prEN ISO 3924

SLOVENSKI STANDARD
01-maj-2026
Naftni proizvodi - Določanje destilacijskega območja - Metoda plinske
kromatografije (ISO/DIS 3924:2026)
Petroleum products - Determination of boiling range distribution - Gas chromatography
method (ISO/DIS 3924:2026)
Mineralölerzeugnisse - Bestimmung des Siedeverlaufs - Gaschromatographisches
Verfahren (ISO/DIS 3924:2026)
Produits pétroliers - Détermination de la répartition dans l'intervalle de distillation -
Méthode par chromatographie en phase gazeuse (ISO/DIS 3924:2026)
Ta slovenski standard je istoveten z: prEN ISO 3924
ICS:
75.080 Naftni proizvodi na splošno Petroleum products in
general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 3924
ISO/TC 28
Petroleum products —
Secretariat: NEN
Determination of boiling range
Voting begins on:
distribution — Gas chromatography
2026-03-03
method
Voting terminates on:
2026-05-26
Produits pétroliers — Détermination de la répartition dans
l'intervalle de distillation — Méthode par chromatographie en
phase gazeuse
ICS: 75.080
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
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Reference number
ISO/DIS 3924:2026(en)
DRAFT
ISO/DIS 3924:2026(en)
International
Standard
ISO/DIS 3924
ISO/TC 28
Petroleum products —
Secretariat: NEN
Determination of boiling range
Voting begins on:
distribution — Gas chromatography
method
Voting terminates on:
Produits pétroliers — Détermination de la répartition dans
l'intervalle de distillation — Méthode par chromatographie en
phase gazeuse
ICS: 75.080
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2026
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Published in Switzerland Reference number
ISO/DIS 3924:2026(en)
ii
ISO/DIS 3924:2026(en)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Reagents and materials . 2
6 Apparatus . 4
7 Sampling . 7
8 Preparation of apparatus . 7
8.1 Column preparation .7
8.1.1 General .7
8.1.2 Packed columns .7
8.1.3 Capillary columns .7
8.2 Chromatograph .8
8.3 Column resolution .8
8.4 Detector response check .9
8.5 Peak skewness .9
9 Calibration .10
9.1 Analysis sequence protocol .10
9.2 Baseline compensation analysis .10
9.3 Retention time versus boiling point calibration .11
9.4 Analysis of reference material . 12
10 Procedure .13
10.1 Sample preparation . 13
10.2 Sample analysis . .14
11 Calculation . 14
12 Expression of results . 14
13 Precision .15
13.1 General . 15
13.2 Repeatability Procedure A . 15
13.3 Reproducibility Procedure A . 15
13.4 Repeatability Procedure B .16
13.5 Reproducibility Procedure B .16
13.6 Bias .16
14 Test report . 17
Annex A (informative) Calculation of ISO 3405 equivalent data .18
Annex B (normative) Reference material specified values and deviation limits .21
Annex C (informative) Boiling points of non-normal n-alkane hydrocarbons.23
Annex D (informative) Boiling point revision .27
Annex E (informative) Alternative hydrogen and nitrogen carrier gases using Procedure B .28
Annex F (informative) Hydrogen and nitrogen carrier gases using Procedure A .35
Bibliography . 41

iii
ISO/DIS 3924:2026(en)
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.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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. Details of any patent
rights identified during the development of the document will be in the Introduction and/or on the ISO list of
patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 28, Petroleum and related products, fuels and
lubricants from natural or synthetic sources.
[1] [2]
This method was originally based on the joined IP 406 and ASTM D2887-16 methods.
This sixth edition cancels and replaces the fifth edition (ISO 3924:2019), which has been technically revised.
The main changes compared with the previous edition are as follows.
— Introduction of bias information for alternative carrier gasses for Procedure A.
— Revision of Figure 2 to define at what height of the peak , the width is to be measured.
— Correct the apparatus and process requirements that are not applicable for Procedure B.
— Update the recommended slice rate for this method.
