Thermo Scientific TSQ 8000, User Manual

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5
Optimizing Your Method
Finding the Best Way to Make an Injection
90 TSQ 8000 Evo User Guide Thermo Scientific
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 flow, or changing the speed of
your injection. You can also try using a hot or cold needle injection. In some cases, adjusting
your injection port liners may give you better results. (For detailed instructions, refer to the
user guide for your autosampler.)
Improving the Way You Prepare Samples
Although sample preparation adds time and expense to the overall analysis, a more focused
method can give you better results. Try extracting your sample in a solvent that increases the
solubility of the analytes of interest, but does not increase the solubility of the other
compounds. If your method allows it, try switching solvents.
You can also use or change the phase of a solid phase extraction cartridge, which gives you
similar results as changing a solvent. You can affect the way you prepare samples by changing
the type of cartridge you are using.
Changing the Dwell Time or Scan Rate
The precision of your data depends on how well you define your chromatographic peak.
Typically, you get good precision when sampling ten times across the chromatographic peak.
In a full scan analysis, increasing the scan rate increases the number of times you have sampled
across the peak. However, increasing the scan rate too much results in mass spectral noise,
which decreases your analytical precision.
In a SIM or SRM analysis, reducing the dwell time will have a similar effect to increasing the
scan rate in full scan. The dwell time is a measure of how long the instrument will average a
SIM or SRM event.To optimize your scan rate or dwell time, select a value that gives you
8-12 points across a chromatographic peak. In timed acquisition mode this optimization is
done automatically, providing you with the longest dwell time or slowest scan rates possible
such that all compounds receive the desired scans across a chromatographic peak.
 To prioritize the dwell times of the problem analytes
1. In the Acquisition Options area, check Allow Dwell Time Prioritization. See Figure 88 .
2. Set the High Priority Multiplier to the desired value.
3. A new Dwell Time Priority option appears in your scan list. The choice are Normal or
High. Choosing High multiplies the dwell times by the value set in the previous step.