Introduction
Data Types
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1-18 ______________________ Finnigan LTQ Hardware Manual _______________________
1.5 Data Types
You can acquire and display mass spectral data (intensity versus
mass-to-charge ratio) with the LTQ in one of two data types:
• Profile data type
• Centroid data type
Profile Data Type
In the profile data type, you can see the shape of the peaks in the mass
spectrum. Each atomic mass unit is divided into approximately 15 sampling
intervals. The intensity of the ion current is determined at each of the
sampling intervals. The intensity at each sampling interval is displayed with
the intensities connected by a continuous line. In general, the profile scan data
type is used when you tune and calibrate the MS detector so that you can
easily see and measure mass resolution.
Centroid Data Type
In the centroid data type, the mass spectrum is displayed as a bar graph. In
this scan data type, the intensities of each set of 15 sampling intervals are
summed. This sum is displayed versus the integral center of mass of the
15 sampling intervals. In general, the centroid scan data type is used for data
acquisition because the scan speed is faster (but the resolution is lower) and
the disk space requirements are smaller. Data processing is also much faster
for centroid data.
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