DE2459945A1 - METHOD AND DEVICE FOR GAS CHROMATOGRAPHIC ANALYSIS - Google Patents

Description

COMPAGNIE S ¹ MiTCAISE DE EAB ¹ PINAGE SA., Paris, France

Method and device for gas chromatographic analysis

The invention relates to a method for gas chromatographic analysis of substances which are present in small amounts in a solvent are included. The invention also relates to a device for carrying out this method.

For a number of years there have been numerous works with the determination of substances that are contained in small quantities in a solvent, in particular with the detection and the determination of small amounts of hydrocarbons in water after extraction with an organic solvent. This work is due to the efforts to combat pollution. TJm the waste water regulations of the authorities, for example for oil refineries or petrochemical plants, is it necessary to determine the amount of hydrocarbons in the wastewater, to prevent pollution of the seas and rivers.

Various analysis methods have therefore already been proposed, which can be divided into several methods

S098 28 / 0B48

ORlGlNAi INSPECTED

let each of the methods used be disadvantageous connected is.

. In one of these known methods, the hydrocarbons with a solvent, for example carbon tetrachloride, pentane or nitrobenzene, extracted and um The small amount of hydrocarbons to be detected is then the solution of hydrocarbons obtained in this way partial evaporation of the solvent used for the extraction concentrated, whereupon a large amount of the sample in a conventional Chromatograph is introduced. Satisfactory results with this method are only obtained with hydrocarbons obtained whose boiling points and polarities differ from the boiling point and the polarity of the solvent used for the extraction differentiate sufficiently. In contrast, the exact detection of hydrocarbons, which is related to these two Properties come close to the solvent, difficult or even impossible because on the right time of the analysis The band resulting from the solvent used for the extraction has not yet ended in the chromatogram obtained and this has a significant tailing. For example, carbon tetrachloride is used to detect hydrocarbons used in water, the boiling points of the hydrocarbons being between 150 and 450 ° C. As proof pentane is used for hydrocarbons with boiling points between 100 and 450 ° G.

I,

The procedure, based on known methods of gas chromatography is based on the fact that during the analysis a programmed temperature and a very high detection sensitivity come into use. However, this almost always leads to a strong drift from the baseline, which is a quantitative one Determination very difficult.

5 09828/0548

7,

Another known method that can be used in the determination of substances which are immiscible with one another, for example hydrocarbons in water, is described in "Water Research", Pergamon Press, 1971, volume 5, pages 54-5 ^to 562. It consists in producing a sufficiently finely divided and stable emulsion of hydrocarbons in water and in a reproducible manner introduced into the chromatograph corresponding sample quantities. The emulsion is produced by ultrasound treatment and stabilized with a surfactant. However, the method is only suitable for the detection of hydrocarbons with at least 7 carbon atoms per molecule and can only be used if the concentration of hydrocarbons is greater than 0.5%.

The object of the invention is to provide a method for gas chromatographic Analysis to create that in a simple way the qualitative and quantitative determination of substances that are contained in a small amount in a solvent, allows, in particular the determination of small amounts of hydrocarbons in an organic solvent.

According to the invention, this object is achieved by the in the characterizing Part of the main claim specified measures resolved. Advantageous refinements of the method according to the invention result when the measures according to the claims 2 to 8 can be realized.

There are four main flow paths in the method according to the invention provided, which are supplied by one and the same carrier gas. These flow paths can be connected to each other via a Four-way valve or generally connected by a switching element or separated from each other. The arrangement of the main flow paths or bypass routes and associated facilities

609828/05

are hereinafter referred to as the analyzer.

The first main flow path has essentially one Injection block and a first column on which separates the substances to be analyzed from the other components of the entered Sample causes.

An arrangement has a second main flow path chromatographic analysis. In this flow path is upstream of the analyzing arrangement, a 3-panel is provided which is intended to hold back the products to be analyzed upstream of the analyzing arrangement.

The third main flow path has essentially one Regulating valve open.

The fourth main flow path has essentially one Throughput controller on.

Furthermore, a life flow path is provided that goes with the second main flow path upstream of the analyzer assembly is connected and which essentially has a shut-off valve or generally an organ that closes or allows opening of the Mebenströmungsweg towards the environment.

