ASTM D5442-93(2003)e1
(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
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.
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-C44 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 gloycols (for example, Carbowax), 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 D 721.
1.4 The values stated in SI units are to be regarded as the 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.
General Information
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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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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An American National Standard
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Designation:D5442–93 (Reapproved 2003)
Standard Test Method for
Analysis of Petroleum Waxes by Gas Chromatography
This standard is issued under the fixed designation D 5442; 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.
´ NOTE—Warning notes were editorially moved into the standard text in August 2003.
1. Scope E 260 Practice for Packed Column Gas Chromatography
E 355 Practice for Gas Chromatography Terms and Rela-
1.1 This test method covers the quantitative determination
tionships
of the carbon number distribution of petroleum waxes in the
range from n-C through n-C by gas chromatography using
17 44
3. Terminology
internal standardization. In addition, the content of normal and
3.1 Definitions of Terms Specific to This Standard:
non-normal hydrocarbons for each carbon number is also
3.1.1 carbon number—a number corresponding to the num-
determined. Material with a carbon number above n-C is
ber of carbon atoms in a hydrocarbon.
determined by its difference from 100 mass % and reported as
3.1.2 cool on-column injection—a sample introduction
C .
45+
technique in gas chromatography where the sample is injected
1.2 This test method is applicable to petroleum derived
inside the front portion of a partition column at a temperature
waxes, including blends of waxes. This test method is not
at or below the boiling point of the most volatile component in
applicable to oxygenated waxes, such as synthetic polyethyl-
2 the sample.
eneglycols(forexample,Carbowax ),ornaturalproductssuch
3.1.3 low volume connector—a metal or glass union de-
as beeswax or carnauba.
signed to connect two lengths of capillary tubing. Usually
1.3 This test method is not directly applicable to waxes with
designed so that the tubing ends are joined with a minimum of
oil content greater than 10 % as determined by Test Method
either dead volume or overlap between them.
D 721.
3.1.4 non(normal paraffın)hydrocarbon (NON)—all other
1.4 The values stated in SI units are to be regarded as the
hydrocarbon types excluding those hydrocarbons with carbon
standard.
atoms in a single length. Includes aromatics, naphthenes, and
1.5 This standard does not purport to address all of the
branched hydrocarbon types.
safety concerns, if any, associated with its use. It is the
3.1.5 normal paraffın—a saturated hydrocarbon which has
responsibility of the user of this standard to consult and
all carbon atoms bonded in a single length, without branching
establish appropriate safety and health practices and deter-
or hydrocarbon rings.
mine the applicability of regulatory limitations prior to use.
3.1.6 wall coated open tube (WCOT)—a term used to
2. Referenced Documents specify capillary columns in which the stationary phase is
coated on the interior surface of the glass or fused silica tube.
2.1 ASTM Standards:
3 Stationary phase may be cross-linked or bonded after coating.
D 721 Test Method for Oil Content of Petroleum Waxes
D 4307 Practice for Preparation of Liquid Blends for Use as
4. Summary of Test Method
Analytical Standards
4.1 Weighedquantitiesofthepetroleumwaxandaninternal
D 4419 Test Method for Determination of Transition Tem-
standardarecompletelydissolvedinanappropriatesolventand
peratures of Petroleum Waxes by Differential Scanning
4 introduced into a gas chromatographic column that separates
Calorimetry (DSC)
the hydrocarbon components by increasing carbon number.
D 4626 Practice for Calculation of Gas Chromatographic
4 The column temperature is linearly increased at a reproducible
Response Factors
rate until the sample is completely eluted from the column.
4.2 The eluted components are detected by a flame ioniza-
This test method is under the jurisdiction of ASTM Committee D02 on
tion detector and recorded on a strip chart or computer system.
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
The individual carbon numbers are identified by comparing the
D02.04.0H on Chromatographic Distribution Methods.
Current edition approved May 10, 2003. Published August 2003. Originally retention times obtained from a qualitative standard with the
approved in 1993. Last previous edition approved in 1998 as D 5442–93 (1998).
Carbowax is a registered trademark of Union Carbide Corp.
Annual Book of ASTM Standards, Vol 05.01.
