oSIST prEN 12916:2023
(Main)Petroleum products - Determination of aromatic hydrocarbon types in middle distillates - High performance liquid chromatography method with refractive index detection
Petroleum products - Determination of aromatic hydrocarbon types in middle distillates - High performance liquid chromatography method with refractive index detection
This document specifies a test method for the determination of the content of mono-aromatic, di-aromatic and tri+-aromatic hydrocarbons in diesel fuels, paraffinic diesel fuels and petroleum distillates.
This document defines two procedures, A and B.
Procedure A is applicable to diesel fuels that may contain fatty acid methyl esters (FAME) up to 30 % (V/V) (as in [1], [2] or [3]) and petroleum distillates in the boiling range from 150 °C to 400 °C (as in [4].
Procedure B is applicable to paraffinic diesel fuels with up to 7 % (V/V) FAME. This procedure does not contain a dilution of the sample in order to determine the low levels of aromatic components in these fuels.
The polycyclic aromatic hydrocarbons content is calculated from the sum of di-aromatic and tri+-aromatic hydrocarbons and the total content of aromatic compounds is calculated from the sum of the individual aromatic hydrocarbon types.
Compounds containing sulfur, nitrogen and oxygen can interfere in the determination; mono-alkenes do not interfere, but conjugated di-alkenes and poly-alkenes, if present, can do so.
NOTE 1 For the purpose of this European Standard, the terms "% (m/m)" and "% (V/V)" are used to represent the mass fraction, µ, and the volume fraction, φ, of a material respectively.
NOTE 2 By convention, the aromatic hydrocarbon types are defined on the basis of their elution characteristics from the specified liquid chromatography column relative to model aromatic compounds. Their quantification is performed using an external calibration with a single aromatic compound for each of them, which may or may not be representative of the aromatics present in the sample. Alternative techniques and test methods may classify and quantify individual aromatic hydrocarbon types differently.
NOTE 3 Backflush is part of laboratory-internal maintenance.
WARNING - The use of this standard can involve hazardous materials, operations and equipment. This standard does not purport to address all of the safety problems associated with its use. It is the responsibility of users of this standard to take appropriate measures to ensure the safety and health of personnel prior to application of the standard, and fulfil statutory and regulatory requirements for this purpose.
Mineralölerzeugnisse - Bestimmung von aromatischen Kohlenwasserstoffgruppen in Mitteldestillaten - Hochleistungsflüssigkeitschromatographie-Verfahren mit Brechzahl-Detektion
Dieses Dokument legt ein Prüfverfahren zur Bestimmung des Gehaltes an monoaromatischen, diaromatischen und tri+-aromatischen Kohlenwasserstoffen in Dieselkraftstoffen, paraffinischen Dieselkraftstoffen und Mineralöldestillaten fest.
Dieses Dokument legt zwei Verfahren fest, A und B.
Verfahren A gilt für Dieselkraftstoffe, die bis zu 30 % (V/V) Fettsäuremethylester (FAME; en: fatty acid methyl ester) (wie in [1], [2] und [3]) sowie Mineralöldestillate im Siedebereich von 150 °C bis 400 °C (wie in [4]) enthalten dürfen.
Verfahren B gilt für paraffinische Dieselkraftstoffe mit bis zu 7 % (V/V) FAME. Dieses Verfahren beinhaltet keine Verdünnung von Proben, damit die geringen Konzentrationen aromatischer Komponenten in diesen Kraftstoffen bestimmt werden können.
Der Gehalt an polycyclischen aromatischen Kohlenwasserstoffen wird als Summe der Gehalte an diaromatischen und tri+-aromatischen Kohlenwasserstoffen berechnet; der Gesamtgehalt an aromatischen Verbindungen errechnet sich aus der Summe der einzelnen aromatischen Kohlenwasserstofftypen.
Verbindungen, die Schwefel, Stickstoff und Sauerstoff enthalten, können die Bestimmung stören; Monoalkene stören nicht, während sich vorhandene konjugierte Diene und Polyene störend auswirken können. Die für dieses Verfahren geltenden Messbereiche sind in Tabelle 2 und Tabelle 3 angegeben.
ANMERKUNG 1 Für die Zwecke dieses Dokuments wird zur Angabe des Massenanteils, µ, einer Substanz der Ausdruck "% (m/m)" und für den Volumenanteil, φ, einer Substanz der Ausdruck "% (V/V)" verwendet.
