Chapter:
Topic:
INSTALLATION
InterfacingThe Liquid Autosarnpling Carousel
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The SRlliquid autosampler is a
multi-position sample injection system
that permits the user to conduct
unattended sampling, injection and
analyses ofmultiple samples. Because
the complete syringe
rinse,
load
and
inject sequence is mechanized and
automated, the injection technique
will
be exact and identical from sample to
sample, eliminating any variation in
injection technique and sample delivery
experienced between different
operators when performing manual
injections. This consistency
will
increase sample precision and
reproducibility•.
FromCODtroI panel ofSRIautosampler comroller
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SRlliquid 8utosampler
CODD"'Cted
to
SRI 8610gas
cbroma1ograph
The
autosampler is controlled
automatically by PeakSimple software
and/or manually at the autosarnpler
control panel shown at left, Through
software control, the autosampler
is
stepped through the sample
vial
positions until
all
samples inserted in
the
carousel
have been injected and
analyzed (without the need for operator
intervention). A simple conunand in the
event table (momentary activation of
relay A) causes the autosampler to
insert, flush, draw and inject the needle
contents
into
the injection
port.
As
soon as
the
needle
has
been withdrawn
from the injection port,
the
autosampler
is
stepped to the next
vial
position to
remain at the
ready
for the next
actuation of relay
A.
The sample
vial
tray may be manually advanced by hand or
by
pressing the TRAY
ADYANCE actuator button. The amount of time (in minutes) that the syringe needle is flushed to
clear the preceding sample
is
selectable using theFLUSHTIME control. The amount of solvent
used
to flush the syringe mayalso be varied
by
adjusting
the
sample pressurizing
gas
pressure. The actual
volume of flush
required
will
be dictated
by
thecharacteristics of
the
sample being injected.
If
not
overly viscous, a sample flush volume ofapproximately 100 nticroliters should be adequate.
If
sample availability
is
limited to small volumes, then the flushmay need to be reduced to economize
onsample consumption. The amount of time
that
the needle remains
in
the injection
port
after the
sample
has
been discharged from the syringe is also selctable using
the
INJEcrION DWELL
control. Selectable in seconds, the control permits the user to choose having the needle withdraw
immediately upon havingdeposited its sample, or to
maintain
the needle in the injection port for an
extended period, permitting any sample containing higher boiling or thermally labile components
adequate time to exit the syringe and enter the injection
port,
High boiling components require longer
needle-injection
port
dwell times
than
volatile components. A setting of I second signifies that the
needle penetrates the septum, injects the sample and
is
withdrawn
immediately,
all
within
the
duration of
ODe
second. Asetting of 4 seconds
permits
the needle
to
dwell in the injection
port
foran
additional 3.5 seconds.
