7. Defining and Running Methods
7.1 Introduction
The OPTIC-4 methods are defined using the Evolution Workstation software running on a host PC
connected to the OPTIC-4 control unit. They can either directly initiated from the PC or saved for a
later use. Refer, to the Evolution Workstation on-line help for more information about defining and
running OPTIC-4 methods.
7.2 Method Types
OPTIC-4 supports five predefined methods of a different type:
1. Split
2. Splitless
3. Large Volume Injection
4. LINEX
5. Expert (full control of all parameters)
7.2.1 Split Methods
OPTIC-4 can be used for both hot split and cold split injections. In virtually all cases, better results
will be obtained using the cold split approach. Cold split injection assumes that analysis starts with
the inlet temperature below boiling point of the solvent. Next temperature is programmed to
temperature usually 50 °C above the maximum elution temperature of the sample. This has the
following advantages:
• Syringe needle discrimination is eliminated, thus ensuring that the fraction of the sample,
which enters the column, is truly representative of the sample as a whole.
• Milder temperature regime experienced by the sample reduces thermal degradation
especially when lower inlet temperature ramp rates are used.
• Better run-to-run reproducibility.
7.2.2 Splitless Methods
OPTIC-4 can be used for both hot splitless and cold splitless injections. In virtually all cases, better
results will be obtained using the cold splitless injection technique for reasons identical to those
described above. The quality of results obtained should be comparable to on-column injection in all
respects but with the added advantage of preventing involatile and particulate matter from reaching
the column. Cold splitless injection is therefore better suited to the analysis of "dirty" samples.
7.2.3 Large Volume Injection Method
In the past, analysts have been used to injecting samples of no more than 2 l into the GC. Since
split/splitless inlets generally have an internal capacity of approximately 2 ml, and 1 l of solvent
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