DE4109858A1 - Vapour emission detection for solid or liquid substances - using gas chromatograph with cooling of gas chromatograph column during collection followed by heating to operating temp. - Google Patents

Abstract

The detection method uses a gas chromatograph. The substance is placed in a specimen vessel and the emitted material driven out and conducted to a gas chromatograph or GC column in the gas phase. The condensed material is collected in a cooled segment of the entry to the column during extraction. The cooled column section is then heated to the operating temp. of the GC. The material is conducted via the connected parts of the column and fed into a detector. The gas chromatogramm is recorded. USE/ADVANTAGE - For use under wide range of conditions, enables detection of materials at acceptable cost.

Description

The invention relates to a method for detecting substances, which are emitted by solid or liquid substances.

The invention aims to demonstrate the detection of such emitters make the effort more effective.

It is known material emissions using the headspace gas chromato examine graph; this creates a balance in the Distribution of volatile components in the gas space and in the material a. The test conditions can only be set to a very limited extent the; they often deviate significantly from the conditions that exist in be there is appropriate or normal use of the material (e.g. DIN 53 743; testing of plastics).

Furthermore, special examination chambers are known in which the ver used gases are circulated. Collecting the emitters on Adsorption tubes or in sample loops and the following one bring the collected emitters into the injector of a GC Losses related to issuers. Also in the desorption of Emitters, which are removed from the material using a solvent were solved, the sampling takes place under significantly different conditions conditions than with the direct transition of the emitters into the gas phase (L. Molhave, Indoor Glimate, Effects on human comfort, per formance and health, Danish Building Research Institute, Ed. P.0. Fanger, O. Valbjorn (1987); G.W. Bayer, M.S. Black, L.M. Galloway, J. Chromatogr. Sci., 26, 168 (1988); L. Molhave, wood research and wood utilization 34, 24 (1982); J. W. Long, R. W. Snyder, J. Spalik, J. Chromatogr. 450, 394 (1988)).

In the known methods, there are examination conditions that the conditions of the intended or actual Differentiate the use of the material considerably. The samples will be always introduced indirectly into the analyzer, be it via Aus  heating sample loops outside the analyzer or via adsorption tubes to be desorbed or via desorbed Solutions. The samples can change and sometimes ver go lore. Also step into the adsorption tube when collecting the samples depending on the type of substance to be adsorbed, more or less large Sample losses.

This raises the task of finding a method with which one can Substances emitted from solid or liquid substances, by means of a gas chromatograph (GC) under such examination areas can prove conditions that differ from the conditions at the determin Intended or actual use of the substances not at all or distinguish as little as possible; the procedure is said to be very different actual conditions may apply.

This object is achieved by a method with following characteristic features:

• - Introducing a sample of the substance to be examined into a sample vessel,
• Expulsion of the emitters from the sample to be examined,
• Passing the emitters over the gas phase into a GC column,
• - Cooling a segment at the entrance to this column and collecting the condensed emitters in this segment during the expulsion from the substance to be examined,
• - Heating the previously cooled segment of the column to the work temperature of the GC,
• - Transfer the collected emitters over the subsequent part the column, introducing it into a detector and registering the Chromatogram.

The sample vessel is connected directly to the GC column. It forms together with the GC column and the analyzer, a unit that according to the introduction of the sample into the sample vessel is closed and remains closed throughout the investigation. The issuers are thus ge by cryofocusing at the entrance to the GC column collects.  

The emitters can be at normal or elevated temperature of the sample be expelled from the sample. This can be done using a carrier gas used during the expulsion through the sample vessel and the GC column is passed. The moisture content of the carrier gas can are between 0% and 95% of the saturation value. The volume flow the carrier gas can be from 0.5 to 50 ml / min. The gas out exchange rate can range from 0.1 to 10 air changes per hour. The Carrier gas for the expulsion can be identical to the carrier gas of the GC be. If the GC carrier gas is a different gas than when it was turned off the GC column will continue to drive after the end of the expulsion Cooling the segment, if necessary flushed with the carrier gas of the GC, before the cooled segment is heated. When driving out the emits that from the sample can also be in the sample vessel and in the GC column reduced pressure.

