ASTM E2677-20

Standard Test Method for Estimating Limits of Detection in Trace Detectors for Explosives and Drugs of Interest

SIGNIFICANCE AND USE
5.1 Commercial trace detectors are used by first responders, security screeners, the military, and law enforcement to detect and identify explosive threats and drugs of interest quickly. These trace detectors typically operate by detecting chemical agents in residues and particles sampled from surfaces and can have detection limits for some compounds extending below 1 ng. A trace detector is set to alarm when its response to any target analyte exceeds a programmed threshold level for that analyte. Factory settings of such levels typically balance sensitivity and selectivity assuming standard operating and deployment conditions.  
5.2 The LOD for a substance is commonly accepted as the smallest amount of that substance that can be reliably detected in a given type of medium by a specific measurement process (2). The analytical signal from this amount shall be high enough above ambient background variation to give statistical confidence that the signal is real. Methods for determining nominal LOD values are well known but pitfalls exist in specific applications. Vendors of trace detectors often report detection limits for only a single compound without defining the meaning of terms or reference to the method of determination.
Note 2: There are several different “detection limits” that can be determined for analytical procedures. These include the minimum detectable value, the instrument detection limit, the method detection limit, the limit of recognition, the limit of quantitation, and the minimum consistently detectable amount. Even when the same terminology is used, there can be differences in the LOD according to nuances in the definition used, the assumed response model, and the type of noise contributing to the measurement.  
5.3 When deployed, the individual performance of a trace detector (for example, realistic LODs) is influenced by: (1) manufacturing differences, history, and maintenance; (2) operating configurations (for example, thermal desorption tem...
SCOPE
1.1 In harmony with the Joint Committee for Guides in Metrology (JCGM) and detection concepts of the International Union of Pure and Applied Chemistry (IUPAC) (1, 2)2, this test method uses a series of replicated measurements of an analyte at dosage levels giving instrumental responses that bracket the critical value, a truncated normal distribution model, and confidence bounds to establish a standard for estimating practical and statistically robust limits of detection.
Note 1: Other standards are available that evaluate the general performance of detection technologies for various analytes in complex matrices (for example, Practice E2520).  
1.2 Here, the limit of detection (LOD90) for a compound is defined to be the lowest mass of that compound deposited on a sampling swab for which there is 90 % confidence that a single measurement in a particular trace detector will have a true detection probability of at least 90 % and a true nondetection probability of at least 90 % when measuring a process blank sample.  
1.3 This particular test method was chosen on the basis of reliability, practicability, and comprehensiveness across tested trace detectors, analytes, and deployment conditions. The calculations involved in this test method are published elsewhere (3), and are performed through an interactive web-based calculator available on the National Institute of Standards and Technology (NIST) site: https://www-s.nist.gov/loda.  
1.4 Intended Users—Trace detector developers and manufacturers, vendors, testing laboratories, and agencies responsible for public safety and enabling effective deterrents to terrorism.  
1.5 While this test method may be applied to any detection technology that produces numerical output, the method is especially applicable to measurement systems influenced by heterogeneous error sources that lead to non-linear and heteroskedastic dose/response relationships and truncated or censored respons...

General Information

• Status: Published
• Publication Date: 31-Jan-2020
• ICS: 13.230 - Explosion protection
• Technical Committee: E54 - Homeland Security Applications
• Drafting Committee: E54.01 - CBRNE Detection and CBRN Protection

Relations

• Replaces: ASTM E2677-14 - Standard Test Method for Determining Limits of Detection in Explosive Trace Detectors
• Effective Date: 01-Feb-2020
• Refers: ASTM E456-13a(2022)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Apr-2022
• Refers: ASTM E2655-14(2020) - Standard Guide for Reporting Uncertainty of Test Results and Use of the Term Measurement Uncertainty in ASTM Test Methods
• Effective Date: 01-Jan-2020
• Refers: ASTM E969-02(2019) - Standard Specification for Glass Volumetric (Transfer) Pipets
• Effective Date: 01-Jul-2019
• Refers: ASTM E288-10(2017) - Standard Specification for Laboratory Glass Volumetric Flasks
• Effective Date: 01-Nov-2017
• Refers: ASTM E456-13A(2017)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Oct-2017
• Refers: ASTM E456-13A(2017)e3 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Oct-2017
• Refers: ASTM E177-14 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-May-2014
• Refers: ASTM E456-13ae2 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 15-Nov-2013
• Refers: ASTM E456-13ae3 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 15-Nov-2013
• Refers: ASTM E456-13a - Standard Terminology Relating to Quality and Statistics
• Effective Date: 15-Nov-2013
• Refers: ASTM E456-13ae1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 15-Nov-2013
• Refers: ASTM E456-13 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 15-Aug-2013
• Refers: ASTM E177-13 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-May-2013
• Refers: ASTM E691-13 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-May-2013

Overview

ASTM E2677-20 is a standardized test method developed by ASTM International for estimating the limits of detection (LOD) in trace detectors designed for explosives and drugs of interest. This method provides a robust, practical, and statistically grounded approach for evaluating the sensitivity of trace detectors commonly used by first responders, security screeners, military personnel, and law enforcement agencies. By harmonizing with international metrology and chemistry guidelines, ASTM E2677-20 supports consistent, reliable measurement standards in security and safety applications.

Key Topics

• Limits of Detection (LOD90): The standard defines LOD as the smallest amount of an analyte that can be reliably detected, with LOD90 referring to the lowest analyte mass providing 90% confidence in detection and nondetection probabilities.
• Measurement Methodology: E2677-20 applies replicated measurements across dosage levels, uses a truncated normal distribution model, and incorporates confidence bounds to yield statistically rigorous LOD estimates.
• Applicability: This test method is particularly suited to any detection technology that produces quantitative numerical results and is influenced by non-linear or heteroskedastic error patterns.
• User Guidance: The method provides actionable steps for detector developers, manufacturers, vendors, testing labs, and public safety agencies to evaluate trace detector performance under realistic deployment scenarios.

