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Environmental Measurement

Glossary of Terms

January 11, 2010

The intent of this glossary is to define terms, commonly used in association with 

detection, quantitation, and calibration in environmental laboratories, which may be 

unfamiliar to the lay person. The definitions are taken from various sources noted in an 

appendix at the end of this document. Offices with definitions fairly unique to their 

programs are noted; otherwise, the definition is considered to be generally accepted 

across all Agency programs. Definitions have been grouped into sections of common 

use. A list of acronyms for the citations is included at the end of the document in an 

appendix, as well.

CALIBRATION TERMS

Calibration – Set of operations that establish, under specified conditions, the relationship 

between values of quantities indicated by a measuring instrument or measuring system, 

or values represented by material measure or a reference material, and the corresponding 

values realized by standards. (ORD) (OW/EAD) (OPP) (OW/TSC) (OAR/OAQPS)

(OECA) (ORCR)

Calibration Blank – See Quality Terms Section.

Calibration Curve – The graphical relationship between the known values, such as 

concentrations, of a series of calibration standards and their instrument response. (ORD)

(OW/EAD) (OPP) (OW/TSC) (OAR/OAQPS) (OECA) (ORCR)

Calibration Method – A defined technical procedure for performing a calibration. 

(ORD) (OPP) (ORCR)

Calibration Standard (CAL) – (1) A substance or reference material used to calibrate 

an instrument. (OPP) (ORCR) (2) A solution prepared from the dilution of stock standard 

solutions. The calibration solutions are used to calibrate the instrument response with 

respect to analyte concentration. (ORD) (OW/EAD) (OPP) (OW/TSC) (OAR/OAQPS)

(OECA) (ORCR) (3) A solution prepared from the primary dilution standard solution 

and/or stock standard solution, and the surrogate analytes. The CAL solutions are used to 

calibrate the instrument response with respect to analyte concentration. (OW/TSC)

Calibration Verification (CV) Solution – A solution of method analytes, used to 

evaluate the performance of the instrument system with respect to a defined set of method 

criteria. (ORD) (ORCR)

Calibration Verification Standard (VER) – (1) The mid-point calibration standard that

is used to verify calibration. (OW/EAD) (OPP) (OAR/OAQPS) (ORCR) (2) A known, 
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standard solution, often from a source different from the calibration standards that is used 

to verify that a calibration is accurate. (OPP) (ORCR)

Continuing Calibration Check (CCC) (or Continuing Calibration Verification 

[CCV]) – (1) An analytical standard prepared from the same source as the calibration 

standards that is analyzed periodically prior to, during, and/or after analysis of samples to 

verify the continued accuracy of an instrument calibration. (ORD) (OW/EAD) (OPP)

(OW/TSC) (OAR/OAQPS) (OECA) (ORCR) (2) A calibration standard containing the 

method analytes and surrogate(s), which is analyzed periodically to verify the accuracy of 

the existing calibration for those analytes. (OW/TSC) (ORCR)

Dynamic Range – The range over which instrument response is used to produce 

analytical results. (ORD) (OW/EAD) (OPP) (OW/TSC) (OAR/OAQPS) (ORCR)

External Standard – A known amount of analyte that is analyzed separately from 

samples as part of a set of calibration standards. The response of the analyte in the 

sample is compared to the response of the analyte in the external standard for 

quantitation. (ORD) (OW/EAD) (OPP) (OW/TSC) (OAR/OAQPS) (ORCR)

Independent Calibration Verification (ICV) – An analytical standard used to verify 

calibration prior to analysis of samples. The ICV is obtained from a separate source than 

the calibration standards, but may be from a different lot from the same vendor. (ORD) 

(OW/EAD) (OPP) (ORCR)

Internal Standard (IS) – (1) A pure analyte (s) added to a sample, extract, or standard 

solution in known amount(s) and used to measure the relative responses of other method 

analytes and surrogates that are components of the same solution. The internal standard 

must be an analyte that is not a desired target analyte. (ORD) (OPP) (OECA) (ORCR) (2) 

A labeled compound used as a reference for quantitation of other labeled compounds and 

for quantitation of a native compound other than the compound of which it is a labeled 

analog. See Internal standard quantitation. (OW/EAD) (OW/TSC) (OAR/OAQPS)

(ORCR)

Internal Standard Quantitation – A means of determining the concentration of (1) a 

naturally occurring (native) compound by reference to a compound other than its labeled 

analog and (2) a labeled compound by reference to another labeled compound. 

(OW/EAD) (OPP) (OW/TSC) (ORCR) (3) A calibration method that uses a labeled 

version of a target analyte or compound that is chemically similar to the target analyte as 

a reference to measure the response of the target analyte over a range of concentrations. 

(ORD) (OAR/OAQPS) (ORCR)

Isotope Dilution – A technique for mass spectrometric quantitation of an analyte of 

interest in which a stable isotope-labeled compound is used as both a surrogate and an 

internal standard for a non-labeled compound. The stable isotope-labeled compound is 

added to the sample that then undergoes preparation and analysis. Losses of the analyte 

during preparation and interferences during analysis should be mirrored in the isotope-
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labeled compound, and thus should not have an adverse effect on quantitation. (ORD)

(OPP) (OAR/OAQPS) (OECA) (ORCR)

Isotope Dilution Quantitation – A means of determining a naturally occurring (native) 

compound by reference to the same compound in which one or more atoms has been 

isotopically enriched. In isotope dilution, labeled compounds are often spiked into each 

sample and allow identification and correction of the concentration of the native 

compounds in the analytical process. (OW/EAD) (OAR/OAQPS) (ORCR)

Labeled Injection Internal Standard – A labeled compound spiked into the 

concentrated extract immediately prior to injection of an aliquot of the extract into the 

LC/MS/MS. (OW/EAD) (OAR/OAQPS) (ORCR)

Quality Control Sample (QCS) or Quality Control Check Sample – (1) A sample 

prepared from method analytes that are obtained from a source external to the laboratory 

and different from the source of calibration standards. The QCS is used to check 

calibration standard integrity. (OW/TSC) (2) See Quality Term Section for an 

alternative definition. (ORD) (OECA) (ORCR) (3) A sample containing all or a subset of 

the analytes at known concentrations. The QCS is obtained from a source external to the 

laboratory or is prepared from a source of standards different from the source of 

calibration standards. It is used to check laboratory performance with test materials 

prepared external to the normal preparation process. (OW/EAD)

Second Source Calibration Standard – A standard obtained or prepared from a source 

independent of the source of standards for the initial calibration that is used to verify the 

correctness of a calibration. The second source standard is used to prepare the 

Independent Calibration Verification sample. (ORD)

DETECTION LIMIT TERMS

A-posteriori Detection – A binary detection decision based upon the observed (net) 

signal and a definite criterion of detection. It corresponds to the critical level, LC.

