CN108389773A - A kind of headspace sampling device and headspace sampling analysis system and method - Google Patents

Abstract

The invention relates to a headspace sampling device, a headspace sampling analysis system and a method. The embodiment of the headspace sampling device provided by the present invention includes: a main body of a columnar structure, one end is provided with a counterbore, and the other end is provided with a sealing hole, and the counterbore and the sealing hole are connected by a communication hole; the diameter of the counterbore and the diameter of the sealing hole The pore diameter is larger than that of the connecting hole, and the pore diameter of the connecting hole is larger than the diameter of the headspace pin; the injection septum is inserted into the counterbore, and it is sealed and closely matched with the counterbore; it can be penetrated by the headspace pin; the sampling connection of the tubular structure One end is sealed and tightly fitted with the sealing hole, and the other end is connected to the sampling tube. Using this embodiment, during the VOC component analysis process of the mass spectrometer, the connection from sampling to sample injection can be perfectly connected, which can not only meet the needs of headspace needle injection but also match the sampling pipeline well, which not only solves the problem of pre-sample Dealing with the problem facilitates multiple needle insertion sampling, and does not introduce any organic solvents, avoiding contamination of the instrument.

Description

Headspace sampling device, headspace sampling analysis system and method

technical field

The invention generally relates to the technical field of analysis of volatile organic compounds in environmental protection technology, and in particular to a headspace sampling device, a headspace sampling analysis system and a method.

Background technique

Environmental pollution caused by rapid economic development has become a hot spot in recent years. Environmental monitoring has developed from the initial analysis of volatile organic compounds (VOC) in the atmosphere to the analysis of VOC in water and VOC concentration in soil. Sensitive analytical equipment plays an important role in the field of environmental monitoring.

Mass spectrometer is a kind of gas component and concentration analysis equipment. When analyzing volatile organic compounds (VOC) components in water quality, it uses headspace sampling, a convenient and fast sample processing method. This method can avoid the tedious sample pretreatment process, and also eliminate the interference of organic solvents on the analysis results. Usually headspace sampling includes five steps: pressurization, sampling, levelling, sample injection and purging. Among them, the sample injection is to inject the VOC volatilized in the collected solution into the mass spectrometer, and then the sample is purged by the carrier gas to complete the final analysis. The existing mass spectrometer sampling system mostly uses a sampling tube for sampling, while the headspace sampler uses a needle to complete the sample injection. In the process from sampling to sample injection, there is a lack of stable and reliable connection between the two, resulting in the use of Mass spectrometers can easily lead to contamination problems when analyzing complex samples.

Contents of the invention

The purpose of the present invention is to provide a headspace sampling device and a headspace sampling analysis system and method. Using the headspace sampling device provided by the embodiment of the present invention can perfectly connect from sampling to sample injection during the VOC component analysis process using a mass spectrometer, which can not only meet the needs of headspace needle injection but also be well integrated with Sample line matching.

In one embodiment of the headspace sampling device provided by the present invention, it includes:

The main body has a columnar structure, one end is provided with a counterbore, and the other end is provided with a sealing hole, and the counterbore and the sealing hole are connected by a communication hole; the diameter of the counterbore and the diameter of the sealing hole are larger than the diameter of the sealing hole the aperture of the communication hole, the aperture of the communication hole is larger than the diameter of the headspace pin;

An injection septum, one end of which is inserted into the counterbore, is sealed and tightly matched with the counterbore; it is made of elastic material and can be penetrated by the headspace pin;

The sampling connection part is a tubular structure, one end is sealed and tightly matched with the sealing hole, and the other end is connected to the sampling tube.

In some embodiments, the sealing hole is provided with an internal tapered thread;

One end of the sampling connection part is provided with an external taper thread; the internal taper thread is in sealing connection with the external taper thread.

In some embodiments, the outer wall of the main body is close to one end of the sealing hole, and more than two tightening platforms are provided along the length direction of the main body for wrench clamping.

In some embodiments, the outer wall of the main body is provided with mounting nuts.

In some embodiments, the main body is cylindrical and made of aluminum; the injection septum is made of rubber.

In some embodiments, one end of the main body portion provided with a counterbore extends radially outwards with an ear-shaped platform.

In some embodiments, one end of the injection septum is inserted into the counterbore, and the other end compresses the ear platform.

