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Why should the gas chromatograph carrier gas be high purity and understand its principle?

Time:2018/10/13   Pageviews:5    Share:
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Gas chromatography is widely used in petroleum, chemical, biochemical, medical and health, food industry, environmental protection and other fields. Carrier gas is an essential part of the laboratory's operation!

Gas chromatograph basic requirements for carrier gas1.5ml GC headspace vials

The carrier gas must be inert, ie not reacted with the sample or stationary phase. Commonly used carrier gases are hydrogen, nitrogen, helium, argon, in addition to combustion-supporting air. These gases are typically supplied by a high pressure cylinder or gas generator and are subjected to purification, stabilization, flow control and measurement before entering the GC system.
So why do you require a high purity carrier gas?

Impure gas as a carrier gas can cause column failure, sample change, hydrogen flame chromatography can lead to increased base flow noise, thermal conductivity chromatography can lead to linear deterioration of the evaluator, so the carrier gas must be purified. For example, if the carrier gas contains impurities, it may pollute the system or deposit in the system, affecting the life of the instrument, and may also produce ghost peaks.

When using gas chromatography, why the carrier gas should be turned on and off first: mainly to protect the device.

For gas chromatographs, temperature is critical. Turn off the gas circuit first, and the temperature cannot be dissipated. It can affect or even burn out the function of some components, such as TCD.

How to get a pure carrier gas

It is recommended that you use a gas purifier to remove moisture impurities from the gas in the gas generator. In particular, when detecting non-methane total hydrocarbons, install a deoxidizing tube to prevent the mixed oxygen from causing peak irregularities.

How gas chromatograph works1.5ml GC headspace vials

The principle of gas chromatography is similar to fractionation. They all utilize the difference in boiling point (or vapor pressure) of the individual components of the mixture to separate the individual components of the mixture. However, fractional distillation is usually used for the separation of a mixture of constants, while gas chromatography separates much less (minor amounts).

The mobile phase (or mobile phase) in the gas chromatograph is a carrier gas, usually using an inert gas such as helium or a poorly reactive gas such as nitrogen. The stationary phase consists of a thin layer of liquid or polymer attached to a layer of inert solid support. The stationary phase is housed in a hollow column made of glass or metal (called a column). An instrument used for performing gas chromatography is called a gas chromatograph (or "gas separator").1.5ml GC headspace vials

The gas sample to be analyzed interacts with the column wall covered with various stationary phases such that different materials are eluted at different times. The time from the start of a substance injection to the occurrence of the peak value of the chromatographic peak is called the retention time of the substance, and the unknown can be characterized by comparing the retention time of the unknown substance with the retention time of the standard substance under the same conditions.

This is the end of the introduction of Why should the gas chromatograph carrier gas be high purity and understand its principle? I hope it can help you.


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