ISO 16014-1:2012
(Main)Plastics — Determination of average molecular mass and molecular mass distribution of polymers using size-exclusion chromatography — Part 1: General principles
Plastics — Determination of average molecular mass and molecular mass distribution of polymers using size-exclusion chromatography — Part 1: General principles
ISO 16014-1:2012 specifies a general method for determining the average molecular mass and the molecular mass distribution of polymers using size-exclusion chromatography (SEC). The average molecular mass and the molecular mass distribution are calculated from a calibration curve constructed using polymer standards if using one of the SEC techniques described in ISO 16014-2 to -4 or from a calibration curve constructed using absolute molecular mass data if using size-exclusion chromatography coupled with light-scattering detection (SEC‑LS) as described in ISO 16014-5.
Plastiques — Détermination de la masse moléculaire moyenne et de la distribution des masses moléculaires de polymères par chromatographie d'exclusion stérique — Partie 1: Principes généraux
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INTERNATIONAL ISO
STANDARD 16014-1
Second edition
2012-07-01
Plastics — Determination of average
molecular mass and molecular mass
distribution of polymers using size-
exclusion chromatography —
Part 1:
General principles
Plastiques — Détermination de la masse moléculaire moyenne
et de la distribution des masses moléculaires des polymères par
chromatographie d’exclusion stérique —
Partie 1: Principes généraux
Reference number
ISO 16014-1:2012(E)
©
ISO 2012
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ISO 16014-1:2012(E)
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ii © ISO 2012 – All rights reserved
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ISO 16014-1:2012(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 3
5 Reagents . 3
5.1 Eluent . 3
5.2 Reagent for column evaluation . 3
5.3 Molecular mass standards . 3
5.4 Reagent for flow rate marker (internal standard) . 4
5.5 Additives . 4
6 Apparatus . 4
6.1 General . 4
6.2 Eluent reservoir . 4
6.3 Pumping system . 4
6.4 Injector . 5
6.5 Columns . 5
6.6 Detector . 7
6.7 Tubing . 8
6.8 Temperature control . 8
6.9 Recorder and plotter . 8
6.10 Data-processing system . 8
6.11 Other components . 8
7 Procedure . 8
8 Data acquisition and processing . 8
8.1 Data acquisition . 8
8.2 Evaluation of data and correction of chromatograms . 9
8.3 Data processing . 9
9 Expression of results .10
9.1 Calibration curve .10
9.2 Calculation of average molecular mass . 11
9.3 Differential molecular mass distribution curve .12
9.4 Cumulative molecular mass distribution curve .13
10 Precision .13
11 Test report .14
11.1 General .14
11.2 Apparatus and measurement parameters .14
11.3 Calibration of the system .14
11.4 Calibration curve .14
11.5 Results .15
Annex A (informative) Supplementary information .16
Annex B (informative) Narrow molecular mass distribution standards .17
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ISO 16014-1:2012(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International
Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 16014-1 was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 5, Physical-
chemical properties.
This second edition cancels and replaces the first edition (ISO 16014-1:2003), which has been technically
revised. The main changes are the following:
a) the normative references have been updated (see Clause 2);
b) the text has been adapted to allow for the fact that a new part, ISO 16014-5, has now been published;
c) Subclause 6.5 (concerning the chromatographic columns used) has been revised;
d) Subclause 8.2 (concerning the evaluation of data and the correction of chromatograms) has been revised.
It also incorporates the Technical Corrigendum ISO 16014-1:2003/Cor.1:2005.
ISO 16014 consists of the following parts, under the general title Plastics — Determination of average molecular
mass and molecular mass distribution of polymers using size-exclusion chromatography:
— Part 1: General principles
— Part 2: Universal calibration method
— Part 3: Low-temperature method
— Part 4: High-temperature method
— Part 5: Method using light-scattering detection
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INTERNATIONAL STANDARD ISO 16014-1:2012(E)
Plastics — Determination of average molecular mass and
molecular mass distribution of polymers using size-exclusion
chromatography —
Part 1:
General principles
1 Scope
This part of ISO 16014 specifies a general method for determining the average molecular mass and the
molecular mass distribution of polymers using size-exclusion chromatography (SEC). The average molecular
mass and the molecular mass distribution are calculated from a calibration curve constructed using polymer
standards if using one of the SEC techniques described in Parts 2 to 4 of this International Standard or from
a calibration curve constructed using absolute molecular mass data if using size-exclusion chromatography
coupled with light-scattering detection (SEC-LS) as described in Part 5 of this International Standard.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced document
(including any amendments) applies.
