The working principle and function characteristics of gas chromatograph <br> With the development of economy and the continuous improvement of analytical technology level, gas chromatograph as a high-efficiency, rapid and high-sensitivity modern analytical instrument is gradually popularized and widely used in China. In particular, the coming of the information age of the gas chromatograph is very fast, and the technology content is getting higher and higher. It is of great practical significance to study how to apply computer technology, intelligent instrument technology and electronic technology in the development of chromatograph systems to improve the intelligence level of chromatographs.
1. Principle of Gas Chromatography Analysis Russian botanist Tswet discovered "chromatography" in 1903. Martin and Synge proposed Liquid-Liquid Partition Chromatography in 1940, and proposed gas in 1941. In lieu of the possibility of liquid as a mobile phase, 11 years later, James and Martin published a gas-Liquid Chromatography method that was relatively complete from theory to practice, and thus won the Nobel Prize in Chemistry in 1952. On this basis, in 1957, MJEGolay pioneered Open-Tubular Column Chromatography, which is customarily called Capillary Column Chromatography. In the late 1960s, high pressure was applied. Pump and chemically bonded stationary phase for liquid chromatography, high performance liquid chromatography (HPLC), capillary supercritical fluid chromatography (SFC) developed in the early 1980s: and in the early 1980s by JORGENSON et al. The development of capillary electrophoresis (CZE) was widely developed and applied in the 1990s; capillary electrochromatography, which combines the advantages of HPLC and CZE, was valued in the late 1990s. By the 21st century, chromatographic science will be in the frontier sciences such as life sciences. Play an irreplaceable important role. G.Guiochon believes that GC and HPLC are the best and most successful examples in the field of analysis.
In the field of modern analytical chemistry, chromatographic analysis is a novel separation analysis method. Chromatography can be used to separate and analyze complex multi-component mixtures and is a method of separation based on the different migration velocities of the molecules. Chromatography is a separation process based on adsorption, partitioning, ion exchange, affinity and molecular size. It utilizes the adsorption capacity, partition coefficient, ion exchange capacity, affinity or molecular size of different components in two phases. Small differences, after a number of consecutive mass exchanges between the two phases, separate the different components. Chromatographic separation is a comprehensive representation of the thermodynamic and kinetic processes of a chromatographic system. A thermodynamic process is a process that is related to the partition coefficient of a component in a system; a kinetic process is a process in which components diffuse and mass transfer between two phases of the system. The thermodynamic properties of the components, mobile phase and stationary phase make the different components have different partition coefficients in the mobile phase and the stationary phase. The size of the partition coefficient reflects the dissolution-volatilization or adsorption-desorption of the components on the stationary phase. Ability. The component with a large partition coefficient has a strong dissolving or adsorbing ability on the stationary phase, so the moving speed in the column is slow; the component having a small partition coefficient dissolves or has a weak adsorption capacity on the stationary phase, so the moving speed in the column is fast. After a certain period of time, due to the difference of the distribution coefficients, the components are differentially moved in the column to achieve the purpose of separation.
(1) Working principle of gas chromatography As a kind of chromatography, gas chromatography is a separation and analysis method of a widely used complex mixture. The gas is the mobile phase, and the liquid which is solid or evenly coated on the carrier is a stationary phase, and the components are continuously distributed between the gas-liquid (solid) phase to realize the separation of the mixed components [t21. After the mixture is separated, the column is separated from the column and enters the detector. The generated ion current signal is amplified, and the chromatographic peaks of each component are drawn on the recorder for identification and quantification purposes. The separation process is carried out in a column, and the packing used for the column is a solid adsorbent or a high boiling liquid coated on an inert support. The sample to be analyzed is brought into the column by the gas mobile phase after being gasified at a high temperature. Since the resistance of the different components in the column is different, the flow is gradually pulled apart to achieve the purpose of separation. As shown in Figure 2-1, after the mixed sample consisting of A and B components is injected into the injector and vaporized instantaneously, the sample is carried by the carrier gas of the mobile phase, passing through the column with the stationary phase, due to The component molecules and the internal stationary phase molecules of the column should undergo adsorption, desorption and dissolution processes, and those components with similar performance structures will have a large separation effect due to the repeated distribution of the molecules in the two phases, and The adsorption and desorption of each sample component are different, and the reaction time is also different. The final result is that the components in the mixed sample are completely separated.
