Gas Chromatograph Injection System Overview The gas chromatograph's injection system functions to analyze the sample directly or after special treatment into the gasification chamber or column of the gas chromatograph. The functions can be divided into the following types according to different functions:
Manual Injection System Microinjector: A manual injection of a sample of a gas or liquid sample using a micro-syringe into a gas chromatograph for analysis. It is widely used for the analysis of heat stable gases and liquid samples with boiling points below 500 °C. There are a wide variety of micro-injectors for gas chromatographs, and different syringes can be used depending on the nature of the sample.
The function of the gas chromatograph's sampling system is to analyze the sample directly or after special treatment into the gasification chamber or column of the gas chromatograph. According to different functions, it can be divided into the following types:
1. Headspace sampling system The headspace sampler is mainly used for the analysis of volatile organic compounds in solid, semi-solid and liquid sample matrices, such as VOCs in water, aroma components in tea, and residual monomers in synthetic polymer materials. Wait.
2, manual injection system micro-injection: use a micro-syringe to extract a certain amount of gas or liquid sample into the gas chromatograph for manual injection analysis. It is widely used for the analysis of heat stable gases and liquid samples with boiling points below 500 °C. There are a wide variety of micro-injectors for gas chromatographs, and different syringes can be used depending on the nature of the sample.
Solid phase microextraction (SPME) injector: Solid phase microextraction is a sample pretreatment technique invented in the 1990s. It can be used to extract organic matter from liquid or gas matrix. The extracted sample can be manually injected into the gas of the gas chromatograph. The chamber is subjected to thermal analytical gasification and then analyzed in a column. This technique is particularly suitable for the analysis of organic matter in water.
3, valve injection system, gas injection valve gas sample using valve injection not only quantitative reproducibility, but also can be isolated from the ambient air, to avoid air contamination of the sample. Manual injection with a syringe is difficult to achieve the above two points. The system with valve injection allows for a special analysis of the combination of multiple columns and multiple valves. The sample tube volume of the gas injection valve is generally above 0.25 ml. Gas Chromatography Injection System Overview (Chromatographic Data)
Liquid injection valve
The liquid injection valve is typically used for on-line sampling analysis of a liquid sample in a device, the sample loop of which is typically a groove having a volume of about 0.1-1.0 microliters at the spool.
4, liquid autosampler liquid autosampler for liquid sample injection, can achieve automated operation, reduce artificial injection errors, reduce manual operating costs. Suitable for analysis of batch samples.
5, thermal desorption system
It is used for the capture of volatile organic compounds in gas samples and then analyzed by thermal desorption of the gas phase chromatograph.
6. Purge and trap system
For the enrichment of volatile organic compounds in solid, semi-solid, liquid sample matrices and direct gas phase chromatography for analysis.
7, thermal cracker injection system
A gas chromatograph equipped with a thermal cracker is called pyrolysis gas chromatography (PGC), which is theoretically applicable to any organic matter that cannot be separated and analyzed by gas chromatography due to poor volatility (thermal decomposition under anaerobic conditions, pyrolysis thereof) The product or fragment is generally related to the structure of the parent compound, usually smaller than the molecular weight of the parent compound, and is suitable for gas chromatography analysis, but is currently mainly used for the analysis of polymers.
Usually, in a gas carrier gas (helium or nitrogen), the polymer sample is heated under anaerobic conditions, and the thermal energy applied to the polymer sample exceeds the bond energy of the molecule, resulting in molecular cleavage of the compound. . Fragmentation of molecules involves the process of losing neutral small molecules, opening polymer chains to produce monomer units or breaking into random chain fragments. The mechanism of thermal cracking of the polymer depends on the type of polymer, but the nature and relative yield of the pyrolysis product are also related to the design of the thermal cracker and the thermal cracking conditions. The key factors affecting the reproducibility of the characteristic pyrolysis fragment yield are: endpoint pyrolysis temperature, heating time or heating rate and injection volume.
Pyrolyzers for solid and high boiling liquids fall into two categories: pulsed and continuous. At present, the commonly used Curie point pyrolyzers and hot wire pyrolyzers belong to the first category, and the furnace pyrolyzers belong to the second category. There are also some special pyrolyzers.
