How to do simple GC configuration
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One gas source two host three pillars four standard materials five other (computer, printer, workstation, etc.)
So how do you buy these parts for your users? In this and next news letters, we will show you how to do a simple GC configuration for your customers.
This time introduces the two items in front (the choice of gas source and host)
The gas source of a gas source gas chromatography can be divided into four categories according to the use: carrier gas, gas, combustion gas, and driving gas.
Carrier gas: Through the entire analysis system, high purity and good quality are required. In general, we require customers to use large manufacturers and good brand of gas, and generally require the use of cylinder gas, it is best not to use a gas generator. Good carrier gas is the basis for ensuring that the analysis can proceed normally. Generally used carrier gases are: nitrogen, hydrogen, argon, helium, and the like.
Gas: Generally use hydrogen, as long as it can guarantee normal ignition, and does not interfere with the analysis. Users can use high purity cylinder gas or hydrogen generators. If the budget is sufficient, it is best to use a hydrogen generator because it is safer.
Gas support: Generally use air, as long as it can play a role in combustion, and does not interfere with the analysis. Users can use high purity cylinder gas or air generators.
Drive gas: generally air.
So when should I match the gas?
When we give the user a gas source, we generally consider it according to the detector:
FID: It needs to be equipped with gas, gas and combustion gas. Generally, it is equipped with nitrogen (high-purity cylinder gas, 40L, with pressure reducing valve), hydrogen (cylinder gas or hydrogen generator), air (cylinder gas or air source).
TCD: Requires carrier gas. In general, in order to increase the sensitivity, we recommend that customers be equipped with hydrogen (high-purity cylinder gas) or helium (high-purity cylinder gas). But if the customer wants to analyze hydrogen, we need to equip with argon or nitrogen or helium.
ECD: Requires carrier gas. Generally, nitrogen (high purity cylinder gas).
FPD: Same as FID.
TSD: Same as FID.
When the customer purchases an automatic valve, it needs to be equipped with a driving gas. Generally speaking, an air cylinder or an air source can be used.
The two host hosts are mainly equipped with two parts for the user: the injection system and the detection system.
Injection system: As the name implies, where the sample enters, it is also used to vaporize the sample. The injection system often hears the following parts: (1) capillary injector; (2) filling injector; (3) headspace injection; (4) thermal analysis injection; (5) valve advancement kind.
Capillary injector: In general, a normal gas chromatograph will have at least one capillary injector or a filling injector. So we have to configure at least one injector (capillary or padding) when we configure the client. When the customer's analysis needs to be equipped with a capillary column: we provide the customer with a capillary injection sampler; when the customer's analysis requires the use of a packed column: we provide the customer with a filling injector. Our factory instruments can be equipped with up to two capillary injectors or three filling injectors or filling/hair injectors.
Fill the injector: See the capillary injector above.
Headspace injection: headspace injection, thermal analysis, and valve injection are all gas injection techniques. It does not conflict with the sampler, which is based on the injection of the sampler and is additionally allocated according to the customer's requirements. Headspace injection is generally used in the determination of volatile components. In more than 90% of cases, the substance to be tested has a boiling point below 120 degrees Celsius. The sample can be solid or liquid. Commonly used in: determination of ethanol in blood, determination of a volatile component in indoor/in-vehicle decorative materials, determination of various solvent residues, and the like.
Thermal Analytical Injection: Typically used for the detection of certain components in indoor/indoor air. Common analysis: TVOC.
Valve injection: Six-port valve injection, commonly used in gas injection. If the customer's sample is in a gaseous state, the valve is often used for high precision requirements.
Detection system: It is a system that converts the collected substances into electrical signals that can be seen on a computer. There are five kinds of detectors commonly used in gas chromatography. According to the substances detected by customers, we need to select a suitable detector.
TCD: is a general-purpose detector. It has a corresponding property to all materials with different thermal conductivity of the carrier gas, but its sensitivity is not high. Generally, only the percentage of the substance can be detected, and the trace substance of the ppm or ppb level cannot be detected. Commonly used in the detection of permanent gases.
FID: Some people say that it is a general-purpose detector, and some people say it is a special-purpose detector. Responsive to organic compounds, ie C/H compounds. The response to compounds containing heteroatoms is weak. Generally, it can be tested at the ppm level. It is a detector that is widely used at present.
ECD: Electronic capture detector. It is a dedicated detector. Extremely sensitive to substances with strong electronegativity. It is generally used for the detection of compounds containing elements such as chlorobromobromoiodooxy. Can do ppb level detection. It is commonly used in the detection of organochlorine pesticide residues and chloroform and carbon tetrachloride.
FPD: is a dedicated detector. Significant response to sulfur and phosphorus compounds. The detection level is between ppm and ppb, and the sensitivity is average. It is commonly used in the detection of organophosphorus pesticide residues and hydrogen sulfide and sulfur dioxide.
TSD: Also called NPD, nitrogen and phosphorus detector. It is a dedicated detector. It can detect compounds containing nitrogen and phosphorus. More sensitive, the detection level is between ppm and ppb. Not very common. Maintenance is more troublesome.