ASTM D5974-96
(Test Method)Standard Test Methods for Fatty and Rosin Acids in Tall Oil Fractionation Products by Capillary Gas Chromatography
Standard Test Methods for Fatty and Rosin Acids in Tall Oil Fractionation Products by Capillary Gas Chromatography
SCOPE
1.1 These test methods cover the determination of the amounts of the individual fatty acids and rosin acids in fractionated tall oil products, using capillary gas chromatographic separation of the volatile methyl esters of these acids.
1.2 Four methods for forming the methyl esters, and two methods for determining the amounts of the individual fatty acids and rosin acids are described.
1.2.1 The classic method for the formation of methyl esters is through the use of diazomethane, but diazomethane is a hazardous and toxic material, and so is no longer the preferred reagent. The use of diazomethane is detailed in the Appendix. Methyl esters may be formed through the use of tetramethylammonium hydroxide (TMAH), trimethylphenylammonium hydroxide (TMPAH), or N,N-dimethylformamide dimethyl acetal (DMF-DMA).
1.2.2 The two methods for determining the amount of the individual fatty acids and rosin acids are the "internal standard" method, which yields absolute values, and the "area percent" method, which yields relative values.
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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Designation: D 5974 – 96
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Test Methods for
Fatty and Rosin Acids in Tall Oil Fractionation Products by
Capillary Gas Chromatography
This standard is issued under the fixed designation D 5974; 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 proven to be a useful tool for such determinations (see Test
Methods D 3008, and D 508) and capillary chromatography,
1.1 These test methods describe the determination of the
described in these test methods, is considered to be the most
amounts of the individual fatty acids and rosin acids in
effective analytical technique currently available. Other tech-
fractionated tall oil products using capillary gas chromato-
niques may be more suitable than gas chromatography where
graphic separation of the volatile methyl esters of these acids.
particular situations exist. For example, the presence of fatty
1.2 Three methods for forming the methyl esters and two
acid esters in the sample would result in transesterification
methods for determining the amounts of the individual fatty
during the derivatization step that may affect the results.
acids and rosin acids are described.
3.2 Due to hydrogen bonding, unmodified tall oil fatty acids
1.3 The methods for forming the methyl esters are through
and rosin acids cannot be volatilized at atmospheric pressure
the use of diazomethane, tetramethylammonium hydroxide
without undergoing decomposition, and so it is necessary to
(TMAH) or trimethylphenylammonium hydroxide (TMPAH).
convert the free acids to the more volatile and more stable
1.4 The two methods for determining the amount of the
derivative, such as the methyl ester, prior to chromatographic
individual fatty acids and rosin acids are the “internal standard”
separation.
method, which yields absolute values and the “area percent”
3.3 These test methods describe three ways to prepare
method, which yields relative values.
methyl esters. Other methylating derivatizing agents (for ex-
1.5 This standard does not purport to address all of the
ample, N,N-dimethylformamide dimethylacetal), may be used
safety concerns, if any, associated with its use. It is the
providing it has been demonstrated that such agents yield
responsibility of the user of this standard to establish appro-
equivalent results to those described herein.
priate safety and health practices and determine the applica-
3.3.1 The classic method is the use of diazomethane. How-
bility of regulatory limitations prior to use.
ever, diazomethane is a hazardous and toxic material. It should
2. Referenced Documents only be used by, or under the supervision of, technically
qualified individuals.
2.1 ASTM Standards:
3.3.2 TMAH causes the isomerization of a sample’s di- and
D 509 Test Methods of Sampling and Grading Rosin
polyunsaturated fatty acids, when it is used in even a slight
D 804 Terminology Relating to Naval Stores, Including Tall
excess. This leads to inaccurate results for the individual fatty
Oil and Related Products
acid components. TMAH should be used for materials contain-
D 3008 Test Method for Resin Acids in Rosin by Gas
ing only rosin acids, or when the identification or quantitation
Chromatography
of individual fatty acid components is not important.
