Glossary of Terms 167
P/N CLS151164 Rev. B LabChip GX Touch/GXII Touch User Manual PerkinElmer, Inc.
Apex
After locating a start point, the peak find algorithm looks for the first
negative slope value and saves the previous point as the apex. If
the value of the apex is less than the minimum peak height limit, the
algorithm starts looking for a new peak.
Assay File
File used by the LabChip GX Touch software to specify assay and
default analysis settings, such as Ladder and marker sizes and
concentrations, peak find settings, expected peaks, and excluded
peaks. LabChip GX Touch assay files have an .asyx file extension.
If the LabChip GxP option is installed, all assay files are stored in
the CDR and are version controlled. Analysis settings in the assay
file cannot be changed in the LabChip GX Touch software. To
change the analysis settings, open the data file in the LabChip GX
Reviewer software.
Baseline
A baseline is established just after the start time setting. After the
overall baseline is established, a local baseline is calculated for
each peak to compensate for baseline drift.
Baseline Subtraction can use either Spline fit or Rolling Ball fit for
the baseline curve algorithm.
• Spline - Creates a smooth line fit to the baseline data points and
subtracts this smooth fit from the data. The Threshold
determines how much the baseline fit follows changes in the
data. Lowering the Threshold below the default value of 20
allows the baseline fit to ignore regions that are slow changes of
real signal peaks and not baseline drift. This spline curve is not
constrained to remain below the signal and may produce
negative signal values when subtracted from the signal.
For isolated peaks, the local peak baseline is a straight line
connecting the start point of the peak with the end point. For peaks
that are very close together, an average baseline is used when the
value between the peaks does not drop to the actual baseline.
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