(OW/TSC)

A-priori Detection – An estimate, based on a knowledge of the probability distribution 

of a net signal, of the detection capabilities of a given measurement process. It 

corresponds to the detection limit, LD. (OW/TSC)

Detection – To have obtained experimental evidence that the analyte concentration is 

greater than zero. (ORD) (OW/EAD) (OPP) (ORCR)

Detection Limit (DL) – (1) See definition for Limit of Detection. (ORD) (OPP) (2) See 

Method Detection Limit. (OW/EAD) (OPP) (3) The minimum concentration of an 

analyte that can be identified, measured and reported with 99% confidence that the 

analyte concentration is greater than zero. This is a statistical determination of precision 

and accurate quantitation is not expected at this level. (OW/TSC) (OECA)
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Instrument Detection Limit (IDL) – The minimum quantity of analyte of the 

concentration equivalent that identifies an analyte signal equal to three times the standard 

deviation of the background signal at the selected wavelength, mass, retention time, or 

absorbance line, etc. (ORD) (ORCR)

LQ – See definition for Minimum Reporting Level. (ORD)

LQ Quantitation Definitions – Quantification Limit (LQ): The smallest detectable 

concentration of analyte greater than the detection limit where the required* accuracy 

(precision & bias) is achieved for the intended purpose. (OW/TSC) (ORCR)

Limit of Detection (LOD)/Limit of Quantification (LOQ) – The LOD and LOQ 

concentrations are calculated by applying the compound‟s calibration curve to the noise 

response of a sample to obtain a value which is then multiplied by a factor of 3 for LOD 

(3 times of noise) and 10 for LOQ (10 times of noise). The responses of the analytes are 

not considered in this approach. Only the noise level is included in the calculation. In 

some cases, the concentration of the lowest calibration standard is treated as the LOQ. 

The LOD is not defined in this case, although the LOD is often assumed to be 1/3 of the 

LOQ. The lowest possible LOD and LOQ values are not critical in these cases. The 

rationale of this approach is that the expected analyte concentrations in the samples are 

high and above the lowest calibration concentration and knowledge of the actual 

LOD/LOA is not necessary. (OPP)

Limit of Detection (LOD) = Detection Limit (DL) = Method Detection Limit (MDL)

– The minimum concentration of an analyte that can be identified, measured, and 

reported with 99% confidence that the analyte concentration is greater than zero. (ORD) 

(OPP) (OAR/OAQPS) (OECA)

Method Detection Limit – (1) The method detection limit (MDL) is defined as the 

minimum concentration of a substance that can be measured and reported with 99% 

confidence that the analyte concentration is greater than zero and is determined from 

analysis of a sample in a given matrix containing the analyte. The MDL is determined 

using the procedure at 40 CFR 136, Appendix B. (OW/EAD) (OPP) (2) See definition 

for Limit of Detection/Detection Limit/Method Detection Limits. (ORD) (OPP)

QUANTITATION LIMIT TERMS

Limit of Quantitation (LOQ) – See definition for Minimum Reporting Level. (ORD)

(ORCR)

Minimum Level (ML) – A minimum level at which the analytical system shall give 

recognizable mass spectra (background corrected) and acceptable calibration points. See 

40 CFR Part 136. (OW/EAD) (ORCR)
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Minimum Reporting Level (MRL) – The minimum concentration that can be reported 

as a quantitated value for a target analyte in a sample following analysis. This defined 

concentration can be no lower than the concentration of the lowest calibration standard 

for that analyte, and can only be used if acceptable quality control criteria for the analyte 

at this concentration are met. (ORD) (OW/EAD) (OPP) (OW/TSC) (ORCR)

Practical Quantitation Level (PQL) – The lowest concentration that can be reliably 

measured within specified limits of precision and accuracy for a specific laboratory 

analytical method during routine laboratory operating conditions. (OPP)

Quality Control Sample (QCS) – (1) A sample made from standards or matrix and used 

to verify acceptability of the results for an analytical batch. Examples of quality control 

samples are method blanks, laboratory duplicates, laboratory control samples, and matrix 

spikes. (ORD) (OECA) (ORCR) (2) See Quality Term Section for an alternative 

definition. (OW/EAD) (OW/TSC)

Quantitation versus Quantification – These are considered equivalent and can be used

interchangeably. Both are commonly used in the literature. (ORD) (OPP) (ORCR)

Reporting Limit – (1) The minimum value below which data are documented as nondetects. (OW/TSC) (OECA) (ORCR) (2) The minimum value of the calibration range. 

Analyte detections between the detection limit and the reporting limit are reported as 

having estimated concentrations. (ORD) (ORCR)

MISCELLANEOUS TERMS

Environmental Laboratory Advisory Board (ELAB) – A Federal Advisory 

Committee, with members appointed by EPA and composed of a balance of non-state, 

non-federal representatives, from the environmental laboratory community, and chaired 

by an ELAB member. (ORD) (OW/EAD) (OPP) (OAR/OAQPS) (ORCR)

National Environmental Laboratory Accreditation Conference (NELAC)* – A 

voluntary organization of State and Federal environmental officials and interest groups 

purposed primarily to establish mutually acceptable standards for accrediting 

environmental laboratories. (ORD) (OW/EAD) (OAR/OAQPS)

* Note: This organization was officially dissolved in January 2007, although some of the 

terminology and definitions established are still used today.

National Environmental Laboratory Accreditation Program (NELAP)* – The 

overall National Environmental Laboratory Accreditation Program of which NELAC is a 

part. (ORD) (OW/EAD) (OAR/OAQPS)

* Note: This program is now managed as part of The NELAC Institute (TNI), since 

NELAC was officially dissolved in January 2007, although some of the terminology and 

definitions established are still used today.
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QUALITY TERMS

Blank – A specimen that is intended to contain none of the analytes of interest and which 

is subjected to the usual analytical or measurement process to establish a zero baseline or 

background value. (OW/TSC) (OAR/OAQPS) (OECA) (ORCR) Different types of 

blanks include:

 Calibration Blank: (1) A sample of analyte-free media which is used to establish 

the low range of a calibration. (ORD) (OAR/OAQPS) (ORCR) (2) A volume of 

reagent water or other reference matrix containing none of the analytes above the 

method detection limits. The calibration blank is a zero standard and can be used 

along with prepared standards to calibrate the instrument. (OW/EAD) (ORCR)

 Equipment Blank: A sample of analyte-free media which has been used to rinse 

common sampling equipment to check effectiveness of decontamination 

procedures. (OW/EAD) (OPP) (OECA) (ORCR)

 Field Blank: (1) Blank prepared in the field by filling a clean container with pure 

de-ionized water and appropriate preservative, if any, for the specific sampling 

activity being undertaken. (ORD) (OPP) (OSWER) (OAR/OAQPS) (OECA)

(ORCR) (2) An aliquot of reagent water or other reference matrix that is placed in 

a sample container in the field, and treated as a sample in all respects, including 

exposure to sampling site conditions, storage, preservation, and all analytical 

procedures. The purpose of the field blank is to determine if the field or sample 

transporting procedures and environments have contaminated the sample. 

