Method Update Rule of 2015: New Method Detection Limit MDL Determination. David Caldwell OK DEQ Laboratory Accreditation Program

Transcription

1 Method Update Rule of 2015: New Method Detection Limit MDL Determination David Caldwell OK DEQ Laboratory Accreditation Program

2 Final Rule Method Update Rule of 2015: This action has been withdrawn from the Office of the Federal Register. Final rule (signed December 15, 2016) The final rule has been signed by the EPA Administrator and is being prepared for publication. Fact sheet Documents related to this rulemaking can be found on EPA s docket at regulations.gov. The Docket Number is EPA-HQ-OW

3 MDLs What are the uses When to use How to maintain the level of sensitivity for compliance reporting of permits How the Laboratory uses method to determine the sensitivity for the compliance testing

4 Why Talk about MDLs? REPORTS B P Q L BELOW PRACTICAL QUANTITATION LIMITS

5 MDLs some uses of Data National Primary Drinking Water Regulations 40 CFR Part 141 Reviews Existing Drinking Water Standards every 6 years Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules 3. Analytical Feasibility To determine if changes in analytical feasibility could possibly support changes to PQLs, EPA relied primarily on two alternate approaches to develop an estimated quantitation limit (EQL): an approach based on the minimum reporting levels (MRLs) ODEQ Water Quality Standards 252:690 Appendix B Wastewater Permit Limits Laboratory MDL and reporting limits Commercial Municipal Industrial Governmental an approach based on method detection limits (MDLs).

6 What is a Method Detection Limit (MDLs) A BRIEF DESCRIPTION OF WHAT IS A METHOD DETECTION LEVEL

7 Principle Rule Changes Old Estimation of Detection Limit Evaluation of Laboratory Fortified Blank MDL=X+t(nn 1,1 =0.99)S Reporting New Estimation of Detection Limit Evaluation of Blanks Evaluation of Laboratory Fortified Blank MDL=X+t(nn 1,1 =0.99)S Testing must be across all instruments used for that method Only use data associated with acceptable calibrations and batch QC. Quarterly Verification Annual Recalculation Reporting

8 MDL=X+t(nn 1,1 =0.99)S MDL- Method Detection Limit X- Standard Deviation of Laboratory Standards t Student T test with degree of freedom Method Detection Limit Calculation

9 PQL Reporting

10 PQL Reporting

11 MDLs are used to identify the minimum concentration of analyte that can be distinguished from a nondetect result. Method Detection Limits Method Detection Level (MDL) for appropriate analytes or method parameters is determined before analyzing samples and is repeated at least annually.

12 Method Detection Limit Laboratory s Use Reflect current operating conditions Incorporate entire analytical process Include data from low-level spikes and (Proposed) method blanks analyzed over multiple days Include (proposed) criteria for evaluating false positives in blanks

13 Method Detection Limit Estimation of level to test The mean plus three times the standard deviation of a set of method blanks, or The concentration value that corresponds to an instrument signal/noise in the range of 3 to 5, or Three times the standard deviation of spiked blanks, or That region of the standard curve where there is a significant change in sensitivity, or Instrumental limitations, or Previously determined MDL.

14 Current MDL Calculations MDL = S * t of spike results Reported MDL Determine the mean and variance of the standards Calculate the mean Calculate the standard Deviation > 10 % RSD Statistical: Student t Test value with degree of freedom Look up Student t Test value for the number of sample analysis one for the degrees of freedom Quantitation Limit will be 3.3 X MDL (Practical Quantitation Limit)

15 Proposed Method of Calculation Run series of seven (7) blanks Run series of seven (7) spikes Compare the blanks vs. spike Greater of the variance is used MDL = S * t of spike results Reported MDL Quantitation Limit will be 3.3 X MDL (Region 6 requirement) Analyze Quarterly MDL check standard

16 Examples Ammonia Testing Permit Limit of 0.2 mg/l (Practical Quantitation Limit) MDL listing from previous year of 0.05 mg/l Practical Quantitation Limit of 0.17 mg/l

17 Example # 1: 1.0 mg/l Estimate Standard 1.0 mg/l 0.97 mg/l 0.94 mg/l 1.12 mg/l 0.98 mg/l 1.05 mg/l 1.10 mg /L Mean mg/l Deviation mg/l

18 Example # 1: Calculations Deviation mg/l Student t Test for 6 degrees of freedom 3.14 MDL = X 3.14 MDL = mg/l PQL = mg/l

19 Example # 2: 0.1 mg/l Estimate Standard Mean mg/l Deviation mg/l

20 Example # 2: Calculations Deviation mg/l Student t Test for 6 degrees of freedom 3.14 MDL = X 3.14 MDL = mg/l PQL = mg/l

21 In Summary Example 1 MDL = mg/l Example 2 MDL = mg/l PQL = mg/l PQL = mg/l Previous Year: MDL listing from previous year of 0.05 mg/l Practical Quantitation Limit of 0.17 mg/l

22 Example Proposed Procedure Blanks Mean mg/l Deviation mg/l 0.1 mg/l Estimate Standard Mean mg/l Deviation mg/l

23 Example Proposed Procedure Deviation mg/l Student t Test for 6 degrees of freedom 3.14 MDL = X 3.14 MDL = mg/l PQL = mg/l verify MDL is within 0.5 to 2.0 times the existing MDL, and fewer than 3%

24 Ammonia Summary Existing Procedure MDL = mg/l Proposed Procedure MDL = mg/l PQL = mg/l PQL = mg/l Laboratory Report Reporting Limit of 0.2 mg/l (Practical Quantitation Limit) MDL listing from previous year of 0.05 mg/l Practical Quantitation Limit of 0.17 mg/l

25 Conclusion

26 Questions David Caldwell