The application of PGC to polymer analysis includes the synthesis of polymers and biopolymers. Major applications in the field of synthetic polymers include fingerprinting, quantitative analysis of copolymer or blend compositions, and structural determinations such as randomization, sequence and branching. Applications in the biopolymer field include the study of bacteria, fungi, carbohydrates and proteins. In addition, PGC has applications in many other areas.
The function of the gas chromatograph's sampling system is to analyze the sample directly or after special treatment into the gasification chamber or column of the gas chromatograph. According to different functions, it can be divided into the following types:
1. Headspace sampling system The headspace sampler is mainly used for the analysis of volatile organic compounds in solid, semi-solid and liquid sample matrices, such as VOCs in water, aroma components in tea, and residual monomers in synthetic polymer materials. Wait.
2, manual injection system micro-injection: use a micro-syringe to extract a certain amount of gas or liquid sample into the gas chromatograph for manual injection analysis. It is widely used for the analysis of heat stable gases and liquid samples with boiling points below 500 °C. There are a wide variety of micro-injectors for gas chromatographs, and different syringes can be used depending on the nature of the sample.
Solid phase microextraction (SPME) injector: Solid phase microextraction is a sample pretreatment technique invented in the 1990s. It can be used to extract organic matter from liquid or gas matrix. The extracted sample can be manually injected into the gas of the gas chromatograph. The chamber is subjected to thermal analytical gasification and then analyzed in a column. This technique is particularly suitable for the analysis of organic matter in water.
3, valve injection system, gas injection valve gas sample using valve injection not only quantitative reproducibility, but also can be isolated from the ambient air, to avoid air contamination of the sample. Manual injection with a syringe is difficult to achieve the above two points. The system with valve injection allows for a special analysis of the combination of multiple columns and multiple valves. The sample tube volume of the gas injection valve is generally above 0.25 ml. Gas Chromatography Injection System Overview (Chromatographic Data)
Liquid injection valve
The liquid injection valve is typically used for on-line sampling analysis of a liquid sample in a device, the sample loop of which is typically a groove having a volume of about 0.1-1.0 microliters at the spool.
4, liquid autosampler liquid autosampler for liquid sample injection, can achieve automated operation, reduce artificial injection errors, reduce manual operating costs. Suitable for analysis of batch samples.
5, thermal desorption system
It is used for the capture of volatile organic compounds in gas samples and then analyzed by thermal desorption of the gas phase chromatograph.
6. Purge and trap system
For the enrichment of volatile organic compounds in solid, semi-solid, liquid sample matrices and direct gas phase chromatography for analysis.
7, thermal cracker injection system
A gas chromatograph equipped with a thermal cracker is called pyrolysis gas chromatography (PGC), which is theoretically applicable to any organic matter that cannot be separated and analyzed by gas chromatography due to poor volatility (thermal decomposition under anaerobic conditions, pyrolysis thereof) The product or fragment is generally related to the structure of the parent compound, usually smaller than the molecular weight of the parent compound, and is suitable for gas chromatography analysis, but is currently mainly used for the analysis of polymers.
Usually, in a gas carrier gas (helium or nitrogen), the polymer sample is heated under anaerobic conditions, and the thermal energy applied to the polymer sample exceeds the bond energy of the molecule, resulting in molecular cleavage of the compound. . Fragmentation of molecules involves the process of losing neutral small molecules, opening polymer chains to produce monomer units or breaking into random chain fragments. The mechanism of thermal cracking of the polymer depends on the type of polymer, but the nature and relative yield of the pyrolysis product are also related to the design of the thermal cracker and the thermal cracking conditions. The key factors affecting the reproducibility of the characteristic pyrolysis fragment yield are: endpoint pyrolysis temperature, heating time or heating rate and injection volume.
Pyrolyzers for solid and high boiling liquids fall into two categories: pulsed and continuous. At present, the commonly used Curie point pyrolyzers and hot wire pyrolyzers belong to the first category, and the furnace pyrolyzers belong to the second category. There are also some special pyrolyzers.
The application of PGC to polymer analysis includes the synthesis of polymers and biopolymers. Major applications in the field of synthetic polymers include fingerprinting, quantitative analysis of copolymer or blend compositions, and structural determinations such as randomization, sequence and branching. Applications in the biopolymer field include the study of bacteria, fungi, carbohydrates and proteins. In addition, PGC has applications in many other areas.
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