CN103558322B - Low temperature pressurized headspace sampling device for determination of volatile substances in the atmosphere by GC-MS - Google Patents

Abstract

The invention relates to a low-temperature pressurization head space sample injection device for measuring volatile substances in the atmosphere through a GC-MS (gas chromatography-mass spectrometer) technology. The low-temperature pressurization head space sample injection device comprises a reciprocating full-glass piston pump which consists of a glass piston cylinder barrel (1), a unidirectional valve a (2), a unidirectional valve b (3), a clamp (4), a crank-link mechanism (5), a micro motor (6) and a worm speed reducer (7), a sampling head space bottle which comprises a head space bottle body (10) and cooling equipment, wherein a seal is arranged at the head space bottle; two injection needle heads with different lengths are inserted into the seal; the long needle head is in contact with the bottom to serve as a gas inlet needle (8); the short needle head is positioned at a bottleneck to serve as a gas exhaust needle (9); the gas inlet needle (8) is connected with the unidirectional valve b (3); the gas exhaust needle (9) is connected to a GC-MS; the head space bottle body (10) is arranged in the cooling equipment (12). Compared with the prior art, the low-temperature pressurization head space sample injection device has the advantages that the efficiency of collecting the volatile components in the atmosphere can be improved, so that the volatile components in the atmosphere can be fully collected and can be subjected to quantitative and qualitative compound analysis in the GC-MS.

Description

Low temperature pressurized headspace sampling device for determination of volatile substances in the atmosphere by GC-MS

technical field

The invention relates to a sampling device, in particular to a low-temperature pressurized headspace sampling device for GC-MS determination of volatile substances in the atmosphere.

Background technique

Gas chromatography-mass spectrometry (GC-MS) is the abbreviation of gas chromatography-mass spectrometry (GC-MS), which is a technology that combines gas chromatography (GC) and mass spectrometer (MS) through an appropriate interface, and uses computer technology to perform joint analysis. GC-MS is the most mature two-spectrum coupling technique. GC-MS is widely used in the separation and identification of complex components. It has the high resolution of GC and the high sensitivity of MS. It is suitable for the analysis of low molecular weight compounds (molecular weight <1000), especially for the analysis of volatile components. Volatile organic compounds (VOCs) are an important class of air pollutants, usually referring to organic compounds with a boiling point of 50-260°C at normal pressure or a saturated vapor pressure exceeding 133.32Pa at room temperature, including hydrocarbons, halogenated hydrocarbons, Aromatic hydrocarbons, polycyclic aromatic hydrocarbons, etc. The composition of VOCs is complex and harmful to human health. It is the precursor of ozone in the atmosphere and one of the important sources of PM2.5. Main hazards: It is easy to produce photochemical smog under the action of sunlight; it has direct toxicity to plants and animals at a certain concentration; it has the risk of carcinogenicity and leukemia to human body.

In recent years, the city has continuously strengthened the protection and governance of the atmospheric environment. While the economy continues to grow, the emissions of major traditional air pollutants such as industrial smoke and dust and sulfur dioxide are showing a downward trend year by year. However, with the economic development of the city, the number of motor vehicles continues to increase, and the total amount of VOCs emitted by man-made sources such as industry and residential life remains high. The city's photochemical smog, urban haze pollution, PM2.5 pollution, ozone (O ₃ ) Compound air pollution problems such as pollution are becoming more and more serious. The headspace sampling device can be connected with various gas chromatographs and mass spectrometers at home and abroad. It is an ideal sampling device for directly introducing volatile components in liquid or solid samples into gas chromatographs for separation and detection. The use of headspace technology can avoid the tedious and tedious sample pretreatment process, prevent the impurities brought by organic solvents from interfering with the analysis, and reduce the pollution of the chromatographic column and the injection port. It is dedicated to the analysis of volatile trace components. Headspace sampling (Head space analysis or HAS) is a gas chromatographic method based on the analysis of vapor composition placed above the sample in a sealed container. It is a new technology that began to develop in the seventies. Its biggest advantage is that it can truly reflect the gas phase composition of the sample, thus revealing the essence of the aroma that people smell. With the rapid development of commercial instrument automation, it has the advantages of good resolution, high sensitivity, strong selectivity, simple sample preparation, and rapid analysis. It is suitable for environmental analysis, solvent residual analysis, gas analysis in blood, and trace analysis of aromatic components in food or natural products. In order to improve the reproducibility of results, it is necessary to pay attention to the constant temperature of the sample and the tight airtightness of the syringe. .

