Newsgroup sci.techniques.mass-spec 1199

Directory

You should have a septum purge restriction in the system; sounds like it
could be either missing (if you have the fixed restrictor) or wide open
(if you have the valved restrictor)
  a)  fixed restriction:  Look for a nickel line from the injector block
terminating in a brass union.  The union may be painted either green or
blue depending on the restriction.  Make sure the restriction is present
and tightened. 
  b)  variable restriction:  Look for a vernier to the right of the
injector (there may be a pair of them if you have both split/splitless and
a SPI injector installed. )  Measure the flow at the valve; should be
about 1 ml/min/pound of head pressure; adjust accordingly.
  c)  check your gc program in the analysis-page/gc edit.  select the set
parameter menu item and make sure that you've got your relays the way you
want them.  sounds like you may be switching to split during desorb and
splitless during the run.
Also check that the quarter-inch graphite seal around the injector liner
is undamaged.  It's only good for about 4-5 liners and then should be
replaced. 
chris
J K Brandau  wrote:
}Our Varian 3400CX gas chromatograph coupled to out Saturn 3 GC/MS has a
}1077 Split/Splitless injector. 
}
}After a BTEX run on the Tekmar 2016 autosampler, the backpressure gauge on
}the GC went to zero! 
}
}We notice when tripping the GC into run mode, the pressure returns. The
}pressure is lost again when GC returns to ready mode. 
}
}We are having a difficult time identifying the problem. Has anyone had a
}similar problem? 
}
}Thanks,
}
}Ken Brandau
}-------------------------------------
}Name: J K Brandau
}E-mail: J K Brandau 
}Date: 1/17/97
}Time: 9:19:27 AM
}
}This message was sent by Chameleon 
}-------------------------------------
}
}
}

The library search routine from the HP chemstation software
driving an HP GC-MSD system produces an output listing
with hits for each chromatogram peak using the mass spectrum
collected at that retention time.  This provides useful data
but does not allow you to have an overall compound type distribution
or I should say a way of classifying the best hits according to their
chemical type, i.e., ketones, aromatics, carboxylic acids,
paraffin, etc.  Anybody heard of some software that would use
such output listing to classify compounds into organic types
and provide an overall type distribution?  This could be useful
if you are to look at and assess various types of oils like 
petroleum crudes, derived oil fractions or pyrolysis oils.
I Hope this will attract some comments and feedback.
Thank you