(OW/EAD) (ORCR)

 Instrument Blank: (1) A clean sample (e.g., distilled water) processed through 

the instrumental steps of the measurement process; used to determine instrument 

contamination. (ORD) (OECA) (2) See Method Blank. (OW/EAD) (ORCR)

 Laboratory Blank: See Method Blank. (ORD) (OW/EAD)

 Laboratory Reagent Blank: See Method Bland. (ORD) (OW/EAD)

 Method Blank: (1) 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) (2) 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) (3) For aqueous analysis, an unspiked or non-fortified reagent water 

sample which proceeds through the entire testing method, including all

preparatory and determinative steps. (ORCR)

 Preparation Blank: See Method Blank. (OW/EAD)

 Reagent Blank (or Method Reagent Blank): (1) A sample consisting of 

reagent(s), without the target analyte or sample matrix, introduced into the 

analytical procedure at the appropriate point and carried through all subsequent 
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steps to determine the contribution of the reagents and of the involved analytical 

steps. (2) A sample consisting of reagent(s), without the target analyte or sample 

matrix, introduced into the analytical procedure at the appropriate point and 

carried through all subsequent steps to determine the contribution of the reagents 

and of the involved analytical steps to error in the observed value. (OPP)

(OAR/OAQPS) (3) See Method Blank. (OW/EAD)

Data Quality Indicators (DQIs) – The quantitative statistics and qualitative descriptors 

that are used to interpret the degree of acceptability or utility of data to the user. The 

principal indicators of data quality are precision, bias, accuracy, representativeness, 

comparability, completeness, and sensitivity. (OW/EAD)

Data Quality Objectives – Qualitative and quantitative statements derived from the 

DQO Planning Process that clarify the purpose of the study, define the most appropriate 

type of information to collect, determine the most appropriate conditions from which to 

collect that information, and specify tolerable levels of potential decision errors. (ORD)

(OW/EAD) (OPP) (OAR/OAQPS) (ORCR)

Graded Approach – (1) The process of basing the level of application of managerial 

controls applied to an item or work according to the intended use of the results and the 

degree of confidence needed in the quality of the results. (OW/EAD) (2) Because of the 

diversity of work conducted through procurements and assistance agreements, EPA 

recognizes that a “one size fits all” approach to quality specifications will not work. 

Therefore, the implementation of the EPA Quality System is based on a graded approach 

to indicate that quality systems for different organizations and programs will vary 

according to the specific objectives and needs of the organization. (OPP) (OAR/OAQPS)

(ORCR)

Initial Precision and Recovery (IPR) (or Initial Demonstration of Proficiency [IDP]

or Initial Demonstration of Capability [IDC]) – Four aliquots of a reference matrix 

spiked with all the analytes of interest and labeled compounds and analyzed to establish 

the ability of the laboratory to generate acceptable precision and recovery. An IPR is 

performed prior to the first time a given method is used and any time the method or 

instrumentation is modified. (ORD) (OW/EAD) (ORCR)

Instrument Performance Check (IPC) – (1) A quality control sample, which may be a 

blank or fortified with analyte that is used to verify instrument performance and 

calibration. (ORD) (OECA) (2) See Ongoing Precision and Recovery Standard (OPR). 

(OW/EAD)

Laboratory Control Sample – (1) A sample matrix, free from the analytes of interest, 

spiked with verified known amounts of analytes or a material containing known and 

verified amounts of analytes from the same source as the calibration standards. It is 

generally used to establish intra-laboratory or analyst specific precision and bias or to 

assess the performance of all or a portion of the measurement system. (ORD) (OPP)

(ORCR) (2) See Ongoing Precision and Recovery Standard (OPR). (OW/EAD)
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Laboratory Duplicate – The analysis or measurements of the variable of interest 

performed identically on two sub-samples of the same sample, usually taken from the 

same container. The results from duplicate analyses are used to evaluate analytical or 

measurement precision and include variability associated with sub-sampling and the 

matrix, but not the precision of field sampling, preservation, or storage internal to the 

laboratory. (ORD) (OW/EAD) (OPP) (OW/TSC) (ORCR)

Laboratory Fortified Blank – See Laboratory Control Sample. (ORD) (OW/EAD)

(OW/TSC) (ORCR)

Laboratory Fortified Sample Matrix – See Matrix Spike. (ORD) (OW/EAD)

(OW/TSC) (ORCR)

Measurement Quality Objectives – Qualitative and quantitative statements of the 

overall level of uncertainty that a decision maker is willing to accept in results or 

decisions derived from measurements. MQOs/DQOs provide the statistical framework 

for planning and managing measurement plans consistent with the data user‟s needs.

(ORD) (OW/EAD) (OPP) (OW/TSC) (OAR/OAQPS) (ORCR)

Ongoing Precision and Recovery Standard (OPR) – A method blank spiked with 

known quantities of analytes. Its purpose is to assure that the results produced by the 

laboratory remain within the limits specified in this method for precision and recovery. 

Also, referred to as a Laboratory Fortified Blank (LFB), Spiked Blank, or Laboratory 

Control Sample (LCS). (OW/EAD)

Performance Based Measurement System (PBMS) – A set of processes wherein the 

data quality needs, mandates, or limitations of a program or project are specified, and 

serve as criteria for selecting appropriate methods to meet those needs in a cost-effective 

manner. (ORD) (OPP) (OAR/OAQPS) (ORCR)

Quality Assurance – An integrated system of management activities involving planning, 

implementation, documentation, assessment, reporting, and quality improvement to 

ensure that a process, item, or service is of the type and quality needed and expected by 

the client. (OW/EAD) (OPP) (OW/TSC) (OAR/OAQPS) (OECA) (ORCR)

Quality Assurance Audits – (1) Each project will be audited by a panel chaired by the 

Quality Assurance Officer or Coordinator and consisting of a Team Leader, the 

chemist(s) who worked on the project, and one chemist not associated with the project. 