— Correct several items in the Annexes as presented during the 2025 systematic review
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
DRAFT International Standard ISO/DIS 3924:2026(en)
Petroleum products — Determination of boiling range
distribution — Gas chromatography method
WARNING — WARNING — The use of this document can involve hazardous materials, operations and
equipment. This document does not purport to address all the safety problems associated with its
use. It is the responsibility of users of this document to take appropriate measures to ensure the
safety and health of personnel prior to application of the document.
1 Scope
This document specifies a method for the determination of the boiling range distribution of petroleum
products. The method is applicable to petroleum products and fractions with a final boiling point of 538 °C
or lower at atmospheric pressure as determined by this document. This document does not apply to gasoline
samples or gasoline components. The method is limited to products having a boiling range greater than 55
°C and having a vapour pressure sufficiently low to permit sampling at ambient temperature.
The document describes two procedures.
a) Procedure A allows a larger selection of columns and analysis conditions, such as packed and capillary
columns as well as a thermal conductivity detector in addition to the flame ionization detector. Analysis
times range from 14 min to 60 min.
b) Procedure B is restricted to only three capillary columns and requires no sample dilution. The analysis
time is reduced to about 8 min.
Both procedures have been successfully applied to samples containing fatty acid methyl esters (FAME) up to
20 % (volume fraction).
NOTE For the purposes of this document, the terms “% (mass fraction)” and “% (volume fraction)” are used to
represent the mass fraction (µ), the volume fraction (φ) of a material.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements 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 3170, Hydrocarbon Liquids — Manual sampling
ISO 3171, Petroleum liquids — Automatic pipeline sampling
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/

ISO/DIS 3924:2026(en)
3.1
initial boiling point
IBP
temperature corresponding to the retention time at which a net area count equal to 0,5 % of the total sample
area under the chromatogram is obtained
3.2
T10, T30, T50, T70, T90
temperature (T) corresponding to the retention time at which a net area count equal to the 10 %, 30 %, 50
%, 70 % or 90 % of the total sample area under the chromatogram is obtained
3.3
final boiling point
FBP
temperature corresponding to the retention time at which a net area count equal to 99,5 % of the total
sample area under the chromatogram is obtained
3.4
slice rate
number of data slices acquired per unit of time used to integrate the continuous (analogue) chromatographic
detector response during an analysis
Note 1 to entry: The slice rate is expressed in Hz (for example, slices per second).
4 Principle
A sample is introduced into a gas chromatographic column, which separates hydrocarbons in the order of
increasing boiling point. The column temperature is raised at a reproducible rate and the area under the
chromatogram is recorded throughout the analysis. Boiling temperatures are assigned to the time axis
from a calibration curve, obtained under the same conditions by running a known mixture of hydrocarbons
covering the boiling range expected in the sample. From these data, the boiling range distribution is
obtained.
[3][4]
Annex A presents a correlation model for the calculation of physical distillationISO 3405 ASTM D6708-
[5]
13 equivalent data from boiling range distribution analysis by gas chromatography determined following
this document.
5 Reagents and materials
5.1 Stationary phase for columns, non-polar, that elutes hydrocarbons in boiling point order.
NOTE The following materials have been used successfully as liquid phases, other stationary phases can be used,
see 6.2.
For packed columns:
— silicone gum rubber UC-W98;
— silicone gum rubber GE-SE-30;
— silicone gum rubber OV-1;
— silicone gum rubber OV-101.
For capillary columns:
— polydimethylsiloxane.
ISO/DIS 3924:2026(en)
5.2 Solid support for packed columns, usually consisting of crushed fire brick or chromatographic
diatomaceous earth.
The particle size and support loading shall be such as to give optimum resolution and analysis time.
NOTE In general, support loadings of 3 % to 10 % have been found most satisfactory.
5.3 Carrier gas, with a minimum purity of 99,995 %, constituted of:
a) helium for use with flame ionization detectors (FIDs) or thermal conductivity detectors;
b) for the use of nitrogen or hydrogen as a carrier gas, see Annex E and Annex F.