Although in the following only of hydrocarbons the Speaking of which, the invention is not limited to this class of substances. Rather, all Chromatograph! heritable products be analyzed according to the Yerfahren according to the invention.

In the first phase of the process are the first main flow path and the second main flow path through the switching element connected with each other; at the same time this connects

S09828 / 0548

Switching element the second main flow path with the fourth Main flow path. -.

The sample, which contains the substances to be analyzed and the solvent, is then introduced. the Substances, such as hydrocarbons, are retained in the first flow path, while the remaining substances, which are not to be analyzed, in particular the solvent, from the device via the regulating valve of the third flow path can be drained. During this phase, the carrier gas flows, "which is an inert gas, such as Argon, nitrogen, helium, is, continuously through the first and third main flow paths on the one hand and the fourth and on the other the second main flow path on the other hand, and also through the secondary flow path, which is preferably opposite the environment is left open.

In the second phase of the method according to the invention the first and second main flow paths are connected to one another. At the same time, the third main flow path is with connected to the fourth main flow path, so that the flowing therein Carrier gas goes off into the open. The hydrocarbons to be analyzed which have been released in the column of the first flow path • will be in the second main flow path transferred and retained in the trap of the second flow path upstream of the analyzer. In the second In the main flow path, only the hydrocarbons that are to be analyzed are transferred.

The third phase of the process is that the Flow paths are connected to one another again as in the first phase and that the hydrocarbons are in the trap

509828/0548

rapidly, released and downstream in the analyzer the trap to be analyzed.

The inventive method for gas chromatographic analysis of substances in a small amount in a Solvents are included, thus includes the following stages:

a) In the first main flow path, the substances which are to be analyzed, separated from the other substances in the sample, whereupon said Substances via a third main flow path, which essentially has a regulating valve, are discharged;

b) then the first main flow path with the second main flow path connected, whereupon the substances to be analyzed before implementation the analysis are transferred to the trap in the second main flow path upstream the analysis device, preferably a chromatography column »is arranged;

c) then on the one hand the first main flow path with the third main flow path and on the other hand the second main flow path with the fourth main flow path connected, after which the to substances to be analyzed are released from the trap of the second main flow path and in the analyzer, that is, preferably in the chromatography column.

An apparatus for carrying out the invention Method is obtained if the specified in claim 9

509823/0548

η _

given characteristics can be realized-

Advantageous further developments of the device according to claim 9 are characterized in claims 10 to 13.

The method according to the invention is preferably used the determination of small amounts of hydrocarbons in a solvent. The! Solvent, in in which the hydrocarbons are dissolved, advantageously that that for the extraction of hydrocarbons from water has been used. .

The invention is explained below with reference to the accompanying drawing, for example. Show in it:

Pig. 1 shows a schematic representation of the device for carrying out the analysis method according to the invention ; -

Pig. 2 to 6. Chromatograms obtained by analyzing various Samples containing traces of hydrocarbons in a solvent were obtained.

According to FIG. 1, the first. Main flow route one Line 17 is supplied to the carrier gas via a line 1 will. The throughput of the carrier gas is controlled with a ■ regulating valve 2 set and checked with a pressure gauge 4. !Further an injection block 6 is provided, into which the sample is introduced, which substances are not to be analyzed, in particular the solvent and the hydrocarbons to be analyzed.

509828/0548

- σ -

Furthermore, a first separation column 7 is provided, which on the one hand separates the substances that are not are to be analyzed and, on the other hand, effected in the hydrocarbons to be analyzed. To be favoured Columns used that are suitable for preparative chromatography, as they do the mentioned separation even with a enable large sample quantities. In addition, a detector 8 is provided, which is a thermal conductivity detector (Katharometer) or a flame ionization detector can act; however, in the latter pail is the flow path provided with a "by-pass" 27 so that only a small volume of the sample is fed into the detector 8. Of the Detector 8 shows the beginning and the end of the elution of the constituents of the sample and also the beginning and the end of the Phases of the method according to the invention. The stationary phase of the first separation column 7 of the first main flow path must be temperature stable in order to avoid any decomposition which would adversely affect the analysis.

