Bunching - Agilent Technologies 8453 Operator's Manual

4
Integration
Peak Recognition
To obtain good performance from the recognition filters, the peak width must
be set close to the width of the actual chromatographic/electropherographic
peaks. During the run, the integrator updates the peak width as necessary to
optimize the integration.
The integrator calculates the updated peak width in different ways, depending
on the instrument configuration:
For LC/CE configurations, the default peak width calculation uses a composite
calculation:
0.3 x (Right Inflection Point - Left Inflection point) + 0.7 x Area/Height
For GC configurations, the default peak width calculation uses area/height.
This calculation does not overestimate the width when peaks are merged
above the half-height point.
In certain types of analysis, for example isothermal GC and isocratic LC
analyses, peaks become significantly broader as the analysis progresses. To
compensate for this, the integrator automatically updates the peak width as
the peaks broaden during the analysis. It does this automatically unless the
updating has been disabled or the peak width has been set to a specific value
with a timed event.
The peak width update is weighted in the following way:
0.75 x (existing peak width) + 0.25 x (width of current peak)
If a timed integration event disables or sets the peak width to a specific value,
the automatic peak width adjustment is disabled.

Bunching

Bunching is the means by which the integrator keeps broadening peaks within
the effective range of the peak recognition filters to maintain good selectivity.
The integrator cannot continue indefinitely to increase the peak width for
broadening peaks. Eventually, the peaks would become so broad that they
could not be seen by the peak recognition filters. To overcome this limitation,
the integrator bunches the data points together, effectively narrowing the peak
while maintaining the same area.
82 Understanding Your Agilent ChemStation