CAUTION — CAUTION — Helium and nitrogen are compressed gases under high pressure. Hydrogen
is an extremely flammable gas under high pressure.
5.4 Hydrogen, grade suitable for FIDs.
CAUTION — Hydrogen is an extremely flammable gas under high pressure.
5.5 Compressed air, free of oil and water, regulated for FIDs.
CAUTION — Compressed air is a gas under high pressure and supports combustion.
5.6 Calibration mixture, consisting of an accurately weighed mixture of n-alkanes covering the range
from C to C and dissolved in carbon disulfide (5.8).
5 44
For packed columns, the final concentration in mass should be approximately 10 parts of the n-alkane
mixture to 100 parts of carbon disulfide. For capillary columns, the final concentration in mass should be
approximately 1 part of the n-alkane mixture to 100 parts of carbon disulfide.
The following mixture of n-alkanes has been found to be satisfactory for most samples: C , C , C , C , C , C ,
5 6 7 8 9 10
C , C , C , C , C , C , C , C , C , C , C . At least one component of the mixture shall have a boiling
12 14 16 18 20 24 28 32 36 40 44
point lower than the initial boiling point (IBP) of the sample and at least one component shall have a boiling
point higher than the final boiling point (FBP) of the sample. The boiling points of n-alkanes are listed in
Table 1.
If the test sample contains significant quantities of n-alkanes that can be identified on the chromatogram,
these peaks can be used as internal boiling point calibration points. However, it is advisable to use the
calibration mixture to be sure of peak identifications.
Propane and butane can be added non-quantitatively to the calibration mixture, if necessary, to conform to
5.6. This can be done by bubbling a small amount of the gaseous hydrocarbon into a septum-sealed vial of
the calibration mixture using a gas syringe.
If stationary phases other than those listed in the note in 5.1 are used, the retention times of a few
alkylbenzenes across the boiling range, such as o-xylene, n-butylbenzene, 1,3,5-tri-isopropylbenzene,
n-decylbenzene and n-tetradecylbenzene, shall also be checked to make certain that the column is separating
according to the boiling point order (see Annex C).
5.7 Reference material, the primary reference material used shall be ASTM reference gas oil no. 1 or no.
2 (as specified in Annex B).
5.8 Carbon disulfide, reagent grade or better (CAS RN 75-15-0).
CAUTION — Carbon disulfide is extremely volatile flammable and toxic.

ISO/DIS 3924:2026(en)
Table 1 — Boiling points of normal n-alkanes
Carbon no. Boiling point Carbon no. Boiling point
°C °C
2 −89 24 391
3 −42 25 402
4 0 26 412
5 36 27 422
6 69 28 431
7 98 29 440
8 126 30 449
9 151 31 458
10 174 32 466
11 196 33 474
12 216 34 481
13 235 35 489
14 254 36 496
15 271 37 503
16 287 38 509
17 302 39 516
18 316 40 522
19 330 41 528
20 344 42 534
21 356 43 540
22 369 44 545
23 380
[4]
NOTE API Project 44 is believed to have provided the original normal paraffin boiling point data that were listed in former
editions of this document. However, over the years, some of the data contained in both API Project 44 (Thermodynamics Research
Center Hydrocarbon Project) and the test methods have changed, and they are no longer equivalent. This table represents the
current normal paraffin boiling point values accepted by ISO, ASTM and the Energy Institute. Annex D contains information
about revised boiling points.
6 Apparatus
6.1 Chromatograph, any gas chromatograph that has the following performance characteristics can be
used.
6.1.1 Detector, of either the flame ionization or thermal conductivity type.
The detector shall have sufficient sensitivity to detect a mass fraction of 1,0 % of dodecane with a peak
height of at least 10 % of full scale under the conditions specified in this document, and without loss of
resolution as defined in 8.3. When operating at this sensitivity level, detector stability shall be such that
a baseline drift of not more than 1 % of full scale per hour is obtained. The detector shall be capable of
operating continuously at a temperature equivalent to the maximum column temperature employed. The
detector shall be connected to the column in such a way that any cold spots between the detector and the
column are avoided.
