HP 5890 Series II Plus Reference Manual page 112

Inlet Systems
Split/splitless capillary inlet
Figure 6-8
External
Plumbing
Trap(s)
Carrier
Gas
Flow Diagram, Split Operation
Due to short sample residence time inside the inlet, the technique
requires rapid volatilization; thus, inlet temperature must be high
enough to ensure this.
The backpressure regulator in the split vent path maintains constant
pressure at the head of the column. Total inlet flow, controlled by a mass
flow controller, divides between a septum purge path and flow down the
inlet insert.
Flow through the insert is divided again, between flow into the column
and flow around the bottom of the insert, up between the outside of the
insert and inlet body, and on to the split vent.
The split ratio is defined as:
where flow rates are volumetric, measured in ml/min.
112
Internal
Capillary
Plumbing
Inlet
Mass
Electronic
Flow
Flow
Controller
Sensor
(optional)
Split Vent Flow Rate + Column Flow Rate
Split Ratio =
(P)
(C)
N.C
(S)
N.O
To
Solenoid
Detector
Valve
Column
Column Flow Rate
Septum
Septum
Purge
Purge
Control
Vent
IN
OUT
Pressure
GA
Gauge
COM
IN
Split
OUT
Vent
Back-
pressure
Regulator