ASTM E928-19
(Test Method)Standard Test Method for Purity by Differential Scanning Calorimetry
Standard Test Method for Purity by Differential Scanning Calorimetry
SIGNIFICANCE AND USE
5.1 The melting temperature range of a compound broadens as the impurity level rises. This phenomenon is described approximately by the van’t Hoff equation for melting point depressions. Measuring and recording the instantaneous heat flow into the specimen as a function of temperature during such a melting process is a practical way for the generation of data suitable for analysis by the van’t Hoff equation.
5.2 The results obtained include: sample purity (expressed as mole percent); enthalpy of fusion (expressed as J/mol); and the melting temperature (expressed in Kelvin) of the pure form of the major component.
5.3 Generally, the repeatability of this test method decreases as the purity level decreases. This test method is ordinarily considered unreliable when the purity level of the major component of the mixture is less than 98.5 mol % or when the incremental enthalpy correction (c) exceeds 20 % of the original detected enthalpy of fusion.
5.4 This test method is used for quality control, specification acceptance, and research.
SCOPE
1.1 This test method describes the determination of purity of materials greater than 98.5 mole percent purity using differential scanning calorimetry and the van’t Hoff equation.
1.2 This test method is applicable to thermally stable compounds with well-defined melting temperatures.
1.3 Determination of purity by this test method is only applicable when the impurity dissolves in the melt and is insoluble in the crystal.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 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.
1.6 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.
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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: E928 − 19
Standard Test Method for
1
Purity by Differential Scanning Calorimetry
This standard is issued under the fixed designation E928; 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* E967Test Method for Temperature Calibration of Differen-
tial Scanning Calorimeters and Differential ThermalAna-
1.1 Thistestmethoddescribesthedeterminationofpurityof
lyzers
materials greater than 98.5 mole percent purity using differen-
E968Practice for Heat Flow Calibration of Differential
tial scanning calorimetry and the van’t Hoff equation.
Scanning Calorimeters
1.2 This test method is applicable to thermally stable
E1970PracticeforStatisticalTreatmentofThermoanalytical
compounds with well-defined melting temperatures.
Data
E2161Terminology Relating to Performance Validation in
1.3 Determination of purity by this test method is only
applicable when the impurity dissolves in the melt and is Thermal Analysis and Rheology
insoluble in the crystal.
3. Terminology
1.4 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
3.1 Definitions—The definitions relating to this standard
standard.
appear in Terminologies E473 and E2161, including baseline,
calibration, detection limit, differential scanning calorimeter,
1.5 This standard does not purport to address all of the
endotherm, extrapolated onset, first-deviation-from-baseline,
safety concerns, if any, associated with its use. It is the
peak quantitation limit, repeatability, reproducibility, and val-
responsibility of the user of this standard to establish appro-
ley.
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
4. Summary of Test Method
1.6 This international standard was developed in accor-
dance with internationally recognized principles on standard-
4.1 This test method is based upon the van’t Hoff equation
ization established in the Decision on Principles for the 3
(1):
Development of International Standards, Guides and Recom-
2
T 5 T 2 RT χ / HF (1)
~ ! ~ !
s o o
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
where:
T = specimen temperature, K,
s
2. Referenced Documents
T = melting temperature of 100% pure material, K,
o
−1 −1
2
R = gas constant (= 8.314 J mol K ),
2.1 ASTM Standards:
χ = mole fraction of impurity,
E473Terminology Relating to Thermal Analysis and Rhe-
−1
H = heat of fusion, J mol , and
ology
F = fraction melted.
E793Test Method for Enthalpies of Fusion and Crystalliza-
tion by Differential Scanning Calorimetry
4.2 This test method consists of melting the test specimen
E794TestMethodforMeltingAndCrystallizationTempera-
that is subjected to a temperature-controlled program while
tures By Thermal Analysis
recording the heat flow into the specimen as a function of
temperature.Theresultingmeltingendothermareaismeasured
to yield the enthalpy of fusion, H.The melting endotherm area
1
is then partitioned into a series of fractional areas (about ten,
ThistestmethodisunderthejurisdictionofASTMCommitteeE37onThermal
Measurements and is the direct responsibility of Subcommittee E37.01 on Calo-
comprisingthefirst10to50%ofthetotalarea).Thefractional
rimetry and Mass Loss.
area, divided by the total area, yields the fraction melted, F.
