ull suuite cänhot ionise every substance The filament is made of carbon O Both L
ID: 3307984 • Letter: U
Question
ull suuite cänhot ionise every substance The filament is made of carbon O Both LC-MS and GC-MS have ionisation sources DQuestion 7 1 pts Explain which effect is likely to be observed when decreasing the heating rate in a temperature programme applied to the GC-MS. Select one option. O Lower expenditure of mobile phase in the separation O Increase in the resolution between chromatographic peaks O It will not affect the separation Lower elution time 1 pts D Question 8 h of the analysis which of the following statements is falset?Explanation / Answer
The setting of the correct temperature
programme is especially important
if an existing method has to be
changed. Changes can be related to:
•
Moving to a different carrier gas;
(higher velocity, cheaper)
•
Operating at a higher linear
velocity; (higher velocity, to reduce
time)
•
Changing column dimensions
(shorter column, faster analysis)
•
Moving from a FID to a vacuum
detector (MS).
When the temperature programme
is not changed the components
will elute at different temperatures,
which will result in a different
chromatogram. the separations are
different when the same programme
and column is used at two different
linear gas velocities. Peaks move
relative from each other and even
peak reversal can happen.
The same chromatogram will
only be obtained if the elution
temperatures are similar. To realize
this, in all cases listed above, the oven
temperature programme needs to be
changed.
There are method translation
programmes available that will
calculate the new programme
conditions.
The new temperature programme (2) is
calculated. When this programme is
used, the elution temperature will be
the same and also the chromatogram
will be the same as before, but
analysis time (3) is reduced by a factor
of 1.92.
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