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Optimizing Your Method
Changing the Chromatographic Separation
Thermo Scientific
If you did not quite get the results you were expecting from your method, use the suggestions
in this chapter to modify it to obtain better results.
Contents
•
Changing the Chromatographic Separation
•
Finding the Best Way to Make an Injection
•
Improving the Way You Prepare Samples
•
Changing the Scan Rate
•
Narrowing the Mass Range
•
Adjusting the Transfer Line Temperature
•
Modifying an Automatic Tune
Peak shapes are defined by the chromatographic conditions. If your peak is too wide, too
narrow or not symmetrical enough, then changing the chromatographic conditions are the
best way to improve your method. You should begin by changing the GC carrier gas flow or
oven temperatures (the initial temperature, initial hold time, ramp temperature, final
temperature for that ramp, and the hold time at that final temperature). These temperatures
can be adjusted for each ramp.
It is important to keep in mind that oven changes are strongly dependent on the nature of the
compounds you are analyzing. At some point, the GC oven has to be above the boiling point
of the compounds you are looking for. If the GC oven is not at the boiling point, the
compounds will not volatilize and they will become immobilized. Changing ramp rates is
usually used to separate coeluting peaks.
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