ASTM E516-95a(2021)

Standard Practice for Testing Thermal Conductivity Detectors Used in Gas Chromatography

SIGNIFICANCE AND USE
3.1 Although it is possible to observe and measure each of the several characteristics of a detector under different and unique conditions, it is the intent of this practice that a complete set of detector specifications should be obtained at the same operating conditions. It should be noted also that to specify a detector’s capability completely, its performance should be measured at several sets of conditions within the useful range of the detector. The terms and tests described in this practice are sufficiently general so that they may be used at whatever conditions may be chosen for other reasons.  
3.2 Linearity and speed of response of the recorder used should be such that it does not distort or otherwise interfere with the performance of the detector. Effective recorder response, Refs. (5, 6) in particular, should be sufficiently fast that it can be neglected in sensitivity of measurements. If additional amplifiers are used between the detector and the final readout device, their characteristics should also first be established.
SCOPE
1.1 This practice is intended to serve as a guide for the testing of the performance of a thermal conductivity detector (TCD) used as the detection component of a gas chromatographic system.  
1.2 This practice is directly applicable to thermal conductivity detectors which employ filament (hot wire) or thermistor sensing elements.  
1.3 This practice is intended to describe the performance of the detector itself independently of the chromatographic column, in terms which the analyst can use to predict overall system performance when the detector is coupled to the column and other chromatography system components.  
1.4 For general gas chromatographic procedures, Practice E260 should be followed except where specific changes are recommended herein for the use of a TCD. For definitions of gas chromatography and its various terms see Practice E355.  
1.5 For general information concerning the principles, construction, and operation of TCD see Refs. (1-4).2  
1.6 The values stated in SI units are to be regarded as 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For specific safety information, see Section 4.3  
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.

General Information

• Status: Published
• Publication Date: 31-Mar-2021
• ICS: 71.040.50 - Physicochemical methods of analysis
• Technical Committee: E13 - Molecular Spectroscopy and Separation Science
• Drafting Committee: E13.19 - Separation Science

Relations

• Refers: ASTM E260-96(2019) - Standard Practice for Packed Column Gas Chromatography
• Effective Date: 01-Sep-2019
• Refers: ASTM E260-96(2011) - Standard Practice for Packed Column Gas Chromatography
• Effective Date: 01-Nov-2011
• Refers: ASTM E355-96(2007) - Standard Practice for Gas Chromatography Terms and Relationships
• Effective Date: 01-Mar-2007
• Refers: ASTM E260-96(2006) - Standard Practice for Packed Column Gas Chromatography
• Effective Date: 01-Mar-2006
• Refers: ASTM E355-96 - Standard Practice for Gas Chromatography Terms and Relationships
• Effective Date: 01-Jan-2001
• Refers: ASTM E260-96 - Standard Practice for Packed Column Gas Chromatography
• Effective Date: 01-Jan-2001
• Refers: ASTM E355-96(2001) - Standard Practice for Gas Chromatography Terms and Relationships
• Effective Date: 01-Jan-2001
• Refers: ASTM E260-96(2001) - Standard Practice for Packed Column Gas Chromatography
• Effective Date: 01-Jan-2001

Overview

ASTM E516-95a(2021): Standard Practice for Testing Thermal Conductivity Detectors Used in Gas Chromatography provides a comprehensive guide for evaluating the performance of thermal conductivity detectors (TCDs) within gas chromatographic systems. Issued by ASTM International, this standard outlines accepted test methods for measuring key characteristics of TCDs such as sensitivity, linear range, dynamic range, response time, noise, and drift. Its focus is on ensuring accuracy and reliability when TCDs are used as analytical components for detecting and quantifying substances in gas chromatography.

This standard applies directly to TCDs that use filament (hot wire) or thermistor sensing elements and is designed to assess the detector's performance independently from other system components. It serves as an important resource for laboratories, manufacturers, and analysts needing consistent and standardized measurements.

Key Topics

• Performance Testing Procedures: Provides methods for measuring sensitivity, minimum detectability, linear range, dynamic range, noise, drift, and response time of TCDs.
• Consistency in Test Conditions: Stresses that all detector specifications should be measured under the same operating conditions, or within the useful range of the detector, to ensure comparable results and accurate predictions of system performance.
• Calculation Methods: Describes accepted approaches such as the exponential decay method, permeation tube method, and dynamic method for evaluating detector response.
• Reporting Requirements: Specifies documentation of all test conditions, including type of detector, geometry, internal volume, carrier gas, flow rates, temperature, detector current, measurement methods, and power supply.
• Safety and Handling: Highlights the responsibility for safe handling of compressed gases and cryogenic liquids, referencing recognized standards and guidance documents for laboratory safety practices.
• Instrument Linearity and Response: Emphasizes that recording equipment must have sufficiently fast response and proper linearity for accurate detector performance measurement.
• Use of SI Units: All values and parameters are to be expressed in SI units to ensure global consistency.