ISO 472, Plastics — Vocabulary
ISO 16014-2:2012, Plastics — Determination of average molecular mass and molecular mass distribution of
polymers using size-exclusion chromatography — Part 2: Universal calibration method
ISO 16014-3, Plastics — Determination of average molecular mass and molecular mass distribution of polymers
using size-exclusion chromatography — Part 3: Low-temperature method
ISO 16014-4, Plastics — Determination of average molecular mass and molecular mass distribution of polymers
using size-exclusion chromatography — Part 4: High-temperature method
ISO 16014-5:2012, Plastics — Determination of average molecular mass and molecular mass distribution of
polymers using size-exclusion chromatography — Part 5: Method using light-scattering detection
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 472 and the following apply.
3.1
size-exclusion chromatography
SEC
a liquid chromatographic technique in which the separation is based on the hydrodynamic volume of molecules
eluting in a column packed with porous non-adsorbing material having pore dimensions that are similar in size
to the molecules being separated
NOTE The term gel permeation chromatography (GPC) should only be used where the porous non-adsorbing packing
material is a gel; however, the term size-exclusion chromatography (SEC) is preferred.
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ISO 16014-1:2012(E)
3.2
light-scattering detection
LS detection
a technique for determining the mass or size of polymer molecules dissolved in solution by measuring the light
scattered by the polymer molecules
3.3
molecular mass
M
sum of the masses of the atoms making up a molecule
NOTE Molecular weight is also used for molecular mass, but is deprecated.
3.4
average molecular mass
four types of average molecular mass are defined by the following equations, where N is the number of
i
molecules of species i of molecular mass M and a is the exponent of the Mark-Houwink-Sakurada equation.
i
3.4.1
number-average molecular mass
M
n
∞
()NM×
∑ ii
i=1
M = (1)
n
∞
N
∑ i
i=1
3.4.2
mass-average molecular mass
M
w
∞
2
()NM×
∑ ii
i=1
M = (2)
w
∞
()NM×
∑ ii
i=1
3.4.3
z-average molecular mass
M
z
∞
3
()NM×
∑ ii
i=1
M = (3)
z
∞
2
()NM×
∑ ii
i=1
3.4.4
viscosity-average molecular mass
M
v
1/a
∞
a+1
()NM×
∑ ii
i=1
M = (4)
v
∞
()NM×
∑ ii
i=1
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ISO 16014-1:2012(E)
4 Principle
A polymer sample is dissolved in a suitable solvent to make a dilute solution. This solution is injected into
the mobile phase and onto the SEC column, which is packed with non-adsorbing material made up of small
particles having pores of similar or varying size. As the polymer sample passes through the column, the
polymer molecules are separated from each other according to the difference in their molecular masses, or
more precisely, the difference in their molecular sizes (i.e. their hydrodynamic volume). In SEC, the larger-
size molecules cannot permeate into the pores, and thus elute faster, while smaller molecules can permeate
into the pores and elute more slowly. The polymer concentration in the eluate is continuously monitored by a
concentration-sensitive detector (coupled to a light-scattering detector if SEC-LS is being used) to give an SEC
chromatogram.
In the SEC techniques described in Parts 2 to 4, the molecular mass at any elution time on the SEC chromatogram
is determined from a calibration curve which is constructed using reference polymer standards with a narrow
molecular mass distribution. In SEC-LS, described in Part 5 of this International Standard), a calibration curve
constructed using absolute molecular mass data obtained from the SEC-LSchromatogram at any elution time is
used. The average molecular mass and the molecular mass distribution of the unknown polymer are calculated
by using the molecular mass and concentration data corresponding to each elution time.
5 Reagents
5.1 Eluent
The required purity of the eluent used for SEC varies with the application, but in general the solvent should be
free of particulate matter and substances that react with the polymer or interfere with detection of the polymer.
