The 2015/2016 TNI Standard and the EPA MDL Update TCEQ 2016 The 2015/2016 TNI Standard and the EPA MDL Update Richard Burrows, Ph.D. TestAmerica Inc.

A Revision to the Method Detection Limit EPA published a revision to the 40 CFR Part 136 MDL procedure in the Federal Register on Thursday February 19th 2015 EPA expects that the rule will be finalized in late 2016

TNI Chemistry Standard Revisions to the Detection, Quantitation and Calibration language in TNI Volume 1 Module 4 (Quality Systems for Chemical Testing) are complete and will be incorporated into the TNI 2015/2016 Standard. The 2015/2016 TNI Standards should be adopted by the States in 2017/2018

MDL and TNI revisions!!?? What if they have different requirements? What if they are implemented at different times? What if different states adopt the new requirements at different times? Will I have to have different detection limits for different states?

Good News The revised MDL and TNI Chemistry standards are fully compatible If you are compliant with the revised EPA MDL then you are also compliant with the current MDL One exception, discussed later If you are compliant with the revised TNI Chemistry standard then you are compliant with the current TNI Chemistry standard

Details of the Modifications Initial MDL

First, what stays the same? Fundamental concept is unchanged What is the lowest result that is qualitatively reliable, i.e., the lowest result that reliably indicates the analyte is in the sample? Fundamental approach is unchanged Describe the distribution as Student’s t times the standard deviation of results

What is different? Requires calculation of a MDL based on blanks as well as a MDL based on spikes (the higher of the two becomes the MDL) Incorporates longer term variance Includes checks for reasonableness Works effectively with various quantitation limit concepts and procedures

Details, details Spiking level 2-10 times estimated MDL Run spiked replicates in at least 3 separate preparation and analysis batches Multiple instruments At least 2 spike replicates on each instrument If blanks give ND, MDLB does not apply Addendum for MDL determined on a specific matrix No 10X rule Use all method blanks unless batch was rejected

Ongoing verification

MDL verification Collect data quarterly Analyze data annually One spike per instrument (two if only one instrument) Requirement is detection Analyze data annually Recalculate MDL based on last two years spike and blank data If within factor of 3 (possibly 2) then lab option to leave unchanged or update If outside that range then update

The TNI MDL Requirements

2009 TNI standard requirements for detection limit “appropriate and relevant for the intended use of the data “all sample processing and analysis steps shall be included” “Each target analyte” Verify with a spike at 1-3 or 1-4 X the LOD – detection above zero Verification is required on each instrument Verification is required annually Only required if reporting below the LOQ Repeat each time there is a change that affects the sensitivity of the analysis

What is the MDL?

Lloyd Currie’s original concept The lowest result that can be reliably distinguished from a blank LD The lowest amount present in a sample that will reliably give a result that is above LC LQ The lowest amount that gives quantitative results Equals the MDL equals the TNI LOD Not routinely used in environmental testing (included in the DOD QAPP) Conceptually, equals TNI LOQ, EPA ML and EPA LLOQ

MDL MDL The method detection limit (MDL) is defined as the minimum measured concentration of a substance that can be reported with 99% confidence that the measured concentration is distinguishable from method blank results MDL 3.14 x Standard Deviation 0 MDL 40 CFR Part 136 0 LC Currie’s Critical Level

What the MDL is (and is not): MDL = Lowest result that can be distinguished from blanks Or, lowest result that means there is actually something in the sample MDL ≠ Lowest amount in a sample that can be reliably detected

MDL and Currie’s LD MDL LD Currie’s LD is the minimum true concentration that is reliably detected (i.e., gives a result above the MDL) MDL LD 1% chance of false negative 0 MDL -- 40 CFR Part 136 0 LC LD Currie’s Detection Level 0 DL (LODDOD)  DOD

What does this mean regarding verification? MDL can be verified by examining blank results MDL cannot be verified with spiked samples (Curries LD could be verified with spiked samples)