Applications

• Security Screening: Used in airport, border, and event security operations to assess the effectiveness of trace detectors for explosives and controlled substances.
• Public Safety and Counter-terrorism: Enables law enforcement and military bodies to determine the true detection capability of their fielded technologies, supporting risk mitigation and tactical preparedness.
• Forensic and Laboratory Testing: Offers testing laboratories a standard protocol for evaluating instrument performance, ensuring reliable evidence detection in forensic investigations.
• Quality Assurance for Detector Manufacturers: Provides a clear, internationally recognized method for manufacturers to validate device sensitivity, calibrate alarm thresholds, and demonstrate product credibility to customers.

Related Standards

Key referenced or related ASTM standards include:

• ASTM E2520: Evaluates general performance of trace explosive chemical detectors.
• ASTM D6091: Practice for 99%/95% Interlaboratory Detection Estimate (IDE) for Analytical Methods.
• ASTM E200, E542, E288, E969, E1154: Cover preparation, calibration, and handling of laboratory solutions and volumetric apparatus.
• ASTM E2655: Guide for reporting uncertainty in measurement results.
• ASTM E2771: Terminology for homeland security applications.

Practical Value

• Harmonization with International Guidelines: Developed in line with recommendations from the Joint Committee for Guides in Metrology (JCGM) and IUPAC, promoting global interoperability.
• Statistically Robust Results: Delivers practical, reliable assessment of the real-world performance of trace detectors, accounting for device variability, environmental factors, and background noise.
• Accessible Calculation Tools: The method is supported by a web-based calculator maintained by NIST, simplifying the application of complex statistical analysis.
• Supports Informed Decision-Making: By quantifying detection limits under realistic operating conditions, ASTME2677-20 helps end users and stakeholders select, deploy, and maintain trace detection systems that meet critical security needs.