In some embodiments, also include:

The cover body is made of aluminum with a thickness of 0.2mm-1mm, and tightly covers the injection septum and the ear-shaped platform.

The present invention also provides an embodiment of a headspace sampling analysis system, including:

Adopt the headspace sampling device in the above-mentioned embodiment;

Headspace sampler, dryer, four-way valve, and mass spectrometer connected in sequence by tubing; also includes:

The casing is used for fixedly installing the headspace sampling device, the dryer, the four-way valve and the mass spectrometer.

The present invention also provides an embodiment of a headspace sampling analysis method, using the above-mentioned headspace sampling analysis system, including steps:

A. The headspace needle penetrates the injection septum, and the gas to be analyzed is introduced into the headspace sampling device, and the gas to be analyzed enters the sampling tube through the counterbore, the communication hole and the sampling connection in sequence;

B. The gas to be analyzed enters the desiccator through the sampling tube, and is discharged after being dehumidified by the desiccator;

C. The gas to be analyzed discharged from the drier enters the mass spectrometer through the four-way valve and through the pipeline;

D. The gas to be analyzed discharged from the dryer is discharged after VOC component analysis;

E. The gas discharged from the mass spectrometer passes through the four-way valve and is discharged from the exhaust outlet.

The headspace sampling device and the headspace sampling analysis system and method provided by the embodiments of the present invention can perfectly connect from sampling to sample injection during the process of VOC component analysis of the gas to be analyzed by using a mass spectrometer, both It can satisfy the headspace needle injection and can be well matched with the sampling pipeline. It not only solves the problem of sample pretreatment, but also facilitates multiple needle sampling, and does not introduce any organic solvents to avoid contamination of the instrument.

Description of drawings

Fig. 1 is a schematic structural view of an embodiment of the headspace sampling device of the present invention;

Fig. 2 is a sectional view of device A-A shown in Fig. 1;

Fig. 3 shows the flowchart of an embodiment of the headspace sampling analysis system of the present invention;

Figure 4 shows the state of the four-way valve when the mass spectrometer in the system shown in Figure 3 works;

Figure 5 shows the state of the four-way valve when the mass spectrometer in the system shown in Figure 3 is not working.

Explanation of reference signs:

10-Headspace sampling device;

100 - the main body;

1001-counterbore; 1002-sealed hole; 1003-connecting hole; 1004-ear platform;

200-injection septum;

300-sampling connection part;

3001-joint body; 3002-ferrule; 3003-fastening nut;

20 - dryer;

30-four-way valve;

301-the first valve port; 302-the second valve port; 303-the third valve port; 304-the fourth valve port;

40 - mass spectrometer.

Detailed ways

The specific implementation manners of the present invention will be described in more detail below in conjunction with the accompanying drawings and examples, so as to better understand the solution of the present invention and its advantages in various aspects. However, the specific embodiments and examples described below are for the purpose of illustration only, rather than limiting the present invention.

An embodiment of the headspace sampling device provided by the present invention, as shown in FIG. 1 , includes: a main body 100 , an injection septum 200 and a sampling connection 300 .

Fig. 2 is a sectional view A-A of the embodiment of the headspace sampling device shown in Fig. 1 . As shown in FIG. 2 , the main body 100 is a columnar structure with a counterbore 1001 at one end and a sealing hole 1002 at the other end. The counterbore 1001 and the sealing hole 1002 are connected by a communication hole 1003 . The aperture diameter of the counterbore 1001 and the aperture diameter of the sealing hole 1002 are larger than the aperture diameter of the communication hole 1003, and the aperture diameter of the communication hole 1003 is larger than the diameter of the headspace pin. Wherein, the diameter of the communication hole 1003 is larger than the diameter of the headspace pin, the smaller the better, so as to avoid the gas to be analyzed remaining on the pipe of the headspace sampling device, resulting in inaccurate analysis results.

In principle, the main body 100 can use any material as a raw material, as long as it can meet the requirements of use. However, starting from practical applications, in a specific embodiment, the main body 100 uses aluminum as a raw material, which is not only easy to process, but also has a relatively light overall weight, and has better economy.

One end of the injection septum 200 is inserted into the counterbore 1001, and it is sealed and closely matched with the counterbore 1001; the other end can protrude or be recessed into the counterbore 1001, but the indentation should not be too much, and the headspace needle should be able to pass through. The gas to be analyzed is introduced into the communication hole 1003 through the injection septum. When the other end of the injection septum 200 protrudes from the main body 100, the sealing and tightness between the end inserted into the counterbore 1001 and the counterbore 1001 should be ensured, and it should not be loosened when the headspace pin is inserted and pulled out many times.

