Gas Chromatography (GC) (IUPAC Compendium of Chemical Terminology):

Lecture 3. Gas chromathography.
Splitless injection.
Used for traces analysis with analyte concentration < 0.01%.
Volume of solution injected is ~ 2 μl.
Injection time is ~ 2 sec (SLOW INJECTION).
Injector temperature ~220 ºC.
~ 80% of the sample is applied to the column.
2 ml/min
0 ml/min
1 ml/min
1ml/min
Solvent trapping. The initial column temperature is set 40 ºC below the boiling point of the
solvent. Therefore the solvent condenses in the beginning of the column and traps the analyte
to produce a narrow plug in the beginning of the column. For solvent trapping, the analyte
concentration should be < 0.01%.
Cold trapping. The initial column temperature is 150 ºC than the boiling points of analytes of
interest. Solvent and low-boiling components are eluted rapidly, whereas high-boiling solutes
remain as narrow band. The column is then rapidly warmed to initiate chromatography of highboiling
solutes. Stationary-phase film thickness must be ≥2 μm.
Cryogenic focusing is the variation of cold trapping for low-boiling solutes. The column is
initially cooled with N 2 or CO 2 .
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Advantages of splitless injection:
suitable for quantitative and qualitative analysis;
narrow peaks of analyte.
Drawbacks:
broad solvent peak;
retention times depend on solvent evaporation speed;
solvent affects the shape of the peaks.
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