EN 15199-4:2021

Petroleum products - Determination of boiling range distribution by gas chromatography method - Part 4: Light fractions of crude oil

This European Standard describes a method for the determination of the boiling range distribution of petroleum products by capillary gas chromatography using flame ionization detection. The standard is applicable to stabilized crude oils and for the boiling range distribution and the recovery up to and including n-nonane. A stabilized crude oil is defined as having a Reid Vapour Pressure equivalent to or less than 82,7 kPa as determined by IP 481 [3].
NOTE   For the purposes of this European Standard, the terms “% (m/m)” and “% (V/V)” are used to represent respectively the mass fraction, ω, and the volume fraction, φ.
WARNING —The use of this European Standard may involve hazardous materials, operations and equipment. This European Standard does not purport to address all of the safety problems associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and to determine the applicability of regulatory limitations prior to use.

Mineralölerzeugnisse - Gaschromatographische Bestimmung des Siedeverlaufes - Teil 4: Leichte Fraktionen des Rohöls

Dieses Dokument beschreibt ein Verfahren zur Bestimmung des Siedeverlaufes von Mineralölerzeugnissen durch Kapillar-Gaschromatographie unter Anwendung der Flammenionisationsdetektion. Dieses Dokument ist anwendbar auf stabilisierte Rohöle und gilt für den Siedeverlauf und die Ausbeute bis einschließlich n-Nonan. Ein stabilisiertes Rohöl ist definiert, einen Reid-Dampfdruck von gleich oder kleiner als 82,7 kPa zu haben, bestimmt nach IP 481 [3].
Anhang C beschreibt einen Algorithmus zur Zusammenführung der mit diesem Verfahren erhaltenen Ergebnisse zur Siedepunktverteilung mit den Ergebnissen nach EN 15199-3. Dies führt zu einem Siedeverlauf und einer Ausbeute bis zu C120.
ANMERKUNG 1 Es gibt keine spezielle Präzisionsangabe für die nach EN 15199-3 und EN 15199-4 erhaltenen kombinierten Ergebnisse. Für die Präzision des Siedeverlaufs bis zu n-Nonan gelten die Präzisionsangaben von EN 15199-4. Für die Präzision des Siedeverlaufs von n-Nonan durch C120 gilt die Präzision von EN 15199-3.
ANMERKUNG 2 Für die Zwecke dieser Europäischen Norm wird zur Angabe des Massenanteils ω einer Substanz der Ausdruck „% (m/m)“ und für den Volumenanteil φ einer Substanz der Ausdruck „% (V/V)“ verwendet.
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 seiner Anwendung 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 de la répartition dans l'intervalle de distillation par méthode de chromatographie en phase gazeuse - Partie 4 : Fractions légères du pétrole brut

Le présent document spécifie une méthode de détermination de la répartition dans l’intervalle de distillation des produits pétroliers par chromatographie en phase gazeuse capillaire avec une détection par ionisation de flamme. Le présent document s’applique aux pétroles bruts stabilisés pour déterminer la répartition dans l'intervalle de distillation ainsi que la récupération jusqu'au n-nonane inclus. Un pétrole brut stabilisé est défini comme ayant une pression de vapeur Reid équivalente à 82,7 kPa ou moins, telle que déterminée selon
l’IP 481 [3].
L'Annexe C présente un algorithme pour fusionner les résultats de la répartition des points d’ébullition obtenus en suivant cette méthode avec ceux obtenus selon l'EN 15199-3. Cela donne une répartition dans l’intervalle de distillation et une récupération jusqu'au C120.
NOTE 1   Il n'y a pas de données de fidélité spécifiques pour les résultats combinés obtenus après la fusion des résultats obtenus selon l'EN 15199-3 et ceux obtenus selon l'EN 15199-4. Pour la fidélité de la répartition dans l’intervalle de distillation jusqu'au n-nonane, les données de fidélité de l'EN 15199-4 s'appliquent. Pour la fidélité de la répartition dans l’intervalle de distillation du n-nonane au C120, la fidélité de l’EN 15199-3 s'applique.
NOTE 2   Pour les besoins de la présente Norme européenne, les termes “% (m/m)” et “% (V/V)” sont utilisés pour représenter respectivement la fraction massique, ω, et la fraction volumique, φ.
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 du 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 - Določanje porazdelitve območja vrelišč z metodo plinske kromatografije - 4. del: Lahke frakcije surovega olja

