Learn why degassing the mobile phase is essential in HPLC. Discover its impact on system performance, accuracy, and the best degassing methods used in modern labs.”
Degassing the mobile phase removes dissolved gases such as oxygen, nitrogen, carbon dioxide, etc. from it.
HPLC is a powerful analytical technique used in the pharmaceuticals industry and the mobile phase plays a vital role in it. No matter how sophisticated your HPLC system is, you cannot perform the analysis if you have not degassed the mobile phase.
In this blog, I will discuss why degassing is important, what happens if you skip it, and the common methods used in laboratories today.
Degassing is performed to remove dissolved gases (mainly oxygen, nitrogen, and carbon dioxide) from the mobile phase solvents before they enter the HPLC system. The following steps explain why this is important:
Chromatogram showing baseline disturbance in the undegassed mobile phase:
1. Prevention of Bubble Formation
When solvents are pumped under high pressure through the HPLC system, dissolved gases can come out of the solution and form air bubbles. These bubbles can cause:
2. Improved Detector Sensitivity
Some detectors, especially UV-Vis detectors, are sensitive to oxygen and other gases that absorb light at certain wavelengths. Degassing helps eliminate false peaks and improves the signal-to-noise ratio.
3. Chemical Stability
Dissolved oxygen can react with sensitive analytes or components of the mobile phase, leading to unwanted side reactions. Removing gases helps maintain chemical stability during analysis.
There are several practical ways to degas mobile phases. The following degassing methods are widely usedin the industries:
The solvent is placed in a vacuum chamber, reducing the pressure so gases escape more readily. This method is widely used and effective for bulk degassing.
Sound waves agitate the solvent, helping release trapped gas. This method is fast and simple but often used in combination with other techniques for better results.
Modern HPLC systems often have built-in membrane-based degassers, which continuously remove gases as the mobile phase flows through. These are convenient and provide consistent degassing.
Helium gas is bubbled through the solvent to displace dissolved air. Since helium is less soluble, it escapes easily, taking the dissolved gases with it. This is one of the most effective methods but can be costly.
Among the above degassing procedures,s Ultrasonication and Vacuum Degassing are widely used in industries
Skipping degassing might not always cause immediate system failure, but it can lead to:
Degassing the mobile phase plays a crucial role in HPLC analysis. Make degassing a routine part of your workflow — your results will thank you!
Related:
Degassing removes dissolved gases like oxygen and nitrogen that can form bubbles under high pressure. These bubbles can disrupt the flow, cause detector noise, baseline instability, and potentially damage the HPLC system. Degassing ensures smoother operation and more reliable results
In-line degassers are highly effective for routine work, especially with gradient methods, and often eliminate the need for manual degassing. However, for high-sensitivity analyses or when using older systems without built-in degassers, additional degassing (like vacuum or helium sparging) may still be beneficial.
Vacuum filtration, followed by vacuum degassing, is typically the best approach. Ultrasonication alone may not remove all gases effectively from viscous or high-salt buffers. Using in-line degassers with buffer-compatible tubing is also a good option for ongoing runs
It depends on the method:
Longer times may be needed for more viscous or gas-rich solvents.
Air bubbles in the detector flow cell can cause:
Further Reading:
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