Summary

Adherence to ASTM E2677-20 ensures that trace detectors for explosives and drugs of interest are tested using a scientifically sound, internationally recognized, and practically applicable protocol. This benefits developers, procurement agents, field operators, and the broader public by promoting confidence in security screening technology. For those involved in public safety, forensic analysis, security screening, or detection technology development, understanding and applying ASTM E2677-20 is essential for ensuring reliable detection of trace levels of hazardous substances.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E2677 − 20
Standard Test Method for
Estimating Limits of Detection in Trace Detectors for
Explosives and Drugs of Interest
This standard is issued under the fixed designation E2677; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope heterogeneous error sources that lead to non-linear and het-
eroskedastic dose/response relationships and truncated or cen-
1.1 In harmony with the Joint Committee for Guides in
sored response distributions at low analyte levels. The proce-
Metrology (JCGM) and detection concepts of the International
2 dures have been tested using explosive and drug compounds in
UnionofPureandAppliedChemistry(IUPAC) (1, 2) ,thistest
trace detectors based on ion mobility spectrometry, gas
method uses a series of replicated measurements of an analyte
chromatography, and mass spectrometry (4). Compounds are
at dosage levels giving instrumental responses that bracket the
deposited as liquid solutions on swabs and dried before use.
critical value, a truncated normal distribution model, and
Background interferences introduced to the test samples were
confidence bounds to establish a standard for estimating
representative of a variety of conditions expected during
practical and statistically robust limits of detection.
deployment, but these conditions were not intended as com-
NOTE 1—Other standards are available that evaluate the general
prehensive in representing all possible scenarios. The user
performance of detection technologies for various analytes in complex
should be aware of the possibility that untested scenarios may
matrices (for example, Practice E2520).
lead to failure in the estimation of a reliable LOD90 value.
1.2 Here, the limit of detection (LOD90) for a compound is
1.6 Units—The values stated in SI units are to be regarded
defined to be the lowest mass of that compound deposited on
as the standard. No other units of measurement are included in
a sampling swab for which there is 90 % confidence that a
this standard.
single measurement in a particular trace detector will have a
1.7 This standard does not purport to address all of the
true detection probability of at least 90 % and a true nonde-
safety concerns, if any, associated with its use. It is the
tection probability of at least 90 % when measuring a process
responsibility of the user of this standard to establish appro-
blank sample.
priate safety, health, and environmental practices and deter-
1.3 This particular test method was chosen on the basis of
mine the applicability of regulatory limitations prior to use.
reliability, practicability, and comprehensiveness across tested
Some specific hazards statements are given in Section 8 on
trace detectors, analytes, and deployment conditions. The
Hazards.
calculations involved in this test method are published else-
1.8 This international standard was developed in accor-
where (3), and are performed through an interactive web-based
dance with internationally recognized principles on standard-
calculator available on the National Institute of Standards and
ization established in the Decision on Principles for the
Technology (NIST) site: https://www-s.nist.gov/loda.
Development of International Standards, Guides and Recom-
1.4 Intended Users—Trace detector developers and
mendations issued by the World Trade Organization Technical
manufacturers, vendors, testing laboratories, and agencies
Barriers to Trade (TBT) Committee.
responsible for public safety and enabling effective deterrents
to terrorism. 2. Referenced Documents
1.5 While this test method may be applied to any detection
2.1 ASTM Standards:
technology that produces numerical output, the method is E177 Practice for Use of the Terms Precision and Bias in
especially applicable to measurement systems influenced by
ASTM Test Methods
E200 Practice for Preparation, Standardization, and Storage
of Standard and Reagent Solutions for ChemicalAnalysis
This test method is under the jurisdiction of ASTM Committee E54 on
E288 Specification for Laboratory Glass Volumetric Flasks
Homeland Security Applications and is the direct responsibility of Subcommittee
E54.01 on CBRNE Sensors and Detectors.
Current edition approved Feb. 1, 2020. Published February 2020. Originally
approved in 2014. Last previous edition approved in 2014 as E2677 – 14. DOI: For referenced ASTM standards, visit the ASTM website, www.astm.org, or
10.1520/E2677-20. contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
The boldface numbers in parentheses refer to a list of references at the end of Standards volume information, refer to the standard’s Document Summary page on
this standard. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2677 − 20
E456 Terminology Relating to Quality and Statistics the effective limit of detection (LOD90) values for those
E542 Practice for Calibration of Laboratory Volumetric analytesandchangingthealphaandbetarisksforthedetection
Apparatus process.
E691 Practice for Conducting an Interlaboratory Study to
3.1.8 critical value, CV, n—instrumentalresponseamplitude
Determine the Precision of a Test Method
at which there is particular confidence that the signal may be
E969 Specification for Glass Volumetric (Transfer) Pipets
attributed to a particular analyte.
E1154 Specification for Piston or Plunger Operated Volu-
3.1.8.1 Discussion—The CV is defined by the desired alpha
metric Apparatus
and beta risks of detection and is a response somewhat below
E1323 Guide for Evaluating Laboratory Measurement Prac-
the mean response of samples prepared at the limit of detec-
tices and the Statistical Analysis of the Resulting Data
tion. A realistic CV is the optimal basis of a single-channel
E2520 Practice for Measuring and Scoring Performance of
detection threshold.
Trace Explosive Chemical Detectors
3.1.9 detection outcome, n—binomial (yes/no) response of
E2655 Guide for Reporting Uncertainty of Test Results and
an analysis within a particular channel (or spectral window) in
Use of the Term Measurement Uncertainty inASTM Test
a trace detector.
Methods
3.1.9.1 Discussion—The channel response is “positive”
E2771 Terminology for Homeland Security Applications
when the signal in the channel meets or exceeds all detection
thresholds; otherwise, the channel response is “negative.”
3. Terminology
3.1.10 detection threshold, n—set of signal characteristics,
3.1 Definitions (also see Terminology E2771):
often user selected, for a particular channel (or spectral
3.1.1 alarm rule, n—user-selectable detector response re-
window) in a trace detector.
quirements that, if met during an analysis, result in a detection
3.1.10.1 Discussion—These characteristics usually include
alarm for a particular compound.
the peak amplitude (optimally, the critical value) but may also
3.1.1.1 Discussion—An alarm rule is a logistical pattern in
include the peak shape, onset time, duration, and position
the detection response matrix for an analysis. The simplest
within a detection window. If the measured signal in that
