Document ID: EPA-HQ-OAR-2009-0837-0018
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2010-06-11T04:00Z

Record of Communication

Subject:  NIST Cost Containment Procedures for Cylinder Analysis

On October 30, 2009, Frank Guenther of the National Institute of
Standards and Technology (NIST) responded to an inquiry from John
Schakenbach of the Environmental Protection Agency (EPA) regarding NIST
procedures to keep cylinder analysis cost as low as possible.

The NIST cost containment strategy is:

1) Receipt of a batch of cylinders all within the same predefined
concentration range allows us to setup instrumentation and form a
calibration curves more efficiently. This has been arraigned in the past
through the contractor and works very well.  Also. scheduling batches of
cylinders to arrive when NIST is ready for them will allow NIST to more
efficiently schedule their resources.

2) The cross interactions of the analytical species on the
instrumentation we use has been modeled well already.  Future work can
make use of that modeling, where we only need to confirm the correction
factors are still good before using them.

3) NIST has agreed to analyze these cylinders to 0.5 % uncertainty (1 %
expanded uncertainty).  The reason for this uncertainty goal is to allow
reasonable certainty when judging a audit cylinder with 2 % expanded
uncertainty.  No reasonable cost gains will be achieved by increasing
our uncertainty to 1 % (2% expanded).

4) Since our uncertainty requirements are relatively high (1 %
expanded), we can use intermediate standards for all of this work.  This
keeps the cost down, because our high value primary standards do not
have to be used. In addition NIST has invested in tri-mix working
standards that will allow us to validate our methods much quicker.

5) In the future we will be working on a FTIR method that may allow us
to further reduce costs by consolidating all analytical work to an
automated instrument.

6) High concentration audit cylinders will always cost less to analyze. 
The lowest concentration audit cylinders will cost NIST approximately 25
% more to analyze.

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