Applications

Implementing ASTM E516-95a(2021) delivers practical value in several key areas:

• Quality Control in Analytical Laboratories: Enables consistent, reproducible testing of TCD performance, supporting reliable results in environmental, petrochemical, pharmaceutical, and food safety analyses.
• TCD Calibration and Verification: Assists manufacturers and users in calibrating detectors for both filament and thermistor types, ensuring each unit meets required sensitivity and accuracy thresholds.
• Comparative Evaluation: Allows laboratories to benchmark various TCDs, assess suitability for specific analyses, and validate instrument performance prior to method implementation.
• Safety Compliance: Reinforces adherence to best practices for gas handling and instrumentation safety.
• Predictive System Performance: By independently characterizing the TCD, analysts can make informed predictions about overall gas chromatography system behavior when integrating detectors with columns and other components.

Related Standards

For comprehensive gas chromatographic procedures and terms:

• ASTM E260: Practice for Packed Column Gas Chromatography
• ASTM E355: Practice for Gas Chromatography Terms and Relationships
• CGAP-1, CGAG-5.4, CGAP-9, CGAV-7, CGAP-12, HB-3: Compressed Gas Association guidelines for safe handling of gases and related infrastructure

Additional context on TCD design and operation is available in referenced literature and technical handbooks cited within ASTM E516-95a(2021).

By following ASTM E516-95a(2021), laboratories and manufacturers ensure reliable, standardized, and high-quality performance assessment of thermal conductivity detectors, a critical component in modern gas chromatographic analysis.