ANMERKUNG 2 Vereinbarungsgemäß werden die aromatischen Kohlenwasserstofftypen auf Basis ihrer charakteristischen Elution von der angegebenen Säule für Flüssigchromatographie relativ zu aromatischen Modellverbindungen festgelegt. Die Quantifizierung erfolgt durch externe Kalibrierung mit einer einzelnen aromatischen Verbindung für jeden Typ, die für die Aromaten in der Probe repräsentativ sein kann. Andere Techniken und Prüfverfahren können die verschiedenen aromatischen Kohlenwasserstofftypen anders klassifizieren und quantifizieren.
ANMERKUNG 3 Rückspülung ist Teil der laborinternen Wartung.
WARNUNG - Die Anwendung dieses Dokuments kann die Anwendung gefährlicher Stoffe, Arbeitsgänge und Geräte mit sich bringen. Dieses Dokument beansprucht nicht, alle damit verbundenen Sicherheitsprobleme zu behandeln. Es liegt in der Verantwortung des Anwenders dieses Dokuments, vor der Anwendung der Norm geeignete Maßnahmen für die Sicherheit und den Gesundheitsschutz des Personals zu ergreifen und dafür Sorge zu tragen, dass behördliche und gesetzliche Maßnahmen eingehalten werden.
Produits pétroliers - Détermination des familles d'hydrocarbures aromatiques dans les distillats moyens - Méthode par chromatographie liquide à haute performance avec détection par réfractométrie différentielle
Le présent document spécifie une méthode pour déterminer la teneur en hydrocarbures mono-aromatiques, di-aromatiques, et tri+-aromatiques des gazoles, des gazoles paraffiniques et des distillats pétroliers.
Le présent document définit deux modes opératoires, A et B.
La procédure A est applicable aux gazoles, qui peuvent contenir des esters méthyliques d’acides gras (EMAG) jusqu’à 30 % (V/V) (comme ceux spécifiés dans [1], [2] ou [3]), et distillats pétroliers d'intervalle d'ébullition de 150 °C à 400 °C (comme ceux spécifiés dans [4]).
La procédure B est applicable aux gazoles paraffiniques qui peuvent contenir jusqu’à 7 % (V/V) d’EMAG. Cette procédure n’implique pas d’étape de dilution de l’échantillon afin de déterminer les faibles teneurs en aromatiques dans ces carburants.
La teneur en hydrocarbures aromatiques polycycliques est calculée à partir de la somme des di-aromatiques, et tri+-aromatiques, et la teneur totale en composés aromatiques est calculée à partir de la somme des teneurs des différentes familles de composés aromatiques.
Les composés soufrés, azotés et oxygénés peuvent interférer dans la mesure. Les mono-oléfines n'interfèrent pas, au contraire des dioléfines conjuguées et des polyoléfines qui peuvent interférer, si elles sont présentes. Les intervalles de mesure qui s’appliquent à cette méthode sont donnés dans le Tableau 2 et le Tableau 3.
NOTE 1 Pour les besoins de le présent document européenne, les expressions « % (m/m) » et « % (V/V) » sont utilisées pour désigner respectivement les fractions massiques, µ, et les fractions volumiques, φ, d’un produit.
NOTE 2 Par convention, le présent document définit les familles d’hydrocarbures aromatiques à partir de leurs caractéristiques d’élution dans la colonne de chromatographie liquide prescrite, et par comparaison aux temps d'élution des composés aromatiques servant de modèle. La quantification est effectuée par étalonnage externe avec un seul composé aromatique par famille d’hydrocarbures aromatiques, ce composé pouvant être ou non représentatif des aromatiques présents dans l’échantillon. Il est possible que des techniques et méthodes alternatives classent et quantifient différemment les familles d'hydrocarbures aromatiques.
NOTE 3 Le rétrobalayage fait partie de la maintenance interne au laboratoire.
AVERTISSEMENT - L'utilisation du présent document peut impliquer la mise en œuvre de produits, d'opérations et d'équipements à caractère dangereux. Le présent document n'est pas censé aborder tous les problèmes de sécurité concernés par son usage. Il est de la responsabilité des utilisateurs de ce présent document de prendre les mesures appropriées pour assurer la sécurité et préserver la santé du personnel avant son application, et pour répondre aux exigences réglementaires et statutaires à cette fin.
