DE102006025932B3 - Sampling device for volatile compounds in gaseous atmospheres allows automated desorption for analysis by enclosure of adsorbent sampling tubes in septum sealed containers for through-needle connection - Google Patents

Abstract

A sampling device comprises a receptacle (1) containing at least one tube (2) holding a solid adsorbent (4), with a clearance between the tube and the inside of the receptacle. For thermal desorption and transfer of sample to an analyzer a top closure septum (5) allows injection (7) and collection (6) of carrier gas after passing down the clearance cavity and up through the sample tube adsorbent. Independent claims are included for a sampling device which allows connections to be made for thermal desorption of samples, particularly by a needle penetrable septum, and the method of using the device. For high fugacity compounds e.g. vinyl chloride samples, the silicon septum may have an aluminium foil covering. The receptacles may be made of glass, aluminium or stainless steel.

Description

The The invention relates to a receptacle having at least one therein recorded sample tubes, in which at least one solid adsorbent for adsorption at least a compound can be arranged, wherein the sample tube in one in the receptacle trained and over only one container opening accessible Cavity is received and a substantially to the side of the Container opening out aligned opening having. The insides of the walls of the cavity and the walls of the sample tube contained in the cavity form a channel from such that desorbed by thermodesorption compounds by one flowing into the channel Carrier gas stream from the inside of the sample tube be transported away, and the receptacle a closure with a Has septum, with which closed the container opening is. Furthermore, the invention relates to a device for the thermal desorption of on adsorbed in solid adsorbents compounds. Furthermore The invention relates to a method for sample preparation for the loading of a Thermodesorbers with the prepared sample, as well as a procedure to operate a thermal desorber.

at the measurement of volatile organic compounds (VOCs volatile organic compounds) indoors the accumulation of the organic compounds on an adsorbent, that is in a sample tube located. Into the sample tube can different adsorbents are introduced, such. Chromosorb, Activated carbons or Tenax TA (2,6-diphenyl-P-phenylene oxide) e.g. B. with a grain of 60/80 mesh.

The Enrichment of the analytes on the adsorbent of the sample tube by means of precise pumps, which pump a certain volume of sample through the sample tube, or by a longer one Measurement with a diffusion cap placed on the sample tube, whereby an integral measured value can be determined.

Also become sample tubes used to introduce substances to be examined into the sample tube, where after defined heating volatile Substances can escape from the sample and be analyzed. Such into the sample tube introduced substances can z. As plastics, earth, films, papers or food.

Sample tubes may be off different materials such. As stainless steel, glazed stainless steel or Glass exist and have z. B. an outer diameter of 6 mm (6.35 mm), an inner diameter of 4 mm and a length of 70 mm.

To collecting on the adsorbent of the sample tube or after insertion a substance to be examined in the sample tube, the tube with closed on both sides applied closure or sealing caps and subsequently e.g. fed to a thermal desorber for analysis.

The Closure or sealing caps of the sample tube are preferred made of metal or PTFE, with the sealing of the sealing caps to the sample tube with an O-ring e.g. made of the material PTFE or Viton. It is to note that due to the possible transport and storage of the sample tubes after loading with chemical substances no lower findings be allowed to result the sample tube so must be sealed absolutely tight.

The Analysis of the sample tube takes place in the laboratory preferably by means of a thermal desorber, the more sample tubes can work off automatically. Here the sample tube becomes fast to temperatures of e.g. 300 ° C heated and the heated chemical substances are on a miniaturized cold trap concentrated. This cold trap will subsequently heated very quickly whereby all substances are transferred immediately to the capillary column of a gas chromatograph. After the gas chromatographic separation is a qualitative and quantitative evaluation e.g. by means of a mass spectrometer or by means of another gas chromatographic detector.

Around several sample tubes evaluate one after the other, these are e.g. in an automatic Thermodesorber set, whereby every 30 minutes a sample tube of the Gas chromatographic analysis is subjected. In different on the market Thermodesorberanordnungen the arrangement is made the sample tube, for example on a tray or on a cylinder with mounts for several Sample tube on the mantle of the cylinder.

