Set your Backflush to Micro GC
As established in our intro article, backflush is an essential fluidic mechanism for light gas analysis. It relies on a pre-column (guard column) to protect the sensitive analytical column from heavy or polar contaminants.
This technical guide demonstrates how to easily adjust the backflush switching time on your Micro GC to ensure full recovery of target analytes while maintaining column protection.
Chromatogram: High-speed 65-second analysis of H2, O2, N2, CH4 and CO
The Backflush allows the protection of the analysis column with a guard pre-column.
Comment régler facilement son backflush afin de protéger sa colonne d’analyse ?
On the Micro GC Fusion®, parameter setup is straightforward: you simply set the Backflush Time parameter in seconds.
Foreflush Phase: Immediately following sample injection, the pre-column and analytical column operate in series. Light target gases travel through the pre-column and enter the analytical column.
Backflush Activation: At the set backflush time, the pneumatic valve actuates to isolate the analytical column. The flow direction in the pre-column reverses, venting trapped heavy matrix components (CO2 moisture, C2+) through the exhaust port. Compounds that successfully transferred into the analytical column continue toward the detector µTCD for quantification.
Step-by-Step Protocol for Setting Backflush Timing:
1. Start with an Under-Set TimeBegin with a intentionally short backflush time—for instance, 5 seconds.Result: No peaks appear on the chromatogram. The backflush actuated too early, venting all target compounds before they could enter the analytical column
2. Increment Step-by-StepIncrease the backflush time by 1-second increments (e.g., set to 6 seconds).Result: Oxygen (O2) and nitrogen (N2) peaks appear. The backflush now allows analytes to transfer onto the MS5A column.
Backflush time adjustment: 5s/6s/7s tests
At a 5-second backflush setting, no signal is detected. All target compounds were backflushed out of the system because the valve timing was too short.
Increasing the timing to 6 seconds brings the target compounds into view. The next step is verifying whether 6 seconds allows complete recovery of oxygen (O2) and nitrogen (N2).
Advancing to 7 seconds confirms full analyte transfer. Because the integrated peak areas at 7 seconds are identical to those at 6 seconds, 6 seconds is validated as the optimal backflush time.
On a molecular sieve column (MS5A), a backflush timing optimized for O2, N2 naturally accommodates carbon monoxide (CO) analysis.
If methane (CH4) is your target analyte, apply this same iterative method by tracking the emergence and peak area plateau of the CH4 signal.
In conclusion, optimizing backflush timing on the Micro GC Fusion® is fast and intuitive. By following this simple step-by-step approach—and leveraging sub-minute run times—you can safeguard your analytical modules without slowing down your lab operations.
More technical content is on the way! In the meantime, browse our blog to discover more guides and expert insights on gas analysis.