Naftni proizvodi - Določevanje aromatskih ogljikovodikov v srednjih destilatih - Metoda tekočinske kromatografije visoke ločljivosti z detekcijo lomnega količnika
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
oSIST prEN 12916:2023
01-junij-2023
Naftni proizvodi - Določevanje aromatskih ogljikovodikov v srednjih destilatih -
Metoda tekočinske kromatografije visoke ločljivosti z detekcijo lomnega količnika
Petroleum products - Determination of aromatic hydrocarbon types in middle distillates -
High performance liquid chromatography method with refractive index detection
Mineralölerzeugnisse - Bestimmung von aromatischen Kohlenwasserstoffgruppen in
Mitteldestillaten - Hochleistungsflüssigkeitschromatographie-Verfahren mit Brechzahl-
Detektion
Produits pétroliers - Détermination des familles d'hydrocarbures aromatiques dans les
distillats moyens - Méthode par chromatographie liquide à haute performance avec
détection par réfractométrie différentielle
Ta slovenski standard je istoveten z: prEN 12916
ICS:
71.040.50 Fizikalnokemijske analitske Physicochemical methods of
metode analysis
75.080 Naftni proizvodi na splošno Petroleum products in
general
oSIST prEN 12916:2023 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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oSIST prEN 12916:2023
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oSIST prEN 12916:2023
DRAFT
EUROPEAN STANDARD
prEN 12916
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2023
ICS 75.080 Will supersede EN 12916:2019+A1:2022
English Version
Petroleum products - Determination of aromatic
hydrocarbon types in middle distillates - High
performance liquid chromatography method with
refractive index detection
Produits pétroliers - Détermination des familles Mineralölerzeugnisse - Bestimmung von aromatischen
d'hydrocarbures aromatiques dans les distillats Kohlenwasserstoffgruppen in Mitteldestillaten -
moyens - Méthode par chromatographie liquide à Hochleistungsflüssigkeitschromatographie-Verfahren
haute performance avec détection par réfractométrie mit Brechzahl-Detektion
différentielle
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 19.
If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations
which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC
Management Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2023 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 12916:2023 E
worldwide for CEN national Members.
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Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 5
4 Principle . 6
5 Reagents and materials . 6
6 Apparatus . 7
7 Sampling . 8
8 Apparatus preparation . 9
9 Calibration . 11
10 Procedure. 13
10.1 Procedure A for diesel fuels and petroleum distillates . 13
10.2 Procedure B for paraffinic diesel fuels . 13
10.3 Procedure A and B continuation . 13
11 Calculation . 15
11.1 Retention times . 15
11.2 Column resolution . 16
11.3 Cut times . 16
11.4 Aromatic hydrocarbons type content . 16
11.5 Polycyclic and total aromatic hydrocarbons content . 17
12 Expression of results . 17
13 Precision . 17
13.1 General . 17
13.2 Repeatability, r . 17
13.3 Reproducibility, R . 17
14 Test report . 18
Annex A (informative) Column selection and use . 19
Annex B (informative) Practical instructions for paraffinic diesel fuel samples . 20
Annex C (informative) Identification of tri+-aromatics . 22
Bibliography . 23
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European foreword
This document (prEN 12916:2023) has been prepared by Technical Committee CEN/TC 19 “Gaseous and
liquid fuels, lubricants and related products of petroleum, synthetic and biological origin”, the secretariat
of which is held by NEN.
The document is currently submitted to the CEN Enquiry.
This document will supersede EN 12916:2019+A1:2022.
Major change compared to the previous version EN 12916:2019+A1:2022 of edition EN 12916:2019 is
the addition of an Annex C with instructions on determination of tri+-aromatics and additional sampling
requirements. This should improve lab precision when testing paraffinic diesel products. Next, the
practical instructions for these type of samples in Annex B have been improved and exemplary
chromatograms have been introduced. The instructions on storage precautions after sampling have been
restricted to paraffinic diesel products only.
The addition of a calibration procedure with refence material ensures better results for all products.
Furthermore, a study executed in 2021 has delivered confirmation of the published precision for PAH
and DAH for concentration range from (6 – 10) % (m/m).