alarm rule would require only a single positive detection
channel meets or exceeds the detection threshold settings, the
response, whereas a more selective rule (useful for minimizing
detection outcome is designated as “positive;” otherwise, the
alpha risk) may require two positive responses in any of three
response is “negative.” One or more position detections are
channels and perhaps a negative response in another channel.
needed within the alarm rules to elicit an alarm for a particular
analyte.Thealarmthresholdforaparticularanalyteisthesame
3.1.2 alarm threshold, n—see detection threshold.
as the detection threshold if the alarm rule uses only one
3.1.3 alpha, α, risk, n—probability of obtaining a positive
channel. If the alarm rule requires two or more positive
detectionoutcome,oralarm,whenanalyzingaprocessblankin
responses, or negative responses in certain channels, the alarm
a properly-operating trace detector.
threshold is a logistical function of the channel signals in-
3.1.4 analyte, n—the particular chemical compound under volved.
consideration.
3.1.11 ion mobility spectrometry, IMS, n—detectiontechnol-
3.1.4.1 Discussion—Pure analyte is used to make reference
ogy commonly used in commercial trace detectors.
solutions by quantitative dissolution into a known amount of
3.1.11.1 Discussion—Typically, samples are heated to va-
solvent. Quantitative depositions of reference solutions are
porize trace analytes of interest, which are then selectively
subsequently used to prepare reference swabs containing
ionized,separatedonthebasisofionmobilitythroughairinan
known amounts of analyte.
analyzer tube, and detected using a Faraday cup. Raw re-
sponses are processed to enhance the chemical signals.
3.1.5 beta, β, risk, n—probability of obtaining a negative
detection outcome, or non-alarm, in a properly operating trace
3.1.12 limit of detection, LOD, n—commonly accepted as
detector when analyzing a swab containing analyte at the mass
the smallest amount of a particular substance that can be
level corresponding to the limit of detection.
reliably detected in a given type of medium by a specific
measurement process.
3.1.6 blank, n—sample swab devoid of analyte.
3.1.12.1 Discussion—May be defined either in terms of the
3.1.6.1 Discussion—If a swab is prepared using the same
instrumental signal response or the analyte mass that elicits the
procedures used in preconditioning the reference swabs and
signal response. Here, the limit of detection (LOD90) is
only pure solvent or a chemical background is deposited, this
defined to be the lowest mass of an analyte deposited on a
swab is called a process blank.
referenceswabforwhichthereis90 %confidencethatasingle
3.1.7 chemical background, n—particular mixture of envi-
measurement in particular trace detector will have a true
ronmental and ambient substances that may be sampled by a
detection probability of at least 90 % and a true nondetection
swab during normal operation of a trace detector in a deploy-
probability of at least 90 % when measuring a process blank
ment area.
sample. Values of LOD90 are performance measures of a
deployed detection system and provide guidance for setting
3.1.7.1 Discussion—Thepresenceofcertainsubstancesona
optimal detection thresholds in that system.
sample or reference swab may interfere with or suppress
expected responses for particular analytes, hence influencing 3.1.12.2 Discussion—LOD90 values are independent of
E2677 − 20
alarm thresholds. However, once the alarm thresholds are set, 4.3 Optional—Using a reproducible method, precondition
the amount of substance needed to consistently elicit an alarm clean swabs with “chemical background.”
is called the LOD-A (Practice E2520). A LOD-A value for a
4.4 Assurethatthetracedetectorisinoperationalreadiness.
substance in a trace detector is greater than or equal to its
4.5 Perform exploratory measurements to determine the
LOD90 value.
significant mass level (SML), which is the lowest level of
3.1.13 LOD90, n—see limit of detection.
analyte mass on a reference swab that gives a mean response
3.1.14 nondetection probability, n—see beta risk. significantly higher than that from process blanks.
3.1.15 process blank, n—see blank.
4.6 Using the SML as a guide, prepare four mass levels of
reference swabs that provide appropriate bracketing of the
3.1.16 reference swabs, n—see swabs.
estimated LOD90 value.
3.1.17 significant mass level, SML, n—lowest mass in a
4.7 Starting at the lowest mass level, run replicates of the
series of prepared mass levels that elicits significantly higher
reference swabs on the trace detector. In turn, run the higher
mean responses in a trace detector compared to the mean
mass levels.
responses from process blanks.
3.1.17.1 Discussion—The SML is a crude estimate of the 4.8 Evaluate data using the web-based calculator at https://
LOD90. www-s.nist.gov/loda. This process returns an estimate of the
LOD90 value as well as upper confidence and tolerance limits.
3.1.18 substrates, n—see swabs.
Options include data plotting and outlier tests. The alpha and
3.1.19 swabs, n—also known as substrates, swipe media,
beta risks may be changed from the default values.
traps, and wipes, swabs are special fabrics made of such
4.9 Consider guidance regarding the setting of an alarm
materials as cotton, fiberglass, or polymers and are designed
threshold in the tested trace detector to achieve a reliable
forwipingsamplesurfacesandholdingresiduescollectedfrom
balance of alpha and beta risks.
those surfaces.
3.1.19.1 Discussion—Distributed by instrument manufac-
5. Significance and Use
turers and consumable suppliers, swabs have particular prop-
5.1 Commercial trace detectors are used by first responders,
erties and shapes designed to fit into the sampling inlets of
security screeners, the military, and law enforcement to detect
trace detectors. Each type of swab has a “sweet spot” for
and identify explosive threats and drugs of interest quickly.
sampling where the detection of analyte is optimized (Practice
These trace detectors typically operate by detecting chemical
E2520). This is generally an area about 1 cm in diameter.
agents in residues and particles sampled from surfaces and can
Please consult with the manufacturer to confirm the location of
have detection limits for some compounds extending below 1
the sweet spot. Swabs containing known amounts of analyte
ng. A trace detector is set to alarm when its response to any
deposited in the sweet spot are called reference swabs.
target analyte exceeds a programmed threshold level for that
3.1.20 swipe media, n—see swabs.
analyte. Factory settings of such levels typically balance
sensitivity and selectivity assuming standard operating and
3.1.21 trace detector, n—device used to identify the pres-
deployment conditions.
ence of particular analytes, with sensitivity allowing detection
of less than one microgram of substance.
5.2 The LOD for a substance is commonly accepted as the
3.1.21.1 Discussion—Trace detectors may be set in general
smallest amount of that substance that can be reliably detected
or specific modes of detection, where firmware allows optimi-
in a given type of medium by a specific measurement process
zation of operational conditions for explosives or drug detec-
(2). The analytical signal from this amount shall be high
tion. In airports for example, trace detectors are commonly set
enough above ambient background variation to give statistical
for explosives-only detection, whereas in prisons they are
confidence that the signal is real. Methods for determining