4 5
Annual Book of ASTM Standards, Vol 05.02. Annual Book of ASTM Standards, Vol 03.06.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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D5442–93 (2003)
retention times of the wax sample. The percent of each 6.2.1 Care must be taken that the sample size chosen does
hydrocarbon number through C is calculated via internal not allow some peaks to exceed the linear range of the detector
standard calculations after applying response factors. or overload the capacity of the column.
4.3 For samples with final boiling points greater than 538°C 6.3 Column(s)—Any column used must meet the chromato-
complete elution of all components may not be achieved under
graphicresolutionspecificationin9.5.WCOTcolumnswith25
the specified conditions. For this reason, the C material is to 30-m lengths and a stationary phase coating of methyl
45+
determined by summing the concentrations of each individual siloxane or 5 % phenyl methyl siloxane have been successfully
carbon number through C and subtracting this total from 100 used. Cross-linked or bonded stationary phases are preferred.
mass %.
6.4 Recorder—A recording potentiometer or equivalent
with a full-scale deflection of 5 mV or less for measuring the
5. Significance and Use
detector signal versus time. Full scale response time should be
2 s or less. Sensitivity and stability should be sufficient to
5.1 The determination of the carbon number distribution of
generate greater than 2-mm recorder deflection for a hydrocar-
petroleumwaxesandthenormalandnon-normalhydrocarbons
bon injection of 0.05 mass % under the analysis conditions
in each can be used for control of production processes as well
employed.
as a guide to performance in many end uses.
6.5 Integrator or Computer—Means must be provided for
5.2 Data resulting from this test method are particularly
integrating the detector signal and summing the peak areas
useful in evaluating petroleum waxes for use in rubber formu-
between specific time intervals. Peak areas can be measured by
lations.
computerorelectronicintegration.Thecomputer,integrator,or
gas chromatograph must have the capability of subtracting the
6. Apparatus
area corresponding to the baseline (blank) from the sample
6.1 Chromatograph—Any gas chromatographic instrument
area, and have the ability to draw the baselines used for peak
thatcanaccommodateaWCOTcolumn,equippedwithaflame
area integration.
ionization detector (FID), and that can be operated at the
conditions given in Table 1 may be employed. The chromato-
7. Reagents and Materials
graph should be equipped with a cool on-column inlet (or
equivalent) for introducing appropriate quantities of sample 7.1 Carrier Gas—Carrier gas appropriate for the flame
ionization detector. Hydrogen and helium have been used
without fractionation. In addition, the gas chromatograph must
be capable of generating a chromatogram where the retention successfully. The minimum purity of the carrier gas used
should be 99.95 mol %. (Warning—Hydrogen and helium are
times of an individual peak have retention time repeatability
within 0.1 min. Refer to Practices E 260 and E 355 for general compressed gases under high pressure. Hydrogen is an ex-
tremely flammable gas.)
information on gas chromatography.
6.2 Sample Introduction System—Any system capable of 7.2 n-hexadecane—Hydrocarbon to be added to samples as
an internal standard. Minimum purity of 98 % is required.
introducing a representative sample onto the front portion of a
WCOTcolumn may be employed. Cool on-column injection is 7.3 Standards for Calibration and Identification—Standard
preferred, however other injection techniques can be used samples of normal paraffins covering the carbon number range
provided the system meets the specification for linearity of (through C ) of the sample are needed for establishing the
response in 9.6. For cool on-column injection, syringes with retention times of the individual paraffins and for calibration
0.15 to 0.25-mm outside diameter needles have been used for quantitative measurements. Hydrocarbons used for stan-
successfully for columns 0.25-mm inside diameter or larger dards must be greater than 95 % purity.
and standard 0.47-mm outside diameter syringe needles have 7.4 Solvent—A liquid (99 % pure) suitable for preparing a
been used for columns 0.53-mm inside diameter or greater.
quantitative mixture of hydrocarbons and for dissolving petro-
leum wax. Cyclohexane has been used successfully.
(Warning—Solvents are flammable and harmful if inhaled.)