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: E516 − 95a (Reapproved 2021)
Standard Practice for
Testing Thermal Conductivity Detectors Used in Gas
Chromatography
This standard is issued under the fixed designation E516; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
1.1 This practice is intended to serve as a guide for the
Barriers to Trade (TBT) Committee.
testing of the performance of a thermal conductivity detector
(TCD) used as the detection component of a gas chromato-
2. Referenced Documents
graphic system.
2.1 ASTM Standards:
1.2 This practice is directly applicable to thermal conduc-
E260Practice for Packed Column Gas Chromatography
tivity detectors which employ filament (hot wire) or thermistor
E355PracticeforGasChromatographyTermsandRelation-
sensing elements.
ships
1.3 This practice is intended to describe the performance of 5
2.2 CGA Standards:
the detector itself independently of the chromatographic
CGAP-1SafeHandlingofCompressedGasesinContainers
column, in terms which the analyst can use to predict overall
CGAG-5.4Standard for Hydrogen Piping Systems at Con-
system performance when the detector is coupled to the
sumer Locations
column and other chromatography system components.
CGAP-9The Inert Gases: Argon, Nitrogen and Helium
1.4 For general gas chromatographic procedures, Practice
CGAV-7Standard Method of Determining Cylinder Valve
E260 should be followed except where specific changes are Outlet Connections for Industrial Gas Mixtures
recommended herein for the use of a TCD. For definitions of
CGAP-12Safe Handling of Cryogenic Liquids
gas chromatography and its various terms see Practice E355. HB-3Handbook of Compressed Gases
1.5 For general information concerning the principles,
2 3. Significance and Use
construction, and operation of TCD see Refs. (1-4).
3.1 Although it is possible to observe and measure each of
1.6 The values stated in SI units are to be regarded as
the several characteristics of a detector under different and
standard. No other units of measurement are included in this
unique conditions, it is the intent of this practice that a
standard.
complete set of detector specifications should be obtained at
1.7 This standard does not purport to address all of the
the same operating conditions. It should be noted also that to
safety concerns, if any, associated with its use. It is the
specify a detector’s capability completely, its performance
responsibility of the user of this standard to establish appro-
should be measured at several sets of conditions within the
priate safety, health, and environmental practices and deter-
useful range of the detector. The terms and tests described in
mine the applicability of regulatory limitations prior to use.
thispracticearesufficientlygeneralsothattheymaybeusedat
For specific safety information, see Section 4.
whatever conditions may be chosen for other reasons.
1.8 This international standard was developed in accor-
3.2 Linearity and speed of response of the recorder used
dance with internationally recognized principles on standard-
should be such that it does not distort or otherwise interfere
ization established in the Decision on Principles for the
with the performance of the detector. Effective recorder
response, Refs. (5, 6) in particular, should be sufficiently fast
that it can be neglected in sensitivity of measurements. If
This practice is under the jurisdiction ofASTM Committee E13 on Molecular
Spectroscopy and Separation Science and is the direct responsibility of Subcom-
mittee E13.19 on Separation Science.
Current edition approved April 1, 2021. Published April 2021. Originally For referenced ASTM standards, visit the ASTM website, www.astm.org, or
approved in 1974. Last previous edition approved in 2013 as E516–95a(2013). contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
DOI: 10.1520/E0516-95AR21. Standards volume information, refer to the standard’s Document Summary page on
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof the ASTM website.
this practice. Available from Compressed Gas Association (CGA), 8484 Westpark Drive,
See Appendix X1. Suite 220 McLean, VA 22102, http://www.cganet.com.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E516 − 95a (2021)
additional amplifiers are used between the detector and the 5.2.5.8 Method of measurement, and
final readout device, their characteristics should also first be
5.2.5.9 Type of power supply (for example, constant
established.
voltage, constant current).
5.2.5.10 For capillary detectors, the make-up gas, carrier,
4. Hazards
and reference flows should be stated.
4.1 Gas Handling Safety—Thesafehandlingofcompressed
5.3 Methods of Measurement:
gases and cryogenic liquids for use in chromatography is the
5.3.1 Sensitivitymaybemeasuredbyanyofthreemethods:
responsibility of every laboratory. The Compressed Gas
5.3.1.1 Experimental decay with exponential dilution flask
Association,(CGA),amembergroupofspecialtyandbulkgas
(8, 9) (see 5.4),
suppliers, publishes the following guidelines to assist the
5.3.1.2 Utilizing the permeation tube (10), under steady-
laboratory chemist to establish a safe work environment.
state conditions (see 5.5),
Applicable CGA publications include: CGAP-1, CGAG-5.4,
5.3.1.3 Utilizing Young’s apparatus (11), under dynamic
CGAP-9, CGAV-7, CGAP-12, and HB-3.
conditions (see 5.6).
5. Sensitivity (Response) 5.3.2 Calculation of TCD sensitivity by utilizing actual
chromatogramsisnotrecommendedbecauseinsuchacasethe
5.1 Definition:
amount of test substance corresponding to the peak cannot be