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1 Scope
This document specifies a test method for the determination of the content of mono-aromatic, di-
aromatic and tri+-aromatic hydrocarbons in diesel fuels, paraffinic diesel fuels and petroleum distillates.
This document defines two procedures, A and B.
Procedure A is applicable to diesel fuels that may contain fatty acid methyl esters (FAME) up to
30 % (V/V) (as in [1], [2] or [3]) and petroleum distillates in the boiling range from 150 °C to 400 °C (as
in [4].
Procedure B is applicable to paraffinic diesel fuels with up to 7 % (V/V) FAME. This procedure does not
contain a dilution of the sample in order to determine the low levels of aromatic components in these
fuels.
The polycyclic aromatic hydrocarbons content is calculated from the sum of di-aromatic and tri+-
aromatic hydrocarbons and the total content of aromatic compounds is calculated from the sum of the
individual aromatic hydrocarbon types.
Compounds containing sulfur, nitrogen and oxygen can interfere in the determination; mono-alkenes do
not interfere, but conjugated di-alkenes and poly-alkenes, if present, can do so. The measurement ranges
that apply to this method are given in Table 2 and Table 3.
NOTE 1 For the purpose of this document, the terms “% (m/m)” and “% (V/V)” are used to represent the mass
fraction, µ, and the volume fraction, φ, of a material respectively.
NOTE 2 By convention, the aromatic hydrocarbon types are defined on the basis of their elution characteristics
from the specified liquid chromatography column relative to model aromatic compounds. Their quantification is
performed using an external calibration with a single aromatic compound for each of them, which can be
representative of the aromatics present in the sample. Alternative techniques and test methods can classify and
quantify individual aromatic hydrocarbon types differently.
NOTE 3 Backflush is part of laboratory-internal maintenance.
WARNING — The use of this document can involve hazardous materials, operations and equipment. This
document does not purport to address all of 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 standard, and fulfil statutory and regulatory requirements for this
purpose.
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.
EN 14214, Liquid petroleum products — Fatty acid methyl esters (FAME) for use in diesel engines and
heating applications — Requirements and test methods
EN ISO 1042, Laboratory glassware — One-mark volumetric flasks (ISO 1042)
EN ISO 3170, Petroleum liquids — Manual sampling (ISO 3170)
EN ISO 3171, Petroleum liquids — Automatic pipeline sampling (ISO 3171)
4
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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:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
3.1
non-aromatic hydrocarbon
compound having a shorter retention time on the specified polar column than the majority of mono-
aromatic hydrocarbons
3.2
mono-aromatic hydrocarbon
MAH
compound having a longer retention time on the specified polar column than the majority of non-
aromatic hydrocarbons, but a shorter retention time than the majority of di-aromatic hydrocarbons
3.3
di-aromatic hydrocarbon
DAH
compound having a longer retention time on the specified polar column than the majority of mono-
aromatic hydrocarbons, but a shorter retention time than the majority of tri+-aromatic hydrocarbons
3.4
tri+-aromatic hydrocarbon
T+AH
compound having a longer retention time on the specified polar column than the majority of di-aromatic
hydrocarbons including chrysene
3.5
polycyclic aromatic hydrocarbon
POLY-AH
sum of the di-aromatic hydrocarbons and tri+-aromatic hydrocarbons
3.6
total aromatic hydrocarbon
sum of the mono-aromatic hydrocarbons, di-aromatic hydrocarbons and tri+-aromatic hydrocarbons
Note 1 to entry: Published and unpublished data indicate that the major constituents for each hydrocarbon type
include:
a) non-aromatic hydrocarbons: cyclic and acyclic alkanes (paraffins and naphthenes), mono-alkenes (if present);
b) MAHs: benzenes, tetralins, indanes and higher naphthenobenzenes (e.g. octahydrophenanthrenes),
thiophenes, styrenes, conjugated polyalkenes;
c) DAHs: naphthalenes, biphenyls, indenes, fluorenes, acenaphthenes, benzothiophenes and dibenzothiophenes;
d) T+AHs: phenanthrenes, pyrenes, fluoranthenes, chrysenes, triphenylenes, benzanthracenes.