(OPP) (2) A systematic and independent examination to determine whether quality 

activities and related results comply with planned arrangements and whether these 

arrangements are implemented effectively and are suitable to achieve objectives. 

(OW/EAD)

Quality Assurance Project Plan (QAPP) – A formal document describing in 

comprehensive detail the necessary quality assurance, quality control, and other technical 
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activities that should be implemented to ensure that the results of the work performed will 

satisfy the stated performance criteria. (ORD) (OW/EAD) (OPP) (OW/TSC)

(OAR/OAQPS) (OECA) (ORCR)

Quality Control – (1) The overall system of technical activities whose purpose is to 

measure and control the quality of a product or service so that it meets the needs of users. 

(ORD) (OPP) (OW/TSC) (OAR/OAQPS) (OECA) (ORCR) (2) The overall system of 

technical activities that measures the attributes and performance of a process, item, or 

service against defined standards to verify that they meet the stated requirements 

established by the customer; operational techniques and activities that are used to fulfill 

requirements for quality. (OW/EAD) COMMENT: Took this from the EPA quality 

manual.

Quality Control Check Sample (QCS) – A sample containing all or a subset of the 

analytes at known concentrations. The QCS is obtained from a source external to the 

laboratory or is prepared from a source of standards different from the source of 

calibration standards. It is used to check laboratory performance with test materials 

prepared external to the normal preparation process. (OW/EAD) (OW/TSC)

Quality Control Sample – (1) An uncontaminated sample matrix spiked with known 

amounts of analytes from a source independent from the calibration standards. It is 

generally used to establish intra-laboratory or analyst specific precision and bias or to 

assess the performance of all or a portion of the measurement system. This does not 

include matrix spikes or laboratory duplicates, which are also QC samples. (OW/EAD) 

(2) A solution of method analytes of known concentrations that is used to fortify an 

aliquot of Laboratory Reagent Blank (LRB) or sample matrix. The QCS is obtained 

from a source external to the laboratory is different from the source of calibration 

standards. It is used to check laboratory performance with externally prepared test 

materials. This is a Performance Evaluation Sample in other arenas. (ORD)

Spiked Blank – See Laboratory Control Sample or OPR. (OW/EAD)

Standard Operating Procedures (SOPs) – (1) A written document outlining an 

analytical method which provides a level of detail intended to allow advanced analysts or 

analysts familiar with the method outlined in the SOP to perform that analytical method. 

(OW/EAD) (OPP) (OW/TSC) (OAR/OAQPS) (OECA) (ORCR) (2) A written document 

which details the method of an operation, analysis or action whose techniques and 

procedures are thoroughly prescribed and which is accepted as the method for performing 

certain routine or repetitive tasks. (ORCR)

Note: ORD uses the term Operating Procedures (OPs) to describe written procedures 

used by a laboratory and SOPs to describe documents of procedures that are performed 

in the same exact manner by multiple laboratories. (ORD)

Systematic Planning – (1) EPA uses systematic planning to plan projects and link goals, 

cost and schedule, and quality criteria with the final outputs. Systematic planning 

ensures that all participants understand the needs and expectations of the customer and 
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the product or results to be provided by the supplier. (ORD) (OPP) (OAR/OAQPS)

(ORCR) (2) A planning process that is based on the scientific method and is based on a 

common sense, graded approach to ensure that the level of detail in planning is 

commensurate with the importance and intended use of the work and the available 

resources. A systematic planning process is performed to ensure that all organizations 

and/or parties who contribute to the quality of the environmental program or use the 

results are identified and that they participate in this process. The systematic planning 

process also provides for direct communication between the customer and the supplier to 

ensure that there is a clear understanding by all participants of the needs and expectations 

of the customer and the product or results to be provided by the supplier. (OW/EAD)

Technical Systems Audit – (1) A thorough, systematic, on-site, qualitative audit of 

facilities, equipment, personnel, training, procedures, record keeping, data validation, 

data management, and reporting aspects of a system. (ORD) (2) A technical audit or 

assessment is a systematic and objective examination of a program or project to 

determine whether environmental data collection activities and related results comply 

with the project‟s quality assurance project plan and other planning documents, are 

implemented effectively, and are suitable to achieve its data quality goals. (OPP) 

(OAR/OAQPS) (ORCR) (3) A thorough, systematic, on-site, qualitative audit of 

facilities, equipment, personnel, training, procedures, record keeping, data validation, 

data management, and reporting aspects of program or project to determine whether 

environmental data collection activities and related results comply with the project‟s 

quality assurance project plan and other planning documents, are implemented 

effectively, and are suitable to achieve its data quality goals. (OW/EAD)

STATISTICAL TERMS

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, which are due to sampling and analytical operations; 

a data quality indicator. (ORD) (OW/EAD) (OPP) (OW/TSC) (OAR/OAQPS) (OECA)

(ORCR)

Alpha, (α) (or False Rejection) – The tolerated probability of a “false positive” (i.e.,

Type I error). See False Positive. (ORD) (OW/EAD) (OPP) (OW/TSC) (OAR/OAQPS)

Beta, (β) (or False Acceptance) – The tolerated probability of a “false negative” (i.e.,

Type II error). See False Negative. (ORD) (OW/EAD) (OPP) (OW/TSC)

(OAR/OAQPS)

Bias – The constant or systematic distortion of a measurement process, different from 

random error, which manifests itself as a persistent positive or negative deviation from 

the known or true value. This can result from improper data collection, poorly calibrated 

analytical or sampling equipment, or limitations or errors in analytical methods and 

techniques. (ORD) (OW/EAD) (OPP) (OW/TSC) (OAR/OAQPS) (OECA) (ORCR)
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Degrees of Freedom – The total number of items in a sample minus the number of 

independent relationships existing among them; the divisor used to calculate a variance 

term; in the simplest cases, it is one less than the number of observations. (ORD)

(OW/EAD) (OPP) (OW/TSC) (OAR/OAQPS) (OECA) (ORCR) General explanation: 

Degrees of freedom refers to how many variables in a single system are free to vary 

independently. Degrees of freedom may by none (0) or many. A single variable 

algebraic equation has no degrees of freedom. This is because there is only 1 right 

answer for the system described by the equation. For example, for the equation, x + 3 = 

4, x is 1. x cannot be anything else. For a 2 variable equation, there is one degree of 

freedom. One variable is “free” to be anything, but once the value for one variable is 

selected, the value for the second one is fixed. For example, for the equation, x + y + 3 = 

8, x is free to vary. The chosen value of x might be 1 or 7 or 1.25 or -2-. But, as soon as 

the value for x is chosen, the equation becomes a single variable equation, and the value 

for y is fixed. If 3 is the value chosen for x, then y must equal 2.