The second main flow path has a line 24, which opens into a trap 11, which in the illustrated case consists of a vessel that is by suitable means 12 on a very low temperature is maintained, for example by a stream of liquid nitrogen. The vessel 11 can through a device 14 are heated, preferably by a low voltage current, which through the jacket of the vessel 11 or by other suitable means such as a moveable furnace. Furthermore is an analytical chromatography column 15 is provided, the Type depends on the type of product to be analyzed. The column 15 is to a detector 16, for example a Flame ionization detector connected. The column 15 and the detector 16 can have an identical column and a

509828/0548

second detector of the same type be connected, resulting in a known arrangement with detectors rotating in opposite directions .

The third main flow path has a line 25 on, which is provided with a valve 10 for regulating the flow rate at the outlet.

The fourth main flow path has a line 18 on, which is fed via line 1 with carrier gas. The throughput of the carrier gas in line 18 is with a Regulating valve 3 is set and checked with a pressure gauge 5.

The lines 17, 18, 24 and 25 open into a multi-way valve with four ways 20, 21, 22, 23 of the different Connects flow paths with one another or separates one from the other.

Finally, there is a bypass flow path with a conduit 26 is provided, which leads to the outside and which in the illustrated embodiment to the second main flow path connected downstream of trap 1 and upstream of column 15 is. This secondary flow path has a shut-off valve 13, which this flow path from the atmosphere to able to separate or connect with it.

The method according to the invention consists of three Main phases together. The following describes the separation of the product to be analyzed from the remaining substances by retention of the former compared to the latter in the first main flow path.

In the first phase only routes 20 and 21 of 509828/0548 are

- ίο -

Four-way valve 9 open, so that the first main flow path with the third main flow path or the second main flow path is connected to the fourth main flow path. Paths 22 and 23 are closed. The valve 13 is open, likewise the valve 10, the secondary flow path and the third main flow path leading to the outside.

The analyzer is operated via line 1 continuously Carrier gas is supplied, which divides the lines 1? and 18 applied. This flows in line 17 Carrier gas through the regulating valve 2, its pressure being checked with the manometer 4-. About the injection block 6 is the Sample, which contains the hydrocarbons to be analyzed in a solvent, fed to the carrier gas. The one from the Carrier gas and the gas stream of the sample flows through the preparative column 7? which are at a temperature close to the ambient temperature is held. The solvent or substances that should not be analyzed will be separated from the products to be analyzed. The end of the elution of the solvent is recorded with the thermal conductivity detector or Eatharometer 8 detected, whereupon the solvent via the path 20 of the four-way valve 9 and the third Main flow path (line 25 and regulating valve 10) the device exits.

During this first phase, the fourth main flow path is simultaneously supplied with carrier gas via line 18, whereby it flows through the regulating valve 3 and its pressure is checked with the manometer 5. Then it occurs over the Path 21 of the valve 9 into the second main flow path via the Line 24, then flows through the trap 11 and is via the secondary flow path whose shut-off valve 13 is open

509828/0548

the line 26 led into the open. While the detector 16 does not provide a signal in the course of this first phase, the detector 8 shows the end of the elution of those compounds of the sample that will not be analyzed later should.

In the second phase of the process, paths 20 and 21 of valve 9 are closed and paths 22 and 23 opened so that the first and second main flow paths or the third and fourth main flow paths with one another are connected. The analyzer will continue to be over the line 1 is supplied with carrier gas which is divided into two parts.

One part of the carrier gas feeds the fourth main flow path. Its throughput is adjusted with the valve 3 and its pressure is checked with the pressure gauge 5. The carrier gas then leaves this flow path and flows via path 23 of the valve 9 into the third main flow path through which it flows before it comes out of the device via line 25 of this Flow path goes off.

The other part of the carrier gas supplies the first main flow path; its throughput is adjusted with valve 2 and its pressure is checked with the pressure gauge 4. It then flows through the first and second main flow path, until it comes to the junction on the second main flow path from where it arrives via the secondary flow path, since the Valve 13 is still open, goes into -reie.