General Information

• Status: Published
• Publication Date: 31-Aug-2021
• Withdrawal Date: 30-Mar-2022
• ICS: 75.080 - Petroleum products in general
• Technical Committee: CEN/TC 19 - Petroleum products, lubricants and related products
• Drafting Committee: CEN/TC 19/WG 9 - Chromatographic test methods
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 01-Sep-2021
• Due Date: 11-Jan-2022
• Completion Date: 01-Sep-2021
• Ref Project: SIST EN 15199-4:2021 - Petroleum products - Determination of boiling range distribution by gas chromatography method - Part 4: Light fractions of crude oil

Relations

• Replaces: EN 15199-4:2015 - Petroleum products - Determination of boiling range distribution by gas chromatography method - Part 4: Light fractions of crude oil
• Effective Date: 31-Jul-2019
• Revised: prEN 15199-4 - Petroleum products - Determination of boiling range distribution by gas chromatography method - Part 4: Light fractions of crude oil
• Effective Date: 05-Mar-2025

Overview

EN 15199-4:2021 is a CEN European Standard that specifies a capillary gas chromatography (GC) method with flame ionization detection (FID) for determining the boiling range distribution (BRD) of the light fractions of stabilized crude oil. The method covers quantitative analysis and recovery of hydrocarbons up to and including n‑nonane (n‑C9). A stabilized crude oil in this context has a Reid Vapour Pressure (RVP) ≤ 82.7 kPa (per IP 481). The procedure uses a pre‑column/backflush arrangement to vent higher‑boiling components while resolving light ends on an analytical column.

Key topics and technical requirements

• Analytical principle: Capillary GC with a pre‑column (backflush) and an analytical PDMS (polydimethylsiloxane) capillary column; identification by comparison with reference chromatograms and a hydrocarbon database.
• Scope limit: Boiling range distribution and recovery reported up to and including n‑nonane (C9).
• Pre‑column configurations: Two options - an isothermal 1 m pre‑column in a heated valve box (six‑port valve for backflush) or a short pre‑column located in a temperature‑programmable injection port.
• Detection & sensitivity: Flame Ionization Detector (FID) capable of detecting 1% mass n‑heptane with a peak height ≥ 10% full‑scale and baseline drift ≤ 1%/hour.
• Reagents & gases: Carrier gas helium or hydrogen (≥ 99.995% purity), combustion gases for FID, internal standard (e.g., hexene‑1 or 3,3‑dimethyl‑1‑butene), carbon disulfide (CS2) as solvent.
• Quantitation: Use of an internal standard, calculation of response factors, and recovery definition (combined mass % of light hydrocarbons up to n‑nonane).
• Safety: Method involves flammable/toxic reagents (CS2, hydrogen) and high temperatures - users must implement appropriate safety measures.
• Data merging: Annex C provides a normative algorithm to merge EN 15199‑4 results with EN 15199‑3 (Simdis) to produce a combined BRD up to C120.

Applications and users

EN 15199‑4:2021 is used where accurate characterization of crude oil light ends is required:

• Petroleum testing laboratories and QC/QA units in refineries
• Crude oil buyers/sellers and custody transfer documentation
• Blending and feedstock evaluation for refinery process planning
• Research institutions and method validation labs
• Environmental and forensic petroleum analyses for volatile fractions

Practical uses include product specification, blend optimization, volatility profiling, modelling of distillation cuts, and supporting combined BRD results when merged with EN 15199‑3.

