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NELAP and TNI Standards Interpretations

TNI has established an avenue for resolution of questions submitted electronically on interpretation of the 2003 NELAC and 2009 TNI Standards. The method for submittal is to complete an on-line form (available here). Use of this entry form ensures that a question is automatically accepted, cataloged and emailed to the NELAP Accreditation Council Chair, the LAS Executive Committee Chair and the TNI Program Administrator for review. A consensus of these three individuals shall determine who oversees the final disposition of the question. Timelines are defined for the NELAP Accreditation Council Chair and LAS Executive Committee Chair to ensure a timely response to the question. Publication of the consensus resolution is then made to the affected parties via email and on this page.

Some SIR submissions are valid questions but do not meet the criteria to be a SIR. Those are being treated as clarification requests and are now addressed with answers termed “Implementation Guidance" that are posted below.

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Section Subject Date
V1M1, Section 4.2.1 Analysis Date for PT Samples 10/05/14
V1M1, Section 4.2.1 (a) Analysis Date for PT Samples 03/13/14
V1M1, Section 6.1 (b) and V1M2 8.2 (c) Corrective Action Date for PTs 10/05/14
V1M1, Section 7.7.3; V2M3, Section 5.1 Reassessment Requirements 04/07/13
V1M2, Section and (a) Technical Director Requirements 03/13/14
V1M2, Section 4.14.1 Method Selection for Internal Audits 01/16/18
V1M2, Section (a) and (b) Technical Director Experience 04/07/14
V1M2, Section (c) Technical Manager Education Requirements 11/28/16
V1M2, Section 5.4.2 Selection of Methods 12/29/11
V1M2, Section 5.4.2 Selection of Methods 10/05/14
V1M2, Section Verification of Disposable Volumetric Dispensing Devices 11/28/16
V1M2, Section Checking Accuracy of Plasticware 02/23/17
V1M2, Section (e) Accuracy Checks of Non-Class A Glassware 01/16/18
V1M2, Section Calibration of Support Equipment 10/05/14
V1M2, Section Certificates of Analysis 04/07/13
V1M2, Section Documentation and Traceability of Consumables 03/13/14
V1M2, Section (d) Traceability of Reagents 10/13/15
V1M4, Section Limit of Detection (LoD) Requirement 02/10/14
V1M4, Section 1.5.4 Second Column Confirmation of PT Results 03/13/14
V1M4, Section 1.6.1-1.6.3 Demonstration of Capability (DOC) 04/07/13
V1M4, Section 1.6.2-1.6.3 Demonstration of Capability for Work Cells 03/13/14
V1M4, Section and (b) Marginal Exceedences and IDOCs 03/13/14
V1M4, Section Matrix Duplicate Precision 02/10/14
V1M5, Section Methods that Specify Colony Counts 01/16/18
V1M5, Section (c) Reagent Water 10/13/15
V1M5, Section 1.7.5.b Microbiological Sample Handling 04/07/13
V1M6, Section 1.5.4 Precision and Uncertainty 10/14/13
V1M6, Section 1.7.1 (a) Calibration of Gamma Detectors 01/07/14
V2M1, Section 6.0 (ISO 17011:2004(E) 6.2.3) Specific Scopes for Assessors 01/16/18
V2M1 (7.7.2-7.7.3) and V2M3 (6.13.2) Reassessments and Surveillance Audits 09/12/13
V2M1, V2M3: 8.2.1 (b) and 7 (b) Key Personnel 10/05/14
V2M2 PT for Biological Testing 10/13/15
V2M2, Section 4.1.1 (f) Secondary AB Notification of Revocation of Lab Accreditation 01/16/18
V2M2, Section 6.3 Multiple Preparation Methods for PTs 10/05/14
V2M3, Section 4.2.4 Assessor Training Requirements 02/10/14
Section Subject Date
2 SCM FoPT (7/1/07); FoPT Table - NELAC Analyte 1935, Footnote 13 01/18/12
2 FoPT Table - List of Analytes Requiring PTs 10/16/17
2 Proficiency Testing - evaluation of less than "<" results 10/12/09
2.2.1, Appendix C.3 PT Result Acceptability Below the PTRL 07/26/11