2015/16 TNI standard requirements for detection limit 2005/16 “reflect current operating conditions” “entire analytical process” “analytes of interest in each test method in quality systems matrix of interest” “Include data from low level spikes and routine method blanks” “Include evaluation of false positive rates” Verification includes a minimum of one low level spike and one blank per quarter per instrument Verification is only required if reporting below the LOQ One option is to follow the EPA MDL procedure

The TNI LOQ Requirements Limit of Quantitation

2009 TNI Standard LOQ 2009 standard Include all sample processing and analysis steps Verify with analysis of a standard at 1-2 times LOQ Verify annually, but not required if the LOD was determined or verified on that instrument No way to determine precision and accuracy

2015/16 TNI Standard LOQ requirements 2016 At least 3X the MDL All processing steps Above lowest calibration standard Verification (initial) At least 7 spikes at of below the LOQ 3 batches on 3 separate days Distribute across instruments, at least 2 per instrument Results must meet identification criteria and be above zero and within the laboratory established recovery criteria

LOQ verification Ongoing One verification sample on each instrument each quarter Must meet identification criteria and be above zero Once per year compile the data and create a statement of precision and accuracy

How Does This All Fit Together?

TNI LOQ and EPA MDL MDL LOQ Initial 7 spikes 3 separate batches 3 separate days 2 per instrument Ongoing One spike per inst. per quarter One spike per inst. per quarter (2 if only one inst.) Meet qualitative ID, above zero

TNI LOQ and EPA MDL Annual calculation requirement is different: MDL Calculate MDL(s) as Students t x Standard Deviation LOQ Create statement of precision and accuracy We will see how this works out in the next Section

Why Do we need a MDL and a LOQ?

Reason #1 that we need MDLs We need to make the Quantitation limit meaningful Applies to MRL, LLOQ, or any quantitation limit Without a MDL, a true concentration at or close to the LOQ is probably going to be reported as a false negative In other words, without a MDL, our quantitation limit is not only not quantitatively reliable, it is not qualitatively reliable either

90% recovery, 9% RSD Spike #1 #2 #3 #4 #5 #6 #7 Mean MDL 10 9 8.3 9.8 9.3 8.1 8.6 10.0 9.0 2.29 Spike True Value = LLOQ MDL = 2.29 Calculated MDL Reported results (without MDL) ND 10

If you don’t report below the LOQ you have a lot of false negatives Bottom Line If you don’t report below the LOQ you have a lot of false negatives You can’t minimize false negatives and false positives at the same level With the LOQ and the MDL, false negatives are controlled at the LOQ and false positives are controlled at the MDL

Reason #2 that we need MDLs MDLs are needed in risk assessment Handling non-detects Substitute a value such as ½ detection limit or detection limit More sophisticated methods such as Maximum Likelihood estimation and Regression on Order statistics These still benefit from a detection limit as low as possible If we do not have a detection limit, the Quantitation limit will become the new Detection limit

How to do a LOQ / MDL study

Select LOQ Choose your LOQ Must be at or above low calibration standard If blanks are non zero, then calculate mean + 3X standard deviation. This will approximate the MDL and spiking level should be at least 2-3 times higher Spike ideally in the range 0.5-1 x LOQ

Run the spiked and blank samples Spikes Minimum 7 spikes Minimum 3 separate batches and three separate days Prep and analytical Minimum 2 on each instrument Blanks Use existing If new method, minimum 7, at least 3 batches, at least 3 days, at least 2 per instrument

Initial evaluation Do the spike results meet qualitative identification criteria in the method? Calculate precision and accuracy, and the MDL Adjust the LOQ if necessary

Good precision, good recovery Spike 1 2 3 4 5 6 7 10 9.5 9.8 10.2 10.6 9.4 9.7 9.9 MEAN STD. DEV MDL S 0.4 1.3 Blanks ND MDL B 0.0 MDL 3X MDL LOQ 3.9 10.0 Success! Spikes work for calculation of the MDL And Verification of the LOQ

