Re: low response

[Yahsi3228]

It may be that your column is now too short, especially if you are doing
splitless injection, to properly cold-trap the more volatile compounds and
make use of the splitless effect. You may need a longer column or a
retention gap.

Are you sure none of the GC conditions (e.g. temperatures, pressures,
injection volume) changed? Make sure you replaced the liner with the
identical type, and that it is packed the same way. Make sure that the
column is properly inserted into the injector, as per manufacturer's
instructions. If these do not work, try changing the split vent charcoal
trap.

-- Adam Patkin
PerkinElmer Life and Analytical Sciences

<evka.d...@gmail.com> wrote in message
news:fvq0h3$8gj$1...@news-int.gatech.edu...
}
} Hello.
} We're using Agilent 6890, 7890 with MS 5973A. Method is focused on
} testing alkylated benzenes, naphthalens and PAHs. After full
} maintainance what is shortening column, changing liner, cleaning
} multiplier and changing filaments peaks start splitting. This problem
} occurs only on front analytes what are very volutile compounds. The
} rest of the run is ok. Calibration standards are prepared in hexane.
} Tailing and splitting of peaks occurs in these compounds. Samples and
} QC(fortified blank) are prepared in pentane. Responses are low
} especially in front compounds.Differences in responses between using
} pentane and hexane are huge. If you know anything about this problem
} we'd appriciate any help.
} Thanks
} Eva
}

[Knight...@epamail.epa.gov]

evka.d...@gmail.com wrote:
} Hello.
} We're using Agilent 6890, 7890 with MS 5973A. Method is focused on
} testing alkylated benzenes, naphthalens and PAHs. After full
} maintainance what is shortening column, changing liner, cleaning

} multiplier and changing filaments peaks start splitting...

It's certainly the case that you may have altered conditions (such as
the previously mentioned column length and injection port conditions)
enough to cause the more volatile components to behave differently
between the carrier solvents pentane and hexane. I'd suggest that it
would be preferable to inject your standards in the same solvent in
which your samples end up and optimize analytical conditions for that
solvent. The conditions may need to be re-optimized after instrument
maintainance, but you won't be dealing with the inherent difference in
the physical characteristics between the two solvents.

Cordially,

Peggy Knight