Page 12 - Shimadzu LCMS-IT-TOF

Optional Software for Accelerating Data Analysis

Formula Predictor

Effectiveness of Accurate MS n
In composition prediction, target constituents having a small mass
and high mass accuracy associated with their measured values, pro-
vide fewer numbers of candidates and greater prediction reliability.
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When using MS data with Formula Predictor, formula prediction
starts with the product ion having the smallest mass, and uses that
result in the effective prediction of the parent ion by reducing the
number of candidates.

Accurate MS Analysis
n
Number of Candidates Candidates decrease exponentially
Mass decreases

Mass
MS n MS 2 MS 1

+
C 17H 26N 2O 5S+H (m/z 371.1641) Composition Prediction Example
MS 1 CH (CH3)2 Take, for example, the case of predicting
371.1654 H3CO N
CH (CH3)2
the elemental composition of the ion at
m/z 371.1645.
HOO2S-O N
H
+
6-hydroxy-5-methoxy-diisopropyltryptamine-sulfate The correct composition is C17H26N2O5S+H
372.1676
373.1664
371.4059 371.8783 (m/z 371.1641).
371.0 371.5 372.0 372.5 373.0 373.5 374.0 m/z
MS of m/z 371.1 190.0848 The composition prediction
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procedure is as follows:
291.2090 (1) Composition Calculated from Mass
158.0610 270.0443
When simply calculating the composition only from
the mass value, the proper composition is ranked fifth.
50 100 150 200 250 300 350 400 450 m/z
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(1) Composition Calculated from Mass (2) Using Isotopic Pattern (3) MS Spectral Filtering (2) Using lsotopic Pattern
# Formula # Formula # Formula When additionally comparing and ranking the isotopic
1 C18 H22 N6 O S 1 C17 H26 N2 O5 S 1 C17 H26 N2 O5 S patterns, the correct composition is ranked first.
2 C10 H18 N12 O4 2 C10 H18 N12 O4 2 C6 H26 N8 O8 S
3 C25 H22 O3 3 C18 H22 N6 O S
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4 C13 H26 N2 O10 4 C9 H22 N8 O8 (3) MS Spectral Filtering
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5 C17 H26 N2 O5 S 5 C13 H26 N2 O10 Finally, taking into account the MS data enables
6 C9 H22 N8 O8 6 C25 H22 O3 12 candidates to be reduced to 2, as shown in
the table.
7 C6 H26 N8 O8 S 7 C6 H26 N8 O8 S
8 C14 H22 N6 O6 8 C8 H26 N4 O12
9 C22 H26 O3 S 9 C14 H22 N6 O6
In this way, using the isotopic patterns enables
10 C8 H26 N4 O12 10 C22 H26 O3 S
the correct formula to achieve a higher rank-
11 C7 H22 N12 O4 S 11 C21 H18 N6 O
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ing. Furthermore, using MS data enables a
12 C21 H18 N6 O 12 C7 H22 N12 O4 S reduction in the number of candidates.
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