Related standards

• EN 15199 series (Parts 1–3) - BRD by GC for other fractions
• EN 15199‑3 (Crude oil Simdis merging to C120)
• Harmonized with IP 601 and ASTM D7900
• IP 481 referenced for RVP determination

Keywords: EN 15199‑4:2021, boiling range distribution, gas chromatography, light fractions of crude oil, capillary GC, flame ionization detector, stabilized crude oil, n‑nonane.

Standards Content (Sample)

SLOVENSKI STANDARD
01-december-2021
Nadomešča:
SIST EN 15199-4:2015
Naftni proizvodi - Določanje porazdelitve območja vrelišč z metodo plinske
kromatografije - 4. del: Lahke frakcije surovega olja
Petroleum products - Determination of boiling range distribution by gas chromatography
method - Part 4: Light fractions of crude oil
Mineralölerzeugnisse - Gaschromatographische Bestimmung des Siedeverlaufes - Teil 4:
Leichte Fraktionen des Rohöls
Produits pétroliers - Détermination de la répartition dans l'intervalle de distillation par
méthode de chromatographie en phase gazeuse - Partie 4 : Fractions légères du pétrole
brut
Ta slovenski standard je istoveten z: EN 15199-4:2021
ICS:
71.040.50 Fizikalnokemijske analitske Physicochemical methods of
metode analysis
75.080 Naftni proizvodi na splošno Petroleum products in
general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 15199-4
EUROPEAN STANDARD
NORME EUROPÉENNE
September 2021
EUROPÄISCHE NORM
ICS 75.080 Supersedes EN 15199-4:2015
English Version
Petroleum products - Determination of boiling range
distribution by gas chromatography method - Part 4: Light
fractions of crude oil
Produits pétroliers - Détermination de la répartition Mineralölerzeugnisse - Gaschromatographische
dans l'intervalle de distillation par méthode de Bestimmung des Siedeverlaufes - Teil 4: Leichte
chromatographie en phase gazeuse - Partie 4 : Fraktionen des Rohöls
Fractions légères du pétrole brut
This European Standard was approved by CEN on 14 June 2021.