2.5 Requirements for Laboratory Testing of PT Study Samples 07/26/11
2.6 Evaluation of Proficiency Testing Results 10/12/09 (d) Supplemental PT Studies for Demonstating Corrective Action (PCB exception) 10/12/09 Data Integrity Procedures 03/10/11 Controlled Documents 04/07/14 (b) Frequency of Document Review 01/25/09 Subcontrator Lab Documentation 11/08/12, (b), (d), (a) Initial Calibration Verification (ICV) Acceptance 04/07/14
5.4.12 Chain of Custody Requirements 04/07/14 Technical Records 01/25/09 Internal Audits 03/29/12,, Chapter 5 Appendix C.1, Chapter 5 Appendix C.2 Certification Statement for Demonstration of Capability 07/26/11 (c) Demonstration of Capability Requirements 10/13/15 Standard Operating Procedures (SOPs) 01/25/09 Demonstration of Capability 01/25/09, Appendix A Biological Tissue QC Matrix 11/08/12;; Appendix C3.3 (b) Non-standard methods / modification of methods 02/22/09 Estimation of Uncertainty of Measurement 01/18/12 (b) Calibration of NIST-traceable References 04/07/14 (h) Calibration Range for pH 10/05/14 (d) Definition of a second source standard 02/22/09 (d) Second Source Calibration Standards 10/05/14 (d) Initial Instrument Calibration (ICAL) - second source for surrogates 10/26/09 Electronic instrument maintenance records 10/26/09 Labeling of Calibrated Equipment 04/16/12 Instrument Calibration - CCVs 01/25/09 Initial Calibration Verification 07/17/11 Reference Standards 03/12/12 Certificate of Analysis for Reagents 04/07/13 (c) Documentation and Labeling of Standards, Reagents, and Reference Materials 07/26/11 Sample Receipt Protocols 10/26/09 Sample Acceptance Plan - communication frequency 10/26/09
5.5.10 Reporting Results 07/26/11
5.5.10 LOD and LOQ in Test Reports 02/23/17 (i) Test Reports - dry or wet weight notations 01/25/09 Identification of Test Method on Test Reports 02/10/13
Appendix B.2.1 and B.2.2 RSD of verification analyses / QC check of assigned value 10/26/09
Appendix C.1 Demonstration of Capability 01/25/09
Appendix C.1 (a), C.3.1, C.3.2 Outside Source vs Secondary Source 11/28/16
Appendix C.1 (e) Demonstration of Capability 02/22/09
Appendix.C.3.1 and C.3.2 Limit of Quantitation (LOQ) Criteria 09/22/14
Appendix C.3.1 Limit of Detection (LOD) 04/07/13
Appendix C.3.5 Limit of Detection (LOD) / Limit of Quantitation (LOQ) 02/10/13
Appendix C.3.1 (b) Limit of Detection (LOD) Verification 07/26/11
Appendix C.3.1 (b) Limit of Detection (LOD) 01/25/09
Appendix C.3.2 Limit of Quantitation (LOQ) 03/12/12
Appendix C.3.2 (c) Confirmation of the Limit of Quantitation (LOQ) 02/10/13
Appendix D.1.1.1 (c) Method Blank Composition 11/28/16
Appendix D. Control Limits including Zero 01/25/09
Appendix D. (c) Evaluation Criteria and Corrective Action 09/18/12
Appendix D. (c) The laboratory does not include all target analytes in the matrix spike mixture over a 2-year period. 01/25/09
Appendix D.1.2.1 MDL determination and the Method Update Rule (MUR) 02/22/09
Appendix D.1.2.1 (b) Comparison of LOD with Blank 10/14/13
Appendix D.1.2.1 (c) The laboratory must have established procedures to relate LOD with LOQ. 01/25/09
Appendix D.1.6 (a) Constant and Consistent Test Conditions 02/22/09
Appendix D.2.8 (s) Holding Time for Effluents 03/12/12
Appendix D.3.1 Microbiological tests - positive sample verification 10/26/09
Appendix D.3.1.a.5 Microbiology, Sterility Checks and Blanks 04/09/12
Appendix D.3.1(a)(2) Microbiology, Sterility Checks and Blanks 01/18/11
Appendix D.3.8.b.2)iv) Autoclave Maintenance 03/29/12
Appendix D.4.4c.3 Radiation, Count Times of Background Measurements 04/07/13
Appendix E.3.2.1 / Chapter 2 2.6 PT evaluations for microbiological data 10/26/09
Appendix F.2.1, F.2.2, F.3 PT Requirements for WET Analysis 07/26/11