optimized for detection of certain drugs of interest.
nominal LOD values are well known but pitfalls exist in
3.1.21.2 Discussion—Explosive trace detectors are com-
specific applications. Vendors of trace detectors often report
monly known as ETDs. Trace detectors for explosives and
detection limits for only a single compound without defining
drugs have been called contraband trace detectors and illicit
the meaning of terms or reference to the method of determi-
drug-ETDs, but these names are imprecise and introduce
nation.
unnecessary legal definitions to the types of substances de-
NOTE 2—There are several different “detection limits” that can be
tected.
determined for analytical procedures. These include the minimum detect-
able value, the instrument detection limit, the method detection limit, the
3.1.22 traps, n—see swabs.
limit of recognition, the limit of quantitation, and the minimum consis-
3.1.23 wipes, n—see swabs.
tently detectable amount. Even when the same terminology is used, there
can be differences in the LOD according to nuances in the definition used,
the assumed response model, and the type of noise contributing to the
4. Summary of Test Method
measurement.
4.1 Prepare reference solutions containing known concen-
5.3 When deployed, the individual performance of a trace
trations of a particular analyte.
detector (for example, realistic LODs) is influenced by: (1)
4.2 Set standard operating conditions for the trace detector. manufacturing differences, history, and maintenance; (2) oper-
If needed, the target analyte is programmed into the database. ating configurations (for example, thermal desorption
E2677 − 20
temperature, analyzer temperature, and type of swab); and (3) be based on multiple-peak responses rather than a single-peak
environmental conditions (for example, ambient humidity and amplitude measurement. Efforts to recognize and quantify
temperature and chemical background). As a result, realistic unique ion fragmentation patterns across both the thermal
LODvaluesforatracedetectormaybepoorlyestimatedbythe desorption and drift-time domains are being developed for
factory specifications. These fundamental measures of perfor- next-generation detectors.
mance are critically important for assessing the ability of an 5.4.7 Diversity of Technologies—The wide variety of trace
instrument to detect trace levels of particular compounds in a detectors and technologies on the market and those under
particularsetting,soareliableandaccessiblemethodisneeded development challenge general response models for accurate
to estimate realistic LOD values, especially in the field. estimation of LOD.
5.4.8 Security—LOD values for explosives in trace detec-
5.4 Technical Challenges and Pitfalls to the Estimation of
tors may not be openly published because of security and
LOD Values in Trace Detectors and the Setting of Optimal
classification issues.
Alarm Thresholds:
5.4.1 Scope—The U.S. Department of Justice lists over 230
6. Apparatus
explosive materials and over 270 controlled drugs having a
6.1 Dispensingdevicecalibratedtodeliver1.00-µLaliquots.
highpotentialforabuse. Therearemanytechnologiesusedfor
trace detection, and instrument manufacturers design their
6.2 Trace detector in operational readiness.
systems and balance operating conditions to provide detection
7. Reagents and Materials
capabilities across as many analytes as possible. However, a
very limited subset of analytes is normally used to test and
7.1 Reference solutions as prepared in 9.2.
verify detector performance. Therefore, default operating con-
7.1.1 Analyte.
ditions and alarm thresholds may not be optimally set to detect
7.1.2 Suitable solvent.
reliably certain compounds deemed important in particular
7.1.3 Volumetric flasks (10 mL).
scenarios.
7.1.4 Pipette to deliver 1-mL aliquots.
5.4.2 Environment—Ambient conditions and chemical
7.1.5 Amber 1- and 10-mL vials with tight caps.
background vary with the deployment location, which would
7.2 Clean swabs designed for the particular trace detector.
influence response sensitivities and LOD values.
7.2.1 Optional—Chemical background or interferent/
5.4.3 Risk Tolerance and Balance—Values of alpha risk
suppressant for treatment of clean swabs.
(false positive probability of process blanks) and beta risk
(false nondetection probability of analytes at the detection
8. Hazards
limit) should be balanced and set according to security priori-
8.1 Safety Data Sheets (SDS) for all chemicals, such as
ties (for example, alert level, probable threat compounds,
analytesandsolvents,shouldbeconsultedbeforeuse.Theuser
throughput requirements, human factors, and risk tolerance).
of this test method should also be aware of the hazards
Thedefaultriskbalanceinatracedetectormaynotbeadequate
associated with the operation of the chosen trace detector.
for the deployment situation.
While not ordinarily considered a hazard, the user should also
5.4.4 Signal Variability (Heteroskedasticity)—The variance
be aware that many trace detectors contain radioactive
in instrument response may not be consistent across analyte
materials, which are either “Generally Licensed” by the
mass levels introduced into the trace detector. In ion mobility
Nuclear Regulatory Commission or “Exempt from Licensing.”
spectrometry (IMS)-based technologies, the physicochemical
In either case, this may require radiation management and
mechanisms underlying atmospheric pressure ionization (with
safety training in some organizations.
a finite number of available reactant ions) and ion mobility
separation may be non-uniform across the response regions.
9. Procedure
Typical methods of LOD estimation usually assume constant
9.1 Prepare reference swabs containing the analyte at
variance.
known levels within the sweet spot with a deposition uncer-
5.4.5 Proprietary Signal Processing—Typical LOD deter-
tainty of less than 5 %. For this purpose, carefully prepare and
minations assume Gaussian distributions and use background
dispense1.00-µLaliquotsofreferencesolutionsontotheswabs
variation as an important parameter. Unfortunately, alarm
using a calibrated pipette. This small volume will help prevent
decisions in trace detectors are rarely based on raw measure-
excessive wicking of the analyte outside the sweet spot or into
ment signals; rather, proprietary algorithms are used to process
the interior of the swab. Please consult with the swab manu-
the raw measurements. This processing may attempt t
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E2677 − 14 E2677 − 20
Standard Test Method for
DeterminingEstimating Limits of Detection in Explosive
Trace Detectors for Explosives and Drugs of Interest
This standard is issued under the fixed designation E2677; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 In harmony with the Joint Committee for Guides in Metrology (JCGM) and detection concepts of the International Union
of Pure and Applied Chemistry (IUPAC) (1, 2, 3) , this test method uses a series of replicated measurements of an analyte at dosage
levels giving instrumental responses that bracket the critical value, a truncated normal distribution model, and confidence bounds
to establish a standard for determiningestimating practical and statistically robust limits of detection to analytes sampled on swabs
by explosive trace detectors (ETDs).detection.
NOTE 1—Other standards are available that evaluate the general performance of detection technologies for various analytes in complex matrices (for
example, Practice E2520).
1.2 Here, the limit of detection (LOD90) for a compound is defined to be the lowest mass of a particular that compound
