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Quality Control Guidelines for SAM Chemical Methods

There are several quality control (QC) considerations that apply when using the methods listed in EPA's Selected Analytical Methods for Environmental Remediation and Recovery (SAM). Having analytical data of appropriate quality requires that laboratories: (1) conduct the necessary QC to ensure that measurement systems are in control and operating correctly; (2) properly document results of the analyses; and (3) properly document measurement system evaluation of the analysis-specific QC, including corrective actions. Information regarding EPA's data quality objectives (DQO) process, considerations and planning is available at Quality Management Tools - Systematic Planning. See: EPA Quality Management Tools.

In addition to the laboratories being capable of generating accurate and precise data during site remediation, they must be able to deliver results in a timely and efficient manner. Therefore, laboratories must be prepared with calibrated instruments, the proper standards, standard analytical procedures, and qualified and trained staff. Laboratories also must be capable of providing rapid turnaround of sample analyses and data reporting. 

The level or amount of QC needed during sample analysis and reporting depends on the intended purpose of the data that are generated (e.g., the decision(s) to be made). The specific needs for data generation should be identified. QC requirements and DQOs should be derived based on those needs, and should be applied consistently across laboratories when multiple laboratories are used. For almost all of the chemical warfare agents (CWAs), most laboratories will not have access to analytical standards for calibration and QC. Use of these agents is strictly controlled by the DoD and access is limited. For information regarding laboratory analysis of samples containing CWAs or laboratory requirements to possess and use ultra-dilute agent standards, please use the contact information provided on the Environmental Response Laboratory Network (ERLN) website. See: ERLN Website.

A minimum set of analytical QC procedures should be planned, documented and conducted for all chemical testing. Some method-specific QC requirements are described in many of the individual methods and will be referenced in any analytical protocols developed to address specific analytes and sample types of concern. Individual methods, sampling and analysis protocols or contractual statements of work should also be consulted to determine if any additional QC might be needed. Analytical QC requirements generally consist of analysis of laboratory control samples to document whether the analytical system is in control; matrix spikes to identify and quantify measurement system accuracy for the media of concern, and at the levels of concern, various blanks as a measure of freedom from contamination; as well as matrix spike duplicates or sample replicates to assess data precision.

In general, for measurement of chemical analytes, appropriate QC includes an initial demonstration of measurement system capability as well as ongoing analysis of standards and other samples to ensure the continued reliability of the analytical results. Examples of appropriate QC include:

  • Demonstration that the measurement system is operating properly
    • Initial calibration
    • Method blanks
  • Demonstration of analytical method suitability for intended use
    • Detection and quantitation limits
    • Precision and recovery (verify measurement system has adequate accuracy)
    • Analyte/matrix/level of concern-specific QC samples (verify that measurement system has adequate sensitivity at levels of concern)
  • Demonstration of continued analytical method reliability
    • Matrix spike/matrix spike duplicates (MS/MSDs) recovery and precision
    • QC samples (system accuracy and sensitivity at levels of concern)
    • Surrogate spikes (where appropriate)
    • Continuing calibration verification
    • Method blanks

QC tests should be consistent with EPA's Good Laboratory Practice Standards and be run as frequently as necessary to ensure the reliability of analytical results. Additional guidance can be found at Quality Management Tools - Overview; in Chapter 1 of EPA SW-846 "Test Methods for Evaluating Solid Waste, Physical/Chemical Methods"; and in EPA's 2005 "Manual for the Certification of Laboratories Analyzing Drinking Water" (EPA 815-R-05-004). As with the identification of needed QC samples, the frequency of QC sampling should be established based on an evaluation of DQOs. The type and frequency of QC tests can be refined over time.

Ensuring data quality also requires that laboratory results are properly assessed and documented. The results of the data quality assessment are included within the data report when transmitted to decision makers. This evaluation is as important as the data for ensuring informed and effective decisions. While some degree of data evaluation is necessary in order to be able to confirm data quality, 100% verification and/or validation is neither necessary nor conducive to efficient decision making in emergency situations. The level of such reviews should be determined based on the specific situation being assessed and on the corresponding DQOs. In every case, the levels of QC and data review necessary to support decision making should be determined as much in advance of data collection as possible.

Please note: The appropriate Technical Contacts page of this website should be consulted regarding appropriate quality assurance (QA) and QC procedures prior to sample analysis. These contacts will consult with the EPA Environmental Response Laboratory Network (ERLN) or WLA coordinator responsible for laboratory activities during the specific event to ensure QA/QC procedures are performed consistently across laboratories. EPA program offices will be responsible for ensuring that the QA/QC practices are implemented.

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