Recoveries of Light Gases

Ambient air samples are generally concentrated using adsorption on absorbents capable of trapping C2 - C12 hydrocarbons and then thermally desorbed into the gas chromatograph. This forum is for the discussion of issues found in the equipment and process of thermal desorption such as its effects on recoveries, retention times, and overall chromatographic effects caused by poor or incorrectly functioning thermal desorbers.
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White Rabbit
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Recoveries of Light Gases

Post by White Rabbit » Wed Dec 09, 2015 7:05 pm

We have a problem with the recovery of light gases. Acetylene, Ethane, Ethylene and sometimes Propane. Since we use response factor from propane for all the targets on the PLOT column if the recovery is lower than it's supposed to be then the recoveries for C4 and C5 gases is higher than expected. Has anyone seen this? Know what causes it?
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Red Queen
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Re: Recoveries of Light Gases

Post by Red Queen » Sat Dec 19, 2015 10:12 am

Losses of acetylene and ethane can be a result of trap break though. If the sample volume is too high (e.g. sample flow too high or sample interval too long) then these light gases will be lost off the trap. Even at -30C these light gases migrate through the trap material so they can be lost off the trap if the flow and time is too great.
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