5.1.1 Sensitivity (response) of the TCD is the signal output
established with sufficient accuracy.
per unit concentration of a test substance in the carrier gas, in
accordance with the following relationship (7):
5.4 Exponential Decay Method:
5.4.1 A mixing vessel of known volume fitted with a
S 5AF /W (1)
c
magnetically driven stirrer is purged with the carrier gas at a
where:
known rate. The effluent from the flask is delivered directly to
S = sensitivity (response), mV·mL/mg,
the detector. A measured quantity of the test substance is
A = integrated peak area, mV·min,
introducedintotheflask,togiveaninitialconcentration, C,of
o
F = carrier gas flow rate (corrected to detector
c
the test substance in the carrier gas, and a timer is started
temperature ), mL/min, and
simultaneously.
W = mass of the test substance in the carrier gas, mg.
5.4.2 The concentration of the test substance in the carrier
5.1.2 If the concentration of the test substance in the carrier
gas at the outlet of the flask, at any time is given as follows:
gas,correspondingtoadetectorsignalisknown,thesensitivity
C 5 C exp@2F t/V # (3)
t o c f
is given by the following relationship:
where:
S 5 E/C (2)
d
C = concentration of the test substance at time t after
t
where:
introduction into the flask, mg/mL,
E = peak height, mV, and
C = initialconcentrationoftestcompoundintroducedinthe
o
C = concentration of the test substance in the carrier gas at
d
flask, mg/mL,
the detector, mg/mL.
F = carrier gas flow rate, corrected to flask temperature
c
mL/min,
5.2 Test Conditions:
t = time, min, and
5.2.1 Normalbutaneisthepreferredstandardtestsubstance.
V = volume of flask, mL.
f
5.2.2 The measurement must be made within the linear
range of the detector.
5.4.3 Todeterminetheconcentrationofthetestsubstanceat
5.2.3 The measurement must be made at a signal level at
thedetector, C ,itisnecessarytoapplythefollowingtempera-
d
least 100 times greater than the minimum detectability (200
ture correction:
times greater than the noise level) at the same conditions.
C 5 C T /T (4)
~ !
d t f d
5.2.4 The rate of drift of the detector at the same conditions
must be stated.
where:
5.2.5 The test substance and the conditions under which the
d
detector sensitivity is measured must be stated. This will
C = concentration of the test substance at the detector,
d
include but not necessarily be limited to the following:
mg/mL,
d
5.2.5.1 Type of detector (for example, platinum-tungsten
T = flask temperature, K, and
f
filament type),
T = detector temperature, K.
d
5.2.5.2 Detector geometry (for example, flow-type,
5.4.4 Thesensitivityofthedetectoratanyconcentrationcan
diffusion-type),
be calculated by:
5.2.5.3 Internal volume of the detector,
5.2.5.4 Carrier gas, S 5 E/C (5)
d
5.2.5.5 Carrier gas flow rate (corrected to detector
where:
temperature),
S = sensitivity, mV·mL/mg,
5.2.5.6 Detector temperature,
E = detector, signal, mV, and
5.2.5.7 Detector current,
E516 − 95a (2021)
5.6.1 In this method a known quantity of test substance is
C = concentration of the test substance at the detector,
d
injected into the flowing carrier gas stream.Alength of empty
mg/mL.
tubing between the sample injection point and the detector
NOTE 1—This method is subject to errors due to inaccuracies in
measuring the flow rate and flask volume. An error of 1% in the permitsthebandtospreadandbedetectedasaGaussianband.
measurement of either variable will propagate to 2% over two decades in
The detector signal is then integrated by any suitable method.
concentration and to 6% over six decades.Therefore, this method should
This method has the advantage that no special equipment or
not be used for concentration ranges of more than two decades over a
devices are required other than conventional chromatographic
single run.
hardware. For detectors optimized for capillary column flow
NOTE 2—A temperature difference of 1°C between flask and flow
rates,uncoated,deactivated,fusedsilicatubingshouldbeused.
measuring apparatus will, if uncompensated, introduce an error of ⁄3 %
into the flow rate.
5.6.2 The sensitivity of the detector is calculated from the
NOTE 3—Extreme care should be taken to avoid unswept volumes
peak area according to 5.1.1.
betweentheflaskandthedetector,asthesewillintroduceadditionalerrors
into the calculations.
NOTE 7—Care should be taken that the peak obtained is sufficiently
widesotheaccuracyoftheintegrationisnotlimitedbytheresponsetime
NOTE4—Flaskvolumesbetween100mLand500mLhavebeenfound
of the detector or of the recording device.
themostconvenient.Largervolumesshouldbeavoidedduetodifficulties
in obtaining efficient mixing and likelihood of temperature gradients. NOTE8—Peakareasobtainedbyintegration(A)orbymultiplyingpeak
i
heightbypeakwidthathalfheight(A )differby6%foraGaussianpeak:
c
5.5 Method Utilizing Permeation Tubes:
A 50.94 A (7)
c i
5.5.1 Permeation tubes consist of a volatile liquid enclosed
in a section of plastic tubing.They provide low concentrations
6. Minimum Detectability
of vapor by diffusion of the vapor through the walls of the
tubing. The rate of diffusion for a given permeation tube is
6.1 Definition—Minimum detectability is the concentration
dependent only on the temperature. As the weight loss over a
of the test substance in the carrier gas which gives a detector
period of time can be easily and accurately measured
signal equal to twice the noise level and is calculated from the
gravimetrically, the rate of diffusion can be accurately deter-
measured sensitivity and noise level values as follows:
