I try to use GC/MS to analyze trialkylamines. Every time after I replaced the septa, liner, or clean up the inlet, the sensitivity of analytes increased. But just after 3-4 injections, the sensitivity dropped. Is there something wrong with inlet?
By Anonymous on Sunday, June 13, 2004 - 12:48 pm:
This phenomenon is not uncommon with molecules containing certain reactive functional groups (like amines). What happens is active sites are formed in the liner that irreversibly bind some of the analytes.
Question: are you dealing with some type of natural water samples (like sea water or well water). I ask because these samples contain salt which act as active sites, once in the system, and very quickly and drastically reduce sensitivity. In the past we have solved this problem by doing solid phase extraction to prepare the samples.
By Haifei Yin on Tuesday, June 15, 2004 - 04:19 pm:
Thanks! I haven't gone that far. Right now I am working only with standards. I use silylanized liner to prevent this kind of problem. But I still have the problem of loss of sensitivity.
By Anonymous on Tuesday, June 15, 2004 - 06:43 pm:
If you are having this problem with standards, my thinking is that the method - as it is now - will never be very reliable. I think you have two options: do a derivatization to make the analytes more amenable to GC analysis, or switch to HPLC.
If you choose to look into derivatization, two companies that sell derivatization supplies are Pierce and Regis.