In the atmospheric sampling device, the volatile substances are adsorbed in the sampling tube and loaded into the headspace sampling bottle, and then heated and pressurized to blow out the volatile components in the atmosphere and enter the GC-MS. The problem with the collection of volatile substances in the atmosphere is that the temperature difference and pressure difference between the inside and outside of the sampling tube can lead to the loss of volatilization of the sample, and the compound cannot be analyzed correctly, which brings great errors and poor reproducibility to the analysis results. Some researchers mentioned in the technical paper of "Brand and Standardization" No. 10, 2012 that in traditional headspace analysis, the injection volume is realized by the injection time or quantitative tube, and is also affected by factors such as temperature and pressure. . As long as the injection conditions can be completely reproduced, the accuracy of quantitative analysis can be guaranteed. In order to solve the above-mentioned problems of large sampling errors and poor reproducibility, this patent invents a low-temperature pressurized headspace sampling device.

Contents of the invention

The object of the present invention is to provide a low-temperature pressurized headspace sampling device for measuring volatile substances in the atmosphere by GC-MS in order to overcome the above-mentioned defects in the prior art.

The object of the present invention can be achieved through the following technical solutions: a low-temperature pressurized headspace sampling device for GC-MS determination of volatile substances in the atmosphere, characterized in that it comprises:

Reciprocating all-glass piston pump, consisting of glass piston cylinder (1), one-way valve a (2), one-way valve b (3), clamping clip (4), crank-link mechanism (5), micro motor (6) Composed of a worm reducer (7), one end of the glass piston cylinder (1) is provided with a parallel check valve a (2) and a check valve b (3), and the piston at the other end passes through the clamping clip (4 ) is sequentially connected to the crank linkage (5), the worm reducer (7), and the micro motor (6), and the one-way valve a (2) is connected to the sampling pipe (13);

The headspace bottle for sampling includes the headspace bottle (10). The headspace bottle is provided with a seal, and two injection needles, one long and one short, are inserted into the seal, wherein the long needle touches the bottom as an air inlet needle (8), and the short needle The mouth of the bottle is used as the exhaust needle (9), the inlet needle (8) is connected to the one-way valve b (3), and the exhaust needle (9) is connected to the GC-MS;

Cooling device, the headspace bottle (10) is placed in the cooling device (12).

The material of the air inlet needle (8) and the exhaust needle (9) is stainless steel.

The material of the headspace bottle (10) is glass, and the headspace bottle (10) maintains tight airtightness through sealing.

The cooling device (12) is a stainless steel container with built-in liquid nitrogen or dry ice.

The exhaust needle (9) is connected to the GC-MS through a pipeline, and a volume flow meter (14) is arranged on the pipeline.

An application of a low-temperature pressurized headspace sampling device for GC-MS determination of volatile substances in the atmosphere, which is characterized in that the online sealing of the sampling tube is used to separate from the direct headspace technology, and the thin metal tube of the gas inlet and outlet is clipped, sealed, cut and then folded Bend, no need to transfer, direct analysis.

Compared with the prior art, the present invention has the following advantages:

1) The condensed water in the sample measured at normal temperature is not easy to evaporate, reducing interference, and the gas in the bottle will generate a certain pressure from low temperature to normal temperature, and the sample can be directly injected.

2) Samples can be taken for a long time to achieve enrichment and improve the sensitivity of qualitative detection;

3), the device is simple, the main structure is made of glass and PEFE, anti-pollution.

Description of drawings

Fig. 1 is the structural representation of reciprocating all-glass piston pump;

Fig. 2 is a structural schematic diagram of a headspace bottle placed in a cooling device;

Fig. 3 is the structural representation of headspace bottle;

Fig. 4 is a structural schematic diagram of a low-temperature pressurized headspace sampling device of the present invention;

Fig. 5 is a schematic diagram of the structure of the headspace bottle before analysis.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

Example

As shown in Figure 1-5, a low-temperature pressurized headspace sampling device for GC-MS determination of volatile substances in the atmosphere, including:

The reciprocating all-glass piston pump consists of a glass piston cylinder 1, a one-way valve a2, a one-way valve b3, a clamping clip 4, a crank linkage mechanism 5, a micro motor 6, and a worm reducer 7, and the glass piston cylinder One end of cylinder 1 is provided with parallel one-way valve a2 and one-way valve b3, and the piston at the other end is sequentially connected to crank linkage mechanism 5, worm reducer 7, and micro motor 6 through clamping clip 4, and said one-way valve a2 is connected to Sampling tube 13;

The headspace bottle for sampling includes the headspace bottle 10. The headspace bottle is provided with a seal, and two injection needles, one long and one short, are inserted into the seal, wherein the long needle touches the bottom as the inlet needle 8, and the short needle is used as the inlet needle 8 at the mouth of the bottle. The exhaust needle 9, the inlet needle 8 are connected to the one-way valve b3, the exhaust needle 9 is connected to the GC-MS through a pipeline, and a volume flowmeter 14 is arranged on the pipeline; the inlet needle 8 and the exhaust needle 9 The material is stainless steel. The material of the headspace bottle 10 is glass, and the headspace bottle 10 maintains tight airtightness by sealing;

Cooling device, the headspace bottle 10 is placed in the cooling device 12 . The cooling device 12 is a stainless steel container with built-in liquid nitrogen or dry ice.