Become a sample tube typically closed with two caps. Each of these caps must be removed automatically before transport to the sample heater and the sample tube must be automated and absolutely gas-tight in the heating device of the thermal desorber are introduced.

For sample tubes on the market, each sample tube must be automatically leak tested prior to analysis as leaking and measurement errors may occur when placed in the heater. For automatic removal of the two sealing caps is a relatively high mechani shear effort required, which is usually solved by a pneumatic device, a Entkappervorrichtung.

Farther In another method, sample tubes are capped on both sides sealed. Here are the introduction of the sample tube in the heater caps are not taken, but on the right and left piercing needles, the flowing carrier gas is supplied to the sample tube.

at the automated thermal desorption represents the sealing of the sample tube In the thermal desorber after removing the caps a big problem because, while the total duration of the heating process (about 20 min) to about 300 ° C of the sample tube a high temperature resistant Seal must be used.

The prior art knows some devices that use a sample application by means of a sample tube. In the DE 36 16 208 C1 The sample tube is transported by means of a push rod, which brings a huge effort, especially in the automated processing of several sample tubes with it.

In the GB 23 37 513 A describes a cap of a sample tube, which does not have to be removed during the analytical analysis. Each of the two caps of the sampling tube is sealed by an O-ring and has a bore through which the gas can flow during analysis.

In the EP 0 816 823 A1 a sampling tube is described, which is sealed with sealed Teflon caps.

In the DE 44 19 596 C1 a thermodisorption device is described, which also works by means of an O-ring sealed sample tube.

In all on-market closure devices of a sample tube makes the handling / removal of the caps a high Effort and a problem in terms of secure sealing dar. Furthermore, a pneumatic Entkappervorrichtung means a increased effort in terms of costs and maintenance.

Of the Invention is based on the object, a method and an apparatus provide a simplified and safe handling of sample tubes in an automated sampler or automated thermal desorber allows.

These Task is solved through a receptacle with at least one sample tube received therein, in which at least one solid Adsorbent for adsorbing at least one compound can be arranged is, taking the sample tube in one in the receptacle trained and over only one container opening accessible cavity is received and a substantially to the side of the container opening aligned opening having. The insides of the walls of the cavity and the walls of the sample tube contained in the cavity form a channel such that compounds desorbed by thermal desorption by an inflowing into the channel Carrier gas stream from the inside of the sample tube be transported away, and the receptacle a closure with a Has septum, with which closed the container opening is. The septum is arranged so that it is the edge of the first opening of the Spanning sample tube and the tube seals. The from the inside of the wall of the cavity and from the wall of the sample tube formed in the cavity formed tube section is with the inside of the sample tube over a for the carrier gas permeable second opening in sample tubes connected.

at the device according to the invention deleted the double-sided seal of the sample tube sealed with O-ring Caps. this leads to essentially to simplify filling / loading of the sample tube and also for the convenience of automated thermal analysis, in particular during heating and secure sealing during the heating process.

A Widely used analysis method for volatile compounds in the concentration range up to in the ppt area provides the headspace analysis and the purge and Trap analysis dar. Here is in standardized glass bottles with a Outside diameter of 23 mm, one height of 75.5 mm, e.g. an aqueous one Sample of 10 ml is introduced, which is then heated and the gas over the Liquid, in which there are virtually all substances in the liquid accumulate on the capillary column a gas chromatograph is transferred. Because the use of these headspace sample bottle types is widespread and numerous samplers are available in the market, using these types of bottles makes it a great advantage if you consider the shape of these bottle types with the existing ones autosampler also for the desorption desorption use can.

A metallic sample bottle used, for example of anodized or coated aluminum or stainless steel, can be easily constructed in the form of the somewhat standardized glass bottles on the market. In this sample bottle can eg a Glass existing sample tube with the preferred dimensions outside diameter 6 mm and inside diameter 4 mm can be adjusted.

Around to allow optimal gas flow in this sample tube, becomes the sample tube on the opening the underside of the sample bottle is slightly turned off with a notch of about 200 microns Depth sanded. Thus, the gas can flow through the sample tube without increased flow resistance. This Purpose can, alternatively or additionally for introducing a notch into the sample tube, also achieved thereby be that on the front of the bore introduced into the sample bottle a flow channel with the depth of about 200 microns is created. Through the gap between sample tube and Drill the metallic sample bottle and the one on the bottom of the sample tube introduced notch is ensured by the sample tube of bottom to top carrier gas stream can.

