Standard Test Method for Determination of Light Hydrocarbons in Stabilized Crude Oils by Gas Chromatography

SIGNIFICANCE AND USE
5.1 Knowledge of the boiling point distribution of stabilized crude oils is important for the marketing, scheduling, and processing of crude oil in the petroleum industry. Test Method D7169 and IP 545 purport to give such a distribution in crude oils, but are susceptible to significant errors in the light ends portion of the distribution as well as in the mass recovery of the whole crude oil due to the interference imposed by the diluent solvent. This test method allows for more accurate determination of the front end of the boiling point distribution curve, in addition to providing important C1 to C9 (nonane) component level information, and more accurate mass recovery at C9 (nonane).
SCOPE
1.1 This test method specifies a method to determine the boiling range distribution of hydrocarbons in stabilized crude oil up to and including n-nonane. A stabilized crude oil is defined as having a Reid Vapor Pressure equivalent to or less than 82.7 kPa. The results of this test method can be combined with those from Test Method D7169 and IP 545 to give a full boiling point distribution of a crude oil. See Test Method D7169 (IP 545) for merging of these results to give a full crude analysis.  
1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are provided for information purposes only.  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

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ASTM D7900-13 - Standard Test Method for Determination of Light Hydrocarbons in Stabilized Crude Oils by Gas Chromatography
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D7900 − 13
Designation:601
Standard Test Method for
Determination of Light Hydrocarbons in Stabilized Crude
1,2
Oils by Gas Chromatography
This standard is issued under the fixed designation D7900; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope Naphthas through n-Nonane by Capillary Gas Chroma-
tography
1.1 This test method specifies a method to determine the
D6729 Test Method for Determination of Individual Com-
boiling range distribution of hydrocarbons in stabilized crude
ponents in Spark Ignition Engine Fuels by 100 Metre
oil up to and including n-nonane. A stabilized crude oil is
Capillary High Resolution Gas Chromatography
defined as having a Reid Vapor Pressure equivalent to or less
D6730 Test Method for Determination of Individual Com-
than 82.7 kPa. The results of this test method can be combined
ponents in Spark Ignition Engine Fuels by 100–Metre
with those from Test Method D7169 and IP 545 to give a full
Capillary (with Precolumn) High-Resolution Gas Chro-
boiling point distribution of a crude oil. See Test Method
matography
D7169 (IP545) for merging of these results to give a full crude
D6733 Test Method for Determination of Individual Com-
analysis.
ponents in Spark Ignition Engine Fuels by 50-Metre
1.2 The values stated in SI units are to be regarded as the
Capillary High Resolution Gas Chromatography
standard. The values given in parentheses are provided for
D7169 Test Method for Boiling Point Distribution of
information purposes only.
Samples with Residues Such as Crude Oils and Atmo-
1.3 This standard does not purport to address all of the
spheric and Vacuum Residues by High Temperature Gas
safety concerns, if any, associated with its use. It is the Chromatography
responsibility of the user of this standard to establish appro-
E355 Practice for Gas ChromatographyTerms and Relation-
priate safety and health practices and determine the applica- ships
bility of regulatory limitations prior to use.
2.2 Energy Institute Standards:
IP 545 Crude Petroleum and Petroleum Products—
2. Referenced Documents
Determination of Boiling Range Distribution of Crude Oil
2.1 ASTM Standards: IP 475 Manual Sampling
IP 476 Automatic Pipeline Sampling
D323 TestMethodforVaporPressureofPetroleumProducts
(Reid Method) 2.3 ISO Standard:
D4057 Practice for Manual Sampling of Petroleum and ISO 4259 Petroleum Products—Determination andApplica-
Petroleum Products tion of Precision Data in Relation to Methods of Test
D4177 Practice for Automatic Sampling of Petroleum and
3. Terminology
Petroleum Products
D5134 Test Method for Detailed Analysis of Petroleum
3.1 Definitions—This test method makes reference to many
common gas chromatographic procedures, terms, and relation-
ships. Detailed definitions can be found in Practice E355.
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
4. Summary of Test Method
Subcommittee D02.04.0L on Gas Chromatography Methods.
Current edition approved Dec. 1, 2013. Published January 2014. DOI: 10.1520/
4.1 An amount of internal standard is quantitatively added
D7900-13.
to an aliquot of the stabilized crude oil. A portion of this
This standard has been developed through the cooperative effort between
mixture is injected into a pre-column in series via a splitter
ASTM and the Energy Institute, London. The IP and ASTM logos imply that the
ASTM and IPstandards are technically equivalent, but their use does not imply that
both standards are editorially identical.
3 4
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Information on Energy Institute Standards can be obtained from the Energy
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Institute at www.energyinst.org.