False Negative – (general definition) An analysis determines the absence of an analyte 

when it is actually present at or above a given concentration or limit. (statistical 

definition) An error of the second kind (type II error), which means failing to reject the 

null hypothesis when it is actually false. (ORD) (OW/EAD) (OPP) (OW/TSC)

(OAR/OAQPS) (ORCR)

False Positive – (general definition) An analysis determines the presence of an analyte 

when it is actually absent at a given concentration or limit. (statistical definition) An error 

of the first kind (type I error), which means rejecting the null hypothesis when it is 

actually true. (ORD) (OW/EAD) (OPP) (OW/TSC) (OAR/OAQPS) (ORCR)

Hypothesis Test – A statistical procedure for determining if a sample provides sufficient 

evidence to reject or accept one statement regarding the population of interest in favor of 

an alternative statement. (ORD) (OW/EAD) (OPP) (OW/TSC) (OAR/OAQPS) (ORCR)

LC DETECTION – LAYPERSON'S DEFINITIONS -

1. Critical Value (LC) - The minimum result which can be reliably discriminated from a 

blank (for example, with a 99% confidence level). (OAR/OAQPS)

2. Critical Value (LC) – The lowest result that can be distinguished from the blank at a 

chosen level, α, of statistical confidence. (OW/EAD) (OW/TSC)

LD DETECTION – LAYPERSON'S DEFINITIONS -

1. Detection Limit (LD) - The lowest true concentration that will almost always be 

detected. 

2. Detection Limit (LD) - The minimum detectable value is smallest amount or 

concentration of a particular substance in a sample that can be reliably detected by a 

specific measurement process. (OAR/OAQPS)

3. Detection Limit (LD) - The minimum true concentration that will return a result above 

the critical value given a specific measurement process and confidence level. (OW/EAD)

(OW/TSC) (OAR/OAQPS)
12

LC DETECTION - STATISTICAL DEFINITIONS -

1. Critical Value (LC) - Smallest measured amount or concentration of analyte in a 

sample that gives rise to a Type I error tolerance of alpha under the null hypothesis that 

the true amount or concentration of analyte in the sample is equal to that of a blank. (The 

alternative hypothesis is that the true amount or concentration of analyte is greater than 

that of a blank.) (OW/TSC)

2. Critical Value (LC) - The minimum observed result such that the lower 100 (1-α)% 

confidence limit on the result is greater than the mean of the method blanks. 

LD DETECTION - STATISTICAL DEFINITIONS -

1. The Minimum Detectable Value (LD) - Once LC is established, LD is the smallest

concentration or amount of analyte at which the tolerance for Type II error is equal to 

beta. 

2. The Minimum Detectable Value (Ld) - The lowest true concentration such that the 

frequency that the result is greater than LC will be 100% (1-β). (OW/TSC)

Median – The middle number or center value of a set of data in which all the data are 

arranged in sequence. (ORD) (OW/EAD) (OPP) (OW/TSC) (OAR/OAQPS) (OECA)

(ORCR)

Outlier – An observation that is shown to have a low probability of belonging to a 

specified data population; any item rejected by the sampler, analyst, or data reviewer, 

usually accompanied by an attendant explanation. (ORD) (OW/EAD) (OPP) (OW/TSC)

(OAR/OAQPS) (OECA) (ORCR)

Percent Relative Standard Deviation (%RSD) – The standard deviation expressed as a 

percentage of the mean (i.e., the coefficient of variation). Mathematically, it is the 

standard deviation divided by the mean times one hundred percent. (ORD) (OW/EAD) 

(OPP) (OW/TSC) (OAR/OAQPS) (OECA) (ORCR)

Precision – The consistency of measurement values quantified by measures of dispersion 

such as the sample standard deviation. Precision must be defined in context – e.g., for a 

certain analyte, matrix, method, perhaps concentration, lab or group of labs. (ORD)

(OW/EAD) (OPP) (OW/TSC) (OAR/OAQPS) (OECA) (ORCR)

Range – The difference between the minimum and the maximum of a set of values.

(ORD) (OW/EAD) (OPP) (OW/TSC) (OAR/OAQPS) (OECA) (ORCR)

Type I Error – See Alpha and False Positive. (ORD) (OW/EAD) (OPP) (OW/TSC)

(OAR/OAQPS) (ORCR)

Type II Error – See Beta and False Negative. (ORD) (OW/EAD) (OPP) (OW/TSC)

(OAR/OAQPS) (ORCR)

Uncertainty – (1) The range of values that contains the true value of what is being 

evaluated at some level of confidence. (OW/EAD) (OPP) (OAR/OAQPS) (2) A measure 

of the total variability associated with sampling and measuring that includes the two 
13

major error components: systematic error (bias) and random error. (ORD) (OECA)

(ORCR)

Uncertainty, Expanded – Quantity defining an interval about the result of a 

measurement that may be expected to encompass a large fraction of the distribution of 

values that could reasonably be attributed to the measurement. (OAR/ORIA/NAREL)

Uncertainty of Measurement – A parameter associated with the result of a measurement 

that characterizes the dispersion of the values that could reasonably be attributed to the

measurement. (OW/EAD) (OECA) (ORCR)

GENERAL ANALYTICAL METHOD DEFINITIONS

Analyst – Any individual who performs analytical methods and associated procedures 

and who is the one responsible for applying required laboratory practices and other 

pertinent quality controls to meet the required level of quality. (ORD) (OW/EAD) (OPP)

(OAR/OAQPS) (OECA) (ORCR)

Analytical Batch – (1) Environmental samples that are prepared and/or analyzed 

together with the same process and personnel and using the same lot(s) of reagents. 

