HP 5890 Series II, Reference Manual

Page: 117 / 244

Inlet Systems
Split/splitless capillary inlet
117
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 (> C
21
), a higher inlet
temperature may be required.