TABLE 1 Typical Operating Conditions
7.5 Linearity Standard—Prepare a weighed mixture of
Column length (m): 25 30 15
n-paraffins covering the range between n-C to n-C and
16 44
Column inside 0.32 0.53 0.25
dissolve the mixture in cyclohexane. Use approximately equal
diameter (mm):
amounts of each of the paraffins and a balance capable of
Stationary phase: DB-1 RTX-1 DB-5
methyl silicone methyl silicone 5 % phenyl methyl
determining mass to within 1 % of the mass of each compound
silicone
added. It is not necessary to include every n-paraffin in this
Film thickness (µm): 0.25 0.25 0.25
mixture so long as the sample contains n-C , n-C , and at
Carrier gas: Helium Helium Helium
16 44
Carrier flow (mL/min): 1.56 5.0 2.3
least one of every fourth n-paraffin. It will be necessary to
Linear velocity (cm/s): 33 35 60
prepare the standard sample in cyclohexane, so that the normal
Column initial 80 80 80
paraffins are completely dissolved in the solvent. Solutions of
temperature (°C):
Program rate (°C/min):10 8 5
0.01 mass % n-paraffin have been used successfully. This
Final temperature (°C):380 340 350
sample must be capped tightly, to prevent solvent loss which
Injection technique: cool on-column cool on-column cool on-column
willchangetheconcentrationofparaffinsinthestandardblend.
Detector temperature 380 400 375
(°C):
NOTE 1—Refer to Practice D 4307 for details of how to prepare
Sample size (µL): 1.0 1.0 1.0
hydrocarbon mixtures.
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D5442–93 (2003)
7.6 Internal Standard Solution—Prepare a dilute solution of 9.3 Baseline Blank—After conditions have been set to meet
internal standard in cyclohexane in two steps as follows: performance requirements, program the column temperature
7.6.1 Prepare a stock solution containing 0.5 mass % n-C upward to the maximum temperature to be used. Once the
in cyclohexane by accurately weighing approximately 0.4 g column oven temperature has reached the maximum tempera-
n-C into a 100 mL volumetric flask. Add 100 mL of ture, cool the column to the selected starting temperature.
cyclohexane and reweigh. Record the mass of n-C to within Without injecting a sample, start the column temperature
0.001 g and the mass of solution (cyclohexane and n-C )to
program, the recording device and the integrator. Make two
within 0.l g.
baseline blank runs to determine if the baseline blank is
7.6.2 Prepare a dilute solution of n-C internal standard by
repeatable. If the detector signal is not stable or if the baseline
diluting one part of stock solution with 99 parts of cyclohex- blanks are not repeatable, then the column should either be
ane. Calculate the concentration of internal standard in the
conditioned further or replaced.
dilute solution using Eq 1.
9.3.1 Baseline Bleed—Observe the detector response from
W 100 % the blank run on the recorder. Some increase in detector
ISTD
C 5 3 (1)
ISTD
W 100
response will be observed at the upper column temperatures
S
due to stationary phase bleed. Column bleed is acceptable so
where:
long as the duplicate baseline blank analyses are repeatable.
C = mass % n-C internal standard in dilute solu-
ISTD 16
The baseline should be a smooth curve, free of any chromato-
tion,
graphic peaks.
W = weight of n-C from 7.6.1,
ISTD 16
9.4 Solvent Blank—Make a 1-µL injection of the cyclohex-
W = weight of cyclohexane plus n-C from 7.6.1,
s 16
100 % = factor to convert weight fraction to mass %, and ane solvent and program the column oven. The solvent is of
100 = dilution factor.
suitable purity if there are no detected peaks within the
retention time range over which the wax samples elute.
8. Sampling
9.5 Column Resolution—Check the efficiency of the GC
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
sample by heating it to 10°C above the temperature at which
20 24
cyclohexane.Thecolumnresolutionmustnotbelessthan30as
the wax is completely molten and then mix well by stirring.
calculated using Eq 2.
Using a clean eyedropper, transfer a few drops to the surface of
a clean sheet of aluminum foil, allow to solidify and break into
2d
R 5 (2)
pieces. The wax can either be used directly as described in
1.699 W1 1 W2!
~
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
processing. This oil must be removed by rinsing the foil with
and 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 Linearity of Response—For quantitative accuracy, de-
9.1 Column Conditioning—Capillary columns with bonded
tector response must be proportional to the mass of hydrocar-
(or cross-linked) stationary phases do not normally need to be
bon 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
...
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