Proficiency Test Samples: What are We Really Testing? Dr. Robert Litman, Dr. Daniel Montgomery, Dr. David McCurdy, @Mr. Stan Morton and Mr. Robert Shannon, Environmental Management Support John Griggs, Director, US EPA National Analytical Radiation Environmental Laboratory (NAREL)

The Analytical Method for a Radionuclide The method ensures that the chemical approach for the radionuclide and matrix, based on an event, will reliably convert the sample into an appropriate sample test source and facilitate acceptable levels of measurement bias and uncertainty?

PT Samples – Traditional Paradigm… One of the biggest challenges for labs: PT samples PT Samples demonstrate methods work as expected based on: Chemical separations are effective (when used) Instrument calibration and performance Analyst Training Suitability of the method for the matrix being analyzed …

What is “Suitability” To paraphrase Gilbert and Sullivan: “Let the PT fit the sample” One method for analysis of, let’s say uranium in ground water, may not be suitable for each of the following matrices: surface water, soil, concrete, vegetation, DRPs… Or paraphrasing the Isotoner commercials in the inverse: “One PT does NOT fit all”

How Do Laboratories Treat PT Samples? Success: When audits note that methods are satisfactory based on PT results For the most part, laboratories do what is asked of them Most clients trust labs to do the analysis correctly Over time, laboratories tailor their methods to pass PT samples This may or may not be good for emergency response samples (although for routine programs, as well)

PT Samples Test Real Analytical Systems Why then: Do PTs utilize the same test configurations again and again? Are radionuclides present in readily soluble form? Are radionuclides (usually) homogenously distributed? Does preservation not reflect regulatory/lab requirements? Are dynamic parent-progeny relationships not usually tested? Are DQOs/MQOs clearly defined? Are turn-around times long and numbers of samples small? Do labs analyze PTs they would never routinely accept?

Soluble, Homogenously-Distributed Radionuclides The same (boring) radionuclides are present again and again but not necessarily the ones in real samples PT samples are homogenously distributed Labs routinely analyze small subsamples of solids without homogenizing and still obtain acceptable results Radionuclides are present in readily soluble form Real samples may contain intractable chemical forms (various redox states, refractory Pu, complexes, compounds) Fused matrix and DRPs would be expected in many events

Realistic DQOs/MQOs and Program Needs Provided to Labs DQOs/MQOs are not usually clearly defined Labs develop methods for PTs with no relationship to routine work Hot labs receive low-level samples and ‘environmental’ labs hot samples Results could be reported and evaluated to take this into account. A hybrid of traditional evaluation measures would show that a method is not suitable for its primary purpose while Z-scores would allow a hot- lab to demonstrate method performance relative to false positives

Realistic DQOs/MQOs and Program Needs Provided to Labs DQOs/MQOs are not usually clearly defined Turn-around times are long and numbers of samples small Some PT programs touch on these issues, but they need to be much more central both to the provider and the lab...

PT Sample Preservation We know that: Iodine is lost from vegetation and filters Zirconium will precipitate even in acid solution Decay chain may not be in equilibrium fission products in equilibrium in PT, or 214Bi/214Pb requested There is no practical preservation technique for all fission and activation products in real-life water … When PT samples are preserved differently from real-life samples results may indicate that all lab processes work even though analysis of samples might fail in real-life

In the End PTs May Provide a Misleading Picture of Performance Labs obtain false sense of security about the performance of their methods Regulators and lab customers use PTs to establish a misguided understanding of data quality and capabilities they can expect from a lab’s methods

Problem #1: What type of matrix? Let’s first assume a radiological event: Urban Environment What commodities, commercial products, or materials are likely to become contaminated? Can samples be created that represent the manner of contamination? If surface contamination: Can they be transported to lab without loss? Can/should the whole sample be analyzed? Can we get a representative part if only analyzing some of it?

We Need to “Right–Size” Samples Sample characteristics should reflect the program in question Analytes/matrix Homogeneity DQOs/MQOs Possibly preservation Other key PT sample characteristics The lab may refuse the sample just as they would a customer’s sample Alternatively, PT programs could offer an alternative evaluation Accept as with alternative MQOs, e.g., Z-score – a low-activity PT would function as a false-positive test of sorts (without significant radio-interferences) for a higher level lab

Example 1:Scabbled Concrete - PT PT based on: A building was contaminated with 241Am following an RDD event. The surface was scabbled to remove the surface contamination. Chemical form of the radionuclide used to spike? How is the PT made (e.g., surface spiked then scabbled)? Who homogenizes the PT? What direction is the laboratory given to decide how much sample? Minimum aliquant size Are MQOs clearly communicated so the lab can determine how much sample to analyze?

A Real-Life Sample? YES An RDD in an urban environment would generate such a sample. The PT form should be representative of the way the surface was contaminated/removed to form the sample. Should there be separate PTs for a sample already homogenized and one that is not?

Problem 2: Radionuclide spike with multiple Oxidation states/Chemical forms? Is the oxidation state important? Can multiple oxidation states be achieved in same PT? Pu, U, Ru, Mo, Np, Cm, I, Fe, etc. Are different chemical constituents accounted for in the PT? Are different matrix configurations accounted for in the PT?

Problem 3: Emergency Response Samples are Unique Can QC samples be available for method validation of ER matrices? High and low activity concentrations depending upon lab Analyte and matrix characteristics Assess carrier/tracer yield? Blank samples used for detectability determination? Measurement uncertainty determination? Can the same data reduction process normally employed be used?

Problem 4: Extraneous Radionuclides Present Should PT samples have radionuclides present that are not of “interest”? Assess the effectiveness of separation capability? Create interferences that must be accounted for in the data reduction process? Which extraneous radionuclides should be added to the PT Do the concentration ratios present realistic problems?

Problem 5: Unannounced Practice Participating laboratories willing to accept 25 -100 samples with Different matrices Three different radionuclides requiring three different methods Two day turn-around-time Number of labs kept to 3-4 per practice

How Do These Issues Get Addressed? Currently – often not addressed which creates a huge gap in the effectiveness of PT programs Need to test: Real sample characteristics Capability AND capacity How many laboratories will participate, who will determine validity of results? How are data processed?

Are We Assessing the Laboratory PT results? How do we evaluate the results? PT sample evaluation should not be arbitrary 80-120% limits are arbitrary. Tie the assessment on DQOs/MQOs provided to labs Z-score, assesses bias. and uncertainty Which analytics should be used? Z-score, t-test, Grubbs test False negative, or positive at LLD Labs must adjust their programs/methods so they will meet requirements What feedback do laboratories get about their methods/results? More would be better

Proficiency Testing Samples are the crux of the issue Multiple levels of testing needed Non-normal radionuclides need to be part of process Result validation and assessment must also be a proficiency test An ink and paper process Should be separate from actual sample analysis How do these efforts get funded?

Questions?