deposited on a sampling swab for which there is 90 % confidence that a single measurement in a particular ETD trace detector will
have a true detection probability of at least 90 % and a true nondetection probability of at least 90 % when measuring a process
blank sample.
1.3 This particular test method was chosen on the basis of reliability, practicability, and comprehensiveness across tested ETDs,
trace detectors, analytes, and deployment conditions. The calculations involved in this test method are published elsewhere (43),
and may be performed consistently with are performed through an interactive web-based toolcalculator available on the National
Institute of Standards and Technology (NIST) site: http://pubapps.nist.gov/loda.https://www-s.nist.gov/loda.
1.4 Intended Users—ETD developers, ETD vendors, ETD buyers, ETD testers, ETD users (first responders, security screeners,
and the military), and Trace detector developers and manufacturers, vendors, testing laboratories, and agencies responsible for
public safety and enabling effective deterrents to terrorism.
1.5 While this test method may be applied to any detection technology that produces numerical output, the method is especially
applicable to measurement systems influenced by heterogeneous error sources that lead to non-linear and heteroskedastic
dose/response relationships and truncated or censored response distributions at low analyte levels. The procedures have been
designed for ion mobility tested using explosive and drug compounds in trace detectors based on ion mobility spectrometry, gas
chromatography, and mass spectrometry (IMS)(4). based ETD systems and tested with low vapor pressure explosive compounds.
Compounds are deposited as liquid solutions on swabs and dried before use. As some swabs are absorbent, this deposition
procedure may not be optimal for those ETD technologies that rely on high coverage of analyte on the surface of the swab.
Background interferences introduced to the test samples were representative of a variety of conditions expected during deployment,
but these conditions were not intended as comprehensive in representing all possible scenarios. The user should be aware of the
possibility that untested scenarios may lead to failure in the determinationestimation of a reliable LOD90 value.
1.6 Units—The values stated in SI units are to be regarded as the standard. No other units of measurement are included in this
standard.
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use. Some specific hazards statements are given in Section 8 on Hazards.
This test method is under the jurisdiction of ASTM Committee E54 on Homeland Security Applications and is the direct responsibility of Subcommittee E54.01 on
CBRNE Sensors and Detectors.
Current edition approved Feb. 1, 2014Feb. 1, 2020. Published February 2014February 2020. Originally approved in 2014. Last previous edition approved in 2014 as
E2677 – 14. DOI: 10.1520/E2677-14.10.1520/E2677-20.
The boldface numbers in parentheses refer to a list of references at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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1.8 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D6091 Practice for 99 %/95 % Interlaboratory Detection Estimate (IDE) for Analytical Methods with Negligible Calibration
Error
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E200 Practice for Preparation, Standardization, and Storage of Standard and Reagent Solutions for Chemical Analysis
E288 Specification for Laboratory Glass Volumetric Flasks
E456 Terminology Relating to Quality and Statistics
E542 Practice for Calibration of Laboratory Volumetric Apparatus
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
E969 Specification for Glass Volumetric (Transfer) Pipets
E1154 Specification for Piston or Plunger Operated Volumetric Apparatus
E1323 Guide for Evaluating Laboratory Measurement Practices and the Statistical Analysis of the Resulting Data
E2520 Practice for Measuring and Scoring Performance of Trace Explosive Chemical Detectors
E2655 Guide for Reporting Uncertainty of Test Results and Use of the Term Measurement Uncertainty in ASTM Test Methods
E2771 Terminology for Homeland Security Applications
3. Terminology
3.1 Definitions:Definitions (also see Terminology E2771):
3.1.1 alarm rule, n—user-selectable explosive trace detector (ETD) response requirements that, if met during an analysis, result
in a detection alarm for a particular compound.
3.1.1.1 Discussion—
An alarm rule is a logistical pattern in the detection response matrix for an analysis. The simplest alarm rule would require only
a single positive detection response, whereas a more selective rule (useful for minimizing alpha risk) may require two positive
responses in any of three channels and perhaps a negative response in another channel.
3.1.2 alarm threshold, n—see detection threshold.
3.1.3 alpha, α, risk, n—probability of obtaining a positive detection outcome, or alarm, when analyzing a process blank in a
properly-operating ETD.trace detector.
3.1.4 analyte, n—the particular chemical compound under consideration.
3.1.4.1 Discussion—
Pure analyte is used to make reference solutions by quantitative dissolution into a known amount of solvent. Quantitative
depositions of reference solutions are subsequently used to prepare reference swabs containing known amounts of analyte.
3.1.5 beta, β, risk, n—probability of obtaining a negative detection outcome, or non-alarm, in a properly operating ETD trace
detector when analyzing a swab containing analyte at the mass level corresponding to the limit of detection.
3.1.6 blank, n—sample swab devoid of analyte.
3.1.6.1 Discussion—
If a swab is prepared using the same procedures used in preconditioning the reference swabs and only pure solvent or a chemical
background is deposited, this swab is called a process blank.
3.1.7 chemical background, n—particular mixture of environmental and ambient substances that may be sampled by a swab
during normal operation of an ETD a trace detector in a deployment area.
3.1.7.1 Discussion—
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
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The presence of certain substances on a sample or reference swab may interfere with or suppress expected ETD responses for
particular analytes, hence influencing the effective limit of detection (LOD90) values for those analytes and changing the alpha
and beta risks for the detection process.
3.1.8 critical value, CV, n—instrumental response amplitude at which there is particular confidence that the signal may be
attributed to a particular analyte.
3.1.8.1 Discussion—
The CV is defined by the desired alpha and beta risks of detection and is a response somewhat below the mean response of samples
prepared at the limit of detection. A realistic CV is the optimal basis of a single-channel detection threshold.
3.1.9 detection outcome, n—binomial (yes/no) response of an analysis within a particular channel (or spectral window) in an
ETD.a trace detector.
3.1.9.1 Discussion—
The channel response is “positive” when the signal in the channel meets or exceeds all detection thresholds; otherwise, the channel
response is “negative.”
3.1.10 detection threshold, n—set of signal characteristics, often user selected, for a particular channel (or spectral window) in
an ETD.a trace detector.
3.1.10.1 Discussion—
These characteristics usually include the peak amplitude (optimally, the critical value) but may also include the peak shape, onset
