does not absorb (“off resonance”). The concentration of the target substance can then be determined from the differences between the “on” and “off resonance” signals.

For cost-effective process analysis with the aim of e.g. B. to determine a sum parameter for the fluorescent aromatics on-line, the application of a single wavelength, for. B. the fourth harmonic of the Nd: YAG laser (266 nm) may be useful. The gas inlet according to the invention can also be used for an inexpensive aromatic-selective LIF detector for gas chromatography. In the HPLC analysis of PAK z. B. Fluorescence detection prior art. The use of the gas inlet according to the invention for a compact vacuum cell for LIF detection thus gave gas chromatography a detector with comparable properties to HPLC fluorescence analysis, but with higher selectivity and sensitivity. The selectivity can also be adjusted by the choice of the excitation location in the supersonic molecular beam 4. Directly under the nozzle 2 is the adiabatic cooling of the - -

Ultrasound molecular beam 4 not yet formed. The selectivity is relatively low here. Further below the nozzle 2, the selectivity is very high due to the cooling of the gas jet 4. Due to the strong bundling of the supersonic molecular beam 4 emerging from the nozzle 2, the sensitivity to the effusive inlet is increased. The use of two or more wavelengths also allows discrimination between aromatics with small and large ^{π systems} . Small aromatics such as benzene, toluene and xylene (BTX) or phenols as well as larger polycyclic aromatics (PAH) can be excited to fluoresce with 266 nm (Nd: YAG) or 248 nm (KrF excimer). With long-wave UV light such. B. 355 nm (third harmonic frequency of the Nd: YAG laser) BTX and comparable small aromatics are not excited, while many larger PAHs at this wavelength can be detected very efficiently via LIF.

Claims

- 1 6 - 23 Patent claims:

1. Pulsable capillary valve consisting of a) a capillary (1) with a constriction (2), which is designed as a nozzle, b) a plunger (3) located in the capillary (1), which moves together with the capillary constriction (2) can form a seal and c) a drive for the tappet.

2. Pulsable capillary valve according to claim 1, characterized in that the constriction (2) is located at one end of the capillaries (1).

3. Pulsable capillary valve according to one of claims 1 or 2, characterized in that the capillary (1) and / or the plunger (3) consist of glass or quartz glass.

4. Pulsable capillary valve according to one of claims 1 to 3, characterized in that the tappet (3) is adapted to the capillary constriction (2) by grinding.

5. Pulsable capillary valve according to one of claims 1 to 4, characterized in that the drive for the tappet (3) takes place indirectly via the capillary (1).

6. Pulsable capillary valve according to one of claims 1 to 5, characterized in that the drive acts directly on the plunger (3).

7. Use of the pulsable capillary valve according to one of claims 1 to 6 as a gas supply for an ion source or as a gas supply for a UV / fuorescence cell.