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. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists 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, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 15199-4:2021 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 4
4 Principle . 5
5 Reagents and materials . 5
6 Apparatus . 5
6.1 Analytical balance capable of weighing to the nearest 0,1 mg . 5
6.2 Gas chromatograph . 5
6.3 Detector . 6
6.4 Pre-column configurations . 7
6.4.1 Heated valve switching box (see Figure B.1) . 7
6.4.2 Injection port (see Figure B.2 and B.3) . 7
6.5 Analytical column . 7
6.5.1 General. 7
6.5.2 Resolution . 7
6.6 Skewness . 8
6.7 Data collection . 8
7 Sampling and sample handling . 9
8 Calculation of response factors . 9
9 Procedure . 10
9.1 Sample preparation . 10
9.2 Determination of backflush time . 10
9.2.1 Initial work . 10
9.2.2 Analytical column . 10
9.2.3 Accelerated analytical column . 10
9.3 Sample analysis . 11
9.3.1 Initial work . 11
9.3.2 Calculation of individual components results . 11
9.3.3 Boiling point distribution of fraction up to and including nonane . 12
10 Reporting . 12
11 Precision . 12
11.1 General. 12
11.2 Repeatability, r . 12
11.3 Reproducibility, R . 12
12 Test report . 13
Annex A (informative) Analysis assistance . 14
Annex B (informative) Apparatus configuration . 21
Annex C (normative) Algorithm for merging boiling point distribution results of EN 15199-3
and EN 15199-4 . 23
Bibliography . 31
European foreword
This document (EN 15199-4:2021) 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.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by March 2022, and conflicting national standards shall be
withdrawn at the latest by March 2022.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 15199-4:2015.
In comparison with the previous edition, the following technical modification has been made.
The document is often used in combination with an analysis of boiling point distribution (Simdis) of crude
oil. Consensus has been reached about the algorithm for merging the results of the light end analysis and
the Simdis analysis. This algorithm is added as normative Annex C
EN 15199 consists of the following parts, under the general title Petroleum products — Determination of
boiling range distribution by gas chromatography method:
— Part 1: Middle distillates and lubricating base oils
— Part 2: Heavy distillates and residual fuels
— Part 3: Crude oil
— Part 4: Light fractions of crude oil
Part 4 is harmonized with IP 601 [1] and ASTM D7900 [2].
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to implement this European Standard: 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, Turkey and the United
Kingdom.
1 Scope
This document specifies a method for the determination of the boiling range distribution of petroleum
products by capillary gas chromatography using flame ionization detection. This document is applicable
to stabilized crude oils and for the boiling range distribution and the recovery up to and including
n-nonane. A stabilized crude oil is defined as having a Reid Vapour Pressure equivalent to or less than
82,7 kPa as determined by IP 481 [3].
Annex C specifies an algorithm for merging the boiling point distribution results obtained using this
method with the results obtained with EN 15199-3. This will result in a boiling range distribution and
recovery up to C120.
NOTE 1 There is no specific precision statement for the combined results obtained after merging the results of
EN 15199-3 and EN 15199-4. For the precision of the boiling range distribution up to n-nonane, the precision
statement of EN 15199-4 applies. For the precision of the boiling range distribution from n-nonane through C120,
the precision of EN 15199-3 applies.
NOTE 2 For the purposes of this document, the terms “% (m/m)” and “% (V/V)” are used to represent
respectively the mass fraction, ω, and the volume fraction, φ.
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 the user of this document to take appropriate measures to ensure safety and health of
personnel prior to application of the document 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 ISO 3170, Petroleum liquids - Manual sampling (ISO 3170)
EN ISO 3171, Petroleum liquids - Automatic pipeline sampling (ISO 3171)
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 https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1
recovery
combined mass percentages of all light hydrocarbon identified in the chromatogram(except the internal
standard peak) of the sample up to and including n-nonane
4 Principle
An amount of internal standard is quantitatively added to an aliquot of the stabilized crude oil. A portion
of this mixture is injected into a pre-column in series via a splitter with a capillary analytical column.
When the n-nonane has quantitatively passed to the analytical column, the pre-column is back-flushed to
vent the higher boiling components. The individual components are identified by comparison with
