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Standard Interpretation



Standard: 2003 NELAC
Section: Appendix C.1 (e)
Link to relevant standard

REQUEST:

We seem to have a difference of opinion in our lab.
We have a manager that feels that the Table 2 of the EPA Method 548.1 give the criteria to be used for %Recovery for DOCs
They are stating that the Concentration used 100 shows a 95% recovery - they are trying to change their acceptance to 95% +/- 20%
Section 9.3 of the method states to use the R value from this table 2. Aren't these only suggestions of R values? At the moment it is +/- 20% of the mean recovery

TNI FINAL RESPONSE:

(Technical Assistance Committee / NELAP Board, 2/19/09)

<em>Note: Laboratories should attempt to reconcile all differences in the interpretation of the NELAC 2003 standards and/or analytical methods with the applicable EPA Program, Regional Office and/or NELAC accreditation body. The following is an opinion of the current TNI Technical Assistance Committee and NELAP Board.</em>

In reviewing EPA Method 548.1, Revision 1.0, section 9.3 it is our interpretation, which concurred with one of EPA�s Cincinnati�s Chemist, that the laboratory�s mean recovery +/-20% with an RSD of 30% is acceptable for the IDOC, then the laboratory may use the same values or tighter for DOCs in accordance with Chapter V, Appendix C, 1.e.

Table 2 of the method was developed only using 7 replicates, therefore it would be best for a laboratory to adhere to limits for accuracy and precision developed using their own mean recovery.