HPLC degasser: why degassing is essential and the advantages of Biotech DEGASi for OEM manufacturers

A degasser for HPLC is one of the most underestimated components in a liquid chromatography system. Without proper degassing of the mobile phase, a single gas bubble leads to a collapsing pressure, an unreadable chromatogram and unreliable analysis results. This article explains why an HPLC degasser is essential, how vacuum degassing works and why HPLC manufacturers and OEM instrument makers choose the DEGASi degassers from Biotech Fluidics.

⏱ approx. 7 minutes reading time

Why is a degasser essential in HPLC?

In an HPLC system, the mobile phase is pumped through a narrow column under high pressure. The pumps, valves and detectors only work accurately if the liquid flow is stable, continuous and completely homogeneous. Gases dissolved in the mobile phase are a direct threat to that stability: with pressure changes or temperature fluctuations, dissolved gases can be released from the liquid as gas bubbles. A single bubble reaching a pump head is enough to disrupt the pressure build-up and interrupt the flow.

The effect on the chromatogram is direct and dramatic. The baseline jumps, peaks become asymmetrical or disappear completely, and reproducibility drops to zero. An HPLC system without proper degassing produces chromatograms that are impossible to interpret. The cause is not the column, not the detector and not the measurement method: it is the mobile phase that has not been properly degassed.

Unstable baseline

Gas bubbles in the detector cell cause sudden spikes in the UV or RI signal that cannot be distinguished from real peaks. Quantification becomes impossible.

Pressure instability and pump damage

A gas bubble in the pump head prevents the chamber from filling completely with each stroke. The pressure fluctuates, the flow becomes pulsating and the pump valves and pistons wear faster.

Non-reproducible retention times

Varying gas concentrations in the mobile phase change the effective composition of the eluent. Retention times shift and the separation is not comparable between injections.

Increased background absorbance

Dissolved oxygen absorbs at low UV wavelengths and increases the background absorbance. This lowers the sensitivity of the detection and unnecessarily raises the limit of detection.

Accelerated column degradation

Pulsating flow due to related pressure fluctuations places mechanical stress on the column packing. Premature void formation in the column head is the result, with a loss of column efficiency.

Longer start-up times

Without a degasser, the system has to be flushed for a long time to gradually remove dissolved gas before stable conditions are reached. A degasser considerably reduces the start-up time.

A single gas bubble is enough

The mobile phase does not need to bubble visibly to cause problems. Dissolved gases are invisible in the bottle but are released as soon as the pressure drops after the pump or the temperature rises in the detector. A system that looks fine can still be systematically affected by dissolved gases that are only released in the detector.

How does a vacuum degasser work?

An inline vacuum degasser places a gas-permeable membrane in the liquid flow, surrounded by a vacuum chamber. The operating principle is based on physical laws: Henry's law describes how the concentration of dissolved gas in a liquid is proportional to the partial pressure of that gas above the liquid. By creating a vacuum on the outside of the membrane, the partial pressure of the gases is brought to zero. As a result, dissolved gas migrates from the higher concentration in the liquid to the low concentration in the vacuum chamber, through the gas-permeable membrane wall. The solvent itself does not pass through the membrane.

1. Mobile phase flows in

The liquid flows through the vacuum chamber via a short length of gas-permeable Systec AF tubing. The tubing has a high gas permeability but does not let the solvent itself through.

2. Vacuum draws gases away

A vacuum pump keeps the chamber at a constant, low pressure level. The concentration gradient drives dissolved gas molecules through the membrane wall into the vacuum chamber.

3. Continuous gas removal

The exhaust point of the vacuum pump is continuously flushed with a small amount of bleed gas. This immediately removes solvent vapours that could enter the pump. This patented design makes solenoid valves unnecessary and results in zero vacuum hysteresis.

4. Tailored vacuum control

A closed control loop continuously adjusts the pump speed to keep the vacuum level constant, regardless of the flow rate or solvent type. As a result, degassing is stable over the entire flow range.

5. Degassed liquid flows out

The mobile phase leaves the degasser with a considerably reduced gas concentration, typically with approx. 50% of the original concentration removed. This is sufficient to stay below the saturation point of the solvent mixture and prevent bubble formation.

50% removal is sufficient and achievable

The aim of an HPLC degasser is not to remove dissolved gas completely. The gas only needs to be reduced to a concentration below the saturation point of the solvent mixture. In practice, this means that approx. 50% removal is sufficient to eliminate bubble formation completely. This is an achievable and efficient goal for a vacuum degasser with a good gas-permeable membrane.

Comparison: degassing methods

There are several methods for removing dissolved gas from a liquid. Not all methods are equally effective for use in an HPLC system.

The crucial component: Systec AF membrane

The heart of every DEGASi degasser is a short length of Systec AF tubing. This amorphous fluoropolymer membrane has an exceptionally high gas permeability combined with minimal solvent permeability. That is the most critical material property for an effective HPLC degasser: the gas must pass through quickly, while the solvent should barely pass through.

Systec AF tubing is compatible with virtually all common HPLC solvents, including acetonitrile, methanol, tetrahydrofuran (THF), dichloromethane and hexane. For special applications with hexafluoroisopropanol (HFIP), specific chamber configurations are available in the DEGASi Integration HFIP series.

Zero vacuum hysteresis thanks to patented bleed venting

The vacuum pump in the DEGASi series has a special port that continuously flushes the pump head with a small amount of bleed gas. This immediately removes solvent vapours that could enter the pump from the vacuum chamber. This patented design eliminates the need for solenoid valves in the system and results in zero vacuum hysteresis: the vacuum level is always exactly at the set level, without delay or fluctuations. The result is more stable degassing and a longer pump life.

Advantages of Biotech DEGASi for OEM manufacturers

For manufacturers of analytical instruments, diagnostic equipment and other precision fluidic systems who want to integrate a degasser into their own product, Biotech Fluidics offers a specific OEM programme. Biotech Fluidics offers a wide range of specifically designed degassers for OEM manufacturers that are integrated into various precision fluid systems worldwide. The components come from the proven DEGASi family, but are combined in a way that is tailored to the customer's specific system requirements.

Fully customised to your specification

Number of flow channels, dimensions, power requirements, connector types, LED status indication and vacuum monitoring are tailored to your instrument. Biotech Fluidics designs the bracket and cabling for your assembly line.

Biocompatible and metal-free versions

For diagnostic, life science and pharmaceutical instruments, fully metal-free and biocompatible flow paths are available. No metal ions in the solvent to affect the analysis.

Fast delivery of standardised modules

Many of the most requested OEM configurations are available from stock or are assembled within a few days. This considerably shortens the lead time of your instrument development and production line.

Tested before shipment

Every OEM degasser is tested before shipment, just like the stand-alone models. You receive a validated component that can be integrated directly into your system without additional qualification.

Broadly compatible with HPLC solvents

The Systec AF membranes are compatible with acetonitrile, methanol, THF, DCM, hexane and HFIP. The right membrane configuration is selected for each solvent combination.

Collaborative innovation

Biotech Fluidics works actively with OEM partners on new instrument generations. From the first design session to series delivery: the team thinks along about the optimal degasser solution for your specific fluidic architecture.

Integration series versus Plus series: what is the difference for OEM?

The DEGASi Integration series is specifically designed for integration into OEM instruments: more compact dimensions, cable outlets for system integration and available in the same channel configurations as the stand-alone Plus series. The Plus series is the stand-alone version for labs that place a separate degasser next to their HPLC system. For OEM applications, the Integration series is the starting point; for further customisation, the Biotech Fluidics OEM programme is the appropriate route.

DEGASi series overview

DEGASI PLUS