ASTM D5442-93(2013)
(Test Method)Standard Test Method for Analysis of Petroleum Waxes by Gas Chromatography
Standard Test Method for Analysis of Petroleum Waxes by Gas Chromatography
SIGNIFICANCE AND USE
5.1 The determination of the carbon number distribution of petroleum waxes and the normal and non-normal hydrocarbons in each can be used for control of production processes as well as a guide to performance in many end uses.
5.2 Data resulting from this test method are particularly useful in evaluating petroleum waxes for use in rubber formulations.
SCOPE
1.1 This test method covers the quantitative determination of the carbon number distribution of petroleum waxes in the range from n-C17 through n-C 44 by gas chromatography using internal standardization. In addition, the content of normal and non-normal hydrocarbons for each carbon number is also determined. Material with a carbon number above n -C44 is determined by its difference from 100 mass % and reported as C45+.
1.2 This test method is applicable to petroleum derived waxes, including blends of waxes. This test method is not applicable to oxygenated waxes, such as synthetic polyethylene glycols (for example, Carbowax2), or natural products such as beeswax or carnauba.
1.3 This test method is not directly applicable to waxes with oil content greater than 10 % as determined by Test Method D721.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 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 consult and establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D5442 − 93 (Reapproved 2013)
Standard Test Method for
Analysis of Petroleum Waxes by Gas Chromatography
This standard is issued under the fixed designation D5442; 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 D4626 Practice for Calculation of Gas Chromatographic
Response Factors
1.1 This test method covers the quantitative determination
E260 Practice for Packed Column Gas Chromatography
of the carbon number distribution of petroleum waxes in the
E355 Practice for Gas Chromatography Terms and Relation-
range from n-C through n-C by gas chromatography using
17 44
ships
internal standardization. In addition, the content of normal and
non-normal hydrocarbons for each carbon number is also
3. Terminology
determined. Material with a carbon number above n -C is
determined by its difference from 100 mass % and reported as 3.1 Definitions of Terms Specific to This Standard:
C . 3.1.1 carbon number—a number corresponding to the num-
45+
ber of carbon atoms in a hydrocarbon.
1.2 This test method is applicable to petroleum derived
3.1.2 cool on-column injection—a sample introduction tech-
waxes, including blends of waxes. This test method is not
nique in gas chromatography where the sample is injected
applicable to oxygenated waxes, such as synthetic polyethyl-
inside the front portion of a partition column at a temperature
eneglycols(forexample,Carbowax ),ornaturalproductssuch
at or below the boiling point of the most volatile component in
as beeswax or carnauba.
the sample.
1.3 This test method is not directly applicable to waxes with
3.1.3 low volume connector—a metal or glass union de-
oil content greater than 10 % as determined by Test Method
signed to connect two lengths of capillary tubing. Usually
D721.
designed so that the tubing ends are joined with a minimum of
1.4 The values stated in SI units are to be regarded as
either dead volume or overlap between them.
standard. No other units of measurement are included in this
3.1.4 non(normal paraffın)hydrocarbon (NON)— all other
standard.
hydrocarbon types excluding those hydrocarbons with carbon
1.5 This standard does not purport to address all of the
atoms in a single length. Includes aromatics, naphthenes, and
safety concerns, if any, associated with its use. It is the
branched hydrocarbon types.
responsibility of the user of this standard to consult and
3.1.5 normal paraffın—a saturated hydrocarbon which has
establish appropriate safety and health practices and deter-
all carbon atoms bonded in a single length, without branching
mine the applicability of regulatory limitations prior to use.
or hydrocarbon rings.
3.1.6 wall coated open tube (WCOT)—a term used to
2. Referenced Documents
specify capillary columns in which the stationary phase is
2.1 ASTM Standards:
coated on the interior surface of the glass or fused silica tube.
D721 Test Method for Oil Content of Petroleum Waxes
Stationary phase may be cross-linked or bonded after coating.
D4307 Practice for Preparation of Liquid Blends for Use as
Analytical Standards
4. Summary of Test Method
4.1 Weighedquantitiesofthepetroleumwaxandaninternal
standardarecompletelydissolvedinanappropriatesolventand
This test method is under the jurisdiction of ASTM Committee D02 on
introduced into a gas chromatographic column that separates
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
the hydrocarbon components by increasing carbon number.
Subcommittee D02.04.0H on Chromatographic Distribution Methods.
Current edition approved May 1, 2013. Published August 2013. Originally
The column temperature is linearly increased at a reproducible
approved in 1993. Last previous edition approved in 2008 as D5442 – 93(2008).
rate until the sample is completely eluted from the column.
DOI: 10.1520/D5442-93R13.
Carbowax is a registered trademark of Union Carbide Corp.
