Method Blank

{
  "id": "MLC-T-ENV-017123",
  "term": "Method Blank",
  "field": "Environment",
  "definition": "1. An analytical control consisting of all reagents, internal standards, and surrogate standards, that is carried through the entire analytical procedure. The method blank is used to define the level of laboratory background and reagent contamination.\n\n2. A blank prepared to represent the sample matrix as closely as possible and analyzed exactly like the calibration standards, samples, and quality control (QC) samples. Results of method blanks provide an estimate of the within-batch variability of the blank response and an indication of bias introduced by the analytical procedure.\n\n3. A sample of a matrix similar to the batch of associated samples (when available) that is free from the analytes of interest and is processed simultaneously with and under the same conditions as samples through all steps of the analytical procedures, and in which no target analytes or interferences are present at concentrations that impact the analytical results for sample analyses. {ORD} {OPP} {OAR/OAQPS} {OECA} {ORCR}\n\n4. An aliquot of reagent water that is treated exactly as a sample including exposure to all glassware, equipment, solvents, reagents, labeled compounds, internal standards, and surrogates that are used with samples. The method blank is used to determine if analytes or interferences are present in the laboratory environment, the reagents, or the apparatus. Also, referred to as a reagent blank. {OW/EAD} {OAR/OAQPS} {ORCR}\n\n5. Method blanks are analyzed to assess background interference or contamination that exists in the analytical system that might lead to the reporting of elevated concentration levels or false positive data. The method blank is defined as an interference-free blank matrix, similar to the sample matrix, to which all reagents are added in the same volumes or proportions as used in sample preparation and carried through the complete sample preparation, cleanup, and determinative procedures. For aqueous analyses, analyte-free reagent water would typically be used. For soil analyses, a purified solid matrix (e.g., Ottawa sand, diatomaceous earth) would typically be used, except for metals analyses. Method blank results are evaluated in conjunction with other QC information to determine the acceptability of the data generated for that batch of samples. MBs are generally considered to be acceptable if target analyte concentrations are less than one half the LLOQ or are less than project-specific requirements. Otherwise, corrective actions may be considered to be taken. A method blank is included with the analysis of every analytical batch of 20 samples or less or as stated in the QAPP or method, whichever is more frequent.{ORCR}\n\n6. A sample of a matrix similar to the batch of associated samples (when available) that is free from the analytes of interest and is processed simultaneously with and under the same conditions as samples through all steps of the analytical procedures, and in which no target analytes or interferences are present at concentrations that impact the analytical results for sample analyses. (ORD)\n\n7. An aliquot of reagent water that is treated exactly as a sample including exposure to all glassware, equipment, solvents, reagents, labeled compounds, internal standards, and surrogates that are used with samples. The method blank is used to determine if analytes or interferences are present in the laboratory environment, the reagents, or the apparatus. Also, referred to as a reagent blank.\n\n8. For aqueous analysis, an unspiked or non-fortified reagent water sample which proceeds through the entire testing method, including all preparatory and determinative steps.\n\n9. Sample used to simulate the sample matrix conditions and analyzed using the exact same calibration standards, samples, and quality control samples. Intended to discover any bias in the analysis and detect within-batch variability of the blank response. [EPA 815-B-04-001]\n\n10. A sample used to simulate the sample matrix conditions and analyzed using the exact same calibration standards, samples, and quality control samples. Intended to discover any bias in the analysis and detect within-batch variability of the blank response.",
  "synonyms": [
    "Laboratory Blank",
    "Preparation Blank"
  ],
  "subject": "Policy and guidance",
  "references": [
    "Underground Storage Tank Sites Guide Glossary",
    "Guidance for Quality Assurance Project Plans",
    "Forum on Environmental Measurements (FEM) Glossary",
    "Environmental Sampling and Analytical Methods (ESAM) Program Glossary",
    "EPA 815-B-04-001"
  ],
  "url": "https://mlchart.com/terminology/environment/method-blank/"
}