GC-TCD issues
Posted: Thu Oct 31, 2019 7:27 pm
Good evening all,
I am hoping to get some advice on how to go about optimising analysis using GC-TCD (Varian CP3800), Helium carrier gas.
I have a method set up for analysis of methane, ethane and CO2. I have a valve switch at 1.6 min that retains Oxygen, Nitrogen and Hydrogen on my molsieve column. Methane is eluted from my Haysep Q column at 1.7 min, CO2 at 2.8 min and ethane 5.8 min. A valve switch at 8.3 min is followed by Oxygen and Nitrogen eluting from the molsieve column at 9.5 and 10 min respectively.
I will need to tweak the protocol to allow for the analysis of propane (when standards arrive). My main issue is having spent a week setting up this protocol, my supervisor is hoping that my limit of detection for ethane is around 500 ppm. Currently, I cannot detect ethane at levels lower than 1000 ppm. As this is my first experience of using GC-TCD I am not really sure if there is a way to improve my limit of detection with my existing columns. If someone could confirm that this is the case, or suggest a different option I would be very grateful.
My second issue is, having set up the above protocol I have been asked if I will be able to calibrate for H2. My understanding is that this will be impossible using Helium as a carrier gas.
I have access to Argon as a carrier gas, which would make H2 analysis possible, however am I naive in thinking I could just switch carrier gases from one to to the next depending on whether I need to analyse H2 or alkane gases?
With thanks,
Rich
https://imgur.com/a/oO9o3Vk
I am hoping to get some advice on how to go about optimising analysis using GC-TCD (Varian CP3800), Helium carrier gas.
I have a method set up for analysis of methane, ethane and CO2. I have a valve switch at 1.6 min that retains Oxygen, Nitrogen and Hydrogen on my molsieve column. Methane is eluted from my Haysep Q column at 1.7 min, CO2 at 2.8 min and ethane 5.8 min. A valve switch at 8.3 min is followed by Oxygen and Nitrogen eluting from the molsieve column at 9.5 and 10 min respectively.
I will need to tweak the protocol to allow for the analysis of propane (when standards arrive). My main issue is having spent a week setting up this protocol, my supervisor is hoping that my limit of detection for ethane is around 500 ppm. Currently, I cannot detect ethane at levels lower than 1000 ppm. As this is my first experience of using GC-TCD I am not really sure if there is a way to improve my limit of detection with my existing columns. If someone could confirm that this is the case, or suggest a different option I would be very grateful.
My second issue is, having set up the above protocol I have been asked if I will be able to calibrate for H2. My understanding is that this will be impossible using Helium as a carrier gas.
I have access to Argon as a carrier gas, which would make H2 analysis possible, however am I naive in thinking I could just switch carrier gases from one to to the next depending on whether I need to analyse H2 or alkane gases?
With thanks,
Rich
https://imgur.com/a/oO9o3Vk