Waters ACQUITY UPLC Operator's, Overview And Maintenance Manual page 28

Filter-time constant comparison
Although the peak shape shows some distortion and the signal output is
Tip:
delayed with different filter-time constants, the peak area remains the same.
Median baseline filter
The median baseline filter enhances the detector's baseline stability by
decreasing the baseline's curvature, facilitating the development of
integration methods. The filter's primary purpose is to reduce the effects of
mobile phase gradient separations that demonstrate gradual compositional
changes. Note that it should not be applied in cases where abrupt gradient
changes, such as steps, are evident.
Generally, the filter does not significantly change peak area, peak height,
peak width or retention times. Nevertheless, it can create baseline distortions
around very wide peaks, and these distortions can affect peak area. Therefore,
it is not recommended for situations where peak widths (measured at 5%
height) are greater than 5% of run time.
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Time (minutes)
0 sec
1 sec
2 sec