mined. Hence, these devices have been proposed as primary
D 52N/S (8)
standards.
where:
5.5.2 Accurately known concentrations can be prepared by
passingagasoverthepreviouslycalibratedpermeationtubeat
D = minimum detectability, mg/mL,
constant temperature. The concentration of the test substance N = noise level, mV, and
S = sensitivity of the detector, mV·mL/mg.
in the gas can then be easily calculated according to the
following relationship:
6.2 Test Conditions—Measure sensitivity in accordance
C 5 R /F (6)
with the specifications given in Section 5. Measure noise level
T c
in accordance with the specifications given in Section 9. Both
where:
measurements have to be carried out at the same conditions
C = concentration of the test substance in the gas, mg/mL,
(for example, carrier gas identity and flow rate, detector
R = permeationrateofthetestsubstanceatthetemperature
T
temperature, and current) and preferably at the same time.
of the permeation tube, mg/min, and
When giving minimum detectability, state the noise level on
F = flow rate of the gas over the tube at the temperature of
c
which the calculation was based.
the tube, mL/min.
NOTE 5—If the flow rate of the gas is measured at a temperature
7. Linear Range
differentfromthetubetemperature,correctionmustbemade,asdescribed
in Appendix X1.
7.1 Definition—The linear range of a TCD is the range of
concentrations of the test substance in the carrier gas, over
5.5.3 When using a permeation tube for the testing of a
which the sensitivity of the detector is constant to within 5 %
TCD, the carrier gas is passing over a previously calibrated
as determined from the linearity plot specified in 7.2.2.
permeation tube containing the test substance at constant
temperatureandintroducedimmediatelyintothedetector,kept 7.1.1 The linear range may be expressed in three different
at the desired temperature. Knowing the concentration of the ways:
test substance in the carrier gas leaving the permeation tube at
7.1.1.1 As the ratio of the upper limit of linearity obtained
the temperature of the tube, the concentration at detector from the linearity plot, and the minimum detectability, both
temperature can be calculated directly, by applying the correc-
measured for the same test substance as follows:
tion specified in 5.4.2. Knowing this value and the detector
L.R. 5 ~C ! /D (9)
d
max
signal,thesensitivityofthedetectorcanbeobtainedaccording
where:
to the equation given in 5.4.4.
L.R. = linear range of the detector,
NOTE 6—Permeation tubes are suitable only for preparing relatively
(C ) = upper limit of linearity obtained from the linearity
d max
low concentrations in the part-per-million range. Hence for detectors of
plot, mg/mL, and
relatively low sensitivity or of higher noise levels, this method may not
D = minimum detectability, mg/mL.
satisfy the criteria given in 5.2.3, which requires that the signal be at least
100 times greater than the noise level.
If the linear range is expressed by this ratio, the minimum
5.6 Dynamic Method: detectability must also be stated.
E516 − 95a (2021)
7.1.1.2 By giving the minimum detectability and the upper upperlimitisthehighestconcentrationatwhichaslightfurther
−6
limit of linearity (for example, from 1×10 mg/mL to increase in concentration will give an observable increase in
−1
2×10 mg/mL). detector signal, and the dynamic range is the ratio of the upper
7.1.1.3 Bygivingthelinearityplotitself,withtheminimum and lower limits. The dynamic range can be greater than the
detectability indicated on the plot. linear range, but obviously cannot be smaller.
8.1.1 Thedynamicrangemaybeexpressedinthreedifferent
7.2 Method of Measurement:
ways:
7.2.1 For the determination of the linear range of a TCD,
8.1.1.1 As the ratio of the upper limit of dynamic range and
eithertheexponentialdecayorthedynamicmethodsdescribed
the minimum detectability by simultaneously stating the mini-
in 5.4 and 5.6 respectively may be used. The permeation tube
mum detectability (for example, 2×10 with a minimum
method (5.5) will not be suitable except for detectors of
−6
detectability of 1×10 mg/mL).
extremely unusual characteristics because of the limited range
8.1.1.2 By giving the minimum detectability and the upper
of concentrations obtainable with that method.
−6
limit of dynamic range (for example, from 1×10 mg/mL to
7.2.2 Measure the sensitivity at various concentrations of
2 mg/mL).
the test substance in the carrier gas in accordance with the
8.1.1.3 By giving the dynamic plot itself with the minimum
methods described above. Plot the sensitivity versus log
detectability indicated on the plot.
concentration on a semilog paper as shown in Fig. 1. Draw a
smooth line through the data points. The upper limit of 8.2 Methods of Measurement:
linearity is given by the intersection of the line with a value 8.2.1 Using the exponential decay method (see 5.4), mea-
0.95× S where S isthehighestvalueofsensitivityonthe sure the detector output signal (E) at various concentrations
max max
fitted curve. (C )ofthetestsubstanceinthecarriergas.Plot Eversus C on
d d
rectilinear graph paper, and draw a smooth curve through the
NOTE9—Thedynamicmethodwillgivesomewhatlargervaluesforthe
data points as shown in Fig. 2.The upper limit of the dynamic
upper limit of linearity as compared to the exponential decay method,
range is the concentration at which the slope is zero.
because the integrated signal will average increments of signal obtained
over the linear range of the detector with those obtained in t
...