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3.7
fatty acid methyl ester
FAME
mixture of fatty acid methyl esters derived from vegetable oil or animal fats and complying to the
specification defined in EN 14214
4 Principle
A known mass of sample is taken and a fixed volume of this sample is injected into a high performance
liquid chromatograph fitted with a polar column. Diesel fuels with a concentration of FAME up to
30 % (V/V) and petroleum distillates need to be diluted with heptane (Procedure A). Paraffinic diesel
fuels are injected neat (Procedure B).
This column has little affinity for non-aromatic hydrocarbons, while exhibiting a strong selectivity for
aromatic hydrocarbons. As a result of this selectivity, the aromatic hydrocarbons are separated from the
non-aromatic hydrocarbons and into distinct bands according to their ring structure, i.e. MAH, DAH and
T+AH compounds.
The column is connected to a refractive index detector which detects the components as they elute from
the column. The electronic signal from the detector is continually monitored by a data processor. The
amplitudes of the signals from the aromatics in the sample are compared with those obtained from
calibration standards in order to calculate the mass fraction of MAHs, DAHs and T+AHs in the sample.
The sum of the DAHs and T+AHs mass fractions is reported as the mass fraction of POLY-AH, and the sum
of the MAHs, DAHs and T+AHs mass fractions is reported as the mass fraction of total aromatic
hydrocarbons.
When following Procedure A, the column may be backflushed after the aromatics have eluted from the
column to allow any remaining components such as FAME to elute in a backflush peak. This will allow for
a better cleaning of the column but care should be taken as it can affect the lifetime of the column.
5 Reagents and materials
WARNING — Aromatic compounds can be volatile and flammable, their vapours can form explosive
mixtures with the air, and they can cause acute or chronicle harm when inhaled or in case of contact with
the skin. In addition, they can be water polluting.
5.1 General
The highest purity reagents and materials available should be used; those required to be of high
performance liquid chromatography (HPLC) grade are commercially available from major suppliers.
5.2 Cyclohexane, of 99 % (m/m) minimum purity (CAS registry number 110-82-7).
NOTE Cyclohexane can contain benzene as an impurity.
5.3 Heptane, HPLC analytical grade, as the mobile phase (CAS registry number 142-82-5).
Batch to batch variation of the solvent water content, viscosity, refractive index, and purity can cause
unpredictable column behaviour. Drying (for example, by standing over activated molecular sieve type
5A) and filtering the mobile phase can help reducing the effect of trace impurities present in the solvent.
It is recommended practice to de-gas the mobile phase before use; this can be done conveniently online
or off-line by helium sparging, vacuum degassing or ultrasonic agitation. A failure to de-gas the mobile
phase can lead to negative peaks.
5.4 1-Phenyldodecane, of 98 % (m/m) minimum purity (CAS registry number 123-01-3).
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5.5 1,2-Dimethylbenzene (o-xylene), of 98 % (m/m) minimum purity (CAS registry number 95-47-
6).
5.6 Hexamethylbenzene, of 98 % (m/m) minimum purity (CAS registry number 87-85-4).
5.7 Naphthalene, of 98 % (m/m) minimum purity (CAS registry number 91-20-3).
5.8 Fluorene, of 98 % (m/m) minimum purity (CAS registry number 86-73-7).
5.9 Phenanthrene, of 98 % (m/m) minimum purity (CAS registry number 85-01-8).
5.10 Dibenzothiophene, of 95 % (m/m) minimum purity (CAS registry number 132-65-0).
5.11 9-Methylanthracene, of 95 % (m/m) minimum purity (CAS registry number 779-02-2).
5.12 Chrysene, of 95 % (m/m) minimum purity (CAS registry number 218-01-9).
5.13 FAME, compliant to EN 14214.
5.14 Reference Material (RM), samples used as reference, and which contain aromatic hydrocarbons
at concentration levels comparable to those of the test sample.
6 Apparatus
6.1 Liquid chromatograph, consisting of a high-performance instrument capable of pumping the
mobile phase at flow rates from 0,5 ml/min to 1,5 ml/min, with a precision better than 0,5 % and a
pulsation of < 1 % full scale deflection under the test conditions described in Clause 8. Make sure that the
equipment for handling or testing the sample is not sensitive to FAME. Recommended materials are
1
Polytetrafluoroethylene, Viton® and Nylon.
6.2 Sample injection system, capable of nominally injecting 10 μl of sample solution with a
repeatability better than 1 %.
Equal and constant volumes of the calibration and sample solutions are injected into the chromatograph.