NOTE It is not desirable to operate thermal conductivity detectors at a temperature higher than the maximum
column temperature employed. Operation at higher temperatures only serves to shorten the useful life of the detector,
and generally contributes to higher noise levels and greater drift.

ISO/DIS 3924:2026(en)
6.1.2 Column temperature programmer, capable of programmed temperature operation over a range
sufficient to establish a retention time of at least 1 min for the IBP (for Procedure A), and to elute the entire
sample within the temperature ramp.
The programming rate shall be sufficiently reproducible to obtain retention time repeatability of 6 s for
each component in the calibration mixture (5.6).
6.1.3 Cryogenic column cooling. Column starting temperatures below ambient will be required if
samples with IBPs of less than 34 °C are to be analysed. This is typically provided by adding a source of
either liquid carbon dioxide or liquid nitrogen, controlled through the oven temperature circuitry.
However, excessively low initial column temperatures shall be avoided, to ensure that the stationary phase
remains liquid. The initial temperature of the column shall be only low enough to obtain a calibration curve
meeting the requirements of this document.
6.1.4 Sample inlet system. Programmed temperature vaporization (PTV) inlets or cool on-column inlets
shall be used for this method.
The sample inlet system shall be connected to the chromatographic column in such a way that any cold spots
between the inlet system and the column are avoided.
6.2 Column. Any column and conditions can be used, provided that, under the conditions of the test,
separations are in the order of boiling points as given in Table 1, and the column resolution, R , is at least
c
three (see 8.3). Typical column operating conditions are given in Table 2, Table 3 and Table 4.
Table 2 — Typical operating conditions for packed columns — Procedure A
Parameter Column 1
Column length (m) 0,7
Column outside diameter (mm) 3,2
Stationary phase OV-101
Per cent stationary phase 5
a
Support material G
Support mesh size (μm) 80/100
Initial column temperature (°C) −40
Final column temperature (°C) 350
Programming rate (°C/min) 10
Carrier gas Helium
Carrier gas flow (ml/min) 30
Inlet Packed inlet
Detector FID
Detector temperature (°C) 370
Injection-port temperature (°C) 370
Sample size (μl), neat sample volume 0,5
a
Dioxosilane.
ISO/DIS 3924:2026(en)
Table 3 — Typical operating conditions for capillary columns — Procedure A
Parameter Column 2 Column 3
Column length (m) 5 10
Column inner diameter (mm) 0,53 0,53
Column PDMS PDMS
Stationary phase thickness (μm) 0,88 2,65
Carrier gas Helium Helium
Carrier gas flow rate (ml/min) 12 20
Initial column temperature (°C) 35 40
Final column temperature (°C) 350 350
Programming rate (°C/min) 10 15
Final time at final column temperature (min) 4 4
Detector FID FID
Detector temperature (°C) 380 350
Programmed temperature
Injector temperature (°C) Cool on-column type
vaporization type
Sample size (μl) 1 0,2
Sample concentration [% (mass fraction)] 10 Neat
Key
PDMS = polydimethylsiloxane.
Table 4 — Typical operating conditions for accelerated analysis — Procedure B
Parameter Column 1 Column 2 Column 3
Column length (m) 10 5 7,5
Column ID (mm) 0,53 0,53 0,53
a
Stationary phase PDMS PDMS PDMS
Stationary phase thickness (µm) 0,88 2,65 1,5
Carrier gas Helium Helium Helium
Carrier gas flow rate (ml/min) 26 35 37
Initial column temperature (°C) 60 40 40 (0,5 min)
Final column temperature (°C) 360 350 360
Oven programming rate (°C/min) 35 35 35
Final time at final column temperature (min) 4 4 4
Detector FID FID FID
Detector temperature (°C) 360 360 365
Injector PTV PTV Cool on-column
Injector initial temperature (°C) 100 100 100 (0,5 min)
Injector programming rate (°C/min) 35 35 35
Injector final temperature (°C) 360 350 350
Sample size (µl) 0,1 0,1 0,1
Dilution concentration Neat Neat Neat
Analysis time (min) 8 7,8 8
Key
PDMS = polydimethylsiloxane.