reference chromatograms and a database of hydrocarbon compounds (see Annex A). The boiling point
distribution and recovery up to and including n-nonane (n-C9) is calculated.
5 Reagents and materials
5.1 Stationary phase for columns, with a bonded polydimethylsiloxane (PDMS) stationary phase for
both the pre-column and the analytical capillary column.
5.2 Compressed gases
5.2.1 Carrier gas, helium or hydrogen of at least 99,995 % (V/V) purity or higher is required. Any
oxygen present shall be removed by a suitable chemical filter.
CAUTION — If hydrogen is used as carrier gas, follow the safety instructions from the GC instrument
manufacturer.
5.2.2 Combustion gases, hydrogen and clean air for the flame ionization detector, and suitable filters
shall be used to ensure adequate gas cleanliness.
5.3 Internal standard, having a baseline resolution from any adjacent eluting peaks (Hexene-1 or
3,3-dimethyl-1-butene (99 % pure) have been found to be suitable).
5.4 Valve switching mixture, a qualitative mixture of approximately 1 % (m/m) of each normal alkane
from pentane to decane.
5.5 Carbon disulfide (CS ), purity 99,7 % (V/V) minimum.
WARNING — Extremely flammable and toxic by inhalation.
6 Apparatus
6.1 Analytical balance capable of weighing to the nearest 0,1 mg
6.2 Gas chromatograph
The typical operational characteristics of the gas chromatograph are described in Table 1.
Two different pre-column configurations are possible.
The first configuration (A) employs a 1 metre column contained in a temperature controlled valve box,
separately controlled. The valve box in this configuration is isothermal (see Annex B).
The second configuration (B) is a short pre-column (a packed injection port liner), that fits into the
injection port. The injection port will be temperature programmed (see Annex B).
6.3 Detector
Flame Ionization Detector with sufficient sensitivity to detect 1 % mass n-heptane with a peak height of
at least 10 % full-scale deflection under the conditions given in the method. When operating at this
sensitivity level, detector stability shall be such that a baseline drift of not more than 1 % per hour is
obtained. The detector shall be connected to the column carefully to avoid any cold spots. The detector
shall be capable of operating at a temperature equivalent to the maximum column temperature used.
Table 1 —Typical chromatographic conditions
Pre- Pre- Analytical Accelerated
column column
Analytical
A B
Column length – m 1,0 0,075 50 or 100 40
Column internal diameter –
2 2,5 0,25 0,10
mm
Column material polydimethylsiloxane
Phase loading – % 5 10
Film thickness – µm   0,5
Injection volume – µL   0,1 0,1
Injector split ratio   100 : 1 600 : 1
Injector temperature – °C 300 100
Pre-column temperature –
200 100
°C
Injector program rate –
°C/min
Final injector temperature –
°C
Initial oven temperature –
35 35
°C
Hold time – min   30 2,6
50 → 45 °C
Oven program rate –°C/min   2
(hold time 3 min)
5 → 60 °C
(hold time 3 min)
9,5 → 200 °C
Final oven temperature – °C
(hold time
(hold time 1 min)
20 min)
Flame Ionization Detector –
300 300
°C
6.4 Pre-column configurations
6.4.1 Heated valve switching box (see Figure B.1)
For the isothermal 1 metre pre-column, a heated valve box is needed with its own temperature control.
The box will contain an automated six-port valve which is used to back-flush the pre-column.
The six-port valve should be made out of material which will not be corroded by the sample (some crude
oils contain high amounts of sulfur components). The valve shall be situated in a heated isothermal oven
and be attached to the injector, pre-column, splitter, analytical column and the detector without any cold
spots.
6.4.2 Injection port (see Figure B.2 and B.3)
A temperature programmable injection port capable of containing a 7,5 cm pre-column, and this injection
port shall be equipped with a back-flush option. This injector can be connected directly to the capillary
column (Figure B.2) or via a splitter (Figure B.3).
6.5 Analytical column
6.5.1 General
The column elutes hydrocarbons in a boiling point order. The eluate from the injector passes through the
pre-column before eluting onto the analytical column.
6.5.2 Resolution
Determine the resolution between the internal standard and the nearest n-paraffin peak as per
Formula (1).
2 tt−
( )
2 1
(1)
Ρ=
1,699 w + w
( )
where
P is the column resolution;
t is the retention time of the first peak (peak 1, see Figure 1);
t is the retention time of the second peak (peak 2, see Figure 1);
w is the peak width at half height of peak 1;
l
w is the peak width at half height of peak 2.
With Hexene-1 as I.S., the resolution is determined between the I.S and n-hexane. The resolution shall be
at least 2,0.
Figure 1 — Determination of resolution
6.6 Skewness
Determine the skew of the n-hexane peak by measuring the width of the leading part of the peak at 5 %
peak height (A) and the width of the following part of the peak at 5 % peak height (B). The ratio (B)/(A)
shall be not less than 1 or more than 4. See Figure 2 for further clarification.