time, duration, and position within a detection window. If the measured signal in that channel meets or exceeds the detection
threshold settings, the detection outcome is designated as “positive;” otherwise, the response is “negative.” One or more position
detections are needed within the alarm rules to elicit an alarm for a particular analyte. The alarm threshold for a particular analyte
is the same as the detection threshold if the alarm rule uses only one channel. If the alarm rule requires two or more positive
responses, or negative responses in certain channels, the alarm threshold is a logistical function of the channel signals involved.
3.1.11 explosive trace detector, ETD, n—device used to identify the presence of small amounts of explosive compounds.
3.1.11.1 Discussion—
ETDs are commonly used at airports by security screeners, who wipe a surface with a swab to collect residues, and then analyze
the swab in the ETD. Explosive vapor detectors (EVDs) are a subset of ETDs that sample air to detect vapors indicative of
explosives.
3.1.12 explosive vapor detector, EVD, n—used to sample air—indoors, outdoors, or within containers—to identify vapors
indicative of the presence of explosives.
3.1.12.1 Discussion—
Detected vapors may be explosive compounds or other chemicals in patterns suggestive of particular explosive formulations.
3.1.11 ion mobility spectrometry, IMS, n—detection technology commonly used in commercial ETDs (for other technologies,
please see Caygill et al trace detectors.(5).
3.1.11.1 Discussion—
Typically, samples are heated to vaporize trace analytes of interest, which are then selectively ionized, separated on the basis of
ion mobility through air in an analyzer tube, and detected using a Faraday cup. Raw responses are processed to enhance the
chemical signals. Further information on IMS may be found in Eiceman and Zarpas (6).
3.1.12 limit of detection, LOD, n—commonly accepted as the smallest amount of a particular substance that can be reliably
detected in a given type of medium by a specific measurement process.
3.1.12.1 Discussion—
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May be defined either in terms of the instrumental signal response or the analyte mass that elicits the signal response. Here, the
limit of detection (LOD90) is defined to be the lowest mass of an analyte deposited on a reference swab for which there is 90 %
confidence that a single measurement in particular ETD trace detector will have a true detection probability of at least 90 % and
a true nondetection probability of at least 90 % when measuring a process blank sample. Values of LOD90 are performance
measures of a deployed detection system and provide guidance for setting optimal ETD detection thresholds in that system.
3.1.12.2 Discussion—
LOD90 values are independent of alarm thresholds. However, once the alarm thresholds are set, the amount of substance needed
to consistently elicit an alarm is called the LOD-A (Practice E2520). A LOD-A value for a substance in a trace detector is greater
than or equal to its LOD90 value.
3.1.13 LOD90, n—see limit of detection.
3.1.14 nondetection probability, n—see beta risk.
3.1.15 process blank, n—see blank.
3.1.16 reference swabs, n—see swabs.
3.1.17 significant mass level, SML, n—lowest mass in a series of prepared mass levels that elicits significantly higher mean
responses in an ETD a trace detector compared to the mean responses from process blanks.
3.1.17.1 Discussion—
The SML is a crude estimate of the LOD90.
3.1.18 substrates, n—see swabs.
3.1.19 swabs, n—also known as substrates, swipe media, traps, and wipes, swabs are special fabrics made of such materials as
cotton, fiberglass, or polymers and are designed for wiping sample surfaces and holding residues collected from those surfaces.
3.1.19.1 Discussion—
Distributed by ETDinstrument manufacturers and consumable suppliers, swabs have particular properties and shapes designed to
fit into the sampling inlets of ETDs. trace detectors. Each type of swab has a “sweet spot” for sampling where the detection of
analyte is optimized (Practice E2520). This is generally an area about 1 cm in diameter. Please consult with the manufacturer to
confirm the location of the sweet spot. Swabs containing known amounts of analyte deposited in the sweet spot are called reference
swabs.
3.1.20 swipe media, n—see swabs.
3.1.21 trace detector, n—device used to identify the presence of particular analytes, with sensitivity allowing detection of less
than one microgram of substance.
3.1.21.1 Discussion—
Trace detectors may be set in general or specific modes of detection, where firmware allows optimization of operational conditions
for explosives or drug detection. In airports for example, trace detectors are commonly set for explosives-only detection, whereas
in prisons they are optimized for detection of certain drugs of interest.
3.1.21.2 Discussion—
Explosive trace detectors are commonly known as ETDs. Trace detectors for explosives and drugs have been called contraband
trace detectors and illicit drug-ETDs, but these names are imprecise and introduce unnecessary legal definitions to the types of
substances detected.
3.1.22 traps, n—see swabs.
3.1.23 wipes, n—see swabs.
4. Summary of Test Method
4.1 Reference solutions are prepared Prepare reference solutions containing known concentrations of a particular analyte.
4.2 Standard Set standard operating conditions for the ETD are set. trace detector. If needed, the target analyte is programmed
into the ETD database.
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4.3 Optional—Using a reproducible method, precondition clean swabs are preconditioned with “chemical background.”
4.4 The ETD is determined to beAssure that the trace detector is in operational readiness.
4.5 Exploratory measurements are performed Perform exploratory measurements to determine the significant mass level
(SML), which is the lowest level of analyte mass on a reference swab that gives a mean response significantly higher than that
from process blanks.
4.6 Using the SML as a guide, prepare four mass levels of reference swabs are prepared that provide appropriate bracketing of
the estimated LOD90 value.
4.7 Starting at the lowest mass level, run replicates of the reference swabs are run on the ETD. trace detector. In turn, run the
higher mass levels are run.levels.
4.8 Data are evaluated using a validated algorithm accessed through a Evaluate data using the web-based calculator at
http://pubapps.nist.gov/loda.https://www-s.nist.gov/loda. This process returns an estimate of the LOD90 value as well as upper
confidence and tolerance limits. Optional tools Options include data plotting and outlier tests. The alpha and beta risks may be
changed from the default values.
4.9 Guidance is given Consider guidance regarding the setting of an alarm threshold in an ETD the tested trace detector to
achieve a reliable balance of alpha and beta risks.
5. Significance and Use
5.1 ETDs Commercial trace detectors are used by first responders, security screeners, the military, and law enforcement to
detect and identify explosive threats quickly. ETDs and drugs of interest quickly. These trace detectors typically operate by
detecting chemical agents in residues and particles sampled from surfaces and can have detection limits for some compounds
extending below 1 ng. An ETD A trace detector is set to alarm when its response to any target analyte exceeds a programmed
threshold level for that analyte. Factory settings of such levels typically balance sensitivity and selectivity assuming standard