6.3 Integrator/computer, used for determining the accumulated area under the chromatogram. This
can be achieved by using a computer-based chromatography data system or an electronic integrator. The

ISO/DIS 3924:2026(en)
integrator/computer system shall have normal chromatographic software for measuring the retention
times and areas of eluting peaks. In addition, the system shall be capable of converting the continuously
integrated detector signal into area slices of fixed duration. These contiguous area slices, collected for the
entire analysis, shall be stored for later processing. The electronic range of the integrator/computer (e.g. 1
V) shall be within the linear range of the detector/electrometer system used. The system shall be capable of
subtracting the area slice of a blank run from the corresponding area slice of a sample run.
NOTE Some gas chromatographs have an algorithm built into their operating software that allows a mathematical
model of the baseline profile to be stored in the memory. This profile can be automatically subtracted from the detector
signal on subsequent sample analysis to compensate for any baseline offset. Some integration systems also store and
automatically subtract a blank analysis from subsequent sample analysis.
6.4 Flow/pressure controllers.
6.4.1 If a packed column is used, the chromatograph shall be equipped with constant-flow controllers
capable of maintaining the carrier gas flow constant over the full operating temperature range.
6.4.2 If a wide-bore capillary column is used, the chromatograph shall be equipped with a controller of
carrier gas flow or pressure appropriate for the inlet used.
6.5 Micro-syringe, used to introduce the sample into the chromatograph. Sample injection can be
either manual or automatic. Automatic sample injection is preferred because it gives better retention time
precision.
7 Sampling
Unless otherwise specified, samples shall be taken by the procedures described in ISO 3170 or ISO 3171.
8 Preparation of apparatus
8.1 Column preparation
8.1.1 General
Any satisfactory method that will produce a column meeting the requirements of 6.2 can be used. The column
shall be conditioned at the maximum operating temperature to reduce baseline shifts due to bleeding of the
column substrate.
8.1.2 Packed columns
An acceptable method of column conditioning, which has been found effective for columns with an initial
loading of 10 % liquid phase, consists of purging the column with carrier gas at the normal flow rate while
holding the column at the maximum operating temperature for 12 h to 16 h.
8.1.3 Capillary columns
Capillary columns shall be conditioned using the following procedure.
a) Install the column following the manufacturer’s instructions. Set the column and detector gas flows.
Ensure that the system is leak free.
b) Allow the system to purge with carrier gas at ambient temperature for at least 30 min. Then increase
the oven temperature by approximately 5 °C/min to 10 °C/min to the final operating temperature and
hold for approximately 30 min.
c) Cycle the chromatograph through its temperature programme several times until a stable baseline is
obtained.
ISO/DIS 3924:2026(en)
NOTE 1 Capillary columns with cross-linked and bonded phases are available from many manufacturers and are
usually preconditioned. These columns have much lower column bleed than packed columns.
NOTE 2 The column is not always connected to the FID when making a first conditioning of the column to overcome
that initial column bleed affects the detector’s sensitivity.
8.2 Chromatograph
Place the chromatograph in service in accordance with the manufacturer’s instructions. Typical operating
conditions are shown in Table 2 and Table 3.
If a FID is used, the deposits formed in the detector from combustion of the silicone decomposition products
shall be removed regularly, as they change the response characteristics of the detector.
8.3 Column resolution
Analyse the calibration mixture under the same conditions as those used for the samples. Using the
procedure illustrated in Figure 1, calculate the resolution, R , from the time between the hexadecane and
c
octadecane peaks at the peak maxima t and t and the widths y and y of the peaks at half height, as given
1 2 1 2
by Formula (1).
