Product Spotlight on FocusLiner™ Inlet Liners

By: Robert F. Wallace, Reporter EU Vol 24

Robert F. Wallace


Supelco now offers the FocusLiner series of inlet liners. These liners incorporate a unique design that prevents shifting of the wool plug during repeated injections or sudden inlet pressure changes. The use of a wool plug in inlet liners has been used for many years to promote the rapid vaporization of the entire sample, minimize mass discrimination, and prevent non-volatile material from entering the column. In addition, by wiping the sample from the needle tip, a wool plug signifi cantly improves reproducibility by preventing droplet formation. The position of the wool plug is critical. It must be located so that the wool plug surrounds the needle tip as the sample is injected.

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The Problem: Traditional Liners with Wool

With traditional inlet liners, the speed of many auto– samplers is suffi cient to force the wool plug down below the optimal position for effective needle wiping. If there is an imperfection in the needle, such as a slight burr, this can grab the wool plug and pull it up towards the septum. Pressure changes, such as those that occur in pulsed splitless injection, can also move the wool plug. Even changing the column or septum can cause a rapid pressure drop and alter the position of the wool plug. Unfortunately, there is no guarantee that once a traditional liner is installed in the injector, the wool plug will stay in the correct position.

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The Solution: FocusLiner Inlet Liners

With a FocusLiner inlet liner, tapers inside the liner stabilize the position of the wool plug, preventing the plug from shifting up or down. Figure 1 depicts this design. The wool plug is always correctly located. This position, unlike that found in a traditional inlet liner, provides a larger

Figure 1. FocusLiner Inlet Liner

surface area, allowing the sample to mix well prior to entering the column. More importantly, the location of the wool plug lets the tip of the needle penetrate the wool for maximum vaporization. The wool plug will also wipe any residual liquid sample from the needle tip to prevent droplet formation. This can improve reproducibility as much as 10 times, reduce solvent tailing, and lower mass discrimination during split injections. The effect is dramatic and typically reduces injection variability by at least 96%.

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The use of a FocusLiner inlet liner provides precise, accurate, and reliable sample injections resulting in enhanced sample vaporization and maximum detection level sensitivity. Supelco offers FocusLiner inlet liners for all major GC instruments, most injection techniques, as well as for 0.10 mm I.D. Fast GC columns.

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  1. Technical Article TA-0004-A, 0.2% RSD’s? It’s Now a Reality with SGE’s FocusLiner, SGE (
  2. Technical Article TA-0043-A, FocusLiner: Improve GC Accuracy and Reproducibility 10 Fold, SGE (

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