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TNI Standards Guidance

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: Quality Systems & Chemistry

Subject: Insufficient Sample Volume

Question 1

What approach is acceptable to demonstrate matrix effects on field samples when the laboratory is not provided with sufficient sample volume to perform an MS/MSD with the sample batch, particularly in the scope of organic 1L extractions? If sufficient volume is not submitted for the MS and/or MSD, then there is also not sufficient volume for a sample and duplicate pair either. Most laboratories are not responsible for sampling and should not be held as such, but some TNI accrediting authorities are citing laboratories for this very issue and have taken a hard "line in the sand" approach on this matter. The laboratory should be responsible for providing sufficient instruction and materials to samplers, but shouldn't be held responsible for something completely beyond their control. If the samplers don't obtain sufficient volume for whatever reason, why is the laboratory responsible? The TNI standard doesn't seem to provide much guidance on what actions that the laboratory should take in this event and mere qualification of data doesn't appear to be an acceptable alternative to the aforementioned TNI accrediting authorities.

2009 TNI Standard EL-V1M4 section Sample Specific Controls states: “The laboratory shall document procedures for determining the effect of the sample matrix on method performance. These procedures relate to the analyses of quality system matrix specific Quality Control (QC) samples and are designed as data quality indicators for a specific sample using the designated method. These controls alone are not used to judge laboratory performance”. “Examples of matrix-specific QC include: Matrix Spike (MS), Matrix Spike Duplicate (MSD), sample duplicates, and surrogate spikes. The laboratory shall have procedures in place for tracking, managing, and handling matrix-specific QC criteria, including spiking appropriate components at appropriate concentrations, calculating recoveries and relative percent difference, and evaluating and reporting results based on performance of the QC samples.”

Laboratories are only required to perform MS and MSD on 5-10% of the samples they receive, depending on the methods for the parameters. It is imperative for labs to plan ahead to ensure one in every 10 samples (or 20, depending on the method) have enough volumes for MS/MSD in order to comply with the QC requirements.

This communication between laboratories and their sample collectors is essential, yet beyond the scope of TNI Standard. It is true that most labs are not responsible for sample collection, however, if the samplers didn't obtain sufficient volume (for whatever reason), the lab is still responsible for complying with QC sample frequencies required by specific methods or TNI standard.  Particularly in the scope of organic 1 liter extractions, laboratory analysts have the option to dilute the sample to sufficient volume, and use the dilution factor in the result calculations. For test parameters or certain circumstances when the samples cannot be diluted, the analysts shall use all resources and tools available (e.g.. adjust sample sequence orders, reject certain samples, etc.) to ensure that the QC frequency requirement is met, in order for the entire batch of analytical data to be considered valid and reportable.  The 2009 TNI Standard EL-V1M4 section states “The laboratory shall have procedures in place for tracking, managing, and handling matrix-specific QC criteria, including spiking appropriate components at appropriate concentrations” so clearly it is the laboratory’s responsibility to have procedures to consistently comply with QC requirements.  The laboratory should establish procedures to respond to variable factors during sample collections effectively, so that the laboratory data quality and integrity is maintained.


2009 TNI Standard

V1M4-2009 Sample Specific Controls