2. System Overview
Most of the gas chromatographs (GC’s) are fitted with basic inlets offering few operating features.
OPTIC-4 is a highly advanced multimode inlet with sophisticated temperature and gas flow control
that can be used for the most demanding GC analyses. This important GC component offers single
inlet capabilities that would typically require two or more inlets. Whether one needs to increase the
GC system sensitivity with the OPTIC-4 large-volume injection capabilities, thermally desorb volatiles
or semi-volatiles from a solid sample, pyrolyze polymers or inject dirty samples, OPTIC-4 can perform
all of these tasks while still allowing standard injections usually performed with a split/splitless inlet.
A standard OPTIC-4 system consists of an inlet, a control unit and the Evolution Workstation control
software. The control software should be installed on a PC running Microsoft Windows 7 or
Windows 10.
The standard system is always supplied with a standard inlet which accepts 5 mm OD x 81 mm long
liners. There is also a ¼ inch version of the inlet, wich works with the ¼ x 3.2 inch thermal desorption
tubes.
OPTIC-4 can be delivered in one of the five configurations. The basic model is OPTIC-4S. It includes
an inlet and a stand-alone electronic controller with the built-in temperature and electronic flow
controls (EFC). OPTIC-4D has an optional auxiliary flow control channel. OPTIC-4SC and OPTIC-4DC
feature an optional cryogenic trap. OPTIC-4PTV is a simplified version of OPTIC-4S, delivered without
any gas control channel.
The main part of this guide contains information, which you are likely to refer to regularly.
Information, which is only occasionally referred to is included in the appendices. Detailed installation
information is also covered in the separate installation guides.
2.1 High Performance
OPTIC-4, when correctly set up, offers a minimum of sample discrimination. Reproducibility is
comparable to on-column injection but offers excellent tolerance of "dirty" samples. Thermal
degradation is less severe than with conventional hot split and splitless inlets and the analyst has
much greater control over the way in which the sample is introduced into the gas chromatograph.
2.2 Advanced Electronic Flow Control
One of the features that sets OPTIC-4 apart from other inlets is its sophisticated gas control system.
OPTIC-4S and OPTIC-4SC have a main flow control unit only, while OPTIC-4-D and OPTIC-4-DC also
have an auxiliary flow control unit.
Main flow control unit has an electronic flow control channel used to control the total carrier gas
flow through the system. It also has a pressure controller to control the inlet pressure. Together,
they are used to control the split flow and the column flow. There is a separate flow control channel
used to control the septum purge flow. Since technically it is extremely difficult to control the
column flow directly, it is programmed using the pressure controller. This is based on the measured
inlet pressure, carrier gas properties, column parameters, and GC oven temperature. Unlike many
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