Thermo Scientific FOCUS GC, Инструкция по эксплуатации

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Chapter 5
S/SL Injection Techniques Split/Splitless Injector (S/SL)
Instruction Manual 101
S/SL Injection Techniques
You use different sample injection techniques for split and splitless applications.
Split Injection Technique
In split injection, only a part of the sample transfers into the column. The rest
discharges through the split line.
The ratio of the split flow to the column flow (the split ratio) determines the
amount of sample that enters the chromatographic column. Figure 5-5 illustrates
the gas flows for the split injection technique.
You inject the sample into a glass liner inside the heated vaporization chamber. In
the chamber, the sample undergoes rapid vaporization. The relatively high gas
flow through the injector carries the vaporized sample rapidly down toward the
head of the column.
At the column head, the sample splits in the split ratio. A portion of the sample
goes into the column, while the remainder is carried out the split line. You set the
column flow and the split flow in the
INLET
menu.
Narrow bore columns, which have inherently low column flows, can produce
relatively high split ratios.
NOTE Hot Empty Needle Injection Technique
To prevent partial sample vaporization within the hot syringe needle and avoid
discrimination of higher boiling components, we recommed to use the Hot Empty Needle
Injection Technique, particularly when performing manual injection. This technique
consists of drawing the sample volume into the syringe barrel followed by a small air gap,
which ensures the syringe needle is empty. You insert the empty needle into the injector,
wait a few seconds, inject the sample rapidly, and immediately remove the syringe.
Using the autosampler (AI/AS 3000 or TriPlus) the Hot Empty Needle Injection Technique
can be automatically selected in the Autosampler Method page of the Data System.
Split injection is suitable for high-concentration sample analysis, headspace
analysis, and isothermal analysis.