E 691 Practice for Conducting an Interlaboratory Study to
3.3.3 TMPAH is the recommended methylating agent when
Determine the Precision of a Test Method
the identification or quantitation of individual di- and polyun-
3. Significance and Use
saturated fatty acids is required. TMPAH produces results that
are very similar to those of diazomethane, but without the
3.1 Tall oil fractionated products derived from tall oil are
hazards that are normally associated with diazomethane. A
important commercial materials primarily composed of fatty
considerable excess of TMPAH may cause isomerization of
acids and rosin acids but also containing some neutral material
conjugated compounds similar to that encountered with
(see Terminology D 804). For many applications, it is neces-
TMAH.
sary to know the level of the individual fatty acids and rosin
3.4 Two test methods for calculating the amounts of the
acids present in these products. Gas chromatography has
individual fatty acids and rosin acids are included in this
standard. When the actual weight percentage of a given
This test method is under the jurisdiction of ASTM Committee D-1 on Paint
compound is required, the “internal standard” method must be
and Related Coatings, Materials, and Applications and is the direct responsibility of
used. This method involves adding a known amount of an
Subcommittee D01.34 on Naval Stores.
Current edition approved June 10, 1996. Published August 1996.
internal standard to a known amount of test material and
Annual Book of ASTM Standards, Vol 06.03.
comparing the area of the peak associated with the internal
Annual Book of ASTM Standards, Vol 14.02.
D 5974
standard with the area of the peak of the individual fatty acid
or rosin acid. The “area percent” method will give the relative
amount of each component by comparing the area of the
appropriate peak to the total area of all peaks. Non-eluting
compounds will lead to erroneous (absolute) results with this
method.
PREPARATION OF METHYL ESTERS
NOTE 1—Any of these three methods can be used with the choice being
dependent on the factors mentioned in 3.3.
4. Conversion By Means of Diazomethane
NOTE 1—Connect four 25 by 200-mm test tubes in the hood as shown.
4.1 Apparatus: Use rubber stoppers on Test Tubes 1 and 4; use cork stoppers on Test
Tubes 2 and 3.
4.1.1 Test Tube, four, 25 by 200 mm.
FIG. 1 Apparatus for Diazomethane Methylation (see Test Method
4.1.2 Standard Laboratory Glassware.
D 3008)
4.2 Reagents and Materials:
4.2.1 Purity of Reagents—Reagent grade chemicals shall be
sample under the delivery tube from Test Tube 4 so that the end
used in all tests. Unless otherwise indicated, it is intended that
of the tube dips beneath the surface of the liquid.
all reagents shall conform to the specifications of the Commit-
4.3.7 Add about1gof diazald to Test Tube 3. Apply
tee on Analytical Reagents of the American Chemical Society,
nitrogen gas to the inlet of Test Tube 1 at such a rate as to
where such specifications are available. Other grades may be
sweep the generated diazomethane through the solution of the
used, provided it is first ascertained that the reagent is of
sample at a moderate rate.
sufficiently high purity to permit its use without lessening the
4.3.8 The esterification is complete when the yellow color
accuracy of the determination.
of excess diazomethane is apparent in the sample vial.
4.2.2 Diazald,N-Methyl-N-Nitroso-p-Toluenesulfonamide,
4.3.9 Evaporate the solution almost to dryness under a very
Chemical Abstracts Service (CAS) No. 80-11-5.
gentle stream of nitrogen on a steam bath in a hood. Dilute with
4.2.3 Diethyl Ether, anhydrous.
ether or other suitable solvent to about 0.5 to 0.6 mL.
4.2.4 2-Ethoxyethanol.
NOTE 3—An alternate procedure would be to use a heat block at 50°C
4.2.5 Methanol, anhydrous.
to evaporate the solvent. Regardless of the method, care must be taken not
4.2.6 Potassium Hydroxide Solution, aqueous, 40 % weight/
to lose the more volatile esters.
volume (w/v).