Standards volume information, refer to the standard’s Document Summary page on Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
the ASTM website. 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7900 − 13
with a capillary analytical column. When the n-nonane has 6.4 Data System—A computer based chromatography data
quantitatively passed to the analytical column, the pre-column system capable of accurately and repeatedly measuring the
is back-flushed to vent the higher boiling components. The retention time and areas of eluting peaks. The system shall be
individual components are identified by comparison with able to acquire data at a rate adequate to accurately measure 10
reference chromatograms and a database of hydrocarbon com- to 20 points around an individual peak. For the accelerated
pounds(seeAppendixX1).Theboilingpointdistributionupto methods (see Table 1), a sampling rate of at least 20 Hz is
and including n-nonane (n-C9) is calculated. recommended.
6.5 Sample Introduction—Sample introduction by means of
5. Significance and Use
an automatic injection is highly recommended.
5.1 Knowledgeoftheboilingpointdistributionofstabilized
6.6 Flame Ionization Detector (FID), with sufficient sensi-
crude oils is important for the marketing, scheduling, and
tivity to detect 0.01 % mass n-heptane with a signal to noise of
processing of crude oil in the petroleum industry. Test Method
greater than five. When operating at this sensitivity level,
D7169 and IP 545 purport to give such a distribution in crude
detector stability shall be such that a baseline drift of not more
oils, but are susceptible to significant errors in the light ends
portionofthedistributionaswellasinthemassrecoveryofthe than 1 % per hour is obtained. The detector shall be connected
to the column so as to avoid any cold spots. The detector shall
whole crude oil due to the interference imposed by the diluent
solvent. This test method allows for more accurate determina- be capable of operating at a temperature equivalent to the
maximum column temperature used.
tion of the front end of the boiling point distribution curve, in
addition to providing important C1 to C9 (nonane) component
6.7 Pre-Column Configurations:
level information, and more accurate mass recovery at C9
6.7.1 Heated Valve Switching Box Configuration—For the
(nonane).
isothermal 1-m pre-column, a heated valve box is needed with
itsowntemperaturecontrol.Theboxwillcontainanautomated
6. Apparatus
six-portvalve,whichisusedtoback-flushthepre-column.The
6.1 Gas Chromatograph, with the operational characteris-
six-port valve should be made out of material that will not be
tics given in Table 1.
corroded by the sample (some crude oils contain high amounts
6.2 Inlet—A temperature programmable vaporizing (PVT)
of sulfur components). The valve shall be situated in a heated
or split/splitless inlet.
isothermal oven and be attached to the injector, pre-column,
6.2.1 Carrier Gas Pneumatic Control—Constant carrier gas
splitter, analytical column, and the detector without any cold
pressure or flow control is required.
spots. An example configuration is given in Fig. X2.1 in
Appendix X2.Alternatively, a Dean Switch type back-flush of
6.3 Column—A fused silica bonded polydimethylsiloxane
the petroleum may also be employed in place of a rotary valve.
coated capillary column and pre-column are employed. See
Table 1 for suggested columns. The analytical column shall 6.7.2 Injection Port Back-Flush Configuration—Atempera-
ture programmable injection port capable of containing a 7.5
elutehydrocarbonsinaboilingpointorder.Theeluatefromthe
injector passes through the pre-column before eluting onto the cm pre-column, and this injection port must be equipped with
analytical column. a back-flush option. This injector can be connected directly to
TABLE 1 Typical Chromatographic Conditions
Pre-column Pre-column Analytical Accelerated
A B Analytical
Column Length—metres 1.0 m 0.075 m 50 or 100 m 40 m
Column Internal Diameter—mm 2 mm 2.5 mm 0.25 mm 0.10 mm
Phase Loading 5 % 10 %
Film Thickness 0.5 um
Injection Volume 0.1 µL 0.1 µL
Injector Split Ratio 100 : 1 600 : 1
Injector Temperature 300°C 100°C
Pre-column Temperature 200°C 100°C
Injector Prog. Rate °C/min 50°C/min
Final Injector Temperature 300°C
Initial Oven Temperature 35°C 35°C
Hold Time 30 min 2.6 min
Oven Program Rate °C/min 2°C/min 50°C/min→ 45°C
(hold time 3 min)
5°C/min→ 60°C
(hold time 3 min)
9.5°C/min→
Final Oven Temperature 200°C (hold time 20 min) 200°C (hold time 1 min)
Flame Ionization Detector 300°C 300°C
D7900 − 13
the capillary column (Fig. X2.2, Appendix X2) or via a splitter
(Fig. X2.3, Appendix X2).
6.8 Analytical Balance, capable of weighing with an accu-
racy of 0.1 mg.
7. Reagents and Materials
7.1 Gas Chromatograph Gases—All of the following gases
shall have a purity of 99.995 % (V/V) or greater. (Warning—
Gases are compressed. Some are flammable, and all gases are
under high pressure.)
NOTE 1—These specifications can be obtained by proper use of filtering
devices and meeting the FID specifications in 6.6.
7.1.1 Carrier Gas—Helium or hydrogen is required. Any
oxygen present shall be removed, for example, by a suitable
chemical filter. If hydrogen is employed as a carrier gas, the
user is advised to follow all manufacturer’s safety guidelines
FIG. 1 Calculation of Peak Skewness (See 9.3.1)
for its use. (Warning—Hydrogen is an extremely flammable
gas under high pressure.)
