Inlet Systems
Split/splitless capillary inlet
A general guideline is that components boiling at least 150^C above the column temperature will be reconcentrated by cold trapping at the head of the column. Components with lower boiling points are reconcentrated via the solvent effect.
Temperature programming
Multiple•rampoven temperature programming is advantageous: the oven is held at an appropriately cool temperature at injection to create an environment for component reconcentration.
It is then programmed upward rather quickly to release lighter components held by the solvent effect; then programmed higher yet, but at a lower rate, to release heavier components held by cold trapping.
Sample requirements
Injection volume is generally in the range 0.5 to 2 ¿l. Individual component concentrations must not be so great as to overload the column. Retention indices for components of interest should be greater than 600. The maximum amount of sample injected without column overload depends upon column bore, loading efficiency, and component polarity.
Inlet temperature
Because gas flow through the inlet insert during injection is reduced to that flowing through the column, sample residence time inside the insert is longer than with split sampling.
For this reason, relatively lower inlet temperatures may be used: a temperature in the range 150 to 200^C is adequate for most samples. Note that lower temperature also reduces volume required by vaporized sample, reducing possibility of sample flash back.
For samples with high boiling components (> C21), a higher inlet temperature may be required.
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