ISQ User Guide - Write Frame of Mind

Optimizing Your Method
If you did not quite get the results you were expecting from your method, you can modify it
in the following ways for better results:
• Change the chromatographic separation
• Find the best way to make an injection
• Change the way you prepare samples
• Change the scan rate
• Change the mass range
• Adjust the transfer line temperature
Changing the Chromatographic Separation
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 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.
Finding the Best Way to Make an Injection
Adjusting the way you get the sample from the needle into the column can sometimes
improve the results of your data. Try modifying the autosampler method, injecting a different
amount of liquid, adjusting the injector port temperature, or changing the speed of your
injection. You can also try using a hot or cold needle injection.
Thermo Scientific ISQ User Guide 75
7