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June 24, 2013
Mr. Lemuel Walker
Clean Water Act ATP Coordinator
U.S. Environmental Protection Agency
Office of Science and Technology
Engineering and Analysis Division
1200 Pennsylvania Avenue, NW (4303T)
Washington, DC 20460
RE: Comments on Draft Methods 624B and 625B
Dear Mr. Walker:
Thank you for providing the Environmental Laboratory Advisory Board (ELAB) with the
opportunity to provide a second round of comments on Methods 624B and 625B. The members
were pleased to see that most of the Board's previously submitted comments have been
incorporated in the current drafts.
While reviewing the methods, we noted that a couple of items seemed important from a more
global perspective, given that they would apply equally to most, if not all, Part 136 methods.
Rather than incorporating these into individual methods such as 624B and 625B, the ELAB
members think that they could be included in a section of Part 136 that applies more generally.
These items are:
1.	There is no requirement for verification that calculated method detection limits (MDLs)
or reporting limits are accurate. ELAB understands that the U.S. Environmental
Protection Agency (EPA) is considering an update to the Part 136 Appendix B MDL
procedure and hopes that some sort of verification procedure could be included.
2.	There is no description of the documentation required for or policies surrounding
manual integration. Possibly this could be added to the QC sections at Part 136.7.
Sincerely,
Patsy Root
Chair, Environmental Laboratory Advisory Board
cc: Lara Phelps

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General Comments — EPA Method 624 Revision B
Section 1.4 The MDLs referenced were determined 33 years ago and should be omitted from
the document. Instead of MDLs, a list of typical ranges for quantitation limits could
be included. If MDL tables are included, a note is needed explaining that they are
just examples, and each laboratory will need to generate its own MDLs.
Section 5.2.2 Add language clarifying that the trap described in this section is just an example.
Section 6.5.5 A statement should be added indicating that acidification has been known to
degrade 2-chloroethylvinyl ether, and if determination of this compound is needed,
it should be performed on the analysis of an unpreserved sample vial.
Section 8.2.5 The data in Table 7 are 24 years old. They were produced under conditions that
have changed significantly since then. ELAB recommends that EPA publish
Method 624B without new tables but should gather data that would allow updating
the tables in a subsequent revision.
Section 8.3.3 See 8.2.5 above. Table 8 in Section 8.3.3.2 is equally old and should be replaced
with the suggested approach in Section 8.2.5.
Section 8.4 This section references a closing calibration. Typically, EPA GC/MS methods using
internal standards do not require a closing calibration. Adding the requirement
without detailed prior study of the potential impact would be a mistake. It is
suggested that this requirement be removed and data gathered for consideration in a
future revision
Section 10 This section is outdated. Although autosamplers are allowed (Section 10.3), it might
be worth rewriting the detail according to more recent practice.
Section 11.2 There should be description of how the BFB is to be evaluated. We recommend
specifying use of either the peak apex, or the average of the apex and the scans
immediately prior to and immediately after the apex (total 3 scans). Background
subtraction should also be used and should be a scan that is not part of the BFB
peak, but is within 20 scans of the peak.
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General Comments — EPA Method 625 Revision B
Section 1.1 This method was validated through an interlaboratory study conducted 29 years
ago. Rather than rely on this statement alone, it would be appropriate to add that
the fundamental chemistry principals originally developed for this method remain
sound and continue to apply.
Section 1.4 The acceptance data in Table 6 are dated. We recommend that EPA publish
Method 625B without new tables but should gather data that would allow updating
the tables in a subsequent revision.
Section 1.5 MDLs referenced were determined 33 years ago and should be omitted from the
document. Instead of MDLs, a list of typical ranges for quantitation limits could be
included. If MDL tables are included, a note is needed explaining that they are just
examples and each laboratory will need to generate its own MDLs.
Section 7.2.1.1 There should be description of how the DFTPP is to be evaluated. ELAB
recommends specifying use of either the peak apex, or the average of the apex and
the scans immediately prior to and immediately after the apex (total 3 scans).
Background subtraction should also be used and should be a scan that is not part of
the DFTPP peak, but is within 20 scans of the peak.
Section 7.1 The data in Tables 4 and 5 are 33 years old. The MDL and retention time data
should be eliminated from the table.
Section 7.3 This section references a closing calibration. Typically, EPA GC/MS methods using
internal standards do not require a closing calibration. Adding the requirement
without detailed prior study of the potential impact would be a mistake. It is
suggested that this requirement be removed and data gathered for consideration in a
future revision
Section 7.3.1 The calibration acceptance criteria in Tables 6 and 8 are expressed in terms of
percent recovery rather than a percent difference from the initial calibration. For
consistency with other EPA methods, calibration acceptance criteria should be
expressed in terms of percent difference from the true value based on the initial
calibration.
Section 8.3.3 The data in Table 6 are dated and cannot possibly compare to real-world spiked
sample data. Because matrix spike results are necessarily dependent on the sample
matrix, ELAB suggests that this requirement be replaced by language instructing
laboratories to develop their individual performance ranges for spiked samples.
Section 16.1 The data presented in Table 7 are 29 years old. ELAB suggests that EPA generate
new and more relevant data. The Board would be interested in assisting with this
process.
Section 16.2 This chromatogram has little value and should be deleted.
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