4.2.7 Toluene.
5. Conversion By Means of Tetramethylammonium
4.3 Procedure:
Hydroxide (TMAH)
4.3.1 Precaution—Diazomethane is explosive and an in-
5.1 Apparatus:
sidious poison. Use extreme care in using the following
5.1.1 Standard Laboratory Equipment.
esterification procedure. The procedure must be performed in a
5.2 Reagents and Materials:
fume hood.
5.2.1 Purity of Reagents, see 4.2.1.
4.3.2 Dissolve the sample from 9.2.2 or 17.1 in 0.5 mL of
5.2.2 Tetramethylammonium Hydroxide Solution,24% in
10 % (v/v) methanol/diethyl ether.
methanol, CAS No. 75-59-2.
NOTE 2—With solid rosin or other samples that are difficult to dissolve,
5.2.3 Tetramethylammonium Hydroxide Solution, 6 % (v/v)
2 to 3 drops of toluene may be added to the vial prior to derivatization to
in methanol. Dilute 25 mL of the reagent described in 5.2.2
assist in dissolving the sample.
with 75 mL of methanol.
4.3.3 Connect four 25 by 200-mm test tubes as shown in 5.2.4 Phenolphthalein Solution, 1 % (w/v) in methanol.
Fig. 1. Use rubber stoppers in Tubes 1 and 4 and cork stoppers
5.2.5 Diethyl Ether, anhydrous.
in Tubes 2 and 3. Connect the tubes with glass tubing as shown. 5.2.6 Methanol, anhydrous.
Draw down the outlet end of the glass tube from Test Tube 4
5.2.7 Acetic Acid, 5 % volume/volume (v/v) in methanol.
to abouta1to 2-mm diameter opening. 5.2.8 Toluene.
4.3.4 Leave Test Tubes 1 and 4 empty to serve as traps. Fill
5.3 Procedure:
Tube 2 about one half full with diethyl ether. 5.3.1 Dissolve the sample from 9.2.2 or 17.1 in about 0.5 to
4.3.5 Add about 10 mL of the KOH solution, 10 mL of
3.0 mL of a 50:50 ether/methanol mixture, add 2 to 3 drops of
2-ethoxyethanol, and 20 mL of diethyl ether to Test Tube 3. phenolphthalein indicator solution, and titrate to a pH of 7.8 to
4.3.6 Place the vial with the methanol/ether solution of the 8.1 or to the very first permanent pink color with a 6 % solution
of TMAH in methanol. If the solution is overtitrated it can be
back titrated with the acetic acid in methanol solution to the
Reagent Chemicals, American Chemical Society Specifications, American
end point. Later, when the solution is injected into the heated
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
injection port of the chromatograph, the tetramethylammonium
listed by the American Chemical Society, see Analar Standards for Laboratory
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
salts are pyrolyzed to methyl esters.
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
MD. NOTE 4—With solid rosin or other samples that are difficult to dissolve,
D 5974
FIG. 2 Typical Chromatogram of Distilled Tall Oil
2 to 3 drops of toluene may be added to the vial prior to the addition of
with a 0.20-μm film thickness of biscyanopropylsiloxane type
TMAH to assist in dissolving the sample.
liquid phase. The recommended referee column is 30 m in
length, 0.32 mm internal diameter with a 0.2-μm film thick-
6. Conversion By Means of Trimethylphenylammonium
ness, that provides for separations equivalent or better than
Hydroxide (TMPAH)
displayed in Fig. 2.
6.1 Apparatus:
NOTE 6—It is desirable that when using the referee column that the
6.1.1 Standard Laboratory Equipment.
calculated resolution for stearic/oleic acid peaks and the abietic/
6.2 Reagents and Materials:
dehydroabietic peaks is approximately 2.0 or greater.
