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Combined Interpretations of the 2003, 2009, and 2016 Standards that apply to Volume 1 of the 2016 TNI Standard

Section: 1.7.3

Question:  The composition of a method blank shall consist of a quality system matrix that is similar to the associated samples and known to be free of analytes of interest. No reference could be found in SW-846 Methods 5035, 8000, and/or 8260 that require a VOA method blank to contain a solid matrix.  In fact, in method 5035 section 8.2 it is stated before processing samples to analyze an organic-free water method blank....  Nothing about adding a solid matrix is mentioned. Adding a solid matrix to a VOA method blank would only potentially add contamination and not be reflective of the cleanliness of the analytical system.  Also if one adds a solid matrix (even if it does not contain analytes of interest) to a VOA method blank, should not the same solid matrix be added to all the samples as well? Basically, is it necessary to add a solid matrix to a VOA method blank when analyzing low level soil samples? Is it the intent of NELAC's definition of a method blank to override what is presented in the method?

TNI Response:  A blank is required to be free of the analytes of interest. Therefore, an appropriate blank for a solid matrix should not contribute contamination.  5.9.3 c) provides the following statements concerning the difference between 5035 and TNI: "The laboratory shall ensure that the essential standards outlined in Technical Modules or mandated methods or regulations (whichever are more stringent) are incorporated into their method manuals. When it is not apparent which is more stringent, the QC in the mandated method or regulations is to be followed."


Question:  There is inconsistency as to whether a data qualifying code must be applied to a sample result for which no target analyte was quantitated at or above the reporting limit, yet for which the same target analyte concentration in the method blank was at or above the reporting limit.  For instance, a laboratory measures a concentration of a target analyte in the method blank at or above the reporting limit.  However, upon evaluation of the nature of the contaminant and the effect on the analysis of each sample within the batch they determine there is no need or benefit to qualify sample results which were not above the reporting limit for the target analyte in question.  They determine, in this specific instance, the blank contamination does not affect the sample results.  At many laboratories and Accrediting Bodies the interpretation of the standard language is: if there is nothing reportable in the sample (e.g., no positive hits above the reporting limit) then there is no effect on the analysis and hence the blank contamination does not affect the sample results.  On the opposite end, an Accrediting Body has been observed to require laboratories to qualify all sample results (i.e., even those for which there were no reportable results) due to method blank contamination at or above the reporting limit.  Additionally, there has been observed inconsistency and a lack of a common understanding between both laboratories and Accrediting Bodies on the original intent of the above standard language.  That is, was it the intent of the standard authors for this language to apply in instances where the measured amount of a target analyte in both the method blank and sample is above the reporting limit and not to apply to sample results where the target analyte is not reportable (e.g., at or below the LOQ).  Please note, in this instance/example, it can be assumed a laboratory is fully complying with the standard in that they are investigating the source and cause of the contamination observed in the method blank, taking and documenting corrective action and reanalyzing and/or appropriately qualifying sample results at or above the reporting limit for a given method.  Please provide clarification on how the standard language is to be interpreted and applied by both laboratories and Accrediting Bodies in the above stated instance.

TNI Response:  Section requires that ALL listed conditions be met before analytical results are qualified due to blank contamination. The laboratory must review the batch to determine the affect of blank contamination on each sample within the batch. The laboratory must reprocess or qualify the data if all the items described in a) through c) are met. The laboratory must document a corrective action if blank contamination is observed and evaluated.


Question:  The Standard states:  "The LCS shall be analyzed at a minimum of one (1) per preparation batch.  Exceptions would be for those analytes for which no spiking solutions are available, such as TSS, TDS, TVS, TS, pH, color, odor, temperature, dissolved oxygen or turbidity."  However, there are now spiking solutions available for some of these analytes such as TSS, TDS, TS, and many labs are using them.  The Standard has not been updated to reflect the availability of these solutions, and this exception has been in effect since at least the 2001 NELAC Standard.  Are labs now required by the Standard to analyze an LCS for TSS, TDS, and TS since spiking solutions are now available?  Is this section being changed in the 2015 Standard?

TNI Response:  A Laboratory Control sample is defined in the definitions as a sample matrix, free from the analytes of interest, spiked with verified known amounts of analytes or a material containing known and verified amounts of analytes and taken through all sample preparation and analytical steps of the procedure unless otherwise noted in a reference method. It is generally used to establish intra-laboratory or analyst specific precision and bias or to assess the performance of all or a portion of the measurement system.  Volume 1 Module 4 Section of the standard states that "Exceptions would be for those analytes for which no spiking solutions are available.” If spiking solutions are now available then an LCS would be required per the standard. The quoted section of the standard is the exception. The examples listed are not an inclusive list and should be expected to change overtime therefore cannot be used as the exception but just as potential examples from the time in which the standard was written.  In addition Volume 1 Module 4 Section of the standard states, "Alternatively, the LCS may consist of a media containing known and verified concentrations of analytes or as Certified Reference Material (CRM)."


Question:  Is it the intent of the standard that when evaluated by the same criteria, a passing MS replace the LCS in its totality or can an individual target compound failure in the LCS be replaced by an individual acceptable result in a matrix spike sample?

TNI Response:  The standards states as a note in that "The matrix spike may be used in place of this control as long as the acceptance criteria are as stringent as for the LCS."  This statement in the standards does not allow a matrix spike to be used in place of a failing LCS either in its totality or for an individual target compound. A matrix spike may however be used in place of an LCS if an LCS is not analyzed as required and the LCS control limits are used to evaluate the MS. If a method has specific requirements for an LCS this note does not supersede those method requirements. The 2009 standard allowed an MS to be used in lieu of an LCS.  The 2016 standard reversed this. This SIR will be obsolete when the 2009 Standard is no longer in use.


Question:  The above section of the 2016 TNI Standard states – "Except where the matrix precludes its use or when not commercially available, surrogate compounds shall be added to all samples, standards, and blanks for all appropriate methods." The term "appropriate" is unclear. Is it the intent of the 2016 TNI Standard to require surrogates for methods like EPA 300.0, which does not require a surrogate, but is similar to EPA 300.1, which does require a surrogate?

TNI Response:  If a method does not require surrogates, it is not the intent of the Standard to require them.


Question:  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; Our laboratory 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 (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 Response:  The components to be spiked SHALL be as specified by the mandated test method. 8082 7.1.2 specifically states  “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 states “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.


Question:  Can control limits include 0?  Marginal exceedances must be random.  If control limits don’t include 0, poor performing analytes will consistently be marginal exceedances.

TNI Response:  The laboratory would have to demonstrate how its data can meet all other aspects of the method and still generate control limits that include a 0% recovery. However, there is no restriction on control limits using 0 - look at PT criteria for soil to see examples of this occurring.  As for marginal exceedances, there's no such thing as a "consistent marginal exceedance", since they are required to be random. Consistent means that there is something wrong in the process or the method just doesn't work for that analyte.