Both manual and automatic sample injection systems, using either complete or partial filling of the
sample loop, can meet these repeatability requirements when used correctly. When using the partial
filling mode, it is recommended that the injection volume is less than half the total loop volume. For
complete filling of the loop, best results are obtained by overfilling the loop at least six times.
The repeatability of the injection system can be checked by comparing peak areas from at least four
injections of the system calibration standard (see 8.4).
Sample and calibration injection volumes different from 10 μl (typically in the range 3 μl to 20 μl) may be
used provided they meet the requirements for injection repeatability, refractive index sensitivity and
linearity (see 9.4), and column resolution (see 8.10).
1
Viton® is the trademark of a fluoroelastomer supplied by the Chemours Company, Wilmington, Delaware 19899
(USA). This information is given for the convenience of users of this document and does not constitute an
endorsement by CEN of the product named. Equivalent products may be used if they can be shown to lead to the
same results.
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6.3 Sample filter, if required (see 10.1 and 10.2), consisting of a microfilter of porosity 0,45 μm or less,
chemically inert towards hydrocarbon solvents, for the removal of particulate matter from the sample
solutions.
NOTE Polytetrafluorethylene (PTFE) filters have been found to be suitable.
6.4 Column system, consisting of a stainless steel HPLC column(s) packed with a commercial 3 μm,
5 μm or 10 μm amino-bonded (or amino/cyano-bonded) silica stationary phase meeting the resolution
requirements given in 8.7, 8.8, 8.10 and 8.12. See Annex A for guidance on the selection and use of suitable
column systems.
6.5 Temperature controls, for different parts of the apparatus (column, sample injection system,
solvent, refractive index detector). Maintain the sample injection system at the same temperature as the
sample solution, for the column a heating block or an air-circulating HPLC column oven may be used.
Also, a temperature-controlled laboratory, capable of maintaining a constant temperature in the range
(20 ± 1) °C to (40 ± 1) °C may be used.
The refractive index detector is sensitive to both sudden and gradual changes in the temperature of the
eluent. All necessary precautions should be taken to establish constant temperature conditions
throughout the liquid chromatograph system. The temperature should be optimized depending on the
stationary phase.
6.6 Refractive index detector, capable of being operated over the refractive index range 1,3 to 1,6
and giving a linear response over the calibration ranges with a suitable output signal for the data system.
If the detector is equipped with a device for independent temperature control, it is recommended that it
is set at the same temperature as the column oven.
6.7 Computer or computing integrator, compatible with the refractive index detector, having a
minimum sampling rate of 1 Hz and capable of peak area and retention time measurements. It shall also
have minimum capabilities for post-analysis data processing such as baseline correction and re-
integration.
The ability to perform automatic peak detection and identification and to calculate sample concentrations
from peak area measurements is recommended but is not essential.
6.8 Volumetric flasks, 10 ml and 100 ml capacity, conforming to grade A of EN ISO 1042.
6.9 Analytical balance, capable of weighing to the nearest 0,1 mg.
7 Sampling
7.1 Unless otherwise specified in the commodity specification, samples shall be taken as described in
EN ISO 3170 or EN ISO 3171 and/or in accordance with the requirements of national standards or
regulations for the sampling of the product under test.
7.2 Paraffinic diesel fuel samples analysed according to Procedure B require additional storage
conditions, as follows.
A storage temperature of 19 °C ± 5 °C shall be maintained. If for some reason, the samples have been
exposed to temperatures above 25 °C for a long period during storage or in custody (that you are aware
of), this shall be reported.
At least 24 h before a test the blend shall be placed at ambient temperature.
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After finishing the tests completely, replace the air by nitrogen or any noble gas before closing the
container tightly.
8 Apparatus preparation
8.1 Ensure that the equipment and any sample distribution system is clean and dry before use.
8.2 Set up the liquid chromatograph (6.1), sample injection system (6.2), column (6.4), refractive index
detector (6.6) and computing integrator (6.7) as in Figure 1 and in accordance with the manufacturer’s
manuals. If a column oven is used (6.5), install the HPLC column in the column oven. Maintain the sample
injection system at the same temperature as the sample solution; in most cases this should be at room
temperature.
Regular maintenance of the liquid chromatograph and its components is important and thus
recommended to ensure consistent performance. Leakages and partial blockage of filters, frits, injector
needles and valve rotors can produce flow rate inconsistencies and poor injector repeatability.