The application of using the above-mentioned device to communicate with GC-MS to measure volatile substances in the atmosphere includes the following steps:

First, connect the gas pipelines in sequence according to Figure 4 (glass piston cylinder 1, one-way valve a2, one-way valve b3, clamping clip 4, crank linkage mechanism 5, air intake needle 8, exhaust needle 9, top Empty bottle 10, sampling tube 13 and volumetric flow meter 14) and circuit (miniature motor 6 and worm reducer 7).

Next, the cooling device 12 is prepared according to FIG. 4, and the thermometer 11 is inserted.

Then, start the air extraction device and the headspace bottle and put the headspace bottle into the cooling pool to pump the gas continuously (the one-way valve a2 and the one-way valve b3 are switched alternately, the one-way valve a2 is opened, the one-way valve b3 is closed, and the micromotor 6 Drive the worm reducer 7 to drive the crank link mechanism 5 and the clamping clip 4, pull the piston, fill the piston cylinder with air sample, then close the one-way valve a2, open the one-way valve b3, push the piston, and pass the air sample through the inlet The gas needle 8 is injected into the headspace bottle 10, and the gas in the headspace bottle 10 is discharged through the exhaust needle, so that it is recycled) to a certain period of time. Due to the throttling effect of the exhaust needle, there is a certain pressure in the headspace bottle. Under certain conditions, volatile substances will be condensed and enriched.

Fourth, use pointed pliers to bend and pinch the inlet needle 8 and exhaust needle 9 according to the order of exhaust first and then air intake, as shown in Figure 5, and pinch off the excess, and put the headspace bottle at room temperature or micro The low temperature method is determined by the headspace method on the GC-MS instrument.

Those of ordinary skill in the technical field should recognize that the above specific embodiments are only used to illustrate the patent of the present invention, and are not used as a limitation to the patent of the present invention, as long as they are within the spirit of the patent of the present invention. The changes and modifications of the above-mentioned specific implementation will fall within the scope of the claims of the patent of the present invention.

Claims (5)

1. A low-temperature pressurized headspace sampling device for GC-MS determination of volatile substances in the atmosphere, characterized in that, comprising: Reciprocating all-glass piston pump, consisting of glass piston cylinder (1), one-way valve a (2), one-way valve b (3), clamping clip (4), crank-link mechanism (5), micro motor (6) Composed of a worm reducer (7), one end of the glass piston cylinder (1) is provided with a parallel check valve a (2) and a check valve b (3), and the piston at the other end passes through the clamping clip (4 ) is connected to the crank linkage (5), the worm reducer (7), and the micromotor (6) in turn, and the one-way valve a (2) is connected to the sampling pipe (13); The headspace bottle for sampling includes the headspace bottle (10). The headspace bottle is provided with a seal, and two injection needles, one long and one short, are inserted into the seal, wherein the long needle touches the bottom as an air inlet needle (8), and the short needle The mouth of the bottle is used as the exhaust needle (9), the inlet needle (8) is connected to the one-way valve b (3), and the exhaust needle (9) is connected to the GC-MS; Cooling equipment, the headspace bottle (10) is placed in the cooling equipment (12); The cooling device (12) is a stainless steel container with built-in liquid nitrogen or dry ice. 2. a kind of GC-MS measurement air volatile substance according to claim 1 is characterized in that, described air inlet needle (8) and exhaust needle (9) The material is stainless steel. 3. a kind of GC-MS according to claim 1 measures volatile matter in the atmosphere and uses low-temperature pressurized headspace sampling device, it is characterized in that, the material of described headspace bottle (10) is glass, headspace Bottle (10) maintains tight airtightness by sealing. 4. a kind of GC-MS measurement atmospheric volatile substance according to claim 1 is characterized in that, described exhaust needle (9) is connected to GC-MS by pipeline , and a volume flow meter (14) is set on the pipeline. 5. a kind of GC-MS according to claim 1 measures the application of low-temperature pressurized headspace sampling device for volatile substances in the atmosphere, it is characterized in that, adopt sampling tube online sealing to break away from direct headspace technology, will enter and exit gas The thin metal tube is clamped flat and closed and then bent after shearing. It can be analyzed directly without transfer.