Key
X time, in s
Y detector signal
t start analysis time
t retention time hexadecane, in s
t retention time octadecane, in s
y width of hexadecane peak at half height, in s
y width of octadecane peak at half height, in s
1 hexadecane
2 octadecane
Figure 1 — Column resolution parameters

ISO/DIS 3924:2026(en)
(1)
where
t is the retention time, in seconds, for hexadecane peak maximum;
t is the retention time, in seconds, for octadecane peak maximum;
y is the width, in seconds, at half height of hexadecane peak;
y is the width, in seconds, at half height of octadecane peak.
The resolution, R , obtained from Formula (1), shall be at least three.
c
8.4 Detector response check
This method assumes that the detector response to petroleum hydrocarbons is proportional to the mass of
individual components. This shall be verified when the system is put into service and whenever any changes
are made to the system or operational parameters. Analyse the calibration mixture (5.6) using the same
conditions as those used for the samples. Calculate the response factor, F , for each n-alkane relative to
n
decane using Formula (2):
(2)
where
F is the relative response factor;
n
m is the mass of the n-alkane in the mixture;
n
A is the peak area of the n-alkane;
n
m is the mass of decane in the mixture;
A is the peak area of decane.
The relative response factor, F , of each n-alkane shall not deviate from 1,0 by more than ±0,1.
n
8.5 Peak skewness
Determine the peak skewness (the ratio A/B) of the largest peak in the calibration mixture (5.6) as shown in
Figure 2.
The peak skewness shall be not less than 0,5 and not more than 2,0. If peak skewness is outside these
parameters, reanalyse the calibration mixture using a smaller sample size or a more dilute solution, if
necessary, to avoid peak distortion.
NOTE Skewness is often an indication of overloading the column that results in displacement of the peak apex
relative to non-overloaded peaks. Distortion in retention time measurement and hence errors in boiling point
determination will be likely if column overloading occurs. The column liquid phase loading has a direct bearing on the
acceptable sample size.
ISO/DIS 3924:2026(en)
Key
X time, in s
Y detector signal
A width of the leading part of the peak at 5 % of peak height, in s
B width of the trailing part of the peak at 5 % of peak height, in s
Figure 2 — Peak skewness
9 Calibration
9.1 Analysis sequence protocol
9.1.1 Define and use for all runs a predetermined schedule of analysis events to achieve maximum
reproducibility. The schedule shall include cooling the oven to the initial starting temperature, equilibration
time, sample injection and system start, and analysis and final temperature hold time.
9.1.2 After the chromatographic conditions have been set to meet performance requirements, programme
the column temperature upward to the maximum temperature to be used and hold that temperature for the
selected time. Following the analysis sequence protocol, cool the column to the initial starting temperature.
9.1.3 During the cool down and equilibration time, prepare the integrator/computer system for data
acquisition. If a retention time or detector response calibration is being performed, use the peak detection
mode. For samples and baseline compensation determinations, use the area slice mode of integration.
The sampling frequency has to be adjusted so that at least a significant number of slices are acquired prior
to the start of elution of sample or solvent. The recommended slice rate for this Procedure A is 1 Hz (one slice
per second), where for Procedure B it is 10 Hz (ten slices per second).
9.1.4 At the exact time set by the schedule, inject either the calibration mixture (5.6) or sample into the
chromatograph, or make no injection (baseline blank). At the time of injection and/or at the start of the
baseline blank, start the chromatograph time cycle and the integrator/computer data acquisition. Follow
this analysis sequence protocol for all subsequent analysis, blanks or calibrations.
9.2 Baseline compensation analysis
9.2.1 A baseline compensation analysis, or baseline blank, shall be performed at least once each day that
the test is run, using the same technique for a sample analysis except that no injection is made.

ISO/DIS 3924:2026(en)
NOTE The blank analysis is necessary due to the normal occurrence of chromatographic baseline rise near the
maximum column temperature. Factors that influence baseline stability are column bleed, septum bleed, detector
temperature control, constancy of carrier and detector gas flows, leaks, instrument drift, etc.
9.2.2 Subtract the blank analysis from the sample analysis to remove any non-sample slice area from the
chromatographic data.