In a preferred embodiment is a first section of the channel through insides of the walls of the Cavity and outsides the walls of the Limited in the cavity recorded sample tube. A second section of the channel is through the interior of the sample tube educated.

Especially the second section of the channel extends in the interior of the tube between the first opening and the second opening.

Of the Cavity is preferred as a substantially cylindrical recess in the receptacle for receiving a substantially cylindrical sample tube educated.

Especially is located in an area of the first section of the channel of the distance between the inside of the wall of the cavity and the wall of the in the cavity recorded sample tube between 1/5 mm and 1/20 mm, and is in particular 1/10 mm.

Of the Cavity may be near the opening Area of the receptacle by a recess, which in particular is cylindrical is formed enlarged be so between the outer side the wall of the sample tube and the inside of the wall of the cavity formed a gap is. This gap allows it, in the implementation the thermal desorption to produce a gas inlet, for example by a lock being pierced by a needle, which in the Gap protrudes.

The Septum is in particular on the sample tube side facing with laminated a metal layer. The septum may be metallic Screw cap or a crimp seal are closed. The Closure with screw cap and septum is identical to the standard type of closure in the widespread headspace analysis. This way will Even at high temperatures, a secure seal both the upper opening of the sample tube as well as the opening reached the sample bottle. The upper opening of the sample tube may be substantially the same side as the opening of the receptacle aligned and closed by the same closure.

The upper opening of the tube is opposite from the septum the environment, but also opposite the cavity that is not from the tube is taken, safely sealed. This creates a closed channel, extending from the opening of the cavity in the area outside of the tube down to the bottom of the cavity and from there over the lower opening of the tube in the interior of the tube to the upper opening of the tube extends. This way takes during the thermal desorption also the carrier gas, which over a suitable gas inlet in the septum into the first section of the Channels initiated and over an outlet in the septum at the upper opening of the sample tube dissipated becomes.

In In this connection it should be noted that the terms "upper" opening and "lower" opening are not restrictive to be viewed. Of course, the orientation of the receptacle and the sample tube arranged therein can be changed as desired. In particular, the receptacle with its contents also arbitrarily tilted or rotated during the actual Desorptionsvorgang be arranged. The terms were chosen only as usual at the filling of the receptacle with a sample tube the opening of the receptacle is oriented upwards (but does not have to be).

Preferably is the upper edge of the sample tube polished or treated so that the edge has a small roughness.

The upper edge of the sample tube may also project beyond the plane defined by the edge of the opening of the receptacle, for example by an amount of 0.1 mm to 1 mm. In this way, the edge of the sample tube can be covered with the septum. While in a location of the upper edge of the sample tube in the plane defined by the edge of the opening of the receptacle, contact with the septum for secure sealing is usually insufficient, protruding beyond the edge of the receptacle opening by projection of the upper edge of the sample tube a certain tension in the septum he testifies, which presses this to the upper edge of the sample tube. In this way, a secure seal is achieved even at high temperatures.

in the Area of the upper and / or lower opening of the sample tube a glass frit can be melted down. A melted down in the sample tube Glass frit facilitates the incorporation of a powdery Adsorbent.

Of the Receptacle for example, made of stainless steel or aluminum, at least in the area of interior walls the cavity passivated, in particular anodized or with an inert coating be provided.

The Task is also solved by a device for the thermal desorption of solid adsorbents adsorbed compounds comprising a receptacle, such as described above, a gas inlet through the closure in the cavity of the receptacle leads, to the feeder a carrier gas in the first section of the channel, as well as a gas outlet, the through the closure leads to the removal of the inert gas from the interior of the sample tube.

Of the Gas inlet and / or the gas outlet can thereby at least one Needle include. The needles are with a passage for gas supply / discharge Mistake.