The injection septum 200 is made of elastic material. On the one hand, when inserted into the counterbore 1001, the expansion of the elastic material is used to seal and closely fit the counterbore 1001; The gas to be analyzed is introduced into the communication hole 1003 . In a specific real-time example, the injection septum is made of rubber. The rubber's hardness, elasticity, and outward expansion when squeezed make the sealing effect and matching effect with the counterbore 1001 very good.

In this embodiment, the sampling connection part 300 is a tubular structure, specifically, a steel pipe may be used as a base material. One end of the sampling connection part 300 is sealed and tightly matched with the sealing hole 1002; the other end is connected with a sampling tube. In other embodiments, the main body 100 and the sampling connection part 300 may also be integrally formed, omitting the sealing connection between the sampling connection part 300 and the main body 100 . But in doing so, it is possible that when a certain part is damaged and needs to be replaced, the entire part needs to be replaced, which is not as economical as manufacturing it separately.

In a specific embodiment, taper threads are used for sealing between the sampling connection part 300 and the sealing hole 1002 . The sealing hole 1002 is provided with an internal taper thread, and one end of the sampling connection part 300 is provided with an external taper thread. The inner taper thread of the sealing hole 1002 is in sealing connection with the outer taper thread of the sampling connection part 300 . Under normal circumstances, the tooth profile of the tapered thread is triangular, mainly relying on the deformation of the tooth to ensure the tightness of the thread pair, and it is mostly used for pipe fittings. The tapered pipe thread has a taper of 16:1, because this feature makes the raw material tape wound on the thread more evenly distributed on the thread, which has better sealing performance, and the steel pipe wall used for the tapered pipe thread is thicker , with higher pressure resistance, so this type of thread is widely used to seal liquid and gas, and can play a good sealing effect. Usually, the outer tapered thread of 300 at the sampling connection part is wrapped with raw material tape, and the outer tapered thread and the inner tapered thread of the sealing hole 1002 are pressed against the raw material tape to fill the thread gap to achieve a sealing effect.

Generally, the sampling connection part 300 is composed of a joint body 3001 , a ferrule 3002 and a fastening nut 3003 . An external taper thread is provided on the outer surface of one end of the joint body 3001 to seal and tightly connect with the internal taper thread of the sealing hole 1002 . Utilize the seamless steel pipe to insert the fastening nut 3003, ferrule 3002 and the other end of the joint body 3001 in sequence; when the ferrule 3002 and the fastening nut 3003 are set on the seamless steel pipe and inserted into the joint body 3001, tighten the fastening nut 3003, At this time, the outside of the front end of the ferrule 3002 is attached to the conical surface of the joint body 3001, and the inner blade evenly bites into the seamless steel pipe to form an effective seal.

The headspace needle can penetrate the injection septum 200 , introduce the gas to be analyzed into the communication hole 1003 , and then enter the sampling tube through the sampling connection part 300 . During this process, the sealing spacer 200 and the counterbore 1001 are sealed and tightly fitted, and the sampling connection part 300 is sealed and tightly fitted with the sealing hole 1002 . The gas to be analyzed is introduced into the communication hole 1003 through the headspace needle, then to the sampling tube, and then enters the instrument through each pipeline for analysis, which realizes the perfect connection from sampling to sample injection, which can meet the needs of headspace needle injection and can be well The perfect match with the sampling pipeline not only solves the problem of sample pretreatment, but also does not introduce any organic solvents, avoiding the pollution of the instrument.

Since the injection septum 200 has elasticity and expansion force, after the headspace needle penetrates the injection septum 200, it will be squeezed by the injection septum 200 and no leakage will occur. After the headspace needle is pulled out from the injection septum 200, under the action of elasticity and expansion force, the hole through which the headspace needle penetrates the injection septum 200 is filled, which still ensures a good sealing effect and can also Guaranteed multiple insertion and extraction sampling of headspace pins.