The blank analysis is typically performed prior to sample analysis, but can be useful if determined between
samples or at the end of a sample sequence to provide additional data regarding instrument operation or
residual sample carry-over from previous sample analysis.
9.2.3 Carry out periodic baseline blank analysis in accordance with the analysis sequence protocol to give
an indication of baseline stability.
9.3 Retention time versus boiling point calibration
9.3.1 It is highly recommended to perform a retention time versus boiling point calibration (see Figure 3)
at least once each day that the test is run. Inject an appropriate aliquot (0,2 μl to 2,0 μl) of the calibration
mixture (5.6) into the chromatograph following the analysis sequence protocol.
Figure 3 — Typical chromatogram of a retention time versus boiling point sample
9.3.2 Prepare a calibration table based on the results of the analysis of the calibration mixture (5.6)
by recording the retention time and the boiling temperature for each component in the mixture. Boiling
temperatures of n-alkanes are listed in Table 1.
9.3.3 Plot the retention time of each peak versus the corresponding boiling temperature for that
component. A typical calibration curve is shown in Figure 4.
9.3.4 Ensure that calibration points bracket the boiling range of the sample at both the low and high ends.
Ideally, the calibration plot of retention time versus boiling temperature should be linear, but it is impractical
to operate the chromatograph such that curvature is eliminated completely.
NOTE The greatest potential for deviation from linearity is associated with the lower boiling point n-alkanes,
which elute from the column relatively quickly and have the largest difference in boiling temperatures. In general, the
lower the sample IBP, the lower the starting point of the analysis will be.

ISO/DIS 3924:2026(en)
9.4 Analysis of reference material
9.4.1 The reference material (5.7) is used to verify both the chromatographic and calculation processes
involved in this method.
A secondary reference material can be used, providing it satisfies the following criteria:
a) it is similar in nature and boiling range to the samples to be analysed;
b) the boiling range distribution values assigned to that obtained by averaging multiple analysis of the
secondary reference material on a system that is first shown to be operating properly with the primary
reference material (5.7).
9.4.2 Analyse the primary reference material (5.7) or a secondary reference material at least once each
day that the test is run. Perform an analysis of the reference material following the analysis sequence
protocol (see 9.1). Collect the area slice data and provide a boiling point distribution report in accordance
with 12.1. See Figure 4 for a typical chromatogram of reference material.
Figure 4 — Typical chromatogram of a reference material
9.4.3 The results of the analysis of the reference material (either batch 1 or batch 2 can be used) shall not
deviate more from the values for that batch given in Annex B than the range specified by the reproducibility
of this document (see 13.3 or 13.5). See Figure 5 for a typical calibration curve.

ISO/DIS 3924:2026(en)
Key
X retention time, in min
Y boiling point, in °C
Figure 5 — Typical calibration curve
10 Procedure
10.1 Sample preparation
10.1.1 The amount of sample injected shall not overload the column stationary phase capacity nor exceed
the detector linear range.
NOTE A narrow boiling range sample will require the injection of a smaller amount than a wider boiling range
sample.
10.1.2 The column stationary phase capacity can be estimated from the chromatogram of the calibration
mixture (5.6). Different volumes of the calibration mixture (5.6) can be injected to find the maximum
amount of a component that the stationary phase can tolerate without overloading (see 8.5, NOTE). Note
the peak height for this amount of sample. The maximum sample signal intensity shall not exceed this peak
height.
ISO/DIS 3924:2026(en)
10.1.3 Samples that are of low enough viscosity to be sampled with a syringe at ambient temperature shall
be injected undiluted. Samples that are too viscous or waxy to be sampled with a syringe shall be diluted
with carbon disulfide (5.8).
10.2 Sample analysis
Using the analysis sequence protocol (see 9.1), inject a sample aliquot into the gas chromatograph. At the
time of injection, start the chromatograph time cycle and the integrator/computer data acquisition.
11 Calculation
11.1 Correct the sample area slices for non-sample detector response by subtracting each blank analysis
area slice from each sample area slice
...