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Setting up your Backflush in Micro GC

As we saw in our first article on the subject, the Backflush is an essential element of the chromatographic analysis of light gases.

CHEMLYS explains how to adjust the backflush in micro GC.

Chromatogram: Analysis in 65s of H2, O2, N2, CH4 and CO

The Backflush allows the protection of the analysis column with a pre-column guard.

How to easily adjust your backflush to protect your analysis column?

With the Micro GC Fusion, it’s very simple. Just set the “backflush time” parameter in seconds.

Initially, the pre-column and the analysis column are in series.

The backflush time is the time at which the pneumatic backflush valve is activated after the sample gas is injected. This action separates the pre-column and the analysis column. The pre-column is backflushed and the compounds that have had time to pass through the analytical column will be separated and detected.

The Backflush time can therefore be adjusted in a practical way :

We start an air analysis (oxygen and nitrogen) with a relatively short backflush time, in our example 5s.

Then we will increase the Backflush time from 1s to 1s until we notice the appearance of interest compounds.

Backflush adjustment, tests at 5s/6s/7s

With a backflush time of 5s, no signal is detected. All the compounds were backflushed. The backflush time was too short.

Then we switch to a 6s setting, the compounds appear. Now we have to make sure that the backflush lets all the oxygen and nitrogen through.

For that we increase again the time to 7s. We see that the area of the compounds is identical. This means that 6s was the right setting.

On the molecular sieve column, if the backflush time is set to oxygen and nitrogen, this setting will also be suitable for carbon monoxide (CO) analysis.

If you want to analyze methane on this column, you have to follow the same procedure focusing on the appearance and disappearance of the methane peak.

In conclusion, setting up your backflush with the MicroGC Fusion is simple and very fast. You have to do it step by step but the analysis is very fast so it doesn’t take much time.

See you soon for more articles, in the meantime feel free to visit our blog to review or discover our technical articles.

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