Good precision, moderate recovery Spike 1 2 3 4 5 6 7 10 7.3 6.9 8.1 7.7 7.9 MEAN STD. DEV MDL S 7.5 0.5 1.4 Blanks ND MDL B 0.0 MDL 3X MDL LOQ 4.3 10.0 Success! Spikes work for calculation of the MDL And Verification of the LOQ

Poor/Moderate precision and recovery Spike 1 2 3 4 5 6 7 10 7.3 7.6 5.7 7.2 7.9 5.3 MEAN STD. DEV MDL S 6.7 1.0 3.2 Blanks ND MDL B 0.0 MDL 3X MDL LOQ 9.7 10.0 Success! Spikes work for calculation of the MDL And Verification of the LOQ

Poor precision, poor recovery Spike 1 2 3 4 5 6 7 10 7.1 3.2 6.5 7.4 3.3 MEAN STD. DEV MDL S 5.1 1.9 6.1 Blanks ND MDL B 0.0 MDL 3X MDL LOQ 18.2 18.0 Marginal! Spikes work for calculation of the MDL And Verification of the LOQ But LOQ must be elevated above the spiking level

Poor precision, poor recovery Spike at ½ desired LOQ Spike 1 2 3 4 5 6 7 2.5 3.55 1.6 3.25 3.7 1.5 1.65 MEAN STD. DEV MDL S 2.54 0.97 3.04 Blanks ND MDL B 0.0 MDL 3X MDL LOQ 9.12 10 Success! Spikes work for calculation of the MDL And Verification of the LOQ

Good precision, elevated blanks Spike 1 2 3 4 5 6 7 10 13.5 12.8 14.2 14.6 13.4 13.7 13.9 MEAN STD. DEV MDL S 0.6 1.8 Blanks 3.1 4.2 3.9 4.4 3.8 3.2 MDL B 0.5 5.3 MDL 3X MDL LOQ 16.0 Marginal! Spikes work for calculation of the MDL And Verification of the LOQ But LOQ must be elevated above the spiking level

Determine the LOQ – with 10% RSD Spike at: 10 If RSD is 10%, the standard deviation is: 1 So MDL would be about: 3 CHECK: Is spike concentration at least 3x MDL? YES: MDL (3) x3 = 9, and 10 is greater than 9. Spike conc. 10 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 c Standard Deviation=1 MDL

Determine the LOQ – with 20% RSD Spike at: 10 If RSD is 20%, the standard deviation is: 2 So MDL would be about: 6 CHECK: Is spike concentration at least 3x MDL? NO: MDL (6) x3 = 18. Ten is not greater than 18. LOQ needs to be at least 18. Spike conc. 10 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Standard Deviation= 2 MDL

4,6-Dinitro-2-methylphenol MDL 100% Recovery

What do we expect if the true value is at the LOQ? Known precision? Known accuracy? Ability to detect and report? Freedom from false negatives?

What do we expect from a true value at the MDL? Known accuracy? Ability to detect and report? Freedom from false negatives? We do expect freedom from false positives (99%) when the analyte is not present

What does this mean to labs? Clear requirements Sensible MDLs Level playing field Low transition costs since existing data can be used Note – labs should start complying with 3 batch rule right now Some additional organizational requirements

What does this mean to data users? MDLs that make sense Much lower rate of false positives, especially for ICP, ICPMS and some general chemistry tests Easier to compare labs In general, more reliable data = better decision making

How much will MDLs change? Analytes with minimal or no detects in blanks, eg most GC/MS analytes at normal levels: Not Much Analytes with frequent detects in blanks, eg, metals, very low level PAH, some general chemistry tests: Depends If the lab is currently adjusting MDLs to avoid excessive false positives, not much If the lab has been pushing MDLs below levels justified by the blanks, potentially quite a bit

Questions?