4.2 The eluted components are detected by a flame ioniza-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
tion detector and recorded on a strip chart or computer system.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
The individual carbon numbers are identified by comparing the
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. retention times obtained from a qualitative standard with the
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5442 − 93 (2013)
TABLE 1 Typical Operating Conditions
6.2.1 Care must be taken that the sample size chosen does
Column length (m): 25 30 15 not allow some peaks to exceed the linear range of the detector
Column inside 0.32 0.53 0.25
or overload the capacity of the column.
diameter (mm):
Stationary phase: DB-1 RTX-1 DB-5
6.3 Column(s)—Any column used must meet the chromato-
methyl silicone methyl silicone 5 % phenyl methyl
graphicresolutionspecificationin9.5.WCOTcolumnswith25
silicone
to 30-m lengths and a stationary phase coating of methyl
Film thickness (µm): 0.25 0.25 0.25
Carrier gas: Helium Helium Helium
siloxane or 5 % phenyl methyl siloxane have been successfully
Carrier flow (mL/min): 1.56 5.0 2.3
used. Cross-linked or bonded stationary phases are preferred.
Linear velocity (cm/s): 33 35 60
Column initial 80 80 80
6.4 Recorder—Arecordingpotentiometerorequivalentwith
temperature (°C):
a full-scale deflection of 5 mV or less for measuring the
Program rate (°C/min):10 8 5
Final temperature (°C):380 340 350 detector signal versus time. Full scale response time should be
Injection technique: cool on-column cool on-column cool on-column
2 s or less. Sensitivity and stability should be sufficient to
Detector temperature 380 400 375
generate greater than 2-mm recorder deflection for a hydrocar-
(°C):
Sample size (µL): 1.0 1.0 1.0 bon injection of 0.05 mass % under the analysis conditions
employed.
6.5 Integrator or Computer—Means must be provided for
retention times of the wax sample. The percent of each
integrating the detector signal and summing the peak areas
hydrocarbon number through C is calculated via internal
between specific time intervals. Peak areas can be measured by
standard calculations after applying response factors.
computerorelectronicintegration.Thecomputer,integrator,or
4.3 For samples with final boiling points greater than 538°C gas chromatograph must have the capability of subtracting the
complete elution of all components may not be achieved under area corresponding to the baseline (blank) from the sample
the specified conditions. For this reason, the C material is area, and have the ability to draw the baselines used for peak
45+
determined by summing the concentrations of each individual area integration.
carbon number through C and subtracting this total from 100
mass %. 7. Reagents and Materials
7.1 Carrier Gas—Carrier gas appropriate for the flame
5. Significance and Use
ionization detector. Hydrogen and helium have been used
5.1 The determination of the carbon number distribution of
successfully. The minimum purity of the carrier gas used
petroleumwaxesandthenormalandnon-normalhydrocarbons
shouldbe99.95mol %.(Warning—Hydrogenandheliumare
in each can be used for control of production processes as well
compressed gases under high pressure. Hydrogen is an ex-
as a guide to performance in many end uses.
tremely flammable gas.)
5.2 Data resulting from this test method are particularly
7.2 n-hexadecane—Hydrocarbon to be added to samples as
useful in evaluating petroleum waxes for use in rubber formu-
an internal standard. Minimum purity of 98 % is required.
lations.
7.3 Standards for Calibration and Identification —Standard
6. Apparatus samples of normal paraffins covering the carbon number range
(through C ) of the sample are needed for establishing the
6.1 Chromatograph—Any gas chromatographic instrument
retention times of the individual paraffins and for calibration
thatcanaccommodateaWCOTcolumn,equippedwithaflame
for quantitative measurements. Hydrocarbons used for stan-
ionization detector (FID), and that can be operated at the
dards must be greater than 95 % purity.
conditions given in Table 1 may be employed. The chromato-
7.4 Solvent—A liquid (99 % pure) suitable for preparing a
graph should be equipped with a cool on-column inlet (or
equivalent) for introducing appropriate quantities of sample quantitative mixture of hydrocarbons and for dissolving petro-
without fractionation. In addition, the gas chromatograph must leum wax. Cyclohexane has been used successfully.
be capable of generating a chromatogram where the retention (Warning—Solvents are flammable and harmful if inhaled.)
times of an individual peak have retention time repeatability
7.5 Linearity Standard—Prepare a weighed mixture of
within 0.1 min. Refer to Practices E260 and E355 for general
n-paraffins covering the range between n-C to n-C and
16 44
information on gas chromatography.
dissolve the mixture in cyclohexane. Use approximately equal
6.2 Sample Introduction System—Any system capable of amounts of each of the paraffins and a balance capable of
introducing a representative sample onto the front portion of a determining mass to within 1 % of the mass of each compound
WCOTcolumn may be employed. Cool on-column injection is added. It is not necessary to include every n-paraffin in this
preferred, however other injection techniques can be used mixture so long as the sample contains n-C , n-C , and at
16 44
provided the system meets the specification for linearity of least one of every fourth n-paraffin. It will be necessary to
response in 9.6. For cool on-column injection, syringes with prepare the standard sample in cyclohexane, so that the normal
0.15 to 0.25-mm outside diameter needles have been used paraffins are completely dissolved in the solvent. Solutions of
successfully for columns 0.25-mm inside diameter or larger 0.01 mass % n-paraffin have been used successfully. This
and standard 0.47-mm outside diameter syringe needles have sample must be capped tightly, to prevent solvent loss which
been used for columns 0.53-mm inside diameter or greater. willchangetheconcentrationofparaffinsinthestandardblend.
