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PAH analysis
Posted: Tue Feb 22, 2011 6:44 am
by Ruben
Hi. I am using a Varian Saturn 2000 GC/ion tap MS system to analyse for PAHs. I am able to get all peaks except the last 4 peaks of an EPA 17 component test mix. Theseae are the benzo(b and K)fluoranthene, benzo(a) pyrene, and the indeno upto dibenzo(ghi)perylene compounds.
I am using a a VF5 column (30m x 0.25um ft x 0.25um duiameter. In addition there peaks often seem to be shifting. AM not sure if it is a method setup or extraction setup.
Can anyone advise why I am unable to elute the last 4 peaks(m/z 252,252,276,278).
Thanks
R
Re: PAH analysis
Posted: Wed Feb 23, 2011 1:44 am
by Don_Hilton
What is the upper temperature of your temperature ramp and what is the temperature of your transfer line to the MS?
Re: PAH analysis
Posted: Thu Feb 24, 2011 5:21 am
by Ruben
The instrument settings are: trap = 150 deg celc, t/fer line = 180 and manifold 170 deg celc.
I am certain these temperatures can be increased, but it was recommended during a routine maintenance by our supplier to keep the instrument settings as above.
Thanks
Re: PAH analysis
Posted: Thu Feb 24, 2011 6:34 am
by Ruben
Apologies, typing error, manifold is set at 70 deg celcius...
Re: PAH analysis
Posted: Thu Feb 24, 2011 12:29 pm
by Don_Hilton
If the end of your chromatographic column passes throug the transfer line, high boilers may be trapped in a cold sport at 180 degrees. I am not familiar with your instrument, so I can not make specific reccomendations.
Re: PAH analysis
Posted: Thu Feb 24, 2011 1:49 pm
by MX304
If the end of your chromatographic column passes throug the transfer line, high boilers may be trapped in a cold sport at 180 degrees. I am not familiar with your instrument, so I can not make specific reccomendations.
That would be my thought as well. We normally go to 280 deg. on the transfer line.
Re: PAH analysis
Posted: Sun Feb 27, 2011 6:25 pm
by RobPelot
I am beginning some work on PAHs right now as well. Just curious, what type of ionization source are you using on your MS?
We were having a similar problem not getting the chrysenes, while having no issue with our lower MW PAHs.
It ended up being our extraction procedure. The method we got from the literature did not have us collecting enough from an Alumina and then a Silica Column. We were leaving the higher MW compounds behind
Re: PAH analysis
Posted: Tue Mar 01, 2011 11:20 am
by boris_gto
what you temperature program and you column. I go to 300 degrC for db-5MS UI
Re: PAH analysis
Posted: Wed May 18, 2011 10:37 am
by jarodw
difficult to say definitively as gc paramters unkown but t/f line T seems way too low for heavy PAH.