Key
1 pump 4 column
2 injection device 5 refractive index detector
3 oven 6 data acquisition system
Figure 1 — Diagrammatic representation of a liquid chromatograph
8.3 Adjust the flow rate of the mobile phase to a constant between 0,8 ml/min and 1,2 ml/min. Allow
the temperature of the column and of the refractive index detector, if it is equipped with temperature
control, to stabilize.
In order to minimize instrument drift, the reference cell of the detector should be filled with mobile phase,
either by flushing mobile phase through the reference cell immediately prior to the analysis, and then
isolating the reference cell to prevent evaporation, or by compensating for evaporation by supplying a
steady flow of mobile phase through the reference cell. The flow should be optimized so that cell
mismatch due to drying-out (reference cell) or temperature or pressure gradients (reference or analysis
cells, depending the type of detector) are minimized; with some detectors this can be accomplished using
a mobile phase flow through the reference cell of one tenth of that through the analysis cell.
8.4 Prepare into a 100 ml volumetric flask (6.8) a system calibration standard 1 (SCS1) by weighing to
the nearest 0,000 1 g:
— (1,0 ± 0,1) g cyclohexane (5.2),
— (0,1 ± 0,01) g 1-phenyldodecane (5.4),
— (0,5 ± 0,05) g 1,2-dimethylbenzene (5.5),
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— (0,1 ± 0,01) g hexamethylbenzene (5.6),
— (0,1 ± 0,01) g naphthalene (5.7),
— (0,05 ± 0,005) g dibenzothiophene (5.10), and
— (0,05 ± 0,005) g 9-methylanthracene (5.11).
Place the flask and its contents into an ultrasonic bath until a visual examination shows that all the
components have dissolved into the 1,2-dimethylbenzene/cyclohexane mixture. Remove from the
ultrasonic bath and make up to the mark with heptane.
The SCS1 may be kept for at least one year if stored in a tightly stoppered bottle in a cool dark place (for
example in a refrigerator).
8.5 Prepare into a 100 ml volumetric flask a system calibration standard 2 (SCS2) by weighing to the
nearest 0,000 1 g, (0,4 ± 0,1) g FAME (5.13) and (0,04 ± 0,01) g chrysene (5.12) and making up to the
mark with heptane (5.3). Place the flask in an ultrasonic bath at 35°C and agitate the solution until the
chrysene has dissolved.
NOTE 25 min has been found to be a suitable time for all the components to become dissolved.
The SCS2 may be kept for at least one year if stored in a tightly stoppered bottle in a cool dark place (for
example in a refrigerator).
8.6 When operating conditions are steady, as indicated by a stable horizontal baseline, inject 10 μl of
the SCS1 (8.4). Ensure the baseline drift over the period of the HPLC analysis run is less than 1 % of the
peak height for cyclohexane.
NOTE A baseline drift greater than this indicates problems with the temperature control of the
column/refractive index detector and/or material eluting from the column.
8.7 Ensure the components of the SCS1 are eluted in the order: cyclohexane, phenyldodecane, 1,2-
dimethylbenzene, hexamethylbenzene, naphthalene, dibenzothiophene and 9-methylanthracene.
8.8 Ensure that baseline separation is obtained between all components of the SCS1 (see Figure 2).
8.9 Measure the retention times of the cyclohexane, phenyldodecane, 1,2-dimethylbenzene,
hexamethylbenzene, dibenzothiophene and 9-methylanthracene peaks using the data system.
8.10 Ensure that the resolution between cyclohexane and 1,2-dimethylbenzene is between 5,7 and 10
(see 11.2).
8.11 Calculate the cut times using the equations given in 11.3.
8.12 Ensure the appearance of SCS2 is homogeneous (8.5) and then, inject 10 μl of the SCS2 and check
the chrysene peak elutes just before or together with the first peak of FAME.
Ensure the retention time of chrysene peak be higher than the retention time of 9-methylanthracene
peak.
Test the column with the SCS2 to verify its performances when starting the method with a new column,
after a period of time of inactivity or when samples with FAME should be run.
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Key
1 cyclohexane 5 naphthalene
2 phenyldodecane 6 dibenzothiophene
3 1,2 dimethylbenzene 7 9-methyl
...
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