1 means that the sample has just entered the column and the two components are evenly mixed together;
2 indicates that the two groups have been partially separated;
3 indicates that the two components have been completely separated;
4 indicates that the separated A and the carrier gas flow out of the column, and B remains in the column and finally carries the same carrier gas out of the column. If the sample contains multiple components, it will also be separated and discharged in the same principle.
Gas Chromatography Samples (2) Characteristics of Gas Chromatography Gas chromatography has the advantages of high efficiency, high sensitivity, high selectivity, fastness, wide application range, and low sample consumption. Not only can it analyze gases, but also liquids and solids, it is one of the main means of modern analysis.
1. High performance, fast analysis speed Filling chromatography has a high number of theoretical plates, so it can analyze components with very similar boiling points and extremely complex mixture of components, and separate and measure once, usually only a few minutes or a few An analysis cycle can be completed in ten minutes. At present, chromatographs that use microprocessors to manipulate and process data have achieved an ideal level of analysis.
2. The greatest advantage of high-selectivity chromatography is that it is best at separating and analyzing multi-component complex systems, ie, components with very similar properties, such as isotopes, isomers, and so on. The separation is achieved by selecting a highly selective solid phase to make a sufficiently large difference in the partition coefficients between the components, which is beyond the spectrum and mass spectrometry.
3. High sensitivity Currently, gas chromatography is mainly used in agriculture to analyze the main components in pesticides, and to analyze trace toxins in seeds and soils. In medical and biochemistry, it is used to solve the analysis of amino acids in drugs and several ppm in blood. The composition and analysis of the problem.
4. Wide range of applications not only for gas analysis, but also for liquids and solids. Samples with a certain vapor pressure and good stability under column temperature conditions can be measured, as long as there is a vapor pressure of 27 to 1330 Pa in a temperature range of 196 to 450 ° C and a material with good thermal stability at the operating temperature [221, principle Both can be analyzed by gas chromatography. Gas chromatography can also be used to determine physicochemical constants and to prepare ultrapure chromatographic reagents with low sample usage; it can also be used as an online instrument for factory automated processes to perform automated analysis.
2. Gas chromatograph
2.1 Basic Structure of Gas Chromatograph The key to chromatographic analysis is to realize the integration of separation and analysis systems. The components separated by the column are detected by a suitable detector, and the generated electrical signal is recorded by a recorder or workstation to obtain a chromatogram consisting of a series of peaks, each peak representing a component flowing out. And the number is equal to the number of components. The time of the outflow can be used to measure the composition of the mixture. Usually, the effluent time or retention time of a component is used as a qualitative basis. The height or area of ​​the peak is a measure of the concentration or content of the component. .
The basic structure of the Chengdu Molar Gas Chromatograph Gas Chromatograph is shown in Figure 2-2. The carrier gas in the gas source is decompressed through the pressure reducing valve, flows through the gas path box, enters the sample introduction device, and brings the injected sample into the column. Finally, the separated components in the column are taken into the chromatographic detection. , for identification and documentation. The system is mainly composed of the following five parts:
1. The gas path system includes a gas source (a cylinder/gas generator for nitrogen, helium, hydrogen, etc., a gas flow line), a gas path control system, also called a carrier gas system; a carrier gas carrying sample passes through the column, and the carrier gas is A pressure gradient is created within the column, and the pressure and pressure gradients are the dynamics of the sample operating within the column. The requirements of the carrier gas system are to provide a pure, stable, metered carrier gas. Generally composed of gas source cylinders, pressure reducing valves and flow meters.
2. The sample introduction system includes an injector, various injection ports and a gasification chamber. The sample is injected into the gasification chamber by the sampler, and is vaporized instantaneously under the action of the high temperature of the gasification chamber, and then enters the gas under the carrier gas. In the column connected to the chamber.
3. Separation System Separation system consists of a column, which is the core component of the chromatograph. Its function is to separate the sample. There are two main types of columns: packed column and capillary column. The column consists of a column tube, a column packing, and the like. The column tube is generally made of a metal tube or a glass tube, and the column is operated in a constant temperature oven.
4. Control system control system The main tasks are: control all temperature and time programs, control various detectors (automatic ignition of (FID, NPD and FPD), chromatogram preservation and reprocessing, preservation of sample analysis conditions, Temperature programming, on/off detector, time to split the injector without splitting, etc.
5. After the sample of the detection and data processing system is separated by the chromatographic column, the components enter the detector sequentially with the carrier gas according to the retention time. The detector converts the incoming components into changes according to time and its concentration or mass. The measured electrical signal is transmitted to the recorder or workstation through necessary amplification, and finally the chromatographic elution curve and the qualitative and quantitative curve, that is, the chromatogram, of the mixed sample are obtained.