Previous Interpretations

List of Topics (click on the topic title to read more)
Clarifying language regarding the checks of pipette tips
Autoclave Performance
Uncertainty Clarification
Detection Limits for TCLP/SPLP Procedures

Clarifying language regarding the checks of pipette tips - NELAC Chapter 5 Appendix D.3.8.b.3.iii states, "Volumetric equipment shall be calibrated as follows: the volume of the disposable volumetric equipment such as sample bottles, disposable pipettes, and micropippette tips shall be checked once per lot." The inclusion of micropipette tips in this standard is an apparent error. The volume of the tips themselves is irrelevant and cannot be independently checked. The volume dispensed is actually determined by the displacement of the pipettor to which the tips are affixed. The accuracy of such mechanical volumetric dispensing devices already must be checked on a quarterly use basis as required by section Checks of the tips provide no additional information on accuracy and are not necessary. This does not relieve the laboratory of the obligation to ensure suitability for use of the tips as required by sections 5.4.6, and

Autoclave Performance - With regard to the pressure check: since PV=nRT, checking the temperature and assuring no leaks (so that V is constant) is sufficient to meet the requirements of the standard.

Uncertainty Clarification - Section "Estimation of Uncertainty of Measurement" has created some confusion. Please note that as a laboratory it is impossible for you to calculate "Total Uncertainty" unless you are given all of the additional pieces from external sources to the lab itself. This section is intended to advise a laboratory to have a "Procedure on Uncertainty for the Laboratory Portion" in place, so that if requested by a client it could be determined. The key language within this section can be found in Section, " ... In certain cases the nature of the test method may preclude rigorous, metrologically and statistically valid, calculation of uncertainty of measurement. In these cases the laboratory shall at least attempt to identify all the components of uncertainty and make a reasonable estimation, and shall ensure that the form of reporting of the result does not give a wrong impression of the uncertainty. ..."

CBOD - If a laboratory is conducting the analysis for CBOD following method 5210B found in the 20th Edition of Standard Methods, then the analyst may over-seed the Glucose-Glutamic Acid (GGA) standard as allowed by the method, but the results must be within the range 198 +/- 30.5 mg/l to be considered acceptable. The laboratory may either meet the above criterion as the acceptance range for GGA recovery, or has the option of developing its own acceptance criteria for GGA recovery under the conditions described below:

  1. The dissolved oxygen uptake from the seed contribution should be between 0.6 - 1.0 mg/l.
  2. In establishing in-house GGA control acceptance limits, the laboratory must use accepted statistical treatments of in-house data for no less than 25 GGA checks over a period of weeks or months (Standard Methods 5210B 6.a.).
  3. The control limits should target the mean value of 164 mg/l, with a range of +/- 26 mg/l, as derived from USEPA's DMRQA/WP performance evaluation database.
  4. The control limits established by the laboratory must be set at three standard deviations from the derived mean, and must not exceed +/- 26 mg/l from the mean as the acceptance range. If the laboratory's calculated acceptance range exceeds +/- 26 mg/l, the laboratory may default to +/- 26 mg/l as its control limit range from the derived mean.
  5. The mean GGA value for CBOD determined by the laboratory cannot be less than 150 mg/l, and should be higher.

The 18th, 19th and 20th Editions of Standard Methods all allow for the laboratory to establish their own limits for BOD and CBOD, but only the 20th Edition addresses the quality control criteria for GGA in CBOD in Section 6 of method 5210B.

The laboratory must treat both the GGA standard and all related samples (including QC samples such as seed blanks and PT samples) in the same way. Evaluation of the various components under CBOD is a check on the inhibitor capacity and its effectiveness. The following terms are defined to help clarify the various components and requirements of the cBOD analysis.

  • CBOD Dilution Water Blank – bottle containing only the buffered dilution water and the nitrification inhibitor.
  • CBOD Seed Blank – bottle containing the same amount of seed that is added to the buffered dilution water for each sample plus the nitrification inhibitor.
  • CBOD Seed Controls – bottle containing larger amounts of seed added to the buffer dilution water plus the nitrification inhibitor, which gives at least 2.0 mg/l depletion.
  • CBOD Seed Contribution – the calculated amount of depletion from the CBOD Seed Control that has been ratioed back to the amount of seed added to each sample.

Detection Limits for TCLP/SPLP Procedures - The Toxicity Characteristic Leaching Procedure/Synthetic Precipitation Leaching Procedure (TCLP/SPLP, SW-846 1311/1312) is not a part of the analytical procedure, and as such is not included in the determination of detection limits. TCLP/SPLP is a procedure to make the sample. The intent of these methods is to leach analytes from a matrix, not to quantitatively extract all target analytes from a sample. As such, it would be inappropriate to spike samples before the leachate procedure. Leachates should be spiked after filtration of the samples and before preservation.

TCLP simulates a leaching process and is not a complete quantitative extraction of the target constituents from the waste sample. The generation of the leachate is defined by the method and the method requires matrix spikes to be added after filtration of the TCLP extract. The leachate does not extract all of the substrate and will vary with each sample matrix. The rate of migration and amount of extract will depend on the substrate, particle size, pH, moisture content and presence of organic acids. TCLP/SPLP extracts should be thought of as a "sample" and not included in the determination of detection limit. Therefore, the standards of Appendix D.1.2 to NELAC Chapter 5 are not applicable to TCLP/SPLP.

Disclaimer: This material represents the opinion of its authors. It is intended solely as guidance and does not include any mandatory requirements except where such requirements are referenced. This guidance does not establish expectations of being implemented universally, exclusively, in whole, or in part.

This guidance does not establish or affect legal rights or obligations and is not finally determinative of the issues it addresses. It does not create any rights enforceable by any party in litigation with TNI, its accreditation bodies, or affiliated institutions. Any decisions made by TNI regarding requirements addressed in this guidance will be made by applying the applicable standards, policies or procedures to the relevant facts.


Module Subject
Microbiology Sample Receipt
Quality Systems Extent of Analytical Records
Quality Systems Conflict of Interest
Quality Systems Control of Records
Quality Systems Use of Measurement Uncertainty
Quality Systems Method Usage and Selection
Quality Systems Required Frequency for Review of Data and Formal Reports
Quality Systems Surrogates
Quality Systems & Chemistry Analytical Batch - Time Constraint
Quality Systems & Chemistry Titrants - Documentation and Verification
Radiochemistry Matrix Spike Requirements