9.3.2 Column Resolution—Determine the resolution be-
7.1.2 Detector Combustion Gases, Air, Hydrogen, and
tween the internal standard and the nearest n-paraffin peak.
Make-up Gas (Helium or Nitrogen). (Warning—Hydrogen is
R 5 2 3 t2 2 t1 ⁄ 1.699w1 1 w2 (1)
~ ! ~ !
anextremelyflammablegasunderhighpressure.)(Warning—
where:
Compressed air is a gas under high pressure and supports
combustion.)
R = the column resolution,
t1 = the retention time of the first peak (peak 1),
7.2 Internal Standard—The internal standard shall have
t2 = the retention time of the second peak (peak 2),
baseline resolution from any adjacent eluting peaks. Hexene-1
w1 = the peak width at half height of peak 1, and
or 3,3–dimethylbutene-1 (99 % pure) have been found to be
w2 = the peak width at half height of peak 2.
suitable.
Forexample,ifHexene-1isusedastheinternalstandard,the
7.3 Valve Timing Mixture/Splitter Linearity Mix—A quanti-
resolution is determined between Hexene-1 and n-hexane. The
tative mixture of approximately 1 % mass of each normal
resolution shall be at least 2.0.
alkane from pentane to decane in hexadecane (99+ % purity).
9.3.3 Detector Response Factor Calculations—Calculate
Accurately record the mass (g) of each normal alkane as well
the flame ionization detector response factor relative to
asthehexadecanesolventandcalculatetheactualmasspercent
methane,whichisconsideredtohavearesponsefactorofunity
of each alkane in the mixture.
(1), for each hydrocarbon group type of a particular carbon
7.4 Viscosity Agent, Carbon disulfide, 99+ % pure,
number using Eq 2.
(Warning—Extremely flammable and toxic liquid) is used as
RRf 5 C 3 C 1 H 3 H 30.7487 ⁄ C 3 C (2)
@~ ! ~ ! # ~ !
aw n aw n aw n
a viscosity reduction agent in the preparation of samples.
where:
8. Sampling
8.1 Samples to be analyzed by this test method must be
obtained using the procedures outlined in Practice D4057 or
Practice D4177 (IP 475 and IP 476, respectively).
8.2 The test specimen to be analyzed must be homogeneous
and free of dust or undissolved material.
9. Preparation of Apparatus
9.1 Chromatograph—Place in service according to manu-
facturer’s instructions. Typical operating conditions are given
in Table 1.
9.2 Column Preparation—Condition analytical columns in
accordance with manufacturer’s instructions.
9.3 System Performance Specification:
9.3.1 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 Fig. 1). FIG. 2 Determination of Resolution (See 9.3.2)
D7900 − 13
the highest alkane required (for example, n-nonane) and partial
RRf = relative response factor for a hydrocarbon type
recovery of the next alkane (for example, decane). (See
group of a particular carbon number,
example chromatogram (Fig. 3).)
C = atomic mass of carbon, 12.011,
aw
C = number of carbon atoms in the hydrocarbon type 9.3.4.2 Accelerated Analytical Column—Set the switching
n
group, of a particular carbon number, time to 30 s and repeat the analysis. Increase or decrease the
H = atomic mass of hydrogen, 1.008,
valvetimetoensuretherecoveryofthehighestalkanerequired
aw
H = numberofhydrogenatomsinthehydrocarbontype
n (forexample,n-nonane)andpartialrecoveryofthenextalkane
group of a particular carbon number, and
(forexample,n-decane).(Seeexamplechromatogram(Fig.3).)
0.7487 = factor to normalize the result to a methane re-
9.3.5 Split Injection Linearity—For systems utilizing split
sponse of unity, (1).
injection, injector linearity must be established to determine
proper quantitative parameters and limits.
9.3.4 Determination of Back-Flush Time—With the pre-
9.3.5.1 Set the injector temperature and split ratio to the
column and analytical column in series, inject an aliquot of the
operating values as indicated in Table 1 for split inlets.
pre-column switch test mixture (7.3) and determine the ratio of
9.3.5.2 Inject 0.1 µL of the splitter linearity mixture (7.3)
the alkanes.
9.3.4.1 Non-Accelerated Analytical Column—Set the into the system.
switching time to one minute and repeat the analysis. Increase 9.3.5.3 Calculatethenormalizedarea%ofthen-C5through
or decrease the valve time to ensure the complete recovery of n-C9 paraffins using Eq 3:
FIG. 3 Example Chromatogram Showing Elution on n-Nonane and n-Decane for Determining Back-Flush Time (See 9.3.4)
D7900 − 13
Corrected Normalized Area % C 5 factors for the components can be transformed to a specific
n
factor belonging to this internal standard, by dividing the
100 3 @~Area C
n
generic response factors by the relative response factor of the
3 RRf C !⁄TA# (3)
n
internal standard (in this case a C olefin for which the
where:
response relative to methane is 0.874).
Area C = integrated peak area of normal alkane C ,
n n
11.2 By summation of all the % m/m per peak up to and
RRf C = theo
...

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