The detectors used are mainly the following: Flame Ionization Detector (Flame Ionization Detector), Thermal Conductivity Detector (TCD), Electron Capture Detector (ECD), Nitrogen Phosphorus Detector NPD (Nitrogen Phosphor Detector), Flame Photometric Detector (FPD), Mass Spectrometry Detector (MSD), this article mainly introduces TCD and FID detectors.
(1) Thermal Conductivity Detector TCD (Thermal Conductivity Detector), the basic principle is that each material has thermal conductivity, and the ability to conduct heat is different. The resistance of the gas in contact with the thermistor is measured by a thermistor. . This type of detection, although not the most sensitive, responds to all samples and is a universal detector.
(2) Flame ionization detector FID (Flame Ionization Detector) generally uses a hydrogen flame. The principle is that when hydrogen is burned, there will be a high temperature region above the flame, and the sample is ionized in this region. Some positive and negative ions are formed, and an electric field is applied around the flame to cause the ions to move in a direction to form a current. After a series of amplifications, an amplified signal is obtained, that is, the detected signal.
FID is only a response to organic compounds and is a selective detector. However, its sensitivity is high, and it is the most widely used. Generally, the instrument is equipped with a double-column double-gas dual detector. The single-column anti-interference ability is poor, the stabilization time is long, and the interference of the double-column is just offset.
2.2 New function analysis of chromatograph In order to enrich the function of the chromatograph and improve its intelligence and automation level, it is proposed to add new functions. mainly includes:
1. The map display function analysis map display is used to analyze the frequency and amplitude of the signal peak of the measured signal, and is used to study the dynamic characteristics of the analyzed object. Real-time curve online display can be realized by using precision op amp, A/D conversion chip and large-screen liquid crystal, so that the operator can know the running status of the instrument in time. The maps in this paper mainly have the following functions: (1) Coordinating the operation and operation of the software and hardware of the whole machine, realizing the automation of data acquisition, processing, instrument calibration, etc.; (2) Providing a convenient man-machine dialogue interface, The user can control, monitor or adjust the operating state of the instrument through the map display interface to get the correct analysis results.
2. Auto-zero function analysis Auto-zeroing is a technique that dynamically offsets the offset voltage and offset voltage drift. It reduces the offset voltage at the opposite input to the pV level [26]. The system automatically zeros to remove the offset caused by the input circuit, the amplifier circuit and analog-to-digital conversion, and the effects of various drifts caused by time and temperature.
The traditional zeroing method of the chromatograph is manually adjusted by the mechanical potentiometer installed on the control panel. Based on the manual zero method and modern IC technology, this paper proposes an automatic zero adjustment method, which uses software to automatically control the hardware method, which realizes automatic zero adjustment conveniently and quickly. The basic idea of ​​the algorithm is to compare the measured value with the preset threshold by comparing the steps of manual zero adjustment to determine whether to return to zero; if not, change the compensation signal size; repeat the above steps until it returns to zero. The method adopts the method of software automatic control adjustment to realize the automation of instrument zero adjustment.
3. Gas chromatograph auto-injection control system When the chromatograph is injected by manual injection, the operation may be inadvertent or the injection port septum leaks, which will cause sample loss. Each time the sample volume is different, the injection interval is not equal, which may cause a certain deviation. The autosampler system overcomes the deficiencies of routine analysis, improves analysis accuracy, and automates injection and partial sample preparation. The autosampler draws the same amount of sample at a time, with the same injection interval, ensuring higher analytical accuracy.
In summary, the automatic sample introduction system has great advantages, and each chromatograph manufacturer attaches great importance to the development of the system. At present, the automatic sample introduction system has been installed as a basic configuration on a gas chromatograph of many manufacturers, thereby performing chromatography. Conditional reproduction, optimization and intelligence provide more reliable and better support.
The National Standard Material Resource Platform is mainly engaged in chemical reagents (high-end reagents, general-purpose reagents, analytical reagents), standard products, reference materials, experimental chromatographic consumables, instrumentation devices and other nearly 200,000 kinds of goods. Another biobw.com agent introduces well-known suppliers at home and abroad, from quality inspection, commodity storage management, professional preservation, logistics and transportation, after-sales service, etc., all links are controlled by professionals. Through online operation and self-delivery logistics, the 3%-5% of the cost saved will be returned to the customer to ensure the high quality and low price of the product. Imported brands include American ACC, US USP, German DR, German weitge, Canadian TRC, Canadian CDN, BEPURE and other well-known brands, with short delivery time and low price. Click on the online customer service to inquire about the purchase.
