LabChip GX/GXII User Manual

Glossary of Terms 260Peak IdentificationPoint-to-Point FitPolynomial FilterFrom the smoothed data, peaks are identified using a hill-climbingalgorithm running along the smoothed data and its first derivative.The slope threshold determines peak start point and end point:• The first point with local derivative above the slope thresholdindicates the start point peak.• The first point where the negative slope on the falling edge ofthe peak drops below the slope threshold indicates the end pointof a peak.The peak baseline is stitched across the peak bottom by takinglocal averages just outside the peak start and end points. The peakheight, measured from the apex down to the peak baseline, mustexceed the minimum peak height specified in the Assay AnalysisWindow to have a bump tagged as a peak.The peak start, end, and baseline can be viewed in the Graph Viewby selecting the Show Peak Baselines option in the Graph ViewProperties. The area of each peak is determined by trapezoidalintegration of the peak signal between peak boundaries and abovethe peak baseline.This curve fit is composed of line segments between each pair ofdata points that are used to interpolate data between the points.The first step the software takes in analyzing the raw data is toapply Data Filtering. Data filtering is performed by means of apolynomial “filter” that is applied to the raw data. The figure belowapproximates the shape of the filter and shows what peaks mayresemble if the filter application is too strong.P/N 127170 Rev. 00 LabChip GX User Manual Caliper Life Sciences, Inc.