The temperature of the preparative column is then increased rapidly, preferably by about 30 ° C. per minute, specifically

509828/0548

except for a temperature that is compatible with the type of filling! for example to about 250, 300 or 400 C, so that the hydrocarbons that were retained until then are released. These flow through the detector 8 and are then fed via the path 22 of the tap 9 into the second main flow path via the line 24. So that is Transfer of the hydrocarbons to be analyzed into the actual analytical flow path completed. The hydrocarbons are kept in the cooled trap 11, which is kept at a low temperature by suitable means 12 is held back. This means 12 can be, for example, an acetone / dry ice cold bath, with the temperature of the bath is about -80 ° C, or liquid nitrogen, the leads to a temperature of about -180 ° C. The temperature of the trap 11 depends on the volatility of the one to be analyzed Products dependent.

After the hydrocarbons to be analyzed have been transferred from the first main flow path to the second one begins the third phase of the procedure. For this purpose, the paths 22 and 23 of the valve 9 are closed, as is the valve 13 of the Tributary flow path. Via the paths 20 and 21 of the valve 9, the second with the fourth main flow path becomes again or the first connected to the third main flow path.

The analyzer is continuously supplied with carrier gas via line 1. A part flows through the first and third main flow path before leaving the device emanates. The other part is fed into the fourth and second main flow paths via the line are connected to one another via the path 21 of the cock 9. The hydrocarbons retained in the trap 11 become

509828/0548

quickly by quickly increasing the temperature of the! "every 11 released with the aid of a suitable device 14. Preferably for this purpose a current of low voltage is sent through the casing of the case 11; but also other institutions are usable. The temperature of the trap 11 is increased to a final temperature which is sufficient to release the retained hydrocarbons; A temperature of about 400 ° G is generally sufficient. The gas stream consisting of hydrocarbons and carrier gas then flows into the analytical column 15, from which the hydrocarbons are eluted. The temperature of the column 15 can be programmed in such a way that optimal Conditions for the elution of the hydrocarbons to be analyzed are present. These are finally detected with the detector 16. During this last phase it delivers the detector 16 corresponds to the hydrocarbons to be analyzed Signals that can be conveniently registered with known devices. By the fact that the to be analyzed If the mixture escapes rapidly from the trap 11 by rapidly increasing the temperature of the trap 11, the mixture becomes almost currently introduced into the analytical column.

With the method according to the invention were excellent Analysis results achieved, in particular with mixtures of hydrocarbons contained in carbon tetrachloride or n-pentane were dissolved.

The following examples are provided for further explanation of the invention. The chromatograms given in FIGS. 2 to 6 were made with the aid of the ones shown schematically in FIG Device received.

509828/0548

Example I.

The preparative column 7 according to FIG. 1 consists of one. Pipe 1 m long and 4 mm internal diameter and contains on a carrier with the trade name "Diatoport-s" (60 to 80 mesh) JO% by weight of a stationary phase which is sold under the name "07 101".

The analytical column 15 according to FIG. 1 consists of a tube 5 m long and 3 ^ 15 mm internal diameter. The tube contains 3% by weight of the stationary phase "OV 101" the carrier "Diatoport-s" (60 to 80 mesh).

The cold trap 11 according to FIG. 1 is formed by a tube approximately 0.25 m long and 3 ₅ 15 mm outer diameter. It contains "Ghromosorb W" (60 to 80 mesh) over a length of 0.10 m.

Helium is used as the carrier gas at a pressure of 5 bar. During the analysis, the following flow rates were determined in cnr per minute:

Preparative
Column 17 Trap 11 Analytical
Pillar 15 Phase 1 60 30th 0 Phase 2 60 60 0 Phase 3 60 30th 30th

509828/0548

The temperature of detectors 8 and 16 was

The analysis is based on 30 microliters liquid state of an extract from carbon tetrachloride and hydrocarbon egg carried out in the wastewater a Petroleum refinery are included. During the first phase, which lasts about 10 minutes, the temperature becomes the preparative Column "7 held at about 25 ° G.

