yufree / pmd

Paired Mass Distance(PMD) analysis for GC/LC-MS based nontarget analysis

Home Page:https://yufree.github.io/pmd

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Multi chargers identification

yufree opened this issue · comments

High frequency pmd would still have multi chargers. The reason is that I only take the mass to charge ratio with 0.5 as multi chargers while the distance could not be used to find which ions is the multi chargers.

Currently solution:

If the mass distance is 0.5 within the retention time group, both of the ions should be excluded for further discussion since both of them are multi chargers.

However, this solution would reduce the information within the data.

Larger mass seems fine with 0.5 Da. Rules are needed to include them.

P1 = [M+2C]/2 P2=[M+C]
P1 * 2-P2 == C
P3 = [M+3C]/3 P4 = [M+C]
P3 * 3-P4 == 2C

Firstly, find P1 (0.5Da), if P2 exists, multi-chargers.

It seems multi-chargers will not influence GlobalStd peak picking. However, mass with .5 and lower than 350 should be removed as multi-chargers.
Fixed the missing issue of high weight ions.