1. Principle of Gas Chromatography Analysis Russian botanist Tswet discovered "chromatography" in 1903. Martin and Synge proposed Liquid-Liquid Partition Chromatography in 1940, and proposed gas in 1941. In lieu of the possibility of liquid as a mobile phase, 11 years later, James and Martin published a gas-Liquid Chromatography method that was relatively complete from theory to practice, and thus won the Nobel Prize in Chemistry in 1952. On this basis, in 1957, MJEGolay pioneered Open-Tubular Column Chromatography, which is customarily called Capillary Column Chromatography. In the late 1960s, high pressure was applied. Pump and chemically bonded stationary phase for liquid chromatography, high performance liquid chromatography (HPLC), capillary supercritical fluid chromatography (SFC) developed in the early 1980s: and in the early 1980s by JORGENSON et al. The development of capillary electrophoresis (CZE) was widely developed and applied in the 1990s; capillary electrochromatography, which combines the advantages of HPLC and CZE, was valued in the late 1990s. By the 21st century, chromatographic science will be in the frontier sciences such as life sciences. Play an irreplaceable important role. G.Guiochon believes that GC and HPLC are the best and most successful examples in the field of analysis.
In the field of modern analytical chemistry, chromatographic analysis is a novel separation analysis method. Chromatography can be used to separate and analyze complex multi-component mixtures and is a method of separation based on the different migration velocities of the molecules. Chromatography is a separation process based on adsorption, partitioning, ion exchange, affinity and molecular size. It utilizes the adsorption capacity, partition coefficient, ion exchange capacity, affinity or molecular size of different components in two phases. Small differences, after a number of consecutive mass exchanges between the two phases, separate the different components. Chromatographic separation is a comprehensive representation of the thermodynamic and kinetic processes of a chromatographic system. A thermodynamic process is a process that is related to the partition coefficient of a component in a system; a kinetic process is a process in which components diffuse and mass transfer between two phases of the system. The thermodynamic properties of the components, mobile phase and stationary phase make the different components have different partition coefficients in the mobile phase and the stationary phase. The size of the partition coefficient reflects the dissolution-volatilization or adsorption-desorption of the components on the stationary phase. Ability. The component with a large partition coefficient has a strong dissolving or adsorbing ability on the stationary phase, so the moving speed in the column is slow; the component having a small partition coefficient dissolves or has a weak adsorption capacity on the stationary phase, so the moving speed in the column is fast. After a certain period of time, due to the difference of the distribution coefficients, the components are differentially moved in the column to achieve the purpose of separation.
(1) Working principle of gas chromatography As a kind of chromatography, gas chromatography is a separation and analysis method of a widely used complex mixture. The gas is the mobile phase, and the liquid which is solid or evenly coated on the carrier is a stationary phase, and the components are continuously distributed between the gas-liquid (solid) phase to realize the separation of the mixed components [t21. After the mixture is separated, the column is separated from the column and enters the detector. The generated ion current signal is amplified, and the chromatographic peaks of each component are drawn on the recorder for identification and quantification purposes. The separation process is carried out in a column, and the packing used for the column is a solid adsorbent or a high boiling liquid coated on an inert support. The sample to be analyzed is brought into the column by the gas mobile phase after being gasified at a high temperature. Since the resistance of the different components in the column is different, the flow is gradually pulled apart to achieve the purpose of separation. As shown in Figure 2-1, after the mixed sample consisting of A and B components is injected into the injector and vaporized instantaneously, the sample is carried by the carrier gas of the mobile phase, passing through the column with the stationary phase, due to The component molecules and the internal stationary phase molecules of the column should undergo adsorption, desorption and dissolution processes, and those components with similar performance structures will have a large separation effect due to the repeated distribution of the molecules in the two phases, and The adsorption and desorption of each sample component are different, and the reaction time is also different. The final result is that the components in the mixed sample are completely separated.
1 means that the sample has just entered the column and the two components are evenly mixed together;
2 indicates that the two groups have been partially separated;
3 indicates that the two components have been completely separated;
4 indicates that the separated A and the carrier gas flow out of the column, and B remains in the column and finally carries the same carrier gas out of the column. If the sample contains multiple components, it will also be separated and discharged in the same principle.