The segment at the entrance to the GC column is heated to a temperature chilled between -250 ° C and about + 10 ° C; the cooling temperature is preferably at least 10 degrees below the working temperature of the GC. The working temperature can range from -20 ° C to + 500 ° C.

It may be appropriate to add one or more to the emitters several known substances on the cooled segment of the GC column which serve as (internal) standard in the analysis.

Purified air can be used as the carrier gas for the expulsion of the emitters or a mixture of 80% pure nitrogen and 20% pure oxygen (synthetic air) or an inert gas (e.g. nitrogen, helium, Carbon dioxide, argon) can be used. One of the be known carrier gases (e.g. nitrogen, helium) are used.

One of the usual devices is used as a detector for the GC, preferably a mass spectrometer or an electron capture detector (EGD); a flame ionization detector (FID); a photo ionization Detector (PID) or a thermal conductivity detector (TCD) are flat if usable. The GC column is one of the known columns e.g. B. a capillary column or a packed column.  

The sample vessel can for example consist of glass and with a Be provided with a glass jacket; it is by connecting to a thermostat temperable.

The carrier gas can be pre-cleaned using activated carbon. The damp speed is concentrated by passing the carrier gas over a Saline solution or by adding a certain amount of moisture saturated air to the carrier gas.

With the method according to the invention, the following can, for example Substances examined and their gaseous emitters analyzed will:

• - Fresh or stored untreated wood
• - Wood treated with wood preservatives
• - Building materials such as insulation boards, rock wool, chipboard, hardboard slabs, tiles, flagstones, bricks
• - Textiles, paper, cardboard, wallpaper, flooring, leather
• - Electrical insulating materials such as foils, plates, electrical lacquer Metals
• - plastic and rubber
• - Coated, painted, painted objects
• - Solvent-free dispersions, paints, tar

The method according to the invention has the following advantages:

• - The emitters are lossless in part of the analyzer collected and analyzed lossless.
• - The components of an emitted mixture can easily Be proven qualitatively and quantitatively.
• - The conditions when the emitters are driven out (temperature, gas pressure, gas type, gas moisture, flow velocity of the gas) can easily with the real conditions in the intended or actual use of the substances mood. In addition, the substances can be if necessary, more severe - other conditions are examined.
• - The substance to be tested and the emitters remain during the Collecting and unchanged during desorption.  
• - The chromatogram does not contain any solvent peaks that are found in others Procedure of sample treatment with a solvent unavoidable are.
• - The analysis data are obtained by coupling the sample collection directly place generated with the detector.
• - The procedure can be used in a wide range of areas conditions - including real conditions - to practical all solid and liquid substances are used.
• - The material surface of the sample can be used for material examinations as a scale reduction of the space to be simulated the volume of the sample vessel can be selected. The sample can be taken at real conditions including the air exchange rate were examined will.
• - Emitters in the concentration range from 10.6 g / m³ to 1 g / m³ can be recorded.

For example, the apparatus shown in FIG. 1 is suitable for the method according to the invention and essentially contains the following parts: a pressurized gas bottle ( 21 ) for the carrier gas for expelling the emitters, the gas pre-cleaning ( 22 ), gas humidification ( 23 ) and moisture measurement ( 24 ); the sample chamber ( 25 ) with a glass sieve bottom - for solid substances to be investigated - with a temperature jacket ( 26 ), temperature measurement ( 27 ) and lockable entrance ( 28 ); the heatable Transferkapil lare ( 29 ) with switching device for another carrier gas; the gas chromatograph ( 30 ) with the segment ( 31 ) at the entrance to the GC capillary, which can be deep-frozen and then heated, the mass spectrometer ( 32 ) and the evaluation unit ( 33 ). All parts are connected by lines.

The process according to the invention is illustrated by the following examples explained without being limited to this.

Example 1: Examination of pine wood

About 2 g of pine wood shavings are placed in the sample container (180 ml) brought. Syn serves as the carrier gas for expelling the emitters synthetic air with a throughput of 1.5 ml per minute and one  Moisture content of 45%, which is achieved by passing the air over a ge saturated K₂C0₃ solution is set at 22 ° C. The sample vessel will also kept at 22 ° C.

