Inlet Systems
Split/splitless capillary inlet
Noting Figures 6•11 and 6•12,the splitless sampling process is as follows:
Before Injection: Carrier gas flow enters through the mass flow controller, into the top of the inlet. A small fraction is split off to purge the septum and insert seal, then flows on to the purge vent.
The remainder flows down the insert where it divides again: a fraction passes into the column while the rest flows around the bottom of the insert, up between the outside of the insert and the inlet body itself, and on to the split vent.
At Injection: A solenoid valve (splitless solenoid valve) is actuated just prior to injection, to prevent carrier flow from exiting at the bottom of the insert. Flow through the insert now passes only through the column.
The remainder flows through the top of the inlet to the split vent, via the solenoid valve and backpressure regulator.
After Injection: At a predefined time after injection, the solenoid valve returns to its original state, restoring purge flow through the inlet insert.
In going from column flow + septum purge flow at injection (typically less than 5 ml/min), to total flow (column + split vent + septum purge) through the inlet (typically 50 to 100 ml/min), residual solvent vapor
(1 to 5% of total injected solvent) is swept from the inlet.
Note that since carrier gas vents through the backpressure regulator, column head pressure (and, therefore, column flow rate) remains constant even when total flow through the insert is changed (injection versus insert purging).
Injection technique, split/splitless sampling
Proper injection technique is required for reproducible, quantitative data. The following steps should yield good results:
1.Rinse the syringe with solvent, completely filling and expelling the syringe several times.
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