(OW/EAD) (OPP) (2) A group of samples, including quality control samples, which are 

processed together using the same method, the same lots of reagents, and at the same 

time or in continuous, sequential time periods. Samples in each batch should be of 

similar composition and share common internal quality control standards. (ORD)

(ORCR)

Analytical Response – A numerical observation whose magnitude is related to the 

amount or concentration of the analyte in a sample. One or more analytical responses (as 

specified by a method) are used, in conjunction with a calibration curve or factor), to 

produce an analytical result. (ORD) (OW/EAD) (OAR/OAQPS) (ORCR)

Analytical Result – (1) A formal numerical estimate of the concentration of an analyte in 

a sample, which is obtained by carrying out once following the procedure specified in an 

analytical method. Note that a method may specify analysis of more than one portion of 

a sample in order to produce one analytical result. (OW/EAD) (2) A formal numerical 

estimate of the concentration of an analyte in a sample obtained by following the 

procedure specified in an analytical method. Note that a method may specify analysis of 

more than one portion of a sample in order to produce one analytical result. (ORD)

(ORCR)

Audit – A systematic evaluation to determine the conformance to quantitative and 

qualitative specifications of some operational function, activity, or quality assurance 

panel. (ORD) (OW/EAD) (OPP) (OAR/OAQPS) (ORCR)

Blind Sample – A sub-sample for analysis with a composition known to the submitter. 

The analyst/laboratory may know the identity of the sample but not its composition. It is 
14

used to test the analyst‟s or laboratory‟s proficiency in the execution of the measurement 

process. (ORD) (OW/EAD) (OPP) (ORCR) Different types of blind samples include:

 Single Blind: (1) A sample submitted to evaluate performance with concentration 

and identity unknown to the analyst. (OW/EAD) (ORCR) (2) A blind sample in 

which the concentration is unknown to the analyst, but is known to the provider. 

(OPP)

 Double Blind: (1) A sample submitted to evaluate performance with 

concentration and identity unknown to the analyst and laboratory. (ORD)

(OW/EAD) (ORCR) (2) A blind sample in which the concentration is unknown to 

the analyst and the provider; acceptance limits are generally calculated from 

results received from double blind samples. (OPP)

Holding Times (or Maximum Allowable Holding Times) – (1) The maximum times 

that samples may be held, after the sample is taken, prior to analysis and still be 

considered valid or not compromised. (OW/EAD) (OPP) (OW/TSC) (OAR/OAQPS)

(ORCR) (2) The maximum times that samples may be held, after the sample is taken 

prior to preparation and/or analysis and still be considered valid or not compromised.

(ORD) (ORCR)

Incurred Compound – A compound that is present in a sample without addition by the 

laboratory. The compound may be essentially alien, but has been introduced to the bulk 

material at some point prior to the material being sampled. Recovery of added (e.g., 

spiked or fortified) compound may be different from incurred compound. (OPP)

Inter-laboratory Procedure Study – (1) A study where a centralized study design 

coordinator sends identical samples to multiple different laboratories for analysis. The 

resulting raw data are analyzed by the study design coordinator by a given procedure to 

provide estimates inter-laboratory accuracy, precision, and/or detection limits. 

(OW/EAD) (OPP) (OAR/OAQPS) (ORCR) (2) An inter-laboratory method validation 

study is a practical testing of the written method on identical materials, usually derived 

from split samples, by a number of laboratories. The study is not intended to evaluate 

laboratories; it is intended to evaluate method reproducibility among laboratories. 

Deviations from the inter-laboratory study protocol should be strongly discouraged, and 

any deviations that occur should be documented. Participating in Inter-laboratory 

Comparison Studies/Programs can be either existing Proficiency Evaluation Programs or 

Round Robin Studies or a combination of programs and studies to assure evaluation of all 

laboratory operations.

Inter-laboratory Test Comparison – Organization, performance and evaluation of tests 

on the same or similar items or materials by two or more laboratories in accordance with 

predetermined conditions. (OPP) (ORCR)

Labeled Compound – (1) A molecule in which one or more of the atoms is isotopically 

enriched, thereby increasing the mass of the molecule. (OW/EAD) (OAR/OAQPS)

(ORCR) (2) A molecule in which one or more of the atoms is isotopically enriched, 

thereby increasing the mass of the molecule. (ORD) (ORCR)
15

Linear Dynamic Range – The concentration range over which instrument response is 

linear. (ORD) (OW/EAD) (OPP) (OW/TSC) (OAR/OAQPS) (OECA) (ORCR)

Matrix – The material of which the sample is composed or the substrate containing the 

analyte of interest, such as waste water, storm water, and biosolids. Also called medium 

or media. (ORD) (OW/EAD) (OPP) (OW/TSC) (OAR/OAQPS) (OECA) (ORCR)

Matrix Effects – Manifestations of non-target analytes or physical/ chemical 

characteristics of a sample that prevents the quantification of the target analyte (i.e., the 

compound or element of interest being effectively quantified by the test method) as it is 

routinely performed, typically adversely impacting the reliability of the determination. 

For example, a matrix effect can give rise to a high or low bias. (ORD) (OW/EAD)

(OW/TSC) (OAR/OAQPS) (OECA) (ORCR)

Matrix Spike (Spiked Sample or Fortified Sample) – A sample prepared by adding a 

known mass of target analyte to a specified amount of matrix sample for which an 

independent estimate of target analyte concentration is available. Matrix spikes are used, 

for example, to determine the effect of the matrix on a method's recovery efficiency.

(ORD) (OW/EAD) (OPP) (OAR/OAQPS) (ORCR)

Matrix Spike (MS) and Matrix Spike Duplicate (MSD) – Two aliquots of the same 

environmental sample to which known quantities of the target analytes are added in the 

laboratory. The MS and MSD are analyzed exactly like a sample, and their purpose is: 

to determine whether the sample matrix contributes bias to the analytical results, and to 

indicate precision associated with laboratory procedures. The background concentrations 

of the analytes in the sample matrix must be determined in a separate aliquot and the 

measured values in the MS and MSD corrected for background concentrations. (ORD)

(OW/EAD) (OPP) (OW/TSC) (OECA) (ORCR)

Maximum Contaminant Level (MCL) – This is a contaminant-specific standard for 

acceptable drinking water under SDWA. MCLs also may be used for purposes of RCRA 

(Resource Conservation and Recovery Act) ground water monitoring to reach 

contaminant-specific clean-up levels. (OW/EAD) (OW/TSC) (ORCR)

Method – (1) See Test Method. (2) Logical sequence of operations, described 

generically, used in the performance of measurements. (ORD) (OW/EAD)

(OAR/OAQPS) (ORCR)

Censored Method – Analytical methods that frequently produce non-numerical 

results for blanks (i.e., ND for „non-detect‟). These nonnumeric values are not 

due to censoring of data. (OW/EAD)

Uncensored Method – Analytical methods that nearly always produce numerical 

values that meet qualitative identification criteria for method blanks. (OW/EAD)

Multi-laboratory Procedure Study – A study where multiple laboratories individually

perform estimates of accuracy, precision, and/or detection limits and those individual 
16

estimates are summarized in some fashion (e.g. averaging, upper or lower confidence 

intervals) to characterize some measure of how well the analytical method performs in

qualified laboratories. (OW/EAD) (OAR/OAQPS) (ORCR)

Native Compound – (1) A molecule in which the atoms all have naturally occurring 

isotopic abundances. (OW/EAD) (OPP) (2) A compound that is present in a sample 

without addition by the laboratory. (ORD) (OAR/OAQPS) (ORCR)

Protocol – A detailed written procedure for field and/or laboratory operation (e.g., 

sampling, analysis), which must be strictly followed. (OAR/OAQPS)

Reagent Water – Water demonstrated to be free from the analytes of interest and 

potentially interfering substances at the method detection limit for the analyte. 

