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Section Subject Date
2 SCM FoPT (7/1/07); FoPT Table - NELAC Analyte 1935, Footnote 13 01/18/12
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
2.7.3.1 (d) Supplemental PT Studies for Demonstating Corrective Action (PCB exception) 10/12/09
5.4.2.6 Data Integrity Procedures 03/10/11
5.4.3.1 Controlled Documents 04/07/14
5.4.3.2.2 (b) Frequency of Document Review 01/25/09
5.4.5.4 Subcontrator Lab Documentation 11/08/12
5.4.9.1, 5.4.10.6 (b), 5.5.5.2.2.1 (d), 5.5.10.3.1 (a) Initial Calibration Verification (ICV) Acceptance 04/07/14
5.4.12 Chain of Custody Requirements 04/07/14
5.4.12.2.2 Technical Records 01/25/09
5.4.13.1 Internal Audits 03/29/12
5.5.2.6.c.3, 5.5.4.2.2.d, Chapter 5 Appendix C.1, Chapter 5 Appendix C.2 Certification Statement for Demonstration of Capability 07/26/11
5.5.4.1.1 Standard Operating Procedures (SOPs) 01/25/09
5.5.4.2.2 Demonstration of Capability 01/25/09
5.5.4.2.2, Appendix A Biological Tissue QC Matrix 11/08/12
5.5.4.4; 5.5.4.5; Appendix C3.3 (b) Non-standard methods / modification of methods 02/22/09
5.5.4.6.1 Estimation of Uncertainty of Measurement 01/18/12
5.5.5.2.1 (b) Calibration of NIST-traceable References 04/07/14
5.5.5.2.2.1 (h) Calibration Range for pH 10/05/14
5.5.5.2.2.1 (d) Definition of a second source standard 02/22/09
5.5.5.2.2.1 (d) Second Source Calibration Standards 10/05/14
5.5.5.2.2.1 (d) Initial Instrument Calibration (ICAL) - second source for surrogates 10/26/09
5.5.5.5 Electronic instrument maintenance records 10/26/09
5.5.5.8 Labeling of Calibrated Equipment 04/16/12
5.5.5.10 Instrument Calibration - CCVs 01/25/09
5.5.5.10 Initial Calibration Verification 07/17/11
5.5.6.3.1 Reference Standards 03/12/12
5.5.6.4 Certificate of Analysis for Reagents 04/07/13
5.5.6.4 (c) Documentation and Labeling of Standards, Reagents, and Reference Materials 07/26/11
5.5.8.3.1 Sample Receipt Protocols 10/26/09
5.5.8.3.2 Sample Acceptance Plan - communication frequency 10/26/09
5.5.10 Reporting Results 07/26/11
5.5.10.2 (i) Test Reports - dry or wet weight notations 01/25/09
5.5.10.2 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 (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.1.1.2.1 Control Limits including Zero 01/25/09
Appendix D.1.1.2.1 (c) Evaluation Criteria and Corrective Action 09/18/12
Appendix D.1.1.3.1 (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 (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 D.1.2.1.b Comparison of LOD with Blank 10/14/13
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
CBOD
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 5.5.5.2.1.e. 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, 5.5.5.1 and 5.5.5.2.

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 5.5.4.6 "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 5.5.4.6.2, " ... 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.

Section Subject Date
V2M1 (7.7.2-7.7.3) and V2M3 (6.13.2) Reassessments and Surveillance Audits 09/12/13
V1M1, 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, 6.1 (b) and V1M2 8.2 (c) Corrective Action Date for PTs 10/05/14
V1M2, Section 4.1.7.2 and 5.2.6.1 (a) Technical Director Requirements 03/13/14
V1M2, 5.4.2 Selection of Methods 10/05/14
V1M2, Section 5.6.4.2 Certificates of Analysis 04/07/13
V1M2, Section 5.6.4.2 Documentation and Traceability of Consumables 03/13/14
V1M2, Section 5.4.2 Selection of Methods 12/29/11
V1M2, 5.2.6.1 (a) and (b) Technical Director Experience 04/07/14
V1M4, Section 1.5.2.1 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 1.6.2.2 and 1.7.4.2 (b) Marginal Exceedences and IDOCs 03/13/14
V1M4, Section 1.7.4.3 Matrix Duplicate Precision 02/10/14
V1M5, Section 1.7.5.b Microbiological Sample Handling 04/07/13
V1M6, 1.5.4 Precision and Uncertainty 10/14/13
V1M6, 1.7.1 (a) Calibration of Gamma Detectors 01/07/14
V1M2, 5.5.13.1.b Calibration of Support Equipment 10/05/14
V1M1, Section 7.7.3; V2M3, Section 5.1 Reassessment Requirements 04/07/13
V2M1, V2M3: 8.2.1 (b) and 7 (b) Key Personnel 10/05/14
V2M2, 6.3 Multiple Preparation Methods for PTs 10/05/14
V2M3, Section 4.2.4 Assessor Training Requirements 02/10/14