Operating Instructions for
Model 7125 Syringe Loading
Sample Injector
mobile phase coming out of the needle port
when the valve is turned from INJECT to
LOAD. Example: 1-mL loop expands 20 uL
upon decompression from 200 bar.
4.2 Warning: When using the Needle Port
Cleaner, empty the syringe slowly to prevent
solvent from squirting back.
4.3 Caution: Use the correct size syringe
needle to prevent damage to the valve.
4.4 Caution: Rinse the valve after using
buffer solutions to prevent crystals from
forming, which can scratch the rotor seal.
5.0 USING PROPER SYRINGES
Use syringes with 0.028-inch O.D. (22
gauge) x 2-inch long needle, without electro
taper, and 90
°
point style. Using the incorrect
needle size will damage the injector.
6.0 INSTALLATION
a) To mount the valve on a panel, remove
the handle by loosening the two handle set
screws. Use the two screws supplied to fasten
the valve to a panel.
b) Replace the handle by tightening the
two set screws on the two flats of the shaft.
c) Connect the two vent tubes (supplied) to
ports 5 and 6. Place the outlet ends of both at
the same horizontal level as that of the needle
port to avoid siphoning. See Fig. 2.
1.0 DESCRIPTION
Model 7125 is a seven-port sample
injection valve in which the sample is loaded
through a built-in needle port in the front of
the valve.
Fig. 1 shows the flow diagram of the
valve. The six small circles represent the
ports in the valve stator. The two heavy arcs
represent the connecting passages in the
rotor seal. The larger circle represents the
needle port.
The sample loop is loaded in through the
needle port in the LOAD position. Rotation of
the knob, 60
°
, switches the valve from LOAD
to INJECT. In the INJECT position the
mobile phase flows through the loop.
2.0 SUPPLIED WITH THE VALVE
Supplied with the valve in a separate bag
are fitting sets for tubing connections and the
items shown below. A 20-uL sample loop is
standard with the valve.
Remove the supplied 22 gauge needle from
the needle port before using the valve.
3.0 SPECIFICATIONS
•Maximum temperature is 80
°
C.
•Valve is set to hold 345 bar (5000 psi). It can
be adjusted to hold up to 483 bar (7000 psi).
•The wetted surfaces are stainless steel,
alumina ceramic, and an inert polymer.
4.0 IMPORTANT SAFETY NOTICES
4.1 Warning: When using sample loops
larger than 100 uL, shield yourself from
d) Connect the pump to port 2 and the
column to port 3. Leave the column discon-
nected from the valve during initial flushing.
7.0 FLUSHING THE INJECTOR
In the INJECT position, flush the needle
port with about 1 mL of mobile phase, using
the needle port cleaner as shown in Fig. 3. At
this time, the pump flushes the loop.
8.0 COMPLETE LOOP LOADING
In complete filling, the volume of sample
injected is set by the volume of the loop (this
includes the valve passages). This method
produces the highest precision.
Overfill the loop with at least two to three
loop volumes of sample. Five to ten loop
volumes will provide even better precision.
An excess of sample is needed because mo-
bile phase near the wall of the loop is dis-
placed slowly, due to the laminar flow pattern
shown in Fig. 4.
To completely fill the loop:
a) See Warning 4.1 and turn to LOAD.
b) Put the syringe into the needle port. You
will feel tightness during the last 2-3 mm of
travel, as the needle passes through the needle
seal and then stops against the stator face.
c) Load the sample.
d) Leave syringe in and turn to INJECT.
LOAD INJECT
9/64 Hex Key
5/64 Hex Key
Needle Port Cleaner
Mounting Screws (2)
Vent Tubes (2)
Figure 1: 7125 Flow Diagram
Correct level
of vent
line ends
Height of
needle port
Figure 2: Correct Position of Vent Lines
9.0 PARTIAL LOOP FILLING
If you only have small quantities of sample,
this is the method of choice. In the partial
filling method the volume of sample injected
is set by the syringe. In this method, no more
than half a loop volume of sample is loaded
into the loop. For example, load no more than
10 uL into a 20 uL loop. With larger volumes
some of the sample is lost out vent tube 6. This
is due to the laminar flow effect shown in
Fig. 4: sample flows down the center of the
loop at twice the average speed.
To partially load the loop:
a) In INJECT, use the Needle Port Cleaner
to flush out the needle port with about 1 mL of
mobile phase. This will flush out contamina-
Flow
Tube Wall
Mobile Phase
Sample
Figure 4: Laminar Flow Effect
Knob of Valve
Figure 3: Use of the Needle Port Cleaner
Needle Guide
CAUTION:
To avoid liquid squirting back
at you, discharge syringe slowly.
Needle Port Cleaner
Syringe Barrel