Gas Chromatography Samples (2) Characteristics of Gas Chromatography Gas chromatography has the advantages of high efficiency, high sensitivity, high selectivity, fastness, wide application range, and low sample consumption. Not only can it analyze gases, but also liquids and solids, it is one of the main means of modern analysis.
1. High performance, fast analysis speed Filling chromatography has a high number of theoretical plates, so it can analyze components with very similar boiling points and extremely complex mixture of components, and separate and measure once, usually only a few minutes or a few An analysis cycle can be completed in ten minutes. At present, chromatographs that use microprocessors to manipulate and process data have achieved an ideal level of analysis.
2. The greatest advantage of high-selectivity chromatography is that it is best at separating and analyzing multi-component complex systems, ie, components with very similar properties, such as isotopes, isomers, and so on. The separation is achieved by selecting a highly selective solid phase to make a sufficiently large difference in the partition coefficients between the components, which is beyond the spectrum and mass spectrometry.
3. High sensitivity Currently, gas chromatography is mainly used in agriculture to analyze the main components in pesticides, and to analyze trace toxins in seeds and soils. In medical and biochemistry, it is used to solve the analysis of amino acids in drugs and several ppm in blood. The composition and analysis of the problem.
4. Wide range of applications not only for gas analysis, but also for liquids and solids. Samples with a certain vapor pressure and good stability under column temperature conditions can be measured, as long as there is a vapor pressure of 27 to 1330 Pa in a temperature range of 196 to 450 ° C and a material with good thermal stability at the operating temperature [221, principle Both can be analyzed by gas chromatography. Gas chromatography can also be used to determine physicochemical constants and to prepare ultrapure chromatographic reagents with low sample usage; it can also be used as an online instrument for factory automated processes to perform automated analysis.
2. Gas chromatograph
2.1 Basic Structure of Gas Chromatograph The key to chromatographic analysis is to realize the integration of separation and analysis systems. The components separated by the column are detected by a suitable detector, and the generated electrical signal is recorded by a recorder or workstation to obtain a chromatogram consisting of a series of peaks, each peak representing a component flowing out. And the number is equal to the number of components. The time of the outflow can be used to measure the composition of the mixture. Usually, the effluent time or retention time of a component is used as a qualitative basis. The height or area of ​​the peak is a measure of the concentration or content of the component. .
The basic structure of the Chengdu Molar Gas Chromatograph Gas Chromatograph is shown in Figure 2-2. The carrier gas in the gas source is decompressed through the pressure reducing valve, flows through the gas path box, enters the sample introduction device, and brings the injected sample into the column. Finally, the separated components in the column are taken into the chromatographic detection. , for identification and documentation. The system is mainly composed of the following five parts:
1. The gas path system includes a gas source (a cylinder/gas generator for nitrogen, helium, hydrogen, etc., a gas flow line), a gas path control system, also called a carrier gas system; a carrier gas carrying sample passes through the column, and the carrier gas is A pressure gradient is created within the column, and the pressure and pressure gradients are the dynamics of the sample operating within the column. The requirements of the carrier gas system are to provide a pure, stable, metered carrier gas. Generally composed of gas source cylinders, pressure reducing valves and flow meters.
2. The sample introduction system includes an injector, various injection ports and a gasification chamber. The sample is injected into the gasification chamber by the sampler, and is vaporized instantaneously under the action of the high temperature of the gasification chamber, and then enters the gas under the carrier gas. In the column connected to the chamber.
3. Separation System Separation system consists of a column, which is the core component of the chromatograph. Its function is to separate the sample. There are two main types of columns: packed column and capillary column. The column consists of a column tube, a column packing, and the like. The column tube is generally made of a metal tube or a glass tube, and the column is operated in a constant temperature oven.
4. Control system control system The main tasks are: control all temperature and time programs, control various detectors (automatic ignition of (FID, NPD and FPD), chromatogram preservation and reprocessing, preservation of sample analysis conditions, Temperature programming, on/off detector, time to split the injector without splitting, etc.
5. After the sample of the detection and data processing system is separated by the chromatographic column, the components enter the detector sequentially with the carrier gas according to the retention time. The detector converts the incoming components into changes according to time and its concentration or mass. The measured electrical signal is transmitted to the recorder or workstation through necessary amplification, and finally the chromatographic elution curve and the qualitative and quantitative curve, that is, the chromatogram, of the mixed sample are obtained.