Current edition approved May 1, 2019. Published May 2019. Originally
Each fractional area is assigned a temperature, T .
approved in 1983. Last previous edition approved in 2014 as E928–08 (2014). s
DOI: 10.1520/E0928-19.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
3
Standards volume information, refer to the standard’s Document Summary page on The boldface numbers in parentheses refer to a list of references at the end of
the ASTM website. this standard.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
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E928 − 19
4.3 Eq1hastheformofY=mX+bwhereY= T,X=1/F, 6. Interferences
s
2
m=−(RT χ)/ H, and b = T . A plot of Y versus X should
o o
6.1 This test method is nonspecific. Many impurities may
produce a straight line with slope m and intercept b.
causethemeltingtemperaturebroadening.Thus,it
...
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: E928 − 08 (Reapproved 2014) E928 − 19
Standard Test Method for
1
Purity by Differential Scanning Calorimetry
This standard is issued under the fixed designation E928; 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 Scope*
1.1 This test method describes the determination of purity of materials greater than 98.5 mole percent purity using differential
scanning calorimetry and the van’t Hoff equation.
1.2 This test method is applicable to thermally stable compounds with well-defined melting temperatures.
1.3 Determination of purity by this test method is only applicable when the impurity dissolves in the melt and is insoluble in
the crystal.
1.4 There is no ISO method equivalent to this test method.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 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.
1.6 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
2.1 ASTM Standards:
E473 Terminology Relating to Thermal Analysis and Rheology
E793 Test Method for Enthalpies of Fusion and Crystallization by Differential Scanning Calorimetry
E794 Test Method for Melting And Crystallization Temperatures By Thermal Analysis
E967 Test Method for Temperature Calibration of Differential Scanning Calorimeters and Differential Thermal Analyzers
E968 Practice for Heat Flow Calibration of Differential Scanning Calorimeters
E1970 Practice for Statistical Treatment of Thermoanalytical Data
E2161 Terminology Relating to Performance Validation in Thermal Analysis and Rheology
3. Terminology
3.1 Definitions—The definitions relating to thermal analysis appearing in Terminologythis standard appear in Terminologies
E473 shalland E2161be considered, including applicable to this test method. baseline, calibration, detection limit, differential
scanning calorimeter, endotherm, extrapolated onset, first-deviation-from-baseline, peak quantitation limit, repeatability,
reproducibility, and valley.
4. Summary of Test Method
3
4.1 This test method is based upon the van’tvan’t Hoff equation:equation (1):
2
T 5 T 2 RT χ / H F (1)
~ ! ~ !
s o o
1
This test method is under the jurisdiction of ASTM Committee E37 on Thermal Measurements and is the direct responsibility of Subcommittee E37.01 on Calorimetry
and Mass Loss.
Current edition approved Aug. 15, 2014May 1, 2019. Published September 2014May 2019. Originally approved in 1983. Last previous edition approved in 20082014 as
E928 – 08.E928 – 08 (2014). DOI: 10.1520/E0928-08R14.10.1520/E0928-19.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’sstandard’s Document Summary page on the ASTM website.
3
Brennan, W. P., DiVito, M. P., Fynas, R. L., Gray, A. P., “An Overview of the Calorimetric Purity Measurement”, in Purity Determinations by Thermal Methods, R. L.
Blaine and C. K. Schoff (Eds.), Special Technical Publication 838, American Society for Testing and Materials, West Conshohocken, PA, 1984, pp. 5–15.The boldface numbers
in parentheses refer to a list of references at the end of this standard.
4
Widman, G., Scherrer, O., “A New Program for DSC Purity Analysis”, Journal of Thermal Analysis, 371987, pp. 1957–1964.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
---------------------- Page: 1 ----------------------
E928 − 19
where:
T = specimen temperature, K,
s
T = melting temperature of 100 % pure material, K,
o
−1 − 1
R = gas constant (= 8.314 J mol K ),
−1 −1
R = gas constant (= 8.314 J mo
...
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