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Standard Interpretation



Standard: 2003 NELAC
Section: Appendix D.1.1.3.1 (c)
Link to relevant standard

REQUEST:

A recent finding our laboratory got was "The laboratory does not include all target analytes in the matrix spike mixture over a 2-year period (EPA 8082)."

We feel that some auditing entities may be overreaching in their interpretation of this section. Our response follows:

EPA 8082 describes the analysis of PCBs in environmental samples. PCBs can be reported as Aroclors or as individual congeners; ENCO reports PCBs as Aroclors.

Section 7.1.2 of the method states that "Aroclor 1016/1260 mixture may be an appropriate choice for spiking" because these two in combination represent all PCBs. Section 8.4 of the method states that "If samples are not expected to contain target analytes, laboratories should use a matrix spike and matrix spike duplicate pair, spiked with the Aroclor 1016/1260 mixture."

Furthermore, the NELAC standard states in Appendix D, section 1.1.2.1 (c), referring to PCBs, that "the spike should be chosen that represents the chemistries and elution patterns of the components to be reported."

Aroclors are a special situation in that they are not a compound, but rather a formulation of different proportions of PCBs.

TNI FINAL RESPONSE:

(Quality Systems Expert Committee/NELAP Board, 10-25-08)

Under D.1.1.3.c Composition
The components to be spiked SHALL be as specified by the mandated test method. 8082 specifically says

7.1.2 'Such samples should contain or be spiked with the compounds of interest in order to determine the percent recovery and the limit of detection for that sample type (see Chapter One). When other materials are not available and spiked samples are used, they should be spiked with the analytes of interest, either specific Aroclors or PCB congeners. When the presence of specific Aroclors is not anticipated, the Aroclor 1016/1260 mixture may be an appropriate choice for spiking.'

and

8.4.1 Documenting the effect of the matrix should include the analysis of at least one matrix spike and one duplicate unspiked sample or one matrix spike/matrix spike duplicate pair. The decision on whether to prepare and analyze duplicate samples or a matrix spike/matrix spike duplicate must be based on a knowledge of the samples in the sample batch. If samples are not expected to contain target analytes, laboratories should use a matrix spike and matrix spike duplicate pair, spiked with the Aroclor 1016/1260 mixture. However, when specific Aroclors are known to be present or expected in samples, the specific Aroclors should be used for spiking. If samples are expected to contain target analytes, then laboratories may use one matrix spike and a duplicate analysis of an unspiked field sample.

The method requires analytes that you may expect in samples. This would mean spike all analytes over a two year period and if you're doing projects of known contamination you have to spike with those the known contaminant. If they can demonstrate that they�ve never seen any PCBs in their laboratory, a case could be made that they could just use 1016/1260 as a spiking mixture. If that can't be demonstrated, then all Aroclors must be spiked over the course of 2 years.