(OW/EAD) (OPP) (OW/TSC) (OAR/OAQPS) (OECA) (ORCR)

Recovery – The degree to which a methodology measures all of the analyte contained in 

a sample, often expressed in percent recovered. (ORD) (OW/EAD) (OW/TSC)

(OAR/OAQPS) (OECA) (ORCR)

Recovery Efficiency – The fraction or percentage of a target analyte measured in a 

sample to which a known amount of the analyte has been added. (ORD) (OPP)

(OAR/OAQPS) (ORCR)

Reference Material – A material or substance, one or more properties of which are 

sufficiently well established to be used for the calibration of an apparatus, the assessment 

of a measurement method, or assigning values to materials. (ORD) (OW/EAD) (OECA)

(ORCR)

Replicate Analyses – The measurements of the variable of interest performed identically 

on two or more sub-samples of the same sample within a short time interval. (ORD)

(OW/EAD) (OPP) (OAR/OAQPS) (OECA) (ORCR)

Sample – A part of a larger whole or a single item of a group; a finite subset of a 

statistical population. A representative sample serves to provide data or information 

concerning the properties of the whole group or population. (OW/EAD) (OPP)

(OAR/OAQPS) (ORCR)

Sensitivity – (1) Sensitivity generally refers to the capability of a method or instrument to 

discriminate between small differences in analyte concentration. (OPP) (OAR/OAQPS)

(ORCR) (2) A qualitative description of an instrument‟s or analytical method‟s detection 

limit. (ORD)

Signal-to-Noise Ratio (S/N) – The height of the signal as measured from the mean 

(average) of the noise to the peak maximum divided by the amplitude of the noise. 

(ORD) (OW/EAD) (OPP) (OW/TSC) (ORCR)
17

Spike – (1) A known quantity of an analyte added to a sample for the purpose of 

determining recovery or efficiency (analyst spikes), or for quality control (blind spikes).

(OW/EAD) (OPP) (OAR/OAQPS) (ORCR) (2) A known quantity of an analyte added to 

a sample for the purpose of determining recovery or efficiency. (ORD) (OECA)

Standard Addition – The addition of a known amount of analyte to the sample in order 

to determine the relative response of the detector to an analyte within the sample matrix. 

The relative response is then used to assess either an operative matrix effect or the sample 

analyte concentration. (ORD) (OW/EAD) (OPP) (OAR/OAQPS) (ORCR)

Standard Deviation – A computed measure of variability indicating the spread of the 

data set around the mean. (ORD) (OPP) (OW/TSC) (OAR/OAQPS) (OECA) (ORCR)

Standard Uncertainty – Uncertainty of the result of a measurement expressed as a 

standard deviation. (ORD) (OW/EAD) (OPP) (ORCR)

Stock Solution – A solution containing an analyte that is prepared using a reference 

material traceable to EPA, the National Institute of Science and Technology (NIST), or a 

source that will attest to the purity and authenticity of the reference material. (ORD)

(OW/EAD) (OPP) (OAR/OAQPS) (ORCR)

Surrogate Standard – A non-target analyte that has similar chemical properties to the 

analyte of interest. The surrogate standard is added to the sample in a known amount and 

used to evaluate the response of the analyte to preparation and analysis procedures.

(ORD) (OW/EAD) (OPP) (OW/TSC) (OAR/OAQPS) (OECA) (ORCR)

Test Method – An adoption of a scientific technique for a specific measurement 

problem, as documented in a laboratory SOP or published by a recognized authority.

(OW/EAD) (OPP) (OAR/OAQPS) (ORCR)

Variability During Routine Operations – Changes during the routine running of 

samples that might contribute to variability of results. This might include instrument drift 

through the course of the day due to changes in the ion source (such as contamination 

from running samples), differences in performance of instruments used for the same 

analysis, difference in technique for different analysts, etc. (OW/EAD) (ORCR)
18

APPENDIX – ACRONYMS

Acronyms Acronym Expansion Glossary Subject

ASQ American Society for Quality Offices, Programs, and References

ASTM American Society for Testing Materials Offices, Programs, and References

BEAD Biological and Economic Analysis Division Offices, Programs, and References

CAL Calibration Standard Calibration

CCC Continuing Calibration Check Calibration

CCV Continuing Calibration Verification Calibration

CFR Code of Federal Regulations Miscellaneous

CV Calibration Verification Calibration

CWA Clean Water Act Miscellaneous

DL Detection Limit Detection and Quantitation Limit

DQO Data Quality Objective Quality Control

EDL Estimated Detection Limit Detection and Quantitation Limit*

ELAB Environmental Laboratory Advisory Board Offices, Programs, and References

EPA Environmental Protection Agency Offices, Programs, and References

eRLN Environmental Response Laboratory Network Offices, Programs, and References

FACA Federal Advisory Committee Act Miscellaneous

FEM Forum on Environmental Measurements Offices, Programs, and References

FNQS False Negative Quality Control Sample Quality Control

ICV Initial (or Independent) Calibration Verification Calibration

IDL Instrument Detection Limit Detection and Quantitation Limit

IDP Initial Demonstration of Proficiency Quality Control

IPC Instrument Performance Check Quality Control

IPR Initial Precision and Recovery Quality Control

IR Interregional Research Project Miscellaneous

IS Internal Standard General Analytical Method

ISO International Standards Organization Miscellaneous

IUPAC International Union of Pure and Applied Chemistry Offices, Programs, and References

LC Critical Level Statistical

LC Laboratory Control Sample Quality Control

LC Liquid Chromatography General Analytical Method

LCMRL Lowest Concentration Minimum Reporting Level Detection and Quantitation Limit