Of the Inventive receptacle is usually outside of the thermal desorber loaded with a sample tube. Then be by means of a septum and a screwed onto the receptacle Cap, the example in the top of the lid a central opening includes, both the opening of the receptacle as well as the upper opening of the sample tube tightly closed. In this form, the receptacle with the sample is stored or transported. For analysis will the receptacle placed in an autosampler, which is a thermal desorber fed. Inside the thermal desorber, the septum will be in the area the upper opening of the sample tube for the production of a gas outlet and in the area of the opening of the receptacle outside of the sample tube pierced by appropriate needles for producing a gas inlet. In this way can be done in a few steps and fully automated the desorption be prepared and carried out.

Prefers The gas inlet and / or the gas outlet respectively comprise at least a needle. One of the needles responsible for the removal of the carrier gas from the inside of the tube is provided is centrally with respect to the opening of the receptacle (and the upper opening of the tube) arranged and protrudes into the interior of the tube.

The Task is also solved by a method of sample preparation for feeding a thermal desorber with the prepared sample using a receptacle as above described, wherein the receptacle with a over exactly a cavity opening accessible Cavity is provided, the sample tube with the first opening for Inlet of a carrier gas and with the second opening to the outlet of a carrier gas in the receptacle with one over exactly one cavity opening accessible cavity is arranged, and the second opening in Aligned substantially to the side of the cavity opening. Both the cavity opening as well as the second opening of the sample tube are sealed with exactly one closure, with the closure a septum with which the edge of the second opening of the sample tube spans to seal the sample tube becomes.

At the Use of this procedure will prevent the openings closed on both sides, at the top and bottom of the sample tube Need to become. In the method according to the invention just have an opening, which spans with exactly one closure, for example a septum can be closed. The septum closes simultaneously also the opening the cavity of the receptacle.

One inventive method for sample preparation for the loading of a thermal desorber with the prepared sample, comprises the steps of: a) providing a receptacle such as described above, b) providing the sample tube in which at least a solid adsorbent for adsorbing at least one compound c) placing the sample tube in the cavity of the receptacle such that an upper opening of the sample tube aligned substantially in the same direction as the opening of the receptacle is, and d) simultaneously closing the opening of the receptacle and the first opening of the sample tube by means of exactly a closure device having a septum, by overstretching the upper opening by means of the septum for sealing the sample tube. The first opening of the sample tube is opposite the opening of the receptacle sealed.

For example, the edge of the first (upper) opening of the sample tube (ie, the opening from which the carrier gas flows out) project beyond the edge of the opening of the receptacle, ie a projection with respect to the opening of the receptacle mebehälters form.

Around a secure seal between the top of the sample tube and the septum is preferably the edge of the upper, to the outlet of the carrier gas certain opening of the sample tube before closing or Sealing polished.

One inventive method For operating a thermal desorber, the steps include: sample preparation, as in the previously described method, e) generation of a gas inlet, but through the closure outside the tube into the cavity, to the feeder a carrier gas in the cavity, and f) generating a gas outlet through the Closure passes into the interior of the tube, for removal of the carrier gas from the sample tube.

Especially the method further comprises the steps of: g) heating the sample tube Desorption temperature, and h) introducing a carrier gas into the gas inlet such that the carrier gas from Gas inlet starting at the outside of the sample tube to a lower opening of the sample tube and from there in the interior of the sample tube through the adsorbent flows to the gas outlet, so that volatile gaseous Substances with the carrier gas out of the sample tube be transported.

Further Advantages, characteristics and features of the invention are in the following detailed description of embodiments with reference the attached Drawings clearly. The drawings show:

1 schematically a section through the metallic sample bottle with sample tube and adsorbent

2 a section through the metallic sample bottle, the septum, the two needles and the cap

3 a section through the sample tube with melted on the bottom glass frit

In 1 becomes a metallic sample bottle 1 with inserted sample tube 2 shown. The carrier gas flows into the room 3 a, between the hole in the sample bottle and the jacket of the sample tube to the bottom of the sample tube and through the sample tube in which the adsorbent 4 located. The outflow direction of the carrier gas flow takes place on the upper end side of the sample tube.

