Adjusting ECD Parameters - Contact Potential/Makeup Gas
Posted: Fri Jul 04, 2008 6:46 am
Hi --
Does anyone have a procedure for determining the optimal contact potential for a Varian ECD on a 3800 GC? What I have been doing is setting the time constant to fast, the ECD mode to zero, and then setting the contact potential at -760 mV. All of this is with the ECD sensitivity at range 10. With these parameters in place, I then measure the ECD voltage and try to increase this value by 0.5 mV. Am I doing this correctly? Is there a certain increment I should be using on the contact potential?
Also, in the experience of those here, does changing the makeup flow gas make such of an enhancement in sensitivity? I'm currently using N2 makeup flow for GC-ECD analysis of explosives. Would switching my makeup gas to Methane/Argon offer much of a sensitivity increase?
My last question involves a bit of explanation. I've found that the CAP mode of operation provides the best sensitivity, but I'm really not sure what the difference is between this mode of operation compared to N2 standard and N2 high. Can anyone explain what the difference is between these three modes of operation?
Thanks so much for any feedback!
-Aaron
Does anyone have a procedure for determining the optimal contact potential for a Varian ECD on a 3800 GC? What I have been doing is setting the time constant to fast, the ECD mode to zero, and then setting the contact potential at -760 mV. All of this is with the ECD sensitivity at range 10. With these parameters in place, I then measure the ECD voltage and try to increase this value by 0.5 mV. Am I doing this correctly? Is there a certain increment I should be using on the contact potential?
Also, in the experience of those here, does changing the makeup flow gas make such of an enhancement in sensitivity? I'm currently using N2 makeup flow for GC-ECD analysis of explosives. Would switching my makeup gas to Methane/Argon offer much of a sensitivity increase?
My last question involves a bit of explanation. I've found that the CAP mode of operation provides the best sensitivity, but I'm really not sure what the difference is between this mode of operation compared to N2 standard and N2 high. Can anyone explain what the difference is between these three modes of operation?
Thanks so much for any feedback!
-Aaron