First, the carrier gas is passed through the sample vessel for 4 hours conducts and discarded before entering the GC column. Under these Conditions create an equilibrium of emissions.

The carrier gas is then introduced into the GC column for 10 minutes conducts and discarded behind the GC column. At the entrance to the GC column becomes an approximately 30 cm long segment before and during the passage cooled the carrier gas with liquid nitrogen; During this time the emitters are condensed and collected in the cooled segment.

The sample vessel is now separated from the GC column. When closed The GC column 3 now connected to the mass spectrometer is split Flushed with helium for minutes. During this time the segment still cooled at the entrance to the GC column.

After removing the nitrogen cooling, the segment is at the entrance heated to + 30 ° C in the GC column and 6 minutes at this temperature temperature kept. Then it gets up to 6 degrees per minute 150 ° C heated. It continues at 15 degrees per minute to 250 ° C heated and held at this temperature for 10 minutes.

The other test conditions are:

• - Perkin-Elmer gas chromatograph 8420
  Column 30 meters long, 0.32 mm inner diameter, 0.25 m SPB 5 carrier gas helium 75 kPa
  Temperature of the connection line of the open coupling with the mass spectrometer 260 ° C.
• - Perkin-Elmer mass spectrometer lTD 800
  1 scan per second, range 35-425 mass units

Fig. 2 shows the diagram of the total ion current of the coupling of the GC with a mass spectrometer.

The identified emitters are:

1 to 6 and 8 to 10: terpenes M 136, e.g. B. α-pinene, β-pinene, camphene, myrcene, terpinolene, β-phellandrene, limonene
7: p-Cymol M 134
11, 12: M 154 terpene alcohols, e.g. B. Linalool, α-terpineol
13: Anethol M 148
14 to 18: Sesquiterpenes M 204, e.g. B. α-caryophyllene, β-caryophyllene, cadines

Example 2: Examination of leather

About 10 g of leather are introduced into the sample vessel. As a carrier gas synthetic air with a throughput of 1.5 ml per minute and a moisture content of 45%, which by excess pass the air over a saturated K₂CO₃ solution at 22 ° C. is posed. The sample vessel is also kept at 22 ° C.

First, the carrier gas is passed through the sample vessel for 12 hours conducts and discarded before entering the GC column. Under these Conditions create an equilibrium of emissions.

The further investigation proceeds under those given in Example 1 Conditions.

The emitters identified are saturated with hydrocarbons 14 to 17 carbon atoms.

Claims (6)

1. A method for detecting substances that are emitted from solid or liquid substances by means of a gas chromatograph (GC), characterized by

• Introduction of a sample of the substance to be examined into a sample vessel,
• Expulsion of the emitters from the sample to be examined,
• Passing the emitters over the gas phase into a GC column,
• Cooling a segment at the entry into this column and collecting the condensed emitters in this segment during the expulsion from the substance to be examined,
• - heating the previously cooled segment of the column to the working temperature of the GC,
• - Transfer of the collected emitters over the subsequent part of the column, introduction into a detector and registration of the chromatogram.

2. The method according to claim 1, characterized by

• - Expulsion at normal or elevated temperature of the sample vessel by means of a carrier gas which is passed through the sample vessel and the GC column, the moisture content of the carrier gas being between 0% and 95% of the saturation value;
• a volume flow of the carrier gas of 0.5 to 50 ml / min;
• a carrier gas for expulsion which is identical to the carrier gas of the GC;
• - A carrier gas for the expulsion, which is different from the carrier gas of the GC and optionally flushing the GC column with the carrier gas for the GC after the end of the expulsion with further cooling of the segment.

3. The method according to claims 1 and 2, characterized by

• - Expulsion of the emitters at reduced pressure in the sample vessel and in the GC column and, if appropriate, at an elevated temperature of the sample vessel with or without carrier gas.

4. The method according to claims 1 to 3, characterized by

• - A temperature of the cooled segment, which is between -250 ° C and about + 10 ° C.

5. The method according to claims 1 to 4, characterized by

• - Introducing one or more known substances on the cooled segment of the GC column as an (inner) standard.

6. The method according to claims 1 to 5, characterized by

• - Detection of the emitters preferably by means of a mass spectrometer or an electron capture detector which is connected to the GC column.