During the second phase, which lasts about 20 minutes, the temperature of the preparative column 7 is increased rapidly to about 250 ° G, by JO ⁰ C per minute, while the temperature of the trap 11 with liquid nitrogen is -180 ° C is held. In the course of the third phase, which also lasts about 20 minutes, the temperature of the trap 11 is quickly brought to about 400 ° G with a low-voltage current flowing through the casing of the trap 11. The temperature of the analytical column 15, which is connected in series, is programmed in the temperature interval between 40 ° and 250 ° C., specifically preferably around 10 ° C. per minute.

The chromatogram obtained is shown in FIG. The beginning of each of the three phases of the analysis is with the letters A, B and G indicated on the coordinate, on the Time "is applied.

This chromatogram can be divided into two parts. The part given above reproduces the signals * which were emitted by the katharometer 8 during phases 1 and 2 are. The part given below reproduces the signals which are generated by the flame ionization detector 16 during the third phase have been submitted. The last-mentioned part represents the chromatographic analysis of the hydrocarbons that originally were included in the sample. It is therefore sufficient for

509828/0548

qualitative and quantitative identification of these hydrocarbons, to refer to a reference chromatogram obtained under the same conditions as common in chromatography. For this purpose, a chromatographic analysis with 30 microliters of a calibration mixture was carried out carried out, which 365 ppm η-paraffins in carbon tetrachloride contains. The reference chromatogram obtained is shown in FIG. The points A ^, B ^ and C ^ give the Beginning of the individual phases again. By comparison with the chromatogram of the sample according to FIG. 2, the analyzed Sample calculated a total content of 225 ppm hydrocarbons.

Example II

It will be 30 microliters, based on the liquid State, of a mixture that contains about 500 ppm naphtha in n-pentane contains, analyzed. In particular there will be a determination of aromatic compounds with 6.7 or 8 carbon atoms each Molecule in the mixture sought, being on the analytical column 15 only a certain part of that on the first column 7 separate components is applied. The analysis is carried out under the following conditions:

The preparative column 7 is the same as in Example I. The analytical column 15 consists of a tube of 2 m length and 3.15 mm outer diameter and contains 30% by weight a polar stationary phase with the trade name "Fractonitril VI" (hexakis - (cyano - 2 '- ethoxy 1, 2, 3, 4, 5, 6) - hexane of sorbitol) on "Ghromosorb P" (60 to 80 mesh). The trap 11 is the same as in Example I. The carrier gas here is also helium at 50 bar, the throughputs being the same as in example I. The temperature of the detectors 8

509828/0548

and 16 is 250 ° C as in the previous example.

During the first phase, which lasts 4 minutes, the temperature of the preparative column 7 is about 25 ° C. During the second phase, which lasts 3.5 minutes, the temperature of the preparative column 7 is preferably increased by 30 ° C. per minute to 250 ° C increases, while the temperature of the trap 11, as in Example I, is kept ^{at -180 0 G by liquid nitrogen.}

During the third phase, which lasts 12 minutes, the temperature of the trap 11 is lowered by a current Voltage that flows through the casing of the trap 11, quickly brought to about 400 ° C .. The temperature of the analytical Column 15 is 130 ° C. The products are then with the Flame ionization detector 16 detected.

Like the chromatogram obtained, which is shown in FIG. 4, in which the beginning of the individual phases with D, E and F is indicated is due to the polarity of the analytical column 15 used by an excellent analysis the aromatic hydrocarbons achieved the desired determination, with the saturated hydrocarbons on this Column to be separated. To carry out their quantitative analysis, it is enough to refer to a reference chromatogram, that with a certain mixture under the same conditions has been received. The chromatogram obtained according to this example is structured in the same way as that according to Fig. 2 and 3i, namely in a part indicated above and a part given below, the latter being that which is of interest for the determination of the hydrocarbons is. ■

509828/0548

Example III

The first column 7 after. Fig. 1 consists of an Eohr . of 1 m length and 4 mm inner diameter and is with "Spherosil XOBO75", ie filled with spheres made of silica. The analytical column 15 according to FIG. 1 consists of a tube 1 m long and 3 »175 mm internal diameter and is also filled with "Spherosil XOBO75".

