What is the Function of Carrier Gas in Gas Chromatography?——Let’s Find Out

From essential attributes and features to its pivotal functions, this blog post will unveil the intricate dance of molecules in the chromatographic column. Join us in exploring the critical roles of carrier gas, understanding the nuances of selecting the right gas, and decoding its impact on the efficiency and success of gas chromatography. Let the chromatographic journey begin!

What is the Carrier Gas in Gas Chromatography?

The carrier gas in gas chromatography plays a pivotal role, characterized by its essential attributes. The carrier gas system incorporates molecular sieves to eliminate water and toxins, and traps can be utilized for added cleanliness. Two-stage pressure balancing minimizes water hammer, and a gas flow controller regulates the gas flow. Heating and filtration through a molecular sieve precede the entry of the carrier gas into the steam chamber, with gas dryers ensuring optimal guidance of the injection and application of the gas sample to the GC column.

Features of Carrier Gas in Gas Chromatography

The features of the carrier gas in gas chromatography are critical for its effective operation. Here are the key points to consider:

1. Dry and Oxygen-Free:    

Carrier gas must be dry, free of oxygen, and chemically inert, serving as the mobile phase in gas chromatography.

2. Commonly Used Helium:   

Helium is the most common choice due to its safety, efficiency comparable to hydrogen, wider flow rate range, and compatibility with many detectors.

3. Alternate Gases Based on Performance:   

Nitrogen, argon, and hydrogen are also employed based on desired performance and the specific detector in use.

4. Storage and Purity:   

All carrier gases are available in pressurized tanks, and pressure regulators, gauges, and flow meters are used to meticulously control gas flow.

5. Optimal Purity Levels:   

Gas supplies should ideally fall between 99.995% to 99.9995% purity range, containing minimal levels (< 0.5 ppm) of oxygen and total hydrocarbons in the tank.

What is the Function of Carrier Gas in Gas Chromatography?

The function of the carrier gas in gas chromatography is integral to the efficiency and success of this analytical technique widely used in laboratory applications. Commonly utilized in quality control, food safety monitoring, and natural product research, gas chromatography relies on carrier gases to transport vaporized sample molecules through the chromatographic column for subsequent separation and detection. This method proves to be more cost-efficient and faster than liquid chromatography.

The carrier gas plays several crucial roles in gas chromatography:

1. Sample Transport: The carrier gas serves as the medium for transporting the sample through the chromatographic system. It carries the vaporized sample from the injection port into the chromatographic column, where the separation of components takes place. 

2. Efficient Separation: The carrier gas significantly influences the efficiency of separation by facilitating the movement of sample components within the chromatographic column. It plays a role in determining factors such as resolution, retention time, and peak shape.

3. Detector Sensitivity: The choice of carrier gas can impact the sensitivity of the detector. It influences the rate at which analyte molecules reach the detector, thereby affecting the overall detection sensitivity of the gas chromatography process. 

Which Gas is Used as Carrier Gas in Gas Chromatography?

The selection of a carrier gas is a critical aspect of gas chromatography (GC), influencing the efficiency and success of the analytical process. Commonly used carrier gases include:

Helium (He): Known for its inertness, thermal stability, and predictable behavior, helium is widely used in GC. However, its availability and cost have become limiting factors in recent years.

Hydrogen (H₂): Hydrogen is another prevalent carrier gas offering faster separations due to its lower viscosity and higher diffusion coefficient compared to helium. Despite its advantages, hydrogen is flammable, necessitating extra safety precautions, including the use of a flame ionization detector (FID).

Nitrogen (N₂): Widely chosen for its chemical inertness, availability, and cost-effectiveness, nitrogen serves as a reliable carrier gas for general-purpose applications in GC.

Argon (Ar): While less common, argon finds application in specific scenarios, such as inductively coupled plasma (ICP) GC, where high-temperature and high-energy environments are present.

In addition to carrier gases, some types of detectors in GC require additional gases for proper operation:

Hydrogen (H₂) for Flame Ionization Detector (FID): FID detectors use a flow of hydrogen gas as fuel for the flame, along with an auxiliary flow of air or oxygen. This detector is favored for its high sensitivity and broad applicability in organic compound analysis.

Makeup Gas: Certain detectors, like electron capture detectors (ECD), may necessitate a separate makeup gas to maintain the detector’s performance and stability. 

Which is the Most Suitable Carrier Gas in Gas Chromatography?

Choosing the most suitable carrier gas is a pivotal decision in gas chromatography, influencing the efficiency and effectiveness of analytical processes. Helium, hydrogen, nitrogen, and argon are among the common carrier gases, each offering distinct advantages and considerations. Helium, known for its inertness and thermal stability, has historically been widely used, although its availability and cost have become limiting factors. Hydrogen, with its lower viscosity and higher diffusion coefficient, allows for faster separations but requires careful handling due to its flammability. Nitrogen, valued for its chemical inertness, availability, and cost-effectiveness, is a reliable choice for general-purpose applications. Argon finds application in specific scenarios, such as inductively coupled plasma GC. The selection depends on factors like the nature of the sample, the sensitivity required, and safety considerations, highlighting the importance of weighing these factors to determine the most suitable carrier gas for a given gas chromatography application.

Conclusion

In summary, the carrier gas in gas chromatography is crucial for efficient and successful analytical processes. Helium, hydrogen, nitrogen, and argon are common choices, each with distinct advantages and considerations. Whether prioritizing inertness, efficiency, or specificity, careful consideration is essential for choosing the most suitable carrier gas for a given gas chromatography application. If you want to learn more about carrier gas, come to Monad and consulate our experts!