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Procedures for Detection and Quantitation

Technical Workgroup

Federal Advisory Committee on Detection and Quantitation Approaches and Uses in Clean Water Act (CWA) Programs

Summary of Technical Work Group Conference Call #42
November 8, 2006
1:00 – 3:00 p.m. EST

The call-in number for all calls is 866 299-3188 and the participant code is 202 566 1045#. The schedule of future Technical Work Group conference calls is:

Action Items

Ken Miller will develop presentations around the pilot study and data analyses/calculations for the 6 December evening session.

The TWG agreed to review the document on matrix effects and submit comments to Triangle by close of business on Friday, November 10.

Larry LaFleur will revise the presentation on comparing limits in the pilot, working with Nicole Shao, and get a revised version to the TWG for the November 22 meeting.

Procedures 101 presenters will review the current presentation and get any necessary revisions to Triangle by November 17.

Triangle will:

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Welcome and Introductions

Bob Wheeler, facilitator, welcomed participants to the call at 1:00 p.m., conducted a roll call of Technical Work Group (TWG) members and observers, and briefly reviewed the agenda for the meeting. He said there were a number of things to cover today, but the primary focus was on finalizing a document on matrix effects that could go to the Policy Work Group for its meeting next week, November 15. Mr. Wheeler rearranged the agenda to have the matrix effects conversation in the second hour so that participants from the subgroup could join the teleconference.

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Meeting Summary Approval

Mr. Wheeler asked for comments to the draft October 25 meeting summary. There were no comments and the group approved the summary as drafted.

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Status of Pilot Study and Data Calculations

Ken Miller reported that the labs have the instructions for two tasks:

  1. Calculation of the LCMRL based on the original spike levels the labs chose; and
  2. Aroclor confirmation for 5 replicates and 3 concentrations.

Mr. Miller said that since the Hubaux-Vos calculator is not yet available, labs will not be asked to calculate that limit. Instead, Mr. Miller said he would calculate those limits using the SAS program. This could potentially put the pilot study back on its original schedule, which recently fell behind schedule by approximately two weeks.

Mr. Miller also said that he has encountered some lab errors that he can easily reconcile, but that other lab errors were not as easily mitigated (e.g. a lab spiking at the wrong concentration).

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TWG and Pilot Design Team Schedule

Bob Wheeler said only one more teleconference meeting remains after this Technical Work Group meeting before the committee December meeting. He reiterated what he said at the start of the meeting that the focus today was on completing a product for matrix effects that would ultimately go to the committee. The focus for the meeting on the 22 November would be a review of and refinement to the presentations for the 6 December evening session. He also said that there was currently one TWG teleconference scheduled after the committee meeting. He suggested that as the group knows more about the status of the pilot study, it may be necessary to schedule more teleconference meetings.

Finally, he said that he anticipates the following products coming from the Technical Work Group for the December meeting:

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Intermittent Method Blank Contamination

Bob Wheeler reminded the group that this would not be a product for the December committee meeting, but would be for the May committee meeting. John Phillips said that the subgroup tasked with addressing this issue was currently working through ways to handle intermittent method blank contamination with relatively small data sets (e.g. less than 20 data points). He said the subgroup was working with Ken Miller to examine some of the existing data with respect to small data sets. The bottom line, he said, was that even with small data sets, less than 1% false positive rates were feasible relative to the whole data set, but that the DL was fairly dramatically affected. The results of examining the existing data will inform the subgroup on what to recommend to the Technical Work Group and on to the committee. Mr. Phillips also indicated the sub-group was working on ways to simplify how to address contamination issues.

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Definitions Rationale

Bob Wheeler said that Triangle sent a document to the group in advance of the teleconference meeting that was drafted by Richard Reding. Mr. Wheeler said Triangle worked with Mr. Reding to review the existing documentation for rationale on how and why the committee agreed to its current set of working definitions.

Mr. Wheeler said the intent of this discussion was to get a definitions document in nearly final form to the Policy Work Group by next week. They would then approve a final version for distribution to the committee.

The group agreed to add the following clarifying points to the rationale for why the committee was deviating from the international definitions for detection and quantitation. The IUPAC definitions:

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Review Procedures 101 and Comparing Limits PowerPoint Presentations

Mr. Wheeler reviewed the agenda for the 6 December evening presentations. He reminded the TWG that during its last meeting, the group agreed to limit the time of presentations on procedures to 5 to 10 minutes each, which allows a good amount of time for committee questions and dialog. He asked the procedure proponents to review the length of their current presentations with the audience in mind. All the procedure proponents committed to reviewing the current presentation and sending any necessary revisions to Triangle.

Larry LaFleur briefly reviewed the presentation titled: "Why it is not appropriate to compare numerical estimates of Lc and Lq derived from different procedures in the pilot." He pointed specifically to two slides (1 and 3) that included questions to the TWG in the comments section. Regarding the comment in slide 1, the group agreed to change "not appropriate" to "inappropriate" in the title.

The group discussion on slide 3 focused on (a) which definitions to include in the slide for tolerance intervals and prediction intervals; and (b) whether including definitions in the slide missed the point of the presentation in presenting that different procedures are drafted with different objectives. For example, some procedures attempt to predict future performance, whereas other procedures attempt to characterize the next single measurement. The group agreed that the latter point was more the focus of the presentation, and that definitions need not be included in the presentation. The group does believe that it should discuss ideas on tolerance versus prediction in more detail at a later date.

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Matrix Effects Subgroup

Bob Wheeler explained to the group that the subgroup on matrix effects was able to discuss the issue via teleconference yesterday. From that discussion, Triangle drafted the document that was distributed to the TWG.

The group talked through the issue of matrix effects and the need, if the committee chooses to address it, to refine the current process (e.g. the EPA "Pumpkin Book") into something that is less open-ended. Marion Kelly from EPA confirmed that the Pumpkin Book - currently being revised - attempts to address known matrix interference in organics. If the committee chooses to make a recommendation around matrix interference, it will be important to consider both scenarios of demonstrating matrix interference for a permit limit, and of accounting for matrix interference in a compliance evaluation. In response to a request for the committee to see the current revisions in the Pumpkin Book, Ms. Kelly said she would inquire as to where the revision was in the approval process at EPA.

Some members of the group acknowledged the importance of resolving this issue at the next committee meeting in light of the policy decisions that will also be considered. The issue is so fundamental to some members of the committee that those policy decisions could be impacted by the outcome of a decision on how to address matrix effects.

The group agreed to review the current document and provide line-edits in tracked changes to Triangle by Friday, November 10. Triangle will work to incorporate those changes in a revised document for distribution to and discussion at the next Policy Work Group Meeting, Wednesday, November 15, 2006.

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Public Comment

There were no public comments.

Wrap-up and Closing

Mr. Wheeler summarized the meeting and the items that will be forwarded to the Policy Work Group for its next meeting (definitions rationale and matrix effects). He said the next TWG meeting is scheduled for November 22. The purpose of that meeting is to walk through the presentations for the December 6 evening session.

Mr. Wheeler thanked everyone for their time and adjourned the meeting at 3:00 PM, ET.

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Attendance

Technical Work Group Members

Triangle Associates: Robert Wheeler and Derek Van Marter

Observers

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