The other working conditions are the same as those given in Example I. The temperature of the two columns 7 and 15 of Fig. 1 is, however. 60 C. To the to be analyzed To transfer products from the first main flow path into the trap 11 of the second main flow path, the temperature becomes the first column 7 preferably by 30 ° C per minute Brought 35O to 400 ° C. During the third phase of the analytical process, namely the analysis in the column 15> the temperature is programmed preferably to 20 ° G per minute 35O to 400 ° C increased. The first, second and third phase lasts 2, 20 or 13 minutes on.

. In Fig. 5 is a chromatogram shown by Analysis of an extract obtained by extracting hydrocarbon-containing contaminated water with carbon tetrachloride is formed.

The reference chromatogram is shown in FIG. 6, obtained by analyzing a solution that is 365 Contains ppm η-paraffins in carbon tetrachloride.

Based on these two chromatograms, the analyzed sample yields 255 PP ¹ ^ hydrocarbons. On the two chromatograms (Fig. 5 and 6) is. the beginning of the

509828/0548

three phases with G, H "and.I for the chromatogram of the sample or GL, IL and I. given for the reference chromatogram.

509828/0548

Claims (15)

Expectations 1. Procedure for gas chromatographic analysis of substances, which are contained in a small amount in a solvent, characterized in that two flow paths for the carrier gas are provided, with the substances to be analyzed separated in the first flow path and into a trap that is upstream a chromatographic column is arranged in a second flow path, whereupon the to substances to be analyzed are released in the trap and separated in the column of the second flow path. 2. The method according to claim 1, characterized in that the other substances except for the substances to be analyzed by a third flow path, which is connected to the first .Strömungsweg during the discharge. 3. The method according to claim i and 2, characterized in that that the separation of the substances to be analyzed from the rest Substances in the first flow path through a chromatographic Pillar. 4. The method according to claim 3> characterized in that the The course of the elution of the remaining substances was determined with a detector arranged in the first flow path downstream of the column will. 5. The method according to claim 3 or 4, characterized in that that to transfer the substances to be analyzed, the first flow path is connected to the second flow path and the The temperature of the column of the first flow path is increased. 6. The method according to claim 5, characterized in that the £ 09828/0544 Temperature of the column of the first flow path to 300 to 400 ° C is increased. 7. The method according to any one of claims 1 to 6, characterized in that that the trap is frozen during the transfer of the substances to be analyzed into the second flow path will. '■ · 8. The method according to .Anspruch 7j, characterized in that the substances to be analyzed in the trap by increasing the Temperature of the trap to be released to about 400 ° C. 9. Device for performing the method according to one of the Claims 1 to 8, characterized in that an injection block (6), a device, in the first flow path (line 17) (7) to separate the substances to be analyzed and a detector (8) and in the second flow path (line 24) a trap (11), an analytical chromatography column (15) and a detector (16) are arranged in a row, wherein the two flow paths (lines 17 and 24) can be connected to one another via a switching element (9). 10. Apparatus according to claim 9? marked by a third flow path (line 25) with a regulating valve (10) and a fourth flow path (line 18) with a flow controller (3). for the carrier gas j where the third (line 25) and the fourth flow path (line 18) via the switching element (9) with each other or with the first (line 17) or can be connected to the second flow path (line 24). 11. Apparatus according to claim 9 or 10, characterized by 509828/0548 a bypass flow path (line 26) with an exhaust valve (13), which is connected to the second flow path (24) downstream of the trap (11) and upstream of the chromatography column (15) connected is. 12. Apparatus according to claim 9? 10 or 11, characterized in that that in the first flow path (line 17) upstream of the injection block (6) a flow controller (2) for the carrier gas is provided. , 13. Device according to one of claims 9 to 12, characterized in that that as a device (7) for separating the substances to be analyzed in the first flow path (line 17) a Chromatography column is provided. 14. Application of the method according to one of claims 1 to 8 for the determination of small amounts of hydrocarbons in one Solvent. 15. Application according to claim 14, characterized in that the Solvent is used to extract the hydrocarbons from water. 509828/0548 Blank page