6.2.1 Purity of Reagents, see 4.2.1.
7.3 Analytical Balance, accurate to 0.1 mg.
6.2.2 Trimethylphenylammonium Hydroxide Solution, 0.2 M
or 0.1 M in methanol, CAS No. 1899-02-1.
8. Reagents
6.2.3 Diethyl Ether, anhydrous.
8.1 Purity of Reagents, see 4.2.1.
6.2.4 Methanol, anhydrous.
8.2 Myristic Acid (Internal Standard), 99 % pure.
6.2.5 Toluene.
6.3 Procedure:
NOTE 7—A higher molecular-weight saturated fatty acid that elutes
later in the chromatogram may be used in place of or in addition to
6.3.1 To the sample from 9.2.2 or 17.1, add 0.5 to 3.0 mL of
myristic acid providing that the alternate internal standard does not coelute
a 50:50 ether/methanol. Add 2 to 3 drops of phenolphthalein
with sample components.
indicator solution to the vial and titrate to the very first
8.3 Stearic Acid, Oleic Acid, Linoleic Acid, Abietic Acid,
permanent pink color with the TMPAH in methanol solution.
and Dehydroabietic Acid—Other high purity reference stan-
Later, when the solution is injected into the heated injection
dards can be added as needed for intended work.
port of the chromatograph, the trimethylphenylammonium
salts are pyrolyzed to their respective methyl esters.
9. Procedure
NOTE 5—With solid rosin or other samples that are difficult to dissolve,
9.1 Preparation of Calibration Standard:
2 to 3 drops of toluene may be added to the vial prior to the addition of
9.1.1 Accurately weigh into a 2-dram vial, milligram quan-
TMPAH to assist in dissolving the sample.
tities of the myristic acid internal standard plus the fatty acid
and rosin acid standards that are anticipated to be in the test
INTERNAL STANDARD METHOD
sample, and record the weights.
7. Apparatus
9.1.2 Convert the calibration standard to the methyl esters
or substituted ammonium salts as described in Sections 4, 5, or
7.1 Gas Chromatograph—An instrument equipped with a
6.
flame ionization detector (FID) that can be operated at condi-
tions given in 10.1.
7.2 Column—A high resolution column having length be-
Column such as Supelco SP 2380, available from Supelco Inc., Bellefonte, PA
tween 15 and 60 m in length, 0.25 to 0.53 mm internal diameter 16823-0048 has been found suitable for this purpose.
D 5974
9.2 Preparation of Test Sample: 12.2 Calculate the absolute value of each peak of interest, as
9.2.1 Accurately weigh ;50 mg of sample and ;15 mg of follows:
myristic acid directly into a 2-dram vial and record the weight.
A 3 RRF 3 W
i i IS
Fatty or rosin acid, % 5 3 100 (2)
A 3 W
IS S
NOTE 8—Rosin samples need to be freshly broken from a larger mass
to ensure the results are not affected by air oxidation of the rosin.
where:
9.2.2 Convert the test sample to methyl esters or substituted
A 5 peak area for fatty or resin acid being determined,
i
ammonium salts as described in Sections 4, 5, or 6.
RRF 5 relative response factor for individual compound
i
being determined,
10. Set-up of Gas Chromatograph (GC)
W 5 weight of internal standard. W 5 weight
IS IS
used 3 purity,
10.1 Set the GC conditions so that they are approximately as
A 5 peak area of internal standard, and
IS
follows:
W 5 sample weight.
S
Column temperature (oven temperature)
Initial 150°C
13. Report
Hold 5 min
Ramp 5°C/min
13.1 Report the percentage of the individual rosin acids to
Final 250°C
the nearest 0.1 %.
Hold 10 min
Injection port temperature 300°C
14. Precision and Bias
Injection port liner glass-split
Detector temperature 325°C
14.1 Internal Standard Method—An interlaboratory study
Carrier gas helium
of the capillary GC determination of fatty and rosin acids in tall
Linear gas velocity 19.5–20.5 cm/s
Spli
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