Of the minimum inner diameter of the hole in the metallic sample bottle is chosen according to the tolerance of the glass tubes so that the maximum outside diameter of the sample tube preferably 1/10 mm smaller than the minimum inner diameter the hole in the metallic sample bottle.

In The representation is a closed by a standard thread sample bottle shown. In principle, a sample bottle with crimp cap be used.

By 2 will seal the metallic sample bottle 1 by means of an aluminum lined septum 5 , the carrier gas feeding needle 7 and the carrier gas laxative needle 6 shown. Through the gas feeding needle 7 Carrier gas flows into the room 3 and thus by the adsorbent 4 in the sample tube 2 , The top of the glass wool plug attached 9 prevents small particles of the adsorbent 4 be transported into the central needle 6 and thus can contaminate the system. The hollow needles used in the process are typically formed at the front with a tip and have on the side of a small bore for gas inlet and gas outlet.

The septum 5 is coated on the adsorbent side facing with a thin aluminum foil. This prevents volatile substances such. As vinyl chloride diffuse through or into the septum, which would lead to lower findings. Through the metallic threaded screw cap 8th becomes the silicone septum 5 on the metallic sample bottle 1 pressed, whereby a secure sealing of the system is ensured even at elevated carrier gas pressures. Also gets through the silicone septum 5 sealed the polished top of the sample tube. The polishing of the top of the sample tube is required because too much roughness of the annular end surface of the sample tube would lead to leaks and thus not 100% of the carrier gas flow would be passed through the adsorbent.

To an increased contact pressure of the septum 5 to reach the sample tube, the sample tube z. B. 1 mm beyond the thread of the sample bottle, whereby the septum bulges upwards and better seals the edge of the polished sample tube.

In 3 is the preferred embodiment of a sample tube 2 shown in glass. On the bottom of the glass tube is a glass frit 10 melted into the sample tube. This prevents the adsorbent from falling out of the sample tube.

Claims (19)

