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Although materials can be desorbed directly from empty tubes, this may result in contamination of the tube as the sample matrix melts or degrades. Using PTFE liners (inserts) protects the inner walls of the tubes and can simplify sample weighing.
PTFE liners are designed to be used with empty stainless steel TD tubes.
Two liners are available: “snug fit” liners which should be used for most powdered/granular samples; and “loose fit” liners which are suitable for “semi-solid” samples which should be smeared around the inside of the liner.
In all cases it is critical that the sample does not ‘plug’ the liner and that carrier gas can continue to flow through the liner unimpeded. “Loose fit” liners may also be inserted into tubes packed with a small bed (approx. 1 cm) of sorbent e.g. Tenax TA. The sorbent ensures that no high boiling debris from the sample matrix can migrate into the flow path of the thermal desorber.
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