7 Questions You’ve Always Wanted to Ask About GC

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1. Why does the inlet require so much troubleshooting?

The inlet is the most common place where problems happen in gas chromatography. This is because:

  • The inlet is subjected to very high temperatures.
  • There are multiple consumables involved in the inlet that need routine maintenance.
  • Some inlet modes, such as splitless injection, result in a slow process which means that target analytes and the inlet are able to interact with each other for some time before the sample enters the column.

When dealing with active analytes, a highly deactivated inlet is necessary to minimize problems that can occur in the inlet, such as asymmetric peak shape and adsorption of target analytes. Zebron™ PLUS liners are rigorously deactivated and tested for activity to ensure reliable results when working with highly active compounds.

2. How can a Zebron PLUS liner with wool improve my GC column lifetime?

Quartz wool in Zebron PLUS liners serves two main purposes:

  1. Wool promotes homogenous vaporization of analytes and solvent in the inlet, and helps effectively transfer them to the head of the GC column.
  2. Wool acts as a filter, trapping non-volatile impurities and preventing them from proceeding further into the GC column.

3. Can I pack or re-pack my liner with wool?

Liners should not be packed or re-packed. When attempts are made to remove wool from the liner or re-pack them with new wool, scratches in the deactivation layer can be created. When wool is forcefully inserted or removed, these scratches can expose active sites, causing peak tailing and poor reproducibility.

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4. My sample is dirty and it produces a residue on my liner after 100 injections. Can I scrub/sonicate my liner and reuse it?

No. It is not recommended to scrub/sonicate your liners. Residue formation indicates contamination. More specifically, this indicates that the sample contains non-volatile impurities.

In such cases, it is recommended to replace, rather than clean, your liner. Sonication in solvent can alter the liner’s deactivation and scrubbing can create scratches and active sites. Both will result in chromatographic problems including and not limited to poor quantitation, analyte breakdown, poor reproducibility, and peak asymmetry.

5. Does the color of a glass liner represent deactivation?

The color of the liner does not determine its inertness. In fact, varying colors can be easily added to liners by using metal salts during manufacturing. The inertness of the liner stems from the deactivation process that the liner undergoes, rather than its color alone.

6. How often should I change my Zebron™ PLUS liner?

It is important to periodically check and maintain your liner. The frequency at which a liner must be changed can be hard to predict as it is entirely dependent on the sample matrix. In general, if you are performing a headspace injection, only the vapors enter the GC inlet so the liner will remain clean for months. However, with a neat matrix injection, it is necessary to check the liner at least twice a week to make sure that it is free of residues. Once a visible residue is noticed, it is time to change the liner.

7. I am using an inert column for my analysis and I still see peak tailing. What could be the reason for this?

For analysis of active compounds, it is extremely important to use both a highly inert column and a highly inert liner. The liner is the first place of potential analyte interaction during GC analysis, and it is important that your analytes are not adsorbed. Zebron PLUS liners undergo a rigorous deactivation process and are tested for inertness to ensure reliable results when working with highly active compounds such as underivatized acids and active bases.

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