Tube LIfetime Calculation in Whitepaper


In the white paper qd = permeation rate measured in ng/min and an example is given as Acetaldehyde at 2751 ng/min. However in the section for calculating the lifetime of the tube, qd is given in units of ng/min/cm and example is given as Acetaldehyde at 45 ng/min/cm.

Can you please clarify how you convert qd (ng/min) to qd (ng/min/cm).

Many thanks,


Submitted from:

Hi Matthew,

ng/min/cm is the permeation rate per active unit length. Multiple qd(ng/min/cm) by the tube length (excluding the crimped ends). Let me know if this answers the question?

Best - Billy

Hi Billy,

I had thought that might be the case but I wanted to check because the examples didn't quite make sense. I worked out that the tube would have to be ~60cm long to have a per cm rate of 45 and a final tube permutation rate of 2751 ng/min.


Got it. The examples had the same analyte but were separate from each other. Best – Billy



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