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

Lecture 3. Gas chromathography.
Split Injection.
Used for samples with analyte concentration > 0.1 %.
Only 0.2 – 2 % of the sample is delivered to column.
Injector temperature is high, e.g. 350 ºC.
102 ml/min
1 ml/min
100 ml/min
1ml/min
The sample is injected rapidly through the septum into evaporation zone. The injector
temperature is kept high to promote fast evaporation. A brisk flow of the carrier gas sweeps
the sample through the mixing chamber. At the split point, small fraction of vapors enters the
column but most passes to waste vent. Split ratio (the proportion of the sample that does not
reach the column) is typically 50:1 to 600:1.
Septum purge gas flow: prevents the column during injection and chromatography from hot
rubber septum gases and the excess of the sample vapors.
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Advantages of split injection:
narrow solute peaks;
suitable for qualitative analysis;
minimize the solvent effect.
Drawbacks:
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requires rather high concentration of analyte;
split ratio makes the quantitative analysis more complex;
not suitable for very expensive or toxic compounds.
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