ASTM D1996-97

Standard Test Method for Determination of Phenolic Antioxidants and Erucamide Slip Additives in Low Density Polyethylene Using Liquid Chromatography (LC)

SCOPE
1.1 This test method describes a liquid chromatograph procedure for the separation of some additives currently used in low density polyethylene. These additives are extracted with 2-propanol prior to liquid chromatographic separation. The ultraviolet absorbance (200 nm) of the compound(s) is measured; quantitation is performed using the internal standard method.
1.2 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. For a specific hazards statement, see Section 9.

General Information

• Status: Historical
• Publication Date: 09-Apr-1997
• Technical Committee: D20 - Plastics
• Drafting Committee: D20.70 - Analytical Methods

Relations

• Replaced By: ASTM D1996-97(2003) - Standard Test Method for Determination of Phenolic Antioxidants and Erucamide Slip Additives in Low Density Polyethylene Using Liquid Chromatography (LC) (Withdrawn 2009)
• Effective Date: 10-Mar-2003

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NOTICE: This standard has either been superceded and replaced by a new version or discontinued.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 1996 – 97
Standard Test Method for
Determination of Phenolic Antioxidants and Erucamide Slip
Additives in Low Density Polyethylene Using Liquid
Chromatography (LC)
This standard is issued under the fixed designation D 1996; 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 * 3.1.4 Irganox 1076—octadecyl 3-(38,58-t-butyl-4-
hydroxyphenyl) propionate.
1.1 This test method describes a liquid chromatograph
3.1.5 Isonox 129—2,28-ethylidene bis(4,6-di-t-butyl hy-
procedure for the separation of some additives currently used
droxybenzene).
in low density polyethylene. These additives are extracted with
3.1.6 Kemamide-E—cis-13-docosenamide, erucamide.
2-propanol prior to liquid chromatographic separation. The
3.1.7 LC—liquid chromatography.
ultraviolet absorbance (200 nm) of the compound(s) is mea-
3.1.8 LDPE—low density polyethylene.
sured; quantitation is performed using the internal standard
3.1.9 Tinuvin P—2(28-hydroxy-58-methyl phenyl) benzot-
method.
riazole, Ciba-Geigy Industrial Chemicals.
1.2 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4. Summary of Test Method
responsibility of the user of this standard to establish appro-
4.1 The LDPE sample is ground to a 20-mesh particle size
priate safety and health practices and determine the applica-
and extracted by refluxing with 2-propanol.
bility of regulatory limitations prior to use. For a specific
4.2 The solvent extract is examined by liquid chromatogra-
hazards statement, see Section 9.
phy.
NOTE 1—There is no similar or equivalent ISO standard.
4.3 Additive concentrations are determined relative to an
internal standard (contained in the solvent) using reverse phase
2. Referenced Documents
chromatography (C-18 column) with ultraviolet (UV) detection
2.1 ASTM Standards:
at 200 nm.
E 131 Terminology Relating to Molecular Spectroscopy
E 177 Practice for Use of the Terms Precision and Bias in 5. Significance and Use
2, 3
ASTM Test Methods
5.1 Separation and identification of stabilizers used in the
E 380 Practice for Use of the International System of Units
manufacture of low density polyethylene are necessary in order
(SI)
to correlate performance properties with polymer composition.
E 682 Practice for Liquid Chromatography Terms and Re-
This test method provides a means to determine the BHT,
lationships
BHEB, Isonox-129, erucamide slip, Irganox-1010 and Irganox-
1076 levels in low density polyethylene samples.
3. Terminology
5.2