The column inle (or injector) provides the means to introduce a sample into a continuous flow of carrier gas. The inlet is a piece of hardware attached to the column head.
Common inlet types are:
S/SL (Split/Splitless) injector; a sample is introduced into a heated small chamber via a syringe through a septum – the heat facilitates volatilization of the sample and sample matrix. The carrier gas then either sweeps the entirety (splitless mode) or a portion (split mode) of the sample into the column. In split mode, a part of the sample/carrier gas mixture in the injection chamber is exhausted through the split vent.
COC (cool on-column) inlet; the sample is here introduced in its entirety without heat.
gas source inlet or gas switching valve; gaseous samples in collection bottles are here hooked up to what is most commonly a six-port switching valve: the carrier gas flow is not interrupted while a sample can be expanded into a previously evacuated sample loop. Upon switching, the contents of the sample loop are switched into the carrier gas stream.
P/T (Purge-and-Trap) system; samples requiring preconcentration or purification can be introduced via such a system, usually hooked up to the S/SL port. The advantage of such a system is that no or few prior enrichment/purification steps in the laboratory are necessary.
In addition, Solid phase microextraction (SPME) (solid phase microextraction) offers a convenient, low-cost alternative to P/T systems with the versatility of a syringe and simple use of the S/SL port.
The 5890 Split/Splitless Epc Inlet system uses pressure to control flow through open tubular, capillary columns. The capillary column flow is not measured directly, but is calculated from the column dimensions, inlet and exit pressures, temperature of the column, and carrier gas type.
The 5890 Split/Splitless Epc inlet is a backpressure regulated system. This simply means that the control and feedback of the pressure comes from “back” or “upstream from” the controlling valve. If the upstream pressure momentarily drops below setpoint, a feedback signal causes the control valve to close more until the pressure rises above the setpoint, after which it will open further. The split flow rate and column flow rate are set independently of each other allowing changes in the split flow and column head pressure with changing the total flow. The Capillary Inlet system can be run in two modes of operation—Split and Splitless. The inlet can equilibrate to pressure setpoint if the following conditions are met:
The capillary inlet system is assembled correctly and is leak free.
The EPC control board is configured correctly and all components are functioning.
There is sufficient carrier supply pressure applied to the GC and the Mass flow controller is turned on.
(80-120 psi for the standard capillary EPC system yielding at least 60 ml/min of total flow.)
The capillary column is installed and configured correctly.