2000-OSM, F1 4-24
different peak areas in adjacent analyses (see Figure 4-23). By selecting “Pk End =Vly” you can
force the routine to call it a valley each time it occurs, thus removing the indecision and stabilizing the
calculations. “Pk End =Base” is used the same way as “Pk End =Vly.” Selecting “Pk End =Vly” or
“Pk End=Base” forces the slope detect algorithm to call the point a valley or a baseline every time,
whichever provides the more accurate data. The difference between the two is shown in Figure 4-23,
where the area within triangle ABC is not measured in “Pk End=Base.” It is important to measure
these peaks the same way every time, for consistency.
TIME
PK END =VLY
TIME
PK END =BASE
PEAK
END
AREA
MEASURED
PEAK
END
AREA
MEASURED
A C
B
Figure 4-23. EXAMPLES OF PEAK END
The remaining baseline commands allow you to project a horizontal baseline between two defined
points on the chromatogram. This projected baseline may be set forward (to measure from the
baseline before the peak) or reverse (to measure from the baseline after the peak). The command to
start a projection must be entered at a time before the slope detect function senses the start of a
peak, and the ending command must be entered at a time before the slope detect routine senses an
end of peak.
“Proj Forward” is a forward projection flag inserted before the start of a desired peak. This sets the
baseline as the start of the peak (see “HBF” in Figure 4-24). “Proj Term” is a flag to end the
projection, thereby identifying the peak or group of peaks to be measured. It is set after “Proj
Forward” and before the end of the peak (see “HBT” in Figure 4-24). Line AB in Figure 4-24
represents the baseline.
C
D
A B
HBF
HBT
TIME
Figure 4-24. EXAMPLE OF FORWARD PROJECTION
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