TCD O2 damage

[Aleksandr Gamble]

I have a question about possible damage to a TCD filament due to O2 exposure. I know that O2 should be removed from the carrier gas and reference gas so that it does not damage the filament. However, I have read at least one paper in which a TCD was used to detect O2 in a gas sample. Would taking several samples a day of gases that are mainly air be likely to adversely affect the TCD performance? I am hoping this amount of O2 would be negligibly small, but it may not be.

Many thanks.

- Alek Gamble

[chromatographer1]

Your simple question (and a very good one at that) does not commend a simple answer.

It depends.

In general, a heated filament seeing oxygen will oxidize and will eventually 'burn out'.

But many filaments are made of metal that may be coated with gold or other coatings which prolong the life of the filament.

High filament temperatures are not recommended in general and a wise operator will heat the filament only as much as needed.

But most commercial TCD detectors are ruggedly designed and will operate for weeks, months, and even years measuring oxygen in gas samples 24 hours a day.

Many process analyzers (GC-TCD based) do not use bare wire filaments but resistors that while less sensitive are able to operate for years at a time without failures.

Some analytical applications will use a TCD to measure some very corrosive analytes and require gold plating and replacement filaments every few months.

I hope I have been helpful.

Rod