NOTICE: This standard has either been superceded and replaced by a new version or discontinued.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.
An American National Standard
Designation: D 1983 – 90 (Reapproved 1995)e1
Standard Test Method for
Fatty Acid Composition by Gas-Liquid Chromatography of
Methyl Esters1
This standard is issued under the fixed designation D 1983; 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.
This standard has been approved for use by agencies of the Department of Defense.
e1 NOTE—Unit of measurement statement added editorially in May 1995.
1. Scope 3. Significance and Use
1.1 This test method establishes standard conditions for the 3.1 This test method provides a means for identifying
separation and identification of methyl esters by gas-liquid vegetable oils as to type by comparing to known standards. It
chromatography. can also be used to detect adulteration of one vegetable oil by
1.2 This test method is applicable to animal and vegetable another.
fatty acids and oils having 8 to 24 carbon atoms. The use of the 3.2 The amount or the proportion of one specific acid can be
polyester liquid phase facilitates the separation of both the used for specification purposes, for example, the amount of
saturated and various unsaturated fatty acid methyl esters on linolenic acid in linseed oil or the percent of linoleic acid in
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the chromatogram obtained. sunflower oil.
1.3 The conditions specified in this test method are not 3.3 By measuring the amount of total eluted acids by use of
suitable for determining epoxy and oxidized fatty acids nor to an internal standard, an estimation may be made of the amount
D 2800 and D 3457.
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fatty acids that have been polymerized. See also Test Methods of polymerization of the fatty acids present in a polymerized
oil.
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1.4 The values stated in SI units are to be regarded as the
standard. The values given in parentheses are for information 4. Apparatus
4.1 Gas Chromatographic Instrument having the following
only.
1.5 This standard does not purport to address all of the minimal characteristics:
safety concerns, if any, associated with its use. ASTM It isD1983-90(1995)e1
the 4.1.1 Column Oven, operated at a constant temperature
responsibility/catalog/standards/astm/2e0d3454-8f5d-4347-93ce-571833d6f251/astm-d1983-90-1995-e1
of the user of this standard to establish appro- between 190 and 210°C.
priate safety and health practices and determine the applica- 4.1.2 Sample Inlet Port, with the heater characteristics
bility of regulatory limitations prior to use. necessary for operation at 60°C higher than the maximum
necessary column oven temperature.
2. Referenced Documents 4.1.3 Detector, of the flame ionization or thermal conduc-
2.1 ASTM Standards: tivity type. If separately thermostatted, it should be maintained
D 2800 Test Method for Preparation of Methyl Esters from at column temperature or hotter.
Oils for Determination of Fatty Acid Composition by 4.1.4 Column, 1.5 to 3.0 m (5 to 10 ft) long, 6.4 mm (1⁄4 in.)
Gas-Liquid Chromatography2 in outside diameter, made of glass, stainless steel, copper, or
D 3457 Test Method for Preparation of Methyl Esters from aluminum packed with 20 weight % of polydiethylene glycol
Fatty Acids for Determination of Fatty Acid Composition succinate polyester (DEGS) liquid phase on 80 to 100 mesh
by Gas-Liquid Chromatography2 acid washed calcined diatomaceous earth.3
4.1.5 Recorder, 0 to 1-mV range, 1-s full-scale deflection
with a chart speed of 13 to 25 mm (1⁄2 to 1 in.)/min, and an
1
attenuator switch to change the recorder range as required; the
This method is under the jurisdiction of ASTM Committee D-1 on Paint and
Related Coatings, Materials, and Applications, and is the direct responsibility of
recorder should be equipped with an integrator if possible.
Subcommittee D01.32 on Drying Oils.
Current edition approved May 25, 1990. Published July 1990. Originally
published as D 1983 – 64 T. Last previous edition D 1983 – 75(1980)e1. 3
Chromosorbs W and P manufactured by Manville Sales Corp., available from
2
Annual Book of ASTM Standards, Vol 06.03. gas chromatography suppliers, have been found satisfactory for this purpose.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1
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 1983
4.1.6 Helium Carrier Gas, pure. where:
4.2 Syringe for Injecting Specimens, fixed needle, 10-µL Y 5 distance between the peak maxima for stearate and
capacity or equivalent with a known and reproducible volume. oleate,
4.3 Electronic or Mechanical Integrator. S 5 base width of the stearate peak, and
O 5 base width of the oleate peak.
