ASTM D5442-93(1998)
(Test Method)Standard Test Method for Analysis of Petroleum Waxes by Gas Chromatography
Standard Test Method for Analysis of Petroleum Waxes by Gas Chromatography
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 difference from 100 mass% and reported as C 45+ .
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, 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 D721.
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. Specific precautionary statements are given in Notes 1 and 2.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: D 5442 – 93 (Reapproved 1998)
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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope D 4626 Practice for Calculation of Chromatographic Re-
sponse Factors
1.1 This test method covers the quantitative determination
E 260 Practice for Packed Column Gas Chromatography
of the carbon number distribution of petroleum waxes in the
E 355 Practice for Gas Chromatography Terms and Rela-
range from n-C through n-C by gas chromatography using
17 44
tionships
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
3.1 Definitions of Terms Specific to This Standard:
determined by difference from 100 mass % and reported as
3.1.1 carbon number—a number corresponding to the num-
C .
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
waxes, including blends of waxes. This test method is not
technique in gas chromatography where the sample is injected
applicable to oxygenated waxes, such as synthetic polyethyl-
2 inside the front portion of a partition column at a temperature
ene glycols (for example, Carbowax ), or natural products such
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
D 721.
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 the
either dead volume or overlap between them.
standard.
3.1.4 non(normal paraffın)hydrocarbon (NON)—all other
1.5 This standard does not purport to address all of the
hydrocarbon types excluding those hydrocarbons with carbon
safety concerns, if any, associated with its use. It is the
atoms in a single length. Includes aromatics, naphthenes, and
responsibility of the user of this standard to consult and
branched hydrocarbon types.
establish appropriate safety and health practices and deter-
3.1.5 normal paraffın—a saturated hydrocarbon which has
mine the applicability of regulatory limitations prior to use.
all carbon atoms bonded in a single length, without branching
Specific precautionary statements are given in Note 1 and Note
or hydrocarbon rings.
2.
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:
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 Weighed quantities of the petroleum wax and an internal
D 4419 Test Method for Determination of Transition Tem-
standard are completely dissolved in an appropriate solvent and
peratures of Petroleum Waxes by Differential Scanning
4 introduced into a gas chromatographic column that separates
Calorimetry
the hydrocarbon components by increasing carbon number.
The column temperature is linearly increased at a reproducible
rate until the sample is completely eluted from the column.
This test method is under the jurisdiction of ASTM Committee D-2 on 4.2 The eluted components are detected by a flame ioniza-
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
tion detector and recorded on a strip chart or computer system.
D02.04.0H on Chromatographic Methods.
The individual carbon numbers are identified by comparing the
Current edition approved Dec. 15, 1993. Published February 1994.
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 14.01.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 5442 – 93 (1998)
retention times obtained from a qualitative standard with the 0.15 to 0.25-mm outside diameter needles have been used
retention times of the wax sample. The percent of each successfully for columns 0.25-mm inside diameter or larger
hydrocarbon number through C is calculated via internal and standard 0.47-mm outside diameter syringe needles have
standard calculations after applying response factors. been used for columns 0.53-mm inside diameter or greater.
4.3 For samples with final boiling points greater than 538°C 6.2.1 Care must be taken that the sample size chosen does
complete elution of all components may not be achieved under not allow some peaks to exceed the linear range of the detector
the specified conditions. For this reason, the C material is or overload the capacity of the column.
45+
determined by summing the concentrations of each individual 6.3 Column(s)—Any column used must meet the chromato-
carbon number through C and subtracting this total from 100 graphic resolution specification in 9.5. WCOT columns with 25
mass %. to 30-m lengths and a stationary phase coating of methyl
siloxane or 5 % phenyl methyl siloxane have been successfully
5. Significance and Use
used. Cross-linked or bonded stationary phases are preferred.
6.4 Recorder—A recording potentiometer or equivalent
5.1 The determination of the carbon number distribution of
with a full-scale deflection of 5 mV or less for measuring the
petroleum waxes and the normal and non-normal hydrocarbons
detector signal versus time. Full scale response time should be
in each can be used for control of production processes as well
2 s or less. Sensitivity and stability should be sufficient to
as a guide to performance in many end uses.
generate greater than 2-mm recorder deflection for a hydrocar-
5.2 Data resulting from this test method are particularly
bon injection of 0.05 mass % under the analysis conditions
useful in evaluating petroleum waxes for use in rubber formu-
employed.
lations.
