Hydrogen as a Carrier Gas in Gas Chromatography

Hydrogen as a Carrier Gas in Gas Chromatography

Gas chromatography is a physical method of separation of the constituent materials of the complex liquid (stationary phase) with the help of the carrier gas like hydrogen, nitrogen or helium (mobile phase).


Gas chromatography is based upon the distribution coefficient of the sample liquid that is put the the stationary phase. When the sample is vaporised by external heating mechanism, the constituents are carried by the carrier gas through the column. It is there in the column, where the distribution coefficient comes into foreplay. It decided the movement of different constituent compounds through it. Hence difference in distribution coefficient will lead to the separation of the compounds.


Hydrogen gas is present in abundance and hence it’s retrieval from an optimum source is quite easy. The main two things that is kept in mind while performing gas chromatography is that the time required for the separation of the constituents is less and the thermal conductivity of the carrier gas must be high because in most of the chromatographs, the thermal conductivity plays an important role in controlling the separation.

Hydrogen being the lightest element to exist is easily available in nature. Moreover the diffusion of the solute particles, in this case the liquid sample molecules, through the chromatograph column is based on the diffusion rate of the carrier gas. Hydrogen having 4 times more diffusion rate than nitrogen, it is preferred as a carrier gas. The time is essentially reduced making the entire separation feasible.

Again, the thermal conductivity of hydrogen is quite high, prior to helium in the line. Due to such a high thermal conductivity, hydrogen serves as best and optimum carrier gas separations of compounds like stearic acid, fatty acids, etc.

Another factor that governs the separation of the components and also the efficiency of the carrier gas used is the linear velocity of the gas along the carrier column. Hydrogen gas can achieve a linear velocity of around 60 cm/sec at a low inlet pressure and hence is best for column heights of 15- 30 metre. Thus, hydrogen gas needs only a pressure valve fixed at the tank to maintain the pressure at a low value. Unlike other gases, no need of high pressure gas tanks are required.


Though hydrogen is very useful as a carrier in gas chromatography, it has some of its own drawbacks. The main two drawbacks of hydrogen that had rendered him as the least chosen option in the past decades are:

  • It is highly inflammable in nature owing to its self- combustible properties. As a result it’s leakage in the air can cause casualties and explosion.
  • It is a highly reactive gas and can hence sometimes react with the liquid components, thereby incorporating contaminations.


Due to depleted availability of the helium gas, hydrogen is now getting preferred. However involving hydrogen in practical life experiments needs some safety precautions. Some of the safety measures are as follow:

  1. Using hydrogen gas detectors that are sensitive within the range of 0.1 to 1% hydrogen concentration in the air.
  2. By using a flow- regulated gas supply for ovens that are not associated with columns. This regulates the gas flow per minute thereby reducing the probability of explosions.
  3. By installing hydrogen gas generators the controls the inflow of gas in the column and also solve the problems of storing it in the reservoir tanks.

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