LCS Laboratory Control Sample Quality Control

LD Detection Limit Detection and Quantitation Limit

Ld Minimum Detectable Value Statistical

LD Minimum Detectable Value Statistical

LFB Laboratory Fortified Blank Quality Control

LFSM Laboratory Fortified Sample Matrix (a.k.a. MS) Quality Control

LFSMD Laboratory Fortified Sample Matrix Duplicate (a.k.a. MSD) Quality Control

LLOQ Lower Level of Quantitation Detection and Quantitation Limit

LOA Limit of Analysis Detection and Quantitation Limit

LOD Limit of Detection Detection and Quantitation Limit

LOQ Limit of Quantitation Detection and Quantitation Limit

LQ Quantification Limit Detection and Quantitation Limit

LQ Quantification Limit Detection and Quantitation Limit

LRB Laboratory Reagent Blank Quality Control

MCL Maximum Contaminant Level General Analytical Method
19

MDL Method Detection Limit Detection and Quantitation Limit

ML Minimum Level of Quantitation Detection and Quantitation Limit

MQL Method Quantitation Limit Detection and Quantitation Limit

MQO Method (or Measurement) Quality Objective Quality Control

MRL Minimum Reporting Limit Detection and Quantitation Limit

MS Mass Spectrometry General Analytical Method

MS Matrix Spike Sample General Analytical Method

MSD Matrix Spike Duplicate Sample General Analytical Method

ND Non-Detect General Analytical Method

NEIC National Enforcement Investigations Center Offices, Programs, and References

NELAC National Environmental Laboratory Accreditation Conference Offices, Programs, and References*

NELAP National Environmental Laboratory Accreditation Program Offices, Programs, and References*

NERL National Exposure Research Laboratory Offices, Programs, and References

NHEERL National Health and Environmental Effects Research Laboratory Offices, Programs, and References

NIST National Institute of Standards and Testing Offices, Programs, and References

OAQPS Office of Air Quality Planning and Standards Offices, Programs, and References

OAR Office of Indoor Air and Radiation Offices, Programs, and References

OCDL Organic Carbon Detection Limit Miscellaneous

OECA Office of Enforcement and Compliance Assurance Offices, Programs, and References

OECD Organization for Economic Cooperation and Development Offices, Programs, and References

OEM Office of Emergency Management Offices, Programs, and References

OP Operating Plan Quality Control

OPP Office of Pesticide Programs Offices, Programs, and References

OPPTS Office of Prevention, Pesticides, and Toxic Substances Offices, Programs, and References

OPR Ongoing Precision and Recovery Quality Control

ORCR Office of Resource Conservation and Recovery Offices, Programs, and References

ORD Office of Research and Development Offices, Programs, and References

OSWER Office of Solid Waste and Emergency Response Offices, Programs, and References

OW/EAD Office of Water/Engineering and Analysis Division Offices, Programs, and References

OW/TSC Office of Water/Technical Support Center Offices, Programs, and References

PBMS Performance Based Measurement System Quality Control

PDL Practical Detection Limit Detection and Quantitation Limit

PDP Pesticide Data Program Offices, Programs, and References

PE Performance Evaluation Quality Control

PLD Practical Limit of Detection Detection and Quantitation Limit

PLQ Practical Limit of Quantitation Detection and Quantitation Limit

PQL Practical Quantitation Limit Detection and Quantitation Limit

QA Quality Assurance Quality Control

QAD Quality Assurance Division Offices, Programs, and References

QAMS Quality Assurance Management Section Offices, Programs, and References

QAPP Quality Assurance Project Plan Quality Control

QC Quality Control Quality Control

QCS Quality Control Sample Calibration

QCS Quality Control Check Sample Calibration

QL Quantitation Limit Detection and Quantitation Limit

RCRA Resource Conservation and Recovery Act Miscellaneous

RF Response Factor Calibration

RSD Relative Standard Deviation Statistical

SDWA Safe Drinking Water Act Miscellaneous

SICP Selected Ion Current Profile General Analytical Method
20

S/N Signal-to-Noise Ratio General Analytical Method

SO Standard Deviation Statistical

SOP Standard Operating Procedure Quality Control

SW Solid Waste Miscellaneous

TNI The NELAC Institute Offices, Programs, and References

UCMR Unregulated Contaminant Monitoring Rule Offices, Programs, and References

USDA United States Department of Agriculture Offices, Programs, and References

USGS United States Geological Survey Offices, Programs, and References

VER Calibration Verification Standard Calibration

VIM International Vocabulary of Basic and General Terms in Meteorology Offices, Programs, and References

Webster's Webster's Dictionary Offices, Programs, and References

WQBEL Water Quality Based Effluent Limit Miscellaneous

*Acronym also listed in the Miscellaneous section of the glossary.
21

APPENDIX – REFERENCES 

1. 2003 NELAC Standard. EPA/600/R-04/003, June 5, 2003.

2. American Society of Testing and Materials (ASTM). 

http://www.astm.org/index.shtml. 

3. American Society for Quality (ASQ). http://www.asq.org/info/glossary/a.html. 

4. Code of Federal Regulations. 40 CFR, Part 136.

5. Compendium of Analytical Nomenclature, 3rd Edition; International Union of Pure 

and Applied Chemistry (IUPAC); 

http://www.iupac.org/publications/analytical_compendium/, 1997.

6. Currie, Lloyd A. Limits for Qualitative Detection and Quantitative Determination. 

Analytical Chemistry. 1968, 586-593.

7. Federal Register Notice. Performance Based Measurement System; Notice of 

Intent. October 6, 1997, 62 FR 52098.

8. Hunt, D.T.E.; Wilson, A.L. The Chemical Analysis of Water, 2nd Edition; The 

Royal Society of Chemistry, Burlington House: London, England, 1986.

9. National Institute of Standards and Technology (NIST). http://www.nist.org/.

10. Osborn, Kenneth; Georgian, Thomas. The Limits of Method Detection Limits. 

Water Environment & Technology. December 2004.

11. Policy Directive; Assuring the Competency of Environmental Protection Agency 

Laboratories; http://www.epa.gov/fem/pdfs/laboratorydirective.pdf; February 23, 

2004.

12. The FEM Method Validation Team; Validation and Peer Review of U. S. 

Environmental Protection Agency Chemical Methods of Analysis; 

http://www.epa.gov/fem/pdfs/chemmethod_validity_guide.pdf; October 14, 2005.

13. U.S. Environmental Protection Agency Quality System for Environmental Data 

and Technology Website; http://www.epa.gov/quality/. 

14. U.S. Environmental Protection Agency Terminology Services Website; 

http://iaspub.epa.gov/sor_internet/registry/termreg/home/overview/home.do. 

15. Webster’s II: New Riverside University Dictionary; The Riverside Publishing 

Company: Boston, MA, 1994.