In one embodiment, the main body 100 is cylindrical, and an ear-shaped platform 1004 extends radially outward from one end provided with the counterbore 1001 . At this time, one end of the injection septum 200 is inserted into the counterbore 1001 , and the other end is pressed against the ear-shaped platform 1004 . At the same time, this embodiment also includes a cover body made of aluminum material with a thickness of about 0.2mm-1mm, and the cover body tightly covers the outside of the injection septum 200 and the ear-shaped platform 1004 . Whether one end of the injection septum 200 is pressed against the ear-shaped platform 1004, or the cover is tightly wrapped on the outside of the injection septum 200 and the ear-shaped platform 1004, the sealing effect between the injection septum 200 and the main body 100 is better. Well, it's stronger, and it's convenient for multiple insertion and extraction of headspace pins. If necessary, the old injection septum 200 can also be removed, and then a new injection septum 200 can be installed with crimping pliers.

In one embodiment, in order to facilitate the installation and use of the device, at the end of the outer wall of the main body 100 close to the sealing hole 1002, more than two tightening platforms are provided along the length direction of the main body 100, so as to facilitate the clamping of the wrench during installation. hold. Wherein, the tightening platform can protrude outward in the radial direction; it can also be a spot-faced plane, whether it is an outwardly protruding plane or a spot-faced plane, it is along the length direction of the main body 100, along the radial direction. outside or inside. Of course, the spot-faced plane should not affect the sealing and tight fit effect between the sealing hole 1002 and the sampling connection part 300 . The outwardly protruding plane shall not affect the installation and use of the device.

At the same time, in this embodiment, the outer wall of the main body 100 is also provided with mounting nuts for easy installation. In a specific embodiment, there are two mounting nuts. When installing the device, pass the main body 100 through the mounting plate, and then press and lock the mounting nuts on both sides of the mounting plate to fasten the main body 100 on the mounting plate. mounting plate. A platform can also be extended radially outwards at a certain position in the middle of the main body 100, so that when the main body 100 passes through the mounting hole on the mounting plate, this platform can play a blocking role, and then on the other side of the mounting plate One side is squeezed and locked with a mounting nut, so that the main body 100 is fastened on the mounting plate. Prevent repeated plugging and unplugging of the sampling line from causing the sealing failure of the sampling line due to repeated force

The present invention also provides an embodiment of a headspace sampling analysis system, as shown in FIG. 3 , which is a schematic flow chart of the system. The system adopts the headspace sampling device 10 in the above-mentioned embodiment, and the system includes: a headspace sampling device 10, a drier 20, a four-way valve 30 and a mass spectrometer 40 connected by pipelines in sequence, wherein the headspace sampling device The sample device 10, the dryer 20, the four-way valve 30 and the mass spectrometer 40 are all installed on the casing. The headspace sampling device 10 is fixed on the mounting plate, the headspace needle penetrates the injection septum 200 and is inserted into the sink hole or the communication hole, and the sampling connection part 300 is connected to the dryer 20 through the sampling tube.

The four-way valve 30 has four valve ports: a first valve port 301 , a second valve port 302 , a third valve port 303 and a fourth valve port 304 . The first valve port 301 is connected to the gas outlet of the dryer 20 through a pipeline; the second valve port 302 is connected to the gas inlet of the mass spectrometer 40 through an inlet hard tube; the third valve port 303 is connected to the gas outlet of the mass spectrometer 40 through an outlet hard tube ; The fourth valve port 304 is connected to the evacuation outlet through a pipeline.

When the mass spectrometer 40 is required to analyze the VOC components of the gas, the first valve port 301 and the second valve port 302 inside the four-way valve 30 are connected, and the third valve port 303 is connected with the fourth valve port 304, as shown in FIG. 3 Show. At this time, the gas to be analyzed is introduced into the counterbore 1001 or the communication hole 1003 of the headspace sampling device 10 through the injection septum 200 through the headspace needle. The gas to be analyzed sequentially passes through the counterbore 1001 , the communication hole 1003 and the sampling connection part 1002 in the headspace sampling device 10 and then enters the sampling tube. The gas to be analyzed enters the drier 20 through the sampling pipe, and is dehumidified in the drier 20 before being discharged. Then, the gas discharged from the drier 20 enters the four-way valve 30 . In the four-way valve 30 , the dried gas enters the mass spectrometer 40 through the first valve port 301 , the second valve port 302 and the hard inlet pipe in sequence.