6.5 Integrator or Computer—Means must be provided for
6. Apparatus
integrating the detector signal and summing the peak areas
between specific time intervals. Peak areas can be measured by
6.1 Chromatograph—Any gas chromatographic instrument
computer or electronic integration. The computer, integrator, or
that can accommodate a WCOT column, equipped with a flame
gas chromatograph must have the capability of subtracting the
ionization detector (FID), and that can be operated at the
area corresponding to the baseline (blank) from the sample
conditions given in Table 1 may be employed. The chromato-
area, and have the ability to draw the baselines used for peak
graph should be equipped with a cool on-column inlet (or
area integration.
equivalent) for introducing appropriate quantities of sample
without fractionation. In addition, the gas chromatograph must
7. Reagents and Materials
be capable of generating a chromatogram where the retention
times of an individual peak have retention time repeatability
7.1 Carrier Gas—Carrier gas appropriate for the flame
within 0.1 min. Refer to Practices E 260 and E 355 for general
ionization detector. Hydrogen and helium have been used
information on gas chromatography.
successfully. The minimum purity of the carrier gas used
6.2 Sample Introduction System—Any system capable of
should be 99.95 mol %.
introducing a representative sample onto the front portion of a
NOTE 1—Warning: Hydrogen and helium are compressed gases under
WCOT column may be employed. Cool on-column injection is
high pressure. Hydrogen is an extremely flammable gas.
preferred, however other injection techniques can be used
7.2 n-hexadecane—Hydrocarbon to be added to samples as
provided the system meets the specification for linearity of
an internal standard. Minimum purity of 98 % is required.
response in 9.6. For cool on-column injection, syringes with
7.3 Standards for Calibration and Identification—Standard
samples of normal paraffins covering the carbon number range
TABLE 1 Typical Operating Conditions
(through C ) of the sample are needed for establishing the
Column length (m): 25 30 15
retention times of the individual paraffins and for calibration
Column inside 0.32 0.53 0.25
for quantitative measurements. Hydrocarbons used for stan-
diameter (mm):
Stationary phase: DB-1 RTX-1 DB-5 dards must be greater than 95 % purity.
methyl silicone methyl silicone 5 % phenyl methyl
7.4 Solvent—A liquid (99 % pure) suitable for preparing a
silicone
quantitative mixture of hydrocarbons and for dissolving petro-
Film thickness 0.25 0.25 0.25
(μm):
leum wax. Cyclohexane has been used successfully.
Carrier gas: Helium Helium Helium
Carrier flow 1.56 5.0 2.3 NOTE 2—Warning: Solvents are flammable and harmful if inhaled.
(mL/min):
7.5 Linearity Standard—Prepare a weighed mixture of
Linear velocity 33 35 60
(cm/s):
n-paraffins covering the range between n-C to n-C and
16 44
Column initial 80 80 80
dissolve the mixture in cyclohexane. Use approximately equal
temperature (°C):
Program rate 10 8 5 amounts of each of the paraffins and a balance capable of
(°C/min):
determining mass to within 1 % of the mass of each compound
Final temperature 380 340 350
added. It is not necessary to include every n-paraffin in this
(°C):
Injection technique: cool on-column cool on-column cool on-column mixture so long as the sample contains n-C , n-C , and at
16 44
Detector tem- 380 400 375
least one of every fourth n-paraffin. It will be necessary to
perature (°C):
prepare the standard sample in cyclohexane, so that the normal
Sample size (μL): 1.0 1.0 1.0
paraffins are completely dissolved in the solvent. Solutions of
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 5442 – 93 (1998)
0.01 mass % n-paraffin have been used successfully. This 9.2 Operating Conditions—Set the chromatographic oper-
sample must be capped tightly, to prevent solvent loss which ating conditions (see Table 1) and allow the system to achieve
will change the concentration of paraffins in the standard blend. all temperature setpoints. The recorder, computer or integrating
device should be connected so that a plot of the detector signal
NOTE 3—Refer to Practice D 4307 for details of how to prepare
vs time can be obtained. Make certain that the FID is ignited
hydrocarbon mixtures.
before proceeding.
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
16 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
16 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
long as the duplicate baseline blank analyses are repeatable.
where:
The baseline should be a smooth curve, free of any chromato-
C = mass % n-C internal standard in dilute solu-
ISTD 16
graphic peaks.
tion,
9.4 Solvent Blank—Make a 1-μL injection of the cyclohex-
W = weight of n-C from 7.6.1,
ISTD 16
ane solvent and program the column oven. The solvent is of
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
column by analyzing, under conditions specified in 10.2, a
8. Sampling
1-μL injection of 0.05 mass % solution of n-C and n-C in
20 24
8.1 To ensure homogeneity, completely mix the entire wax
cyclohexane. The column resolution must not be less than 30 as
sample by heating it to 10°C above the temperature at which
calculated using Eq 2.
the wax is completely molten and then mix well by stirring.
2d
Using a clean eyedropper, transfer a few drops to the surface of
R 5 (2)
1.699 W1 1 W2
~ !
a clean sheet of aluminum foil, allow to solidify and break into
pieces. The wax can either be used directly as described in
where:
Section 11 or placed in a sealed sample vial until ready for use.
d = distance (mm) between the peak maxima of n-C
8.1.1 Aluminum foil usually contains a thin film of oil from
and n-C ,
processing. This oil must be removed by rinsing the foil with
W1 = peak width (mm) at half height of n-C , and
solvent such as hexane or mineral spirits, prior to use.
W2 = peak width (mm) at half height of n-C .
9.6 Linearity of Response—For quantitative accuracy, de-
9. Preparation of Apparatus
tector response must be proportional to the mass of hydrocar-
bon injected, and the response of the non-normal paraffins is
9.1 Column Conditioning—Capillary columns with bonded
assumed to be equivalent to the
...
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