- A gas mixture, produced either synthetically or by pumping natural air into
a high-pressure cylinder, that has been systematically analyzed to assign a
concentration value to a molecule or concentration values to several molecules
- An inert gas that constantly flows through the
chromatography column and
detector. Carrier gas mobilizes the sample by pushing it
through the column. 'Inert' refers to non-reactivity of the carrier gas with the
sample and a low response of the detector to the carrier gas.
- A class of fully chlorinated/fluorinated carbon-based molecules of the
general formula CnCljFk where j + k = 2n +2, k and j > 0. Uses have included
refrigeration, aerosol propellants, foam blowing, and cleaning solvents.
- A length of metal or fused silica tubing filled or coated with one or more
packing material that separates the compounds of
interest as the sample mixture passes through.
- A sensor that produces a measurable signal when certain molecules pass through it
Electron-capture detector (ECD)
- A detector that is especially sensitive to halogen-containing molecules. Thermal
electrons generated by the radioactive decay of 63Ni create a small, steady
current within the detector. This current is measurably reduced when certain
molecules capture electrons as they pass through the detector.
Gas chromatograph (GC)
- A type of instrument based on the injection of component mixtures onto a
chromatography column, separation of the
components as the mixture passes through the column, and sensing of the
components of interest as they elute into a detector.
Gas sampling valve (GSV)
- A multiple-port, two-position valve that changes the direction of gas flows
through chromatography columns and other
parts of an instrument. Used to fill a sample loop
with sample then inject the loop contents onto the column.
- A class of carbon-based molecules having at least one halogen (fluorine,
chlorine, iodine) atom.
- A class of brominated halocarbons of the general
formula CnBriCljFk where i + j + k = 2n + 2, i and k
> 0. Halons are typically used as fire extinguishing agents.
- A granular, solid-phase powder, sometimes also coated with a liquid phase, that
is used to fill a chromatography column.
The packing material of a column is chosen for its ability to separate the
molecules of interest from one another. Packing materials typically separate
molecules by their size (molecular sieves), boiling points, or polarities.
- A length of hollow metal tubing whose fixed volume is filled with sample to a
repeatable pressure and its contents injected onto a chromatography column.
Consistent sample loop volume, pressure and temperature ensure that the same
amount of sample is injected for every analysis.
Stream selection valve (SSV)
- A multiple-port, multiple-position valve that determines the source of gas
flowing through sample loops. Used to alternately analyze air samples and