Additives such as antioxidants and salts can be used to prevent the degradation of the eluent, the aggregation
of polymer molecules, the adsorption of the polymer on the packing material and for other purposes. A
mixed eluent may also be used in the SEC techniques described in Parts 2 to 4 to modify the solubility and
the refractive index, or to reduce the cost of the mobile phase. A mixed eluent cannot be used for SEC-LS
measurements, however, because the polymer selectively adsorbs the components of the mixed eluent, thus
giving an erroneous result.
5.2 Reagent for column evaluation
A low molecular mass compound is used for the determination of the theoretical plate number, asymmetry
factor and resolution factor of the column.
5.3 Molecular mass standards
The test methods described in Parts 2 to 4 of this International Standard are not absolute methods but relative
ones, and require a calibration curve for the calculation of the average molecular mass and the molecular mass
distribution from the SEC chromatogram. This calibration curve is plotted using standards of known molecular
mass and narrow molecular mass distribution. The value of M and/or M of the standard determined by an
w n
absolute method, such as light scattering, membrane osmometry, vapour pressure osmometry, ultracentrifugation
or end-group analysis. The polydispersity M /M is calculated by dividing the absolute value of M by the
w n w
absolute value of M . The polydispersity of the polymer standards shall lie within the following ranges:
n
3
M < 2 × 10 M /M < 1,20
p w n
3 6
2 × 10 ≤ M < 10 M /M < 1,10
p w n
6
10 ≤ M M /M < 1,20
p w n
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ISO 16014-1:2012(E)
where
M is the mass-average molecular mass;
w
M is the number-average molecular mass;
n
M is the molecular mass at peak maximum.
p
M can be calculated from Equation (5):
p
12/
MM=×()M (5)
pn w
NOTE Some commercially available molecular mass standards specify the value of M and M but not M . In such
w n p
cases, Equation (5) can be used to provide the value of M , provided the molecular mass distribution of the polymer
p
sample is a logarithmic normal distribution.
Some examples of commercially available molecular mass standards are given in Annex B.
In the case of SEC-LS (see Part 5 of this International Standard), such molecular mass standards are
unnecessary because SEC-LS is an absolute method.
5.4 Reagent for flow rate marker (internal standard)
A low molecular mass compound is used to monitor the accuracy of the elution time, i.e. to evaluate whether
or not the data are within the specification.
5.5 Additives
Additives to the eluents may be used to improve SEC performance and prevent sample degradation and the like.
6 Apparatus
6.1 General
A schematic diagram of an SEC system is shown in Figure 1. The essential components are an eluent reservoir,
a pumping system, an injector, column(s), a detector, tubing, a recorder, a temperature-control system, and
a data-processing system. For SEC-LS measurements, a light-scattering detector, i.e. a molecular-mass-
sensitive detector, is coupled to the normal (concentration-sensitive) detector. Any light-scattering detector that
meets the requirements specified for this method may be used.
6.2 Eluent reservoir
The eluent reservoir should preferably have sufficient capacity to hold the amount of eluent required for column
calibration and successive measurements. Dissolved air in the eluent should preferably be removed before use
by placing the solvent in a suitable container designed to reduce the pressure and placing this container in an
ultrasonic bath, or by using a vacuum degasser between the reservoir and the pumping system. Particles in
the eluent may be removed by membrane filtration. It is desirable in addition to bubble an inert gas through the
eluent in the reservoir and blanket the surface of the eluent with the gas, and to shield the reservoir from light.
6.3 Pumping system
A constant, pulseless flow of eluent through the column is desirable. The flow rate should preferably be
3
approximately 1 cm /min for a column of approximately 8 mm inner diameter. The SEC system shall have an
overall flow-rate precision of within ±0,3 %. Lower flow rates are recommended for high molecular mass and/or
shear-sensitive polymers and viscous eluents. To keep the flow rate constant, temperature control providing a
stability of at least ±1 °C is required for the pumping system.
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ISO 16014-1:2012(E)
The flow rate shall be monitored by the use of an internal standard, or by a direct method such as volume or
mass measurements (see Annex A, Clause A.2), and corrected in the event of significant deviations. In the
methods described in Parts 2 to 4 of this International Standard, knowledge of the value of the flow rate is
not required because the method is a
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