Table 3.

Flag Identifiers for PFAS Stock Quality Assessment.

Flag	Definition
E	Caution: suspected to be present but not confirmed
F	Caution: incorrect MW; biological activity unreliable
Fde	Caution: degradation evident, may be due to solvent or other unidentified source
Fns	Caution: no sample detected; biological activity unreliable
I	Isomers - two or more isomers detected
M	Defined mixture - two or more components present
P	Pseudo-parent or adduct monitored, no direct confirmation of parent analyte
W	Sample withdrawn
Z	MW confirmed, no purity information available