2019.06.18_CCO.p11_NCDWRTestAmericaTechnicalSummary

MEMORANDUM

Date: 6/14/2019

To: Dr. Lam Leung, Chemours
CC: Mike Aucoin, AECOM
From: Eric Redman, Director of Technical Services

Subject: LC/MS/MS Method Performance for DFSA, MMF, MTP, and PPF Acid

This technical memorandum addresses questions regarding observed variability in the
determination of 4 analytes (DFSA, MMF, MTP, and PPF Acid) by Eurofins TestAmerica’s current
LC/MS/MS methodology known as the ‘Table 3+’ analytical method.

DFSA, MMF, MTP, and PPF Acid are very small molecules by LC/MS/MS standards,
consisting of just one or two fully fluorinated carbons with one or two terminal acidic
moieties (carboxylic and/or sulfonic).

The size, structure, and highly polar nature of these molecules create a variety of technical
challenges for LC/MS analysis. Due to the size and structure of DFSA, MMF, MTP, and PPF Acid
there are relatively few characteristic mass fragments or mass transitions that can be used to
identify them in the LC/MS/MS methodology, and the identification elements that exist are not
unique to DFSA, MMF, MTP, and PPF Acid. These analytes are therefore prone to a large range of
chemical interferences that can adversely impact the performance of the analytical method.

The small and highly polar nature of DFSA, MMF, MTP, and PPF Acid also means that these
analytes are not easily retained under the usual LC/MS/MS chromatographic conditions. Poor
retention in turn means that these analytes cannot be chromatographically separated or resolved
from physical or chemical interferences, and are therefore more susceptible to adverse impacts
from these co-eluting interferences. These can be manifest as discreet interferences that mimic the
MS/MS response of DFSA, MMF, MTP, and PPF Acid and either obscure their presence (false
negatives) or impart a positive bias (false positives). Additionally, non-discreet or bulk interferences
such as dissolved solids, high ionic content, and naturally occurring organic and ionic compounds
(humic acid or NOM) can create severe ion suppression and enhancement effects in the LC/MS/MS
analysis. DFSA and MMF are further prone to variable impacts from ionic substances (including pH
differences) due to their unusual di-acidic character.

The combination of multiple properties that can adversely impact analytical performance means that
current ‘Table 3+’ analytical procedures will generate variable and potentially unreliable results for
DFSA, MMF, MTP, and PPF Acid in samples. Analytical performance for DFSA, MMF, MTP, and
PPF Acid has been demonstrated to be reliable in the absence of matrix interferences, but a
growing body of empirical evidence including sample duplicate and matrix spike results indicates
that matrix effects have a significant adverse impact in field samples.