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Right solutions….

Environmental Division. Reporting Limit Verification Samples – A Laboratory Perspective on Verifying Reporting Limits and Calculating Limits of Detection. Right solutions…. ….Right partner. 2009 EPA Quality Management Conference May 12 – 14, 2009 San Antonio, TX. Robert P. Di Rienzo

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Right solutions….

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  1. Environmental Division Reporting Limit Verification Samples – A Laboratory Perspective on Verifying Reporting Limits and Calculating Limits of Detection Right solutions…. ….Right partner

  2. 2009 EPA Quality Management Conference May 12 – 14, 2009 San Antonio, TX Robert P. Di Rienzo Quality Assurance Manager ALS Laboratory Group

  3. Definitions and Requirements • The Process of Reporting Limit Verification Samples (RLVS) • Data Collection and Statistics • Decisions and Uncertainty at the Reporting Limit (LOQ) • Our Least Favorite Discussion – Limit of Detection (LOD)

  4. Definitions and Requirements Reporting Limit Verification Sample Reporting Limit Verification Sample (RLVS) is a quality system matrix spiked sample prepared to have a concentration at or below the desired reporting limit and taken through the entire preparation and analytical process.

  5. Definitions and Requirements Reporting Limit Reporting Limit – A client-specified lowest concentration value that meets project specified requirements for quantitative data with known precision and bias for a specific analyte in a specific matrix

  6. Definitions and Requirements Limits of Quantitation The minimum levels, concentrations, or quantities of a target variable (e.g., target analyte) that can be reported with a specified degree of confidence. Limits of Quantitation The lowest concentration that produces a quantitative result within specified limits of precision and bias. For DoD projects, the LOQ shall be set at or above the concentration of the lowest initial calibration standard.

  7. Definitions and Requirements Limits of Quantitation (LOQ): Establishment and Verification of LOQ

  8. Definitions and Requirements Precision: The degree to which a set of observations or measurements of the same property, obtained under similar conditions, conform to themselves; a data quality indicator. Precision is usually expressed as standard deviation, variance or range, in either absolute or relative terms. Bias: The systematic or persistent distortion of a measurement process, which causes errors in one direction (i.e., the expected sample measurement is different from the sample’s true value). Accuracy: The degree of agreement between an observed value and an accepted reference value. Accuracy includes a combination of random error (precision) and systematic error (bias) components that are due to sampling and analytical operations; a data quality indicator.

  9. Definitions and Requirements Coefficient of variation: The coefficient of variation (CV or Sr) is a normalized measure of dispersion or a probability distribution. It is defined as the ratio of standard deviation to the mean.

  10. The Process of Reporting Limit Verification Samples (RLVS) Reporting Limit Verification Samples (RLVS) are analyzed in each batch of samples. RLVS is a spiked LCS sample at or below the reporting limit. These samples are used to assess precision and bias at the reporting limit. These samples are used to calculate uncertainty and control limits at the reporting limit and may be used as a data quality indicators on a project specific basis.

  11. Data Collection and Statistics JUST KIDDING!!!!!

  12. Data Collection and Statistics

  13. Data Collection and Statistics

  14. Data Collection and Statistics

  15. Data Collection and Statistics

  16. Data Collection and Statistics

  17. Data Collection and Statistics

  18. Data Collection and Statistics

  19. Data Collection and Statistics

  20. Data Collection and Statistics

  21. Data Collection and Statistics

  22. Data Collection and Statistics

  23. Decisions and Uncertainty at the Reporting Limit (LOQ) 28

  24. Decisions and Uncertainty at the Reporting Limit (LOQ)

  25. Decisions and Uncertainty at the Reporting Limit (LOQ) The Sr value may be used to calculate uncertainty at the reporting limit (RL). The calculation takes into consideration precision and bias and calculates uncertainty at the 95% confidence level. RL ( 1 ± 2(Sr)) or RL ± (RL(2Sr))

  26. Our Least Favorite Discussion – Limit of Detection (LOD) D-13

  27. Our Least Favorite Discussion – Limit of Detection (LOD)

  28. Our Least Favorite Discussion – Limit of Detection (LOD) • The Sr value must meet the following criteria to be used for LOD calculations. Verification Test = 0.05 ≤ Sr ≤ 0.5 • If Sr > 0.5, the RL is too low; Adjust RL to higher concentration and repeat RLVS measurements. • If Sr < 0.05, the RL may be too high; Possibly adjust RL to a lower concentration and repeat RLVS measurements.

  29. Our Least Favorite Discussion – Limit of Detection (LOD) Limit of Detection Calculation using RLVS LOD = Bo + Sr(RL) Bo = Average Blank Value (MB, or CCB) or 0 Sr = Coefficient of Variation from RLVS measurements RL = Reporting Limit (Concentration of RLVS)

  30. Our Least Favorite Discussion – Limit of Detection (LOD) 40 CFR Part B MDL dated 11/24/08 = 0.215 ug/L

  31. Our Least Favorite Discussion – Limit of Detection (LOD) 40 CFR Part B MDL dated 11/24/08 = 0.0949 ug/L

  32. Our Least Favorite Discussion – Limit of Detection (LOD) 40 CFR Part B MDL dated 8/08/08 = 29.9 ug/L

  33. Our Least Favorite Discussion – Limit of Detection (LOD) 40 CFR Part B MDL dated 2/25/08 = 11.9 ug/L

  34. Our Least Favorite Discussion – Limit of Detection (LOD) 40 CFR Part B MDL dated 10/9/08 = 0.0617 ug/L

  35. Our Least Favorite Discussion – Limit of Detection (LOD) 40 CFR Part B MDL dated 8/12/08 = 0.469 ug/kg

  36. Our Least Favorite Discussion – Limit of Detection (LOD)

  37. Conclusions • RLVS on a batch basis will generate data for uncertainty at the reporting limit. • An assessment of the reporting limit can be made from the coefficient of variation (Sr) • Precision and bias at the reporting limit is significantly different than at the LCS level.

  38. Conclusions • The value and adjustment of the reporting limit is based on precision and bias of RLVS measurements. • The use of RLVS measurements at the reporting limit allows the data user to assess the reporting limit by matrix, method(s), and analyte and not by calibration standards. • Coefficient of variation (Sr) is a measure of dispersion and can be used to make a valid estimations of the LOD.

  39. Questions? Robert P. Di Rienzo Quality Assurance Manager ALS Laboratory Group, Environmental Division (Salt Lake City, UT) Bob.DiRienzo@alsenviro.com (801) 266-7700

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