Figure 2 —Calculation of peak skewness
6.7 Data collection
A PC based chromatography data system or integrator with suitable software can be used. For systems
using the analytical column, a data -sampling rate of 5 Hz is the recommended minimum.
For systems using the accelerated analytical column, a data-sampling rate of 20 Hz is required.
7 Sampling and sample handling
Take samples in accordance with either EN ISO 3170 or EN ISO 3171.
8 Calculation of response factors
Calculate the flame ionization detector response factor relative to methane, which is considered to have
a response factor of unity (= 1), for each hydrocarbon group type of a particular carbon number using
Formula (2).
 
C ×+C H × H × 0,748 7
( ) ( )
aw n aw n
 
RRf = (2)
C × C
( )
aw n
where
RRf is relative response factor for a hydrocarbon type group of a particular carbon number;
C is atomic mass of carbon, 12,011;
aw
C is number of carbon atoms in the hydrocarbon type group, of a particular carbon
n
number;
H is atomic mass of hydrogen, 1,008,
aw
H is number of hydrogen atoms in the hydrocarbon type group of a particular carbon
n
number, and 0,748 7 is factor to normalize the result to a methane response of unity
(= 1).
Table 2 gives some response factors already calculated.
Table 2 — Calculated response factors for hydrocarbons
No. of Carbon Naphthenes Paraffins Cyclic olefins Mono-olefins Aromatics
atoms
3  0,916  0,874
4  0,906  0,874
5 0,874 0,899 0,849 0,874
6 0,874 0,895 0,853 0,874 0,811
7 0,874 0,892 0,856 0,874 0,820
8 0,874 0,890 0,859 0,874 0,827
9 0,874 0,888 0,860 0,874 0,832
9 Procedure
9.1 Sample preparation
Weigh to the nearest 0,1 mg, approximately 5 g ± 0,2 g of sample into a tared, screw-capped vial.
Add approximately 0,15 g ± 0,02 g of internal standard and reweigh to the nearest 0,1 mg. Where the
mass of available sample is less than 5 g, the internal standard shall be added to create the equivalent of
a 3 % concentration.
Gently mix the two liquids without causing the sample to degas. Carbon disulfide (5.5) can be added to
improve the viscosity of the sample.
Fill the sample into GC vials with a minimum amount of headspace. Store the vials in a sub ambient
cupboard until use.
NOTE The amount of sample and internal standard taken can vary according to the level of Iight-end
components in the sample and the amount of the sample available.
9.2 Determination of backflush time
9.2.1 Initial work
With the pre-column and analytical column in series, inject an aliquot of the pre-column switch test
mixture (5.4) and determine the ratio of the alkanes.
9.2.2 Analytical column
Set the switching time to 1 min and repeat the analysis. Increase or decrease the valve time to ensure the
complete recovery of the highest alkane required (e.g. nonane) and partly recovery of the next alkane
(e.g. decane). (See 9.3.1 and the example chromatogram in Figure 3).
9.2.3 Accelerated analytical column
Set the switching time to 30 s and repeat the analysis. Increase or decrease the valve time to ensure the
recovery of the highest alkane required (e.g. nonane) and partly recovery of the next alkane (e.g. decane).
(For assistance in the identification of individual components see [1] and [2] and example chromatogram
(Figure 3)).
Key
1 n-Pentane 3 n-Heptane 5 n-Nonane
2 n-Hexane 4 n-Octane 6 n-Decane
Figure 3 — Example chromatogram showing elution for determining backflush time
9.3 Sample analysis
9.3.1 Initial work
Inject a suitable aliquot of the sample and internal standard onto the inlet of the pre-column which is in
series with the analytical column. At the time determined above (9.2) switch the valve and back-flush the
high boilers to vent.
The valve time reflects the highest carbon number required. As a general rule, if zC is required, then
(z+1)C should be eluted.
9.3.2 Calculation of individual components results
Calculate each of the individual hydrocarbons up to and including n-nonane the mass fraction ω using
Q
Formula (3):
A ⋅ RRf
QQ
ω ×ω (3)
Q IS
A ⋅ RRf
IS IS
where
RRf and RRf are the relative response factors relative to methane respectively for
Q IS
component Q and the internal standard IS as calculated in Clause 8;
A and A
are the areas resulting from the integration of the chromatographic detector
Q IS
signal within the specified retention time interval for component Q and for the
internal standard IS, respectively; and
ω is the mass fraction (in %) of
...