in case you mean 13C labeled aldrin, you have at least two options:

1) if you know the carbons that are stable-isotopically labeled in the aldrin and you are aware of the fragmentation pattern, you might transfer those information to the labeled analogue using ChemDraw or other software to obtain the precursor and product ions.

2) perform product ion scan of your 13C aldrin, identify product ions and by knowing them, create the MRM.

Thank you

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