D5442 − 93 (2013)
NOTE 1—Refer to Practice D4307 for details of how to prepare
9.3 Baseline Blank—After conditions have been set to meet
hydrocarbon mixtures.
performance requirements, program the column temperature
7.6 Internal Standard Solution—Prepare a dilute solution of upward to the maximum temperature to be used. Once the
internal standard in cyclohexane in two steps as follows: column oven temperature has reached the maximum
7.6.1 Prepare a stock solution containing 0.5 mass % n-C temperature, cool the column to the selected starting tempera-
in cyclohexane by accurately weighing approximately 0.4 g ture. Without injecting a sample, start the column temperature
n-C into a 100 mL volumetric flask. Add 100 mL of program, the recording device and the integrator. Make two
cyclohexane and reweigh. Record the mass of n-C to within baseline blank runs to determine if the baseline blank is
0.001 g and the mass of solution (cyclohexane and n-C )to repeatable. If the detector signal is not stable or if the baseline
within 0.l g. blanks are not repeatable, then the column should either be
7.6.2 Prepare a dilute solution of n-C internal standard by conditioned further or replaced.
diluting one part of stock solution with 99 parts of cyclo- 9.3.1 Baseline Bleed—Observe the detector response from
hexane. Calculate the concentration of internal standard in the
the blank run on the recorder. Some increase in detector
dilute solution using Eq 1. response will be observed at the upper column temperatures
due to stationary phase bleed. Column bleed is acceptable so
W 100%
ISTD
C 5 3 (1)
long as the duplicate baseline blank analyses are repeatable.
ISTD
W 100
S
The baseline should be a smooth curve, free of any chromato-
where:
graphic peaks.
C = mass % n-C internal standard in dilute solution,
ISTD 16
9.4 Solvent Blank—Make a 1-µL injection of the cyclo-
W = weight of n-C from 7.6.1,
ISTD 16
hexanesolventandprogramthecolumnoven.Thesolventisof
W = weight of cyclohexane plus n-C from 7.6.1,
s 16
suitable purity if there are no detected peaks within the
100 % = factor to convert weight fraction to mass %, and
retention time range over which the wax samples elute.
100 = dilution factor.
9.5 Column Resolution—Check the efficiency of the GC
8. Sampling
column by analyzing, under conditions specified in 10.2,a
8.1 To ensure homogeneity, completely mix the entire wax
1-µL injection of 0.05 mass % solution of n-C and n-C in
20 24
sample by heating it to 10°C above the temperature at which
cyclohexane.Thecolumnresolutionmustnotbelessthan30as
the wax is completely molten and then mix well by stirring.
calculated using Eq 2.
Usingacleaneyedropper,transferafewdropstothesurfaceof
2d
a clean sheet of aluminum foil, allow to solidify and break into
R 5 (2)
1.699 W11W2
~ !
pieces. The wax can either be used directly as described in
Section 11 or placed in a sealed sample vial until ready for use.
where:
8.1.1 Aluminum foil usually contains a thin film of oil from
d = distance (mm) between the peak maxima of n-C and
processing. This oil must be removed by rinsing the foil with
n-C ,
solvent such as hexane or mineral spirits, prior to use.
W1 = peak width (mm) at half height of n-C , and
W2 = peak width (mm) at half height of n-C .
9. Preparation of Apparatus
9.6 LinearityofResponse—Forquantitativeaccuracy,detec-
9.1 Column Conditioning—Capillary columns with bonded
tor response must be proportional to the mass of hydrocarbon
(or cross-linked) stationary phases do not normally need to be
injected, and the response of the non-normal paraffins is
conditioned; however, it is good chromatographic practice to
assumed to be equivalent to the response of the n-paraffin with
briefly condition a new column as described below.
the same carbon number. In addition, sample injection tech-
9.1.1 Install the column in the chromatographic oven and
nique and sample solution properties must be such that
connectonecolumnendtothesampleinletsystem.Turnonthe
representative sample is introduced to the gas chromatograph
source of carrier gas and set the flow controller (or pressure
without discrimination. Before use, the analysis system must
regulator) to the flow rate to be used in the analysis. Increase
be shown to confo
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