WHAT IT IS
A degasser in liquid chromatography (LC) is the component that removes dissolved gases from the mobile phase before it enters the pump. Oxygen, nitrogen, and other gases can form bubbles under high pressure or during solvent mixing, leading to pump instability, baseline noise, or detector interference. By continuously degassing solvents, the unit ensures stable flow, reliable gradients, and reproducible results.
HOW IT WORKS
The degasser is positioned between the solvent reservoir and the pump. Mobile phase flows through channels or membranes exposed to a low-pressure environment, which reduces gas solubility and allows dissolved gases to escape. The system operates continuously during analysis, so no manual degassing steps are needed.
TYPES
Vacuum-Membrane Degassers
Working Principle – Solvent flows through gas-permeable hollow fibers under vacuum. Dissolved gases diffuse through the membrane into the vacuum chamber.
Strengths – Highly efficient, continuous, and suitable for most LC solvents.
Limitations – Membranes may degrade with aggressive solvents or high salt concentrations.
Inline Vacuum Chamber Degassers
Working Principle – Solvent passes through a chamber connected to a vacuum pump, releasing dissolved gases.
Strengths – Simple design; effective for most routine LC.
Limitations – Larger dead volume; slower gradient response compared with membrane systems.
Helium Sparging (Traditional Method)
Working Principle – Helium is bubbled through solvent bottles to displace dissolved gases.
Strengths – Effective and inexpensive.
Limitations – Consumes helium, requires gas supply, and cannot be automated. Rarely used in modern LC.
Sonication (Manual Method)
Working Principle – Solvents are placed in an ultrasonic bath, which releases dissolved gases.
Strengths – Low-cost option for labs without built-in degassers.
Limitations – Manual, time-consuming, and less reproducible.
KEY FEATURES
Continuous Online Operation: Removes gases during analysis without manual preparation.
Compatibility: Works with water, buffers, and most organic solvents.
Low Dead Volume Designs: Maintains fast gradient response in UHPLC.
Integration Options: Built-in modules or stand-alone units for older systems.
Performance Tracking: Some systems monitor vacuum level or membrane condition for maintenance alerts.
IMPACT ON PERFORMANCE
Baseline Stability: Eliminates detector noise caused by bubbles.
Pump Reliability: Prevents cavitation and flow interruptions.
Gradient Precision: Maintains accurate solvent composition throughout runs.
Reproducibility: Ensures consistent chromatographic performance between runs.
Operational Efficiency: Reduces manual preparation and saves time.
CHALLENGES AND LIMITATIONS
Maintenance: Membranes and vacuum pumps wear out and need replacement.
Solvent Limits: Aggressive solvents or buffers shorten membrane life.
Residual Gases: No degasser removes 100% of dissolved gases; critical analyses may need additional preparation.
Cost: Advanced membrane systems add to instrument price.
System Backpressure: Blocked membranes or channels may increase resistance and affect flow.