Voyager DP-263-S Betriebsanweisung PDF herunterladen (Seite 338)

100

101

Chapter 6 Acquiring Mass Spectra

6-26 PerSeptive Biosystems

• Signal intensity of reference and analyte peaks is in

the same range—Signal intensity of reference and

analyte peaks should be of similar magnitude. If they

are not in the same range, you may see weak analyte

peaks with poor signal-to-noise ratio while the internal

standard is adequate, or saturated internal standard

peaks with adequate analyte peaks.

• No contaminants present—Unresolved contaminants

can affect peak shape.

• Two internal reference masses that bracket the

mass range of interest—Best results are obtained

when masses above and below the mass of interest are

correctly identified.

NOTE: Although not required, using more than two

reference masses can help to minimize the effects of

an asymmetrical reference peak.

• Internal reference masses are within the same

range as analyte masses—Best results are obtained

when masses are in the same range. For example,

reference masses of 904 and 1,570 are adequate when

evaluating an analyte mass of 1,296 Da.

During mass

calibration and

peak detection

When calibrating mass (described in the

Data Explorer

Software User’s Guide,

Section 5.3, Manual Calibration) and

detecting peaks (described in the

Data Explorer Software

User’s Guide,

Section 3.2, Peak Detection), the following

factors contribute to the accuracy of mass measurements:

• Use Centroid mass instead of Apex mass—Before

calibrating, set peak labels to Centroid. Centroid mass

is the best representation of peak position. Apex mass

represents the highest data point.

• Set Centroid Percent to 50%—Lower settings can

include noise or contaminant peaks. Higher settings

may not include adequate data to ensure accurate

mass assignment.

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