2019.03.27_CCO.p21_537-DW-vs-Mod-for-Chemours

EPA 537.1 – 537 Modified Comparison
537.1 537 Modified
Sample collection/preservation 250ml polyethylene bottles
preserved with Trizma.
250ml polyethylene bottles -
only preserved with Trizma if
from a finished chlorinated
water source.
Sample storage 0 – 6 degrees C not frozen until
extraction
0 – 6 degrees C not frozen until
extraction
Holding time 14 days from collection for
extraction. 28 days from
extraction to analysis.
14 days from collection for
extraction. 28 days from
extraction to analysis.
Calibration Model Internal Standard Isotope Dilution
Internal standards Internal standards are added to
each sample to measure the
relative response of other
method analytes and surrogates
that are components of the
sample solution.
Use of injection standards to
monitor matrix interference and
used to calculate the recoveries
of the sample extraction
standards.
Surrogates Added to each sample and QC
during extraction to monitor
method performance
Use of extraction standards
which are isotopically labeled
analogs for every target
compound (when available)
spiked into all samples and QC
during extraction. Where a
labeled isotope is not available,
the closest eluting, chemically
similar isotope is chosen.
Spike concentrations Rotate spike concentrations
between a low, mid and high
level spike
Single spike level.
Peak Asymmetry factor Calculated as per EPA 537
Version 1.1
Not calculated
MRL Confirmation Performed as per EPA Method
537 Version 1.1 Section 9. In
Not performed. An MDL study is
performed.
addition an MDL study is
performed.
Field Reagent Blanks Processed as per EPA 537
Version 1.1 Sec. 8.3
Field blanks may be submitted
by the client but are not
collected or processed as per
EPA 537 Version 1.1.
Sample Prep Follows verbatim EPA 537
Version 1.1
Uses a Weak Anion Exchange
SPE cartridge with an elution
profile developed in-house.
Initial Calibration • Min. 5 levels of
calibration standards –
low point at the MRL.
• Calibration curve forced
through zero and can be
concentration weighted
1/x.
• Acceptance criteria:
CAL1 – ±50% of true
value. All other
calibration points ±30%
of true value.
• RPD between the high
and low areas for each
internal standard must
be ≤20%.
• Analyze a technical
grade standard for PFOA
to aid in identifying and
integrating linear and
branched isomers of
PFOA.
• Peak asymmetry factor –
Must be calculated with
every ICAL. The first 2
eluting peaks in the mid-
level calibration
• Min. 5 levels of
calibration standards –
low point at the LOQ.
• Analyze an MDL
standard to ensure all
compounds can be
detected.
• Calibration curve forced
through zero with a
concentration weighting
of 1/x.
• SN for all ions used for
quantifications must be
≥10:1.
• Analyze a technical
grade standard for PFOA
to aid in identifying and
integrating linear and
branched isomers of
PFOA.
• Acceptance criteria:
CAL1 – ±50% of true
value. All other
calibration points ±30%
of true value. R2≥0.99
for each analyte.
standard must fall within
the range of 0.8-1.5
• ICV from a 2nd source
analyzed with each ICAL.
Each analyte must be
within ±30% of the true
value
• ICV from a 2nd source
analyzed with each ICAL.
Each analyte must be
within ±30% of the true
value
Continuing Calibration Check
(CCC/CCV)
• Run at the beginning and
end of every 10 samples
and at the end of the
sequence.
• Opening CCC must be at
the MRL level. All
subsequent CCCs should
alternate between the
mid and high
concentration cal
standards.
• Absolute IS areas must
be within 70-140% of the
areas measured in the
most recent CCC and
within 50-150% of the
average areas measured
during the initial
calibration.
• Acceptance criteria for
all target compounds
and surrogates: ±30% of
true value for mid and
high concentration
standards. For the MRL
level CCC, all target
compounds and
surrogates: ±50% of true
value
• Run at the beginning and
end of every 10 samples
and at the end of the
sequence.
• CCV run after the ICAL at
the CAL3 level.
Subsequent CCVs
alternate between the
low, mid and high points
of the curve.
• Acceptance criteria:
±30% of true value.
• Absolute areas of the
injections standards
must be within 50-150%
of the average areas
measured during the
initial calibration.

Sample analysis • Internal standard • Injection standard
recoveries should be
within ±50% of the
average areas measured
during the initial
calibration and 70-140%
of the response from the
most recent CCC.
• Surrogate recoveries
must be within 70-130%.

recoveries should be
within ±50% of the
average areas measured
during the initial
calibration.
• Extraction standard
recoveries should be
within the lab generated
statistical QC limits.
Method Blank/Lab Reagent
Blank
• No target analytes above
the MDL which is greater
than 1/3 the MRL.
• No target analytes above
the reporting limit.
LCS/LFB • All recoveries within 70-
130% except the low
concentration spike
which must recover
within 50-150%.
• Must be within lab
generated statistical
windows.
MS/MSD • All recoveries within 70-
130% except the low
concentration spike
which must recover
within 50-150%.
• RPD ≤30%
• Should be within the
advisory window of 70-
130% or the lab
generated statistical
windows when enough
data points are available
to generate statistical
windows.
• RPD ≤30%