The DoD ELAP Detection & Quantitation Guidance for Projects Managers and Data Users

The DoD Environmental Data Quality Workgroup (EDQW) recently issued a fact sheet on detection and quantitation to assist project managers and data users of laboratory data for DoD projects.  The Department of Defense Environmental Laboratory Accreditation Program (DoD ELAP) requires environmental laboratory conformance to the DoD Quality Systems Manual (DoD QSM).  The QSM has specific criteria that must be adhered to for compliance with DoD ELAP laboratory testing protocol, including specifications for detection and quantitation. 

The EDQW guidance sheet is geared to assist project manager or other decision-makers that use environmental laboratory data to accomplish one or more of the following tasks for a DoD project:

• Determine whether a chemical substance is present in an environmental sample at or above some threshold value or action level;

• Verify that a pollutant concentration remains below a permit limit;

• Evaluate potential risks to human health or the environment;

• Monitor changes in concentrations of contaminants; or

• Determine the effectiveness of remediation activities.

Key points covered in the fact sheet include several informative topics specific to DoD ELAP projects. Here are some of the highlights.

Measures of Sensitivity: DL, LOD, and LOQ

DL (Detection Limit): The smallest analyte concentration that can be demonstrated to be different from zero or a blank concentration with 99% confidence.

LOD (Limit of Detection): The lowest concentration for reliable reporting of a non detect of a specific analyte in a specific matrix with a specific method at 99% confidence. 

LOQ (Limit of Quantitation):  The smallest concentration that produces a quantitative result with known and recorded precision and bias. For DoD/DOE projects, the LOQ shall be set at or above the concentration of the lowest initial calibration standard and within the calibration range. 

Here’s an illustrative relationship of the DoD measures of sensitivity:

DL   <   LOD   <   LOQ

 

DoD QSM Requirements

Requirements for the DL, LOD and the LOQ are contained in DoD QSM, Module 4. A few specific requirements that Project Managers and Data Users should be familiar with include:

• Laboratories are required to verify measures of sensitivity, in terms of the LOD and LOQ, at least quarterly.

• Laboratories shall establish a detection limit (DL) for each suite of analyte-matrix-method, including surrogates. The DL shall be used to determine the LOD for each analyte and matrix as well as for all preparatory and cleanup methods routinely used on samples.

• After each DL determination, the laboratory must establish the LOD. It is specific to each suite of analyte, matrix, and method (including sample preparation).

• The laboratory must establish the LOD by spiking a quality system matrix at a concentration of at least 2 times but no greater than four times the DL.

• The signal to noise (S/N) ratio at the LOD must be at least three, and the results must meet all method requirements for analyte identification. The DL and LOD must be reported for all analyte-matrix-method suites unless it is not applicable to the test or specifically excluded by project requirements.

• The laboratory procedure for establishing the LOQ must empirically demonstrate precision and bias at the LOQ for each suite of analyte-matrix-method, including surrogates. The LOQ and associated precision and bias must meet client requirements and must be reported. If the method is modified, precision and bias at the new LOQ must be demonstrated and reported For DoD/DOE projects, the LOQ must be set within the calibration range, including the lowest calibration level.

Establishing Project-Specific Requirements for Method Sensitivity

The fact sheet also explains that DoD project teams should establish their project-specific requirements for method sensitivity in terms of a Reporting Limit (RL) for each analyte and matrix. The RL is a client-specified lowest concentration value that meets project requirements for quantitative data with known precision and bias for a specific analyte in a specific matrix. The RL cannot be less than the LOQ, if precision and bias of the RL and the LOQ are identical. 

If the LOQ for a particular analytical method or laboratory cannot meet the RL, then a project team has four options:

1. Consult with the laboratory to improve method performance or modify the method to achieve a lower LOQ.

2. Select a different method with an LOQ less than or equal to the RL.

3. Raise the RL.

4. If no other options are available to meet project needs, allow for increased level of

uncertainty such that adjusted LOQ can meet RL. This LOQ must be verified.

The EDQW states that precision and bias must be taken into consideration when assessing the LOQ versus the RL. Data below the RL may be reported; however, they are estimated values if less than the LOQ. Although data reporting and flagging requirements are project-specific, all reported LOD and LOQ shall be adjusted for the size of sample aliquots, concentration/dilution factors, and percent solids.

Understanding and Documenting Uncertainty for Low-Concentration Data

Detection and quantitation limits are laboratory specific. The EDQW fact sheet offers five steps that project managers may take to document measurement uncertainty for low concentration data.

• As part of the laboratory selection process, provide the laboratory with project-specific RLs, including precision and bias, for each analyte and matrix. Ask the laboratory to provide its DL, LOD, and LOQ with associated precision and bias for each target analyte in each matrix of concern (e.g., reagent water, clean sand, etc.) and verify that these values meet project-specific RLs. Request laboratory SOPs for establishing the DL and for establishing and verifying the LOD and LOQ.

• Ask the laboratory to verify the LOD by processing an LOD verification check sample with each batch of samples. This is a quality control sample that is spiked at a concentration at or slightly above the LOD to evaluate whether the analyte of interest is in fact “detectable” in the matrix of interest. To accurately report non-detects, set the reporting for non-detects to “less than the LOD” or report the LOD with a “U” flag.

• If the project involves the collection of unusual or difficult matrices, or if the project-specific RL is near the LOQ, ask the laboratory to verify the LOQ in the project-specific matrix by analyzing a minimum of four replicate samples with known concentrations at the LOQ.

• Review low concentration raw data (e.g., chromatograms). If a result is reported above the DL, make sure that the signal-to-noise ratio is at least 3.

• Compare sample result with blank results. If sample results (including chromatograms) cannot be distinguished from blank results, the data may not be useable for decision making.

For a complete read of the EDQW fact sheet on DoD ELAP detection and quantitation you can access the document here.

DoD ELAP laboratory accreditation is specific to sample matrix, analytical method, parameters,  compounds, and elements. The QSM was developed by the DoD Environmental Data Quality Workgroup (EDQW) and the DOE Consolidated Auto Program (DOECAP). Conformance to the DoD QSM is mandatory for environmental laboratories performing analytical testing in support of DoD projects.  

Merit Laboratories maintains DoD ELAP accreditation and is designated a Small Business Enterprise (SBE) and Woman-Owned Business Enterprise (WBE).  Merit’s DoD ELAP accreditation includes aqueous and solid sample matrices for a diverse range of analytical methods for organics, wet chemistry, and metals. Please contact Merit to learn more how about it can assist you on your next DoD project.