The dry gas is discharged as waste gas after VOC analysis in the mass spectrometer 40 . Exhausted waste gas enters the four-way valve 30 through the outlet hard pipe, passes through the third valve port 303 and the fourth valve port 304 in sequence in the four-way valve 30, and then is discharged from the exhaust outlet. That is, the method for performing headspace sampling analysis using this embodiment includes the following steps:

A. The headspace needle penetrates the injection septum, introduces the gas to be analyzed into the headspace sampling device, and the gas to be analyzed enters the sampling tube through the counterbore, the connecting hole and the sampling connection in turn;

B. The gas to be analyzed enters the dryer through the sampling tube, and is discharged after being dehumidified by the dryer;

C. The gas to be analyzed discharged from the dryer enters the mass spectrometer through the four-way valve and the pipeline;

D. The gas entering the mass spectrometer is discharged after being analyzed by VOC components;

E. The gas discharged from the mass spectrometer passes through the four-way valve and is discharged through the pipeline.

When the mass spectrometer 40 is not required to analyze the VOC components of the gas, the first valve port 301 and the fourth valve port 304 inside the four-way valve 30 are communicated, and the second valve port 302 is communicated with the third valve port 303, as shown in Figure 4 shown. At this time, the gas introduced through the headspace needle passes through the headspace sampling device 10 , the dryer 20 , the first valve port 301 and the fourth valve port 304 in sequence, and then is directly discharged from the exhaust outlet. A closed loop is formed between the second valve port 302 , the mass spectrometer 40 and the third valve port 303 .

Finally, it should be noted that obviously, the above-mentioned embodiments are only examples for clearly illustrating the present invention, rather than limiting the implementation. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. However, the obvious changes or variations derived therefrom are still within the protection scope of the present invention.

Claims (10)

1. A headspace sampling device, characterized in that, comprising: The main body is a columnar structure, one end is provided with a counterbore, and the other end is provided with a sealing hole, and the counterbore and the sealing hole are connected by a communication hole; the diameter of the counterbore and the diameter of the sealing hole are larger than the diameter of the sealing hole The aperture of the communicating hole, the aperture of the communicating hole is greater than the diameter of the headspace pin; an injection septum, inserted into the counterbore, sealed and tightly fitted with the counterbore; capable of being penetrated by the headspace pin; The sampling connection part is a tubular structure, one end is sealed and tightly matched with the sealing hole, and the other end is connected to the sampling tube. 2. The headspace sampling device according to claim 1, wherein the sealing hole is provided with an internal taper thread; One end of the sampling connection part is provided with an external taper thread; the internal taper thread is in sealing connection with the external taper thread. 3. The headspace sampling device according to claim 1, characterized in that, the outer wall of the main body is close to one end of the sealing hole, and more than two tightening platforms are arranged along the length direction of the main body. Hold it with a wrench. 4. The headspace sampling device according to claim 1, wherein a mounting nut is provided on the outer wall of the main body. 5 . The headspace sampling device according to claim 1 , wherein the main body is cylindrical and made of aluminum; the injection septum is made of rubber. 6 . The headspace sampling device according to claim 1 , wherein one end of the main body is provided with a counterbore, and an ear-shaped platform extends radially outward. 7 . 7. The headspace sampling device according to claim 6, wherein one end of the injection septum is inserted into the counterbore, and the other end is pressed against the ear-shaped platform. 8. The headspace sampling device according to claim 7, further comprising: The cover body is made of aluminum with a thickness of 0.2mm-1mm, and tightly covers the injection septum and the ear-shaped platform. 9. A headspace sampling analysis system using the headspace sampling device according to any one of claims 1-8, characterized in that it comprises: The headspace sampling device, desiccator, four-way valve and mass spectrometer connected sequentially through pipelines; The casing is used for fixedly installing the headspace sampling device, the dryer, the four-way valve and the mass spectrometer. 10. A headspace sampling analysis method, characterized in that, adopting the headspace sampling analysis system according to claim 9, comprising the steps of: A. The headspace needle penetrates the injection septum, and the gas to be analyzed is introduced into the headspace sampling device, and the gas to be analyzed enters the sampling tube through the counterbore, the communication hole and the sampling connection in sequence; B. The gas to be analyzed enters the desiccator through the sampling tube, and is discharged after being dehumidified by the desiccator; C. The gas to be analyzed discharged from the drier enters the mass spectrometer through the four-way valve and through the pipeline; D, the gas entering the mass spectrometer is discharged after VOC component analysis; E. The gas discharged from the mass spectrometer passes through the four-way valve and is discharged from the exhaust outlet.