The detectors used are mainly the following: Flame Ionization Detector (Flame Ionization Detector), Thermal Conductivity Detector (TCD), Electron Capture Detector (ECD), Nitrogen Phosphorus Detector NPD (Nitrogen Phosphor Detector), Flame Photometric Detector (FPD), Mass Spectrometry Detector (MSD), this article mainly introduces TCD and FID detectors.
(1) Thermal Conductivity Detector TCD (Thermal Conductivity Detector), the basic principle is that each material has thermal conductivity, and the ability to conduct heat is different. The resistance of the gas in contact with the thermistor is measured by a thermistor. . This type of detection, although not the most sensitive, responds to all samples and is a universal detector.
(2) Flame ionization detector FID (Flame Ionization Detector) generally uses a hydrogen flame. The principle is that when hydrogen is burned, there will be a high temperature region above the flame, and the sample is ionized in this region. Some positive and negative ions are formed, and an electric field is applied around the flame to cause the ions to move in a direction to form a current. After a series of amplifications, an amplified signal is obtained, that is, the detected signal.
FID is only a response to organic compounds and is a selective detector. However, its sensitivity is high, and it is the most widely used. Generally, the instrument is equipped with a double-column double-gas dual detector. The single-column anti-interference ability is poor, the stabilization time is long, and the interference of the double-column is just offset.
2.2 New function analysis of chromatograph In order to enrich the function of the chromatograph and improve its intelligence and automation level, it is proposed to add new functions. mainly includes:
1. The map display function analysis map display is used to analyze the frequency and amplitude of the signal peak of the measured signal, and is used to study the dynamic characteristics of the analyzed object. Real-time curve online display can be realized by using precision op amp, A/D conversion chip and large-screen liquid crystal, so that the operator can know the running status of the instrument in time. The maps in this paper mainly have the following functions: (1) Coordinating the operation and operation of the software and hardware of the whole machine, realizing the automation of data acquisition, processing, instrument calibration, etc.; (2) Providing a convenient man-machine dialogue interface, The user can control, monitor or adjust the operating state of the instrument through the map display interface to get the correct analysis results.
2. Auto-zero function analysis Auto-zeroing is a technique that dynamically offsets the offset voltage and offset voltage drift. It reduces the offset voltage at the opposite input to the pV level [26]. The system automatically zeros to remove the offset caused by the input circuit, the amplifier circuit and analog-to-digital conversion, and the effects of various drifts caused by time and temperature.
The traditional zeroing method of the chromatograph is manually adjusted by the mechanical potentiometer installed on the control panel. Based on the manual zero method and modern IC technology, this paper proposes an automatic zero adjustment method, which uses software to automatically control the hardware method, which realizes automatic zero adjustment conveniently and quickly. The basic idea of ​​the algorithm is to compare the measured value with the preset threshold by comparing the steps of manual zero adjustment to determine whether to return to zero; if not, change the compensation signal size; repeat the above steps until it returns to zero. The method adopts the method of software automatic control adjustment to realize the automation of instrument zero adjustment.
3. Gas chromatograph auto-injection control system When the chromatograph is injected by manual injection, the operation may be inadvertent or the injection port septum leaks, which will cause sample loss. Each time the sample volume is different, the injection interval is not equal, which may cause a certain deviation. The autosampler system overcomes the deficiencies of routine analysis, improves analysis accuracy, and automates injection and partial sample preparation. The autosampler draws the same amount of sample at a time, with the same injection interval, ensuring higher analytical accuracy.
In summary, the automatic sample introduction system has great advantages, and each chromatograph manufacturer attaches great importance to the development of the system. At present, the automatic sample introduction system has been installed as a basic configuration on a gas chromatograph of many manufacturers, thereby performing chromatography. Conditional reproduction, optimization and intelligence provide more reliable and better support.
The National Standard Material Resource Platform is mainly engaged in chemical reagents (high-end reagents, general-purpose reagents, analytical reagents), standard products, reference materials, experimental chromatographic consumables, instrumentation devices and other nearly 200,000 kinds of goods. Another biobw.com agent introduces well-known suppliers at home and abroad, from quality inspection, commodity storage management, professional preservation, logistics and transportation, after-sales service, etc., all links are controlled by professionals. Through online operation and self-delivery logistics, the 3%-5% of the cost saved will be returned to the customer to ensure the high quality and low price of the product. Imported brands include American ACC, US USP, German DR, German weitge, Canadian TRC, Canadian CDN, BEPURE and other well-known brands, with short delivery time and low price. Click on the online customer service to inquire about the purchase.
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