helium measurement

[tigerk2001]

hi
I would like to know which detector is the best if I want to measure 1ppm Helium in Nitrogen. Which detector is sensitive enough.

thank you

[chromatographer1]

Tigerk,

About the only detector that can measure helium at 1 ppm is a TCD and you should be able to measure at that level if you use nitrogen as the carrier gas. Nitrogen should be five or six nines purity or as pure as possible as far as helium is concerned.

I would use a 3 to 6 meter Carboxen 1000 packed column, 1/16" OD 1.0 or 1.25 mm ID , a moderately slow flow rate and use at least a 1mL loop at ambient temperatures if possible. The only probable impurity that might give you a false reading is Neon.

best wishes,

Rod

[tigerk2001]

what will be the LDL if I used pure N2 as carrier gas for the measurement of Helium?

[chromatographer1]

My guess would be with a TCD the limit would be in the range of 1-10ppm, even less depending upon a lot of factors. I recall measuring 1-10 ppm of hydrogen in an application about 20 years ago. Helium's LDL should be similar.

best wishes,

Rod