Calibrating
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4
Parameters
Perform auto peak matching
–
When enabled,
matches peaks in the reference file to
those in the acquired file.
Peak window
–
Specifies the maximum mass difference between the reference peaks
and the expected position of corresponding peaks in the acquired spectrum. Normal
operating range is 0.3 to 1.5 da.
Initial error
–
Specifies the maximum mass difference you will allow between the first
reference peak the software chooses (for its position at or near the center of the calibration
range) and the peak it corresponds to in the acquired spectrum.
Note:
Increasing Peak window and Initial Error values may result in incorrect peak
matching.
Intensity threshold
–
Specifies the lower intensity limit of peaks that form the calibration
curve. The threshold is expressed as a percentage of the most intense peak of the
acquired spectrum. Normal operating range is 0 to 5%.
Note:
MassLynx does not use any peaks in the acquired spectrum that fall below the
Intensity threshold parameter.
Polynomial order
–
Once MassLynx matches each peak in the reference spectrum to one
in the acquired spectrum, it calculates the mass difference (the acquired mass less the
reference mass) for each peak pair. It then plots these differences as points on a graph
and fits a smooth curve through the points. This parameter, set to values 0 to 5,
determines the type of curve MassLynx draws:
•
Polynomial order = 0 – a horizontal baseline
•
Polynomial order = 1 – a linear curve
•
Polynomial order = 2 – a quadratic curve
•
Polynomial order = 3 – a cubic curve
•
Polynomial order = 4 – a fourth-order curve
•
Polynomial order = 5 – a fifth-order curve
Waters suggests a polynomial order of 2 for calibrations that use sodium cesium iodide as
the reference solution and where the calibrated mass range starts below 100 da and
extends through 650 da. Use
polynomial order 4
for the wide mass ranges at the high end
of the mass scale (600 to 1000+ da) and for calibrating with widely spaced reference
peaks.
Intensity weighting
–
Weights the curve toward points that represent the more intense
acquired peaks. Thus each point’s weight equals the square root of the acquired peak’s
intensity.
Summary of Contents for Micromass ZQ 2000
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