5. Reagents
NOTE 3—These values should be determined on a sample containing
5.1 Standard Fatty Acid Methyl Ester containing approxi-
approximately equal quantities of oleate and stearate esters using a
mately equal quantities of oleic and stearic methyl esters, for specimen size such that these peaks are 25 to 50 % of the chart width. If
optimizing operating conditions. the peak resolution is equal to or greater than 1.0 the column and
instrument are in satisfactory condition. All columns when used will show
6. Preparation of Apparatus a gradual loss in peak resolution. When the value becomes less than 1.0,
6.1 Start the flow of helium gas through the apparatus and a new column should be installed.
adjust the inlet port, column, and detector, if individually
thermostatted, to their operating conditions as given in 4.1. 7. Calibration
Record a base line to check for stability of the instrument. 7.1 Determine calibration factors to correct for nonlinearity
Normally a new column with the DEGS liquid phase must be of instrument response due to molecular weight differences. In
preconditioned by maintaining it at its operating temperature most cases the standard mixtures are not made up with exactly
with helium flowing through it for 24 h or until the recorder the same weights of each ester. The units of area per weight
base line is stable at the most sensitive attenuation setting to be percent must be calculated by dividing the area of each peak in
used. the standard mixture by its weight percent. Then relative
response values can be calculated by dividing this number by
NOTE 1—At no time should the detector filament current (thermal
conductance (TC) detector) be turned on when helium gas is not flowing the units of area per weight percent obtained for the palmitate.
through the detector. Compare the calculated values with those listed in Table 1;
make sure that they are nearly the same.
6.2 The proper gas flow rate should permit elution of
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linolenic and shorter chain methyl esters in 30 min or less. The NOTE 4—Careful workers in the field have reported variations in
inlet pressure and gas flow necessary to accomplish this varies relative response when the ratio of one fatty acid to another in a standard
between columns and instruments used but are relatively mixture is greatly changed. The magnitude of the variation is generally
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constant for a single apparatus. It should not be necessary to
exceed 280 kPa (40 psi) for the gas pressure at the inlet of the
considered close enough to the precision of the test method that it does not
appear practical to use these small corrections in routine work. However,
for precise analysis the corrections may be desirable.
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flow control capillaries. A constant gas flow should be main-
tained throughout the duration of an analysis to maintain 8. Procedure
linearity of signal response. Polyester stationary phases are 8.1 Using the same condition as for the standard record the
very susceptible to oxygen damage and hydrolysis. The use of chromatogram of the fatty acid methyl esters prepared in
gas purifiers and oxygen removers is recommended ASTM forD1983-90(1995)e1
the accordance with Test Methods D 2800 or D 3457 using attenu-
carrier gas. /catalog/standards/astm/2e0d3454-8f5d-4347-93ce-571833d6f251/astm-d1983-90-1995-e1
ation settings that provide peak heights of principal compo-
6.3 Take up 0.5 to 3 µL of fatty acid ester standard (see 5.1) nents between 15 and 85 % of full scale. Observe the usual
into the syringe. Wipe the needle tip, pierce the septum of the cautions described in 6 through 6.5 in the chromatogramming
sample inlet port, quickly discharge the specimen, and with- of the standard methyl ester.
draw the needle immediately. Note on the recorder chart the
NOTE 5—High-boiling constituents, polymers, unsaponifiables, and
small peak caused by air which marks the sample introduction
rosin acids that may be present in appreciable amounts in certain types of
reference point. This will be followed immediately by the ether fatty acids are likely not to be eluted from the column and thus cause
solvent peak if there is some residual solvent left in the sample. errors. By using an internal standard, these errors can not only be
The specimen size must be adjusted so that the major peak does eliminated, but if the interest is in only certain of the fatty acids present,
not exceed the linearity range of the detector. Check manufac- these can readily be calculated on the original sample basis without
turer’s specification. measuring all the peaks.
NOTE 2—The specimen must be discharged rapidly so that uniform 8.2 After all the peaks have been traced and the pen has
flash vaporization occurs or the phenomenon of “tailing” may occur which returned to the base line, remove the chart for identification.
precludes the possibility of sharp separations.
6.4 Having determined the optimum conditions, inject a
TABLE 1 Relative Retention and Relative Response Values for
second specimen of the methyl ester standard (see 5.1) and
Methyl Esters of Fatty Acids
watch the recorder pen to see that the peaks do not go off scale.
Relative Relative
Change the setting of the attenuator if necessary to keep the Ester
Retention Response
peaks on the chart paper. Note the attenuation on the chart at
Myristate 0.56 1.03
the point that changes are made. Palmitate 1.00 1.00
6.5 Determine the instrument and column performance by Margarate 1.32 0.99
Stearate 1.70 0.97
noting the separation of the oleate and stearate peaks (see 6.4).
Oleate 1.94 0.95
This separation is expressed as peak resolution, R, as follows: Linoleate 2.31 0.92
Linolenate 3.00 0.90
R 5 2Y/~S 1 O!
