Ethane and other hydrocarbons - FTIR Gas Cell Analysis
Posted: Wed Jun 01, 2016 8:43 pm
Hello all,
First of all, sorry if this is in the wrong section but I did not see anything for FTIR, and this is certainly gas phase related.
So I have a gas cell for my Varian 660 FTIR and I am trying to use it to get certified on a few methods: MIL-PRF-27210 (Aviator's Breathing Oxygen), CGA G-4.3 (Commodity Specifications for Oxygen), CGA G-7.1 (commodity Specifications for air), and NFPA 1989 (Breathign Air Quality for Emergency Services).
All of these methods specify a "gas cell equipped infrared analyzer" but I have been having trouble with the non-methane hydrocarbon part. Methane has two distinct peaks that can be used, the 3000 cm^-1 region (the total hydrocarbon region), or the 1305 cm^-1 region which is a much better predictor for methane when other hydrocarbons are present. Using 1305 cm^-1 region for methane has given me solid, repeatable results. With ethane, it too has two distinct peaks, the same 3000 cm^-1 region as methane and other hydrocarbons, but it also has another peak around 1400 but this happens to be right in the water vapor region and causes the peak to basically be unusable.
Basically, I don't understand how they are doing non-methane hydrocarbons as methane equivalent when you can't distinguish methane from ethane from butane from octane in the total hydrocarbon region. If anyone has any experience with gas analysis on the FTIR at all it would be terrific to have another contact.
First of all, sorry if this is in the wrong section but I did not see anything for FTIR, and this is certainly gas phase related.
So I have a gas cell for my Varian 660 FTIR and I am trying to use it to get certified on a few methods: MIL-PRF-27210 (Aviator's Breathing Oxygen), CGA G-4.3 (Commodity Specifications for Oxygen), CGA G-7.1 (commodity Specifications for air), and NFPA 1989 (Breathign Air Quality for Emergency Services).
All of these methods specify a "gas cell equipped infrared analyzer" but I have been having trouble with the non-methane hydrocarbon part. Methane has two distinct peaks that can be used, the 3000 cm^-1 region (the total hydrocarbon region), or the 1305 cm^-1 region which is a much better predictor for methane when other hydrocarbons are present. Using 1305 cm^-1 region for methane has given me solid, repeatable results. With ethane, it too has two distinct peaks, the same 3000 cm^-1 region as methane and other hydrocarbons, but it also has another peak around 1400 but this happens to be right in the water vapor region and causes the peak to basically be unusable.
Basically, I don't understand how they are doing non-methane hydrocarbons as methane equivalent when you can't distinguish methane from ethane from butane from octane in the total hydrocarbon region. If anyone has any experience with gas analysis on the FTIR at all it would be terrific to have another contact.