operating and deployment conditions.
5.2 A LOD The LOD for a substance is commonly accepted as the smallest amount of a particular that substance that can be
reliably detected in a given type of medium by a specific measurement process (2, 3). The analytical signal from this amount shall
be high enough above ambient background variation to give statistical confidence that the signal is real. Methods for determining
nominal LOD values are well known (for example, Hubaux and Vos (7) and Practice D6091), but pitfalls exist in specific
applications. Vendors of ETDs trace detectors often report detection limits for only a single compound without defining the
meaning of terms or reference to the method of determination.
NOTE 2—There are several different “detection limits” that can be determined for analytical procedures. These include the minimum detectable value,
the instrument detection limit, the method detection limit, the limit of recognition, and the limit of quantitation. quantitation, and the minimum
consistently detectable amount. Even when the same terminology is used, there can be differences in the LOD according to nuances in the definition used,
the assumed response model, and the type of noise contributing to the measurement.
5.3 When deployed, the individual ETD performance performance of a trace detector (for example, realistic LODs) is influenced
by: (1) ETD manufacturing differences, history, and maintenance; (2) ETD operating configurations (for example, thermal
desorption temperature, analyzer temperature, and type of swab); and (3) environmental conditions (for example, ambient humidity
and temperature and chemical background). As a result, realistic LOD values for an ETD a trace detector may be poorly estimated
by the factory specifications. These fundamental measures of ETD performance are critically important for assessing the ability
of an ETDinstrument to detect trace levels of particular compounds in a particular setting, so a reliable and accessible method is
needed to determineestimate realistic LOD values, especially in the field.
5.4 Technical Challenges and Pitfalls to the DeterminationEstimation of LOD Values in ETDs Trace Detectors and the Setting
of Optimal Alarm Thresholds:
5.4.1 Scope—There are The U.S. Department of Justice lists over 230 explosive materials currently listed by the Bureau of
Alcohol, Tobacco, Firearms, and Explosives.and over 270 controlled drugs having a high potential for abuse. There are many
technologies used for trace detection, and ETDinstrument manufacturers design their systems and balance operating conditions to
provide detection capabilities across as many analytes as possible. However, a very limited subset of analytes is normally used to
test and verify ETDdetector performance. Therefore, default ETD operating conditions and alarm thresholds may not be optimally
set to detect reliably certain compounds deemed important in particular scenarios.
5.4.2 Environment—Ambient conditions and chemical background vary with the deployment location, which would influence
ETD response sensitivities and LOD values.
5.4.3 Risk Tolerance and Balance—Values of alpha risk (false positive probability of process blanks) and beta risk (false
nondetection probability of analytes at the detection limit) should be balanced and set according to security priorities (for example,
Available from http://www.gpo.gov/fdsys/pkg/FR-2012-09-20/pdf/2012-23241.pdf.A list of controlled drugs is available from https://www.deadiversion.usdoj.gov/
schedules/orangebook/e_cs_sched.pdf.
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alert level, probable threat compounds, throughput requirements, human factors, and risk tolerance). The default risk balance in
an ETD a trace detector may not be adequate for the deployment situation.
5.4.4 Signal Variability (Heteroscedasticity)—(Heteroskedasticity)—The variance in instrument response may not be consistent
across analyte mass levels introduced into the ETD. trace detector. In ion mobility spectrometry (IMS)-based technologies, the
physicochemical mechanisms underlying atmospheric pressure ionization (with a finite number of available reactant ions) and ion
mobility separation may be non-uniform across the ETD response regions. Typical methods of LOD determinationestimation
usually assume constant variance.
5.4.5 Proprietary Signal Processing—Typical LOD determinations assume Gaussian distributions and use background variation
as an important parameter. Unfortunately, alarm decisions in ETDs trace detectors are rarely based on raw measurement signals;
rather, proprietary algorithms are used to process the raw measurements. This processing may attempt to minimize alpha risk by
truncating or dampening background signals, so background signals may be absent or the true distribution in these processed
signals may be non-Gaussian, confounding the calculation of an accurate LOD.
5.4.6 Multivariate Considerations—To improve selectivity and decrease alpha risk, alarm decisions in ETDs trace detectors may
be based on multiple-peak responses rather than a single-peak amplitude measurement. Additionally, efforts Efforts to recognize
and quantify unique ion fragmentation patterns across both the thermal desorption and drift-time domains are being developed for
next-generation detectors.
5.4.7 Diversity of Technologies—The wide variety of ETDs trace detectors and technologies on the market and those under
development challenge general response models for accurate estimation of LOD.
5.4.8 Security—LOD values for explosives in ETDs cannot trace detectors may not be openly published because of security and
classification issues.
6. Apparatus
6.1 Dispensing device calibrated to deliver 1.00-μL aliquots.
6.2 ETD Trace detector in operational readiness.
7. Reagents and Materials
7.1 Reference solutions as prepared in 9.2.
7.1.1 Analyte.
7.1.2 Suitable solvent.
7.1.3 Volumetric flasks (10 mL).
7.1.4 Pipette to deliver 1-mL aliquots.
7.1.5 Amber 1- and 10-mL vials with tight caps.
7.2 Clean swabs designed for the particular ETD.trace detector.
7.2.1 Optional—Chemical background or interferent/suppressant for treatment of clean swabs.
8. Hazards
8.1 Safety Data Sheets (SDS) for all chemicals, such as analytes and solvents, should be consulted before use. The user of this
test method should also be aware of the hazards associated with the operation of the chosen ETD. trace detector. While not
ordinarily considered a hazard, the user should also be aware that many ETDs trace detectors contain radioactive materials, which
are either “Generally Licensed” by the Nuclear Regulatory Commission or “Exempt from Licensing.” In either case, this may
require radiation management and safety training in some organizations.
9. Procedure
9.1 Reference swabs shall be prepared Prepare reference swabs containing the analyte at known levels within the sweet spot
with an a deposition uncertainty of less than 5 %. A few organizations use drop-on-demand inkjet printing for the purposeFor this
purpose, carefully prepare and dispense 1.00-μL aliquots of (reference8, 9), but since these dispensing systems are not widely
available, we recommend the traditional approach in which standard solutions are prepared and dispensed solutions onto the swabs
using a calibrated dispensing device that can deliver 1.00-μL aliquots. pipette. This small volume will help prevent excessive
wicking of the analyte outside the sweet spot or into the interior of the swab. Please consult with the swab manufacturer to confirm
the location of the sweet spot. Calibrations of volumetri
...