Chapter:
Topic:
INSTALLATION
Analytical Column Installation (continued)
The injection port of theSRI chromatograph isdesigned specifically for direct injection ontoa
0.53mmJ.D. wide-bore capillary column. Asample, injected usinga chromatography syringe
equipped with a 26gauge needle, isdeposited directly intothe column. The injector
IS
supplied with a
liS" 0 .0. stainless steel0.53mmcapillarycolumnadapter that guides the syringe needle into the
capillary column entrance.
The
sample is then injected onto thecolumn.
The
user's sample injection
technique (sample loading, needle insertion
and
injection) should bequick, preciseand reproducible.
I
0.53mm. J.D.
fused
silica
column
-0
I
Capillary
coI_
adapIer
(1ocaled
inside iJljection
port)
DIRECT INJECTION INTO ACAPn.LARY COLUMN
Thewide-bore capillarycolumn adapter ismachined from liS" stainless steel
and
accepts the
insertion ofO.Smm0.0. tubing (the outer dimension of 0.53mm J.D. capillarycolumn tubing). The
injection endof the adapter is conical and "funnels" theneedle into the columntubing inserted into
theadapter from thecolumnend. Aslot cut in theadapter prevents carrier
gas
flow
restrictions
caused
by
overtightened
septa.
Byguiding the injection needle well into the analytical column tubing,
the sample may be deposited as a liquid onto the stationary phase of the column without exposing the
sample tocontact withhOI metalor glass surfaces.
The capillary columnadapter is locatedwithin the assembly that forms the injection
port
when
a 0.53mmJ.D. column is in use. The injection
port
is constructed froma liS" stainless steel
Swagelok* bulkhead fitting
that
has
beenmodified topermit the connection of a
gas
sourcedirectly
into the fitting through thehexagonal flangeat the bulkhead.
This
modification permits the
introduction of carrier gas into theinjector. The endof the injector bulkhead fitting located in the
ovencompartment accepts a liS" Swagelok* nul
and
graphite reducing ferrule (AUtech
RF200/0.8-G)
used tosecure thecapillary column in the injector. At theother endof thebulkhead
fitting, facing theuser, a liS" septum nut is used to secure a formed silicone septum inplace in front
of
the
column, sealing the injection
port.
The septumnut should
be
finger-tightened. Two rubber
O-rings are installed on the injector where the
septum
nut isattached.
The
septum
nut shouldnever
be
tightened beyond
the
pointwhere the nut contacts theouterO-ring.
Capillary
column
adapIer
I
I
118- SwageloJc-
bulkhead
fitting
SRI CAPn.LARY COLUMN/INJECTION PORT DET
All.
The injection port is compact
and has
a lowthermal mass. Sincemost of the injector body is
locatedwithin the column oven, the injector andoven temperatures are alwaysequal (the standard
injector is not supplied
with
any provision for independent heating. Heated
on-column
injection is
available as anoption). Resultant sample component
peaks
are sharp andexhibit
minintal
or no
tailing. This isdue
to
the injection of the sample directly onto thecolumn and ata temperature below
the sample solvent boiling point. Decomposition of thermally-sensitive sample compounds does not
occurand artifact formation is minimized because the sample is not subjected
to
vaporization and
recondensation, asoccurs inhigh temperature injectors.