Containers ( 1 ) with at least one sample tube ( 2 ), in which at least one solid adsorbent ( 4 ) is arranged for the adsorption of at least one compound, wherein the sample tube ( 2 ) in a receptacle ( 1 ) is formed and accessible via only one container opening cavity and having a substantially to the side of the container opening oriented first opening, wherein the inner sides of the walls of the cavity and the walls of the sample tube accommodated in the cavity ( 2 ) form a channel such that compounds desorbed by thermodesorption by a carrier gas stream flowing into the channel from the inside of the sample tube ( 2 ) are transportable, and wherein the receptacle ( 1 ) a closure ( 5 . 8th ) with a septum ( 5 ), with which the container opening is closed, characterized in that the septum ( 5 ) is arranged such that it the edge of the first opening of the sample tube ( 2 ) and seals the tube, and that from the inside of the wall of the cavity and from the wall of the sample tube accommodated in the cavity ( 2 ) formed with the interior of the sample tube ( 2 ) via a carrier gas permeable second opening in the sample tube ( 2 ) connected is. Containers ( 1 ) according to claim 1, characterized in that a first portion of the channel through inner sides of the walls of the cavity and outer sides of the walls of the sample tube (in the cavity) received ( 2 ), a second section of the channel through the interior of the sample tube ( 2 ) is formed. Containers ( 1 ) according to claim 2, characterized in that the second portion of the channel extends in the interior of the tube between the first opening and the second opening. Containers ( 1 ) according to one of the preceding claims, characterized in that the cavity as a substantially cylindrical recess in the receptacle ( 1 ) for receiving a substantially cylindrical sample tube ( 2 ) is trained. Containers ( 1 ) according to one of claims 2 to 4, characterized in that in a region of the first portion of the channel, the distance between the inside of the wall of the cavity and the wall of the sample tube ( 2 ) is between 1/5 mm and 1/20 mm, in particular 1/10 mm. Containers ( 1 ) according to one of claims 1 to 5, characterized in that the cavity in the region near the opening of the receptacle ( 1 ) is formed enlarged by a recess, which is in particular cylindrical, so that between the outer side of the wall of the sample tube ( 2 ) and the inside of the wall of the cavity a space ( 3 ) is trained. Containers ( 1 ) according to claim 6, characterized in that the septum ( 5 ) is laminated with a metal layer. Containers ( 1 ) according to one of the preceding claims, characterized in that the upper edge of the sample tube ( 2 ) from the edge of the opening of the receptacle ( 1 ) defined level, in particular by an amount of 0.1 mm to 1 mm. Containers ( 1 ) according to one of claims 1 to 8, characterized in that the upper edge of the sample tube ( 2 ) is polished. Containers ( 1 ) according to one of claims 1 to 9, characterized in that in the region of the first and / or second opening of the sample tube ( 2 ) a glass frit ( 10 ) is melted down. Containers ( 1 ) according to one of claims 1 to 10, characterized in that the receptacle ( 1 ) Passivated at least in the region of the inner walls of the cavity, in particular anodized or provided with an inert coating. Device for thermal desorption of solid adsorbents ( 4 ) adsorbed compounds, comprising a receptacle ( 1 ) according to one of claims 7 to 11, and a gas inlet ( 7 ) passing through the closure into the cavity of the receptacle ( 1 ), for supplying a carrier gas into the first section of the channel, and a gas outlet ( 6 ), which leads through the closure, for removing the carrier gas from the interior of the sample tube ( 2 ). Apparatus according to claim 12, characterized in that the gas inlet ( 7 ) and / or the gas outlet ( 6 ) at least one needle ( 6 . 7 ). Apparatus according to claim 12 or 13, characterized in that the gas outlet ( 6 ) substantially centrally into the upper opening of the sample tube ( 2 ) and the gas inlet ( 7 ) offset laterally from the gas outlet ( 6 ) in the first channel section ( 3 protrudes. Method for sample preparation for feeding a thermal desorber with the prepared sample using a receptacle according to one of claims 1 to 11, characterized in that the receptacle ( 1 ) is provided with a cavity accessible via exactly one cavity opening, the sample tube ( 2 ) with the first opening to the inlet of a carrier gas and with the second opening to the outlet of a carrier gas in the receptacle ( 1 ), wherein the second opening is aligned substantially towards the side of the cavity opening, and that both the cavity opening and the second opening of the sample tube ( 2 ) with exactly one closure ( 5 . 8th ), the closure being a septum ( 5 ), with which the edge of the second opening of the sample tube ( 2 ) is spanned to seal the sample tube. A sample preparation method for loading a thermal desorber with the prepared sample, comprising the steps of: a. Provision of a receptacle ( 1 ) according to one of claims 1 to 11, b. Provision of the sample tube ( 2 ), in which at least one solid adsorbent ( 4 ) is arranged to adsorb at least one compound, c. Insertion of the sample tube ( 2 ) in the cavity of the receptacle ( 1 ) such that an upper opening of the sample tube ( 2 ) in substantially the same direction as the opening of the receptacle ( 1 ), and d. simultaneous closing of the opening of the receptacle ( 1 ) and the first opening of the sample tube ( 2 ) by means of the closure device ( 5 . 8th ), which is a septum ( 5 ) by spanning the first opening by means of the septum ( 5 ) for sealing the sample tube ( 2 ). A method according to claim 15 or 16, characterized in that the edge of the upper, to the outlet of the carrier gas certain opening of the sample tube ( 2 ) is polished before sealing or sealing. A method of operating a thermal desorber, comprising the steps of: sample preparation according to one of claims 16 or 17, e. Generation of a gas inlet ( 7 ) leading through the closure outside the tube into the cavity, for supplying a carrier gas into the cavity, and f. Generation of a gas outlet ( 6 ), which leads through the closure into the interior of the tube, for removing the carrier gas from the sample tube ( 2 ). A method according to claim 18, characterized in that the method further comprises the following steps: g. Heating the sample tube to desorption temperature, and h. Introducing a carrier gas into the gas inlet ( 7 ) such that the carrier gas from the gas inlet ( 7 ) on the outside of the sample tube ( 2 ) to a lower opening of the sample tube ( 2 ) and from there in the interior of the sample tube ( 2 ) through the adsorbent to the gas outlet ( 6 ) flows, so that volatile gaseous substances with the carrier gas from the sample tube ( 2 ) are transported out.