Ranking of molecular formulas

1 Ranking of molecular formulas Calculation of match values for molecular formulas 

For a given mass spectrum I and molecular formula let p,i e n be all molecular formulas that satisfy (Gr2) and (Con) of Theorem 1.23, and additionally fulfill 

14 Example (Match value of / = C6H12O2 for spectrum I from Ex. 8.2) Table 8.5 lists the molecular formulas /S, c that satisfy (Frag), (Gr2), and (Con). The last column gives the value of x, as solution of Equation (8.7). 

Detailed inspection of ranking lists reveals that the top positions are usually occupied by molecular formulas containing several elements. This is because the number of possible fragment formulas are higher for these candidates than for those made of few elements. In particular, molecular formulas made of several monoisotopic elements 

Now that we are able to calculate match values for molecular formulas with respect to a mass spectrum and to establish ranking lists, there is another issue How meiny candidates in a hit list should be considered if the correct candidate is to be included with a predefined probability  

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Table 8.6. Ranking of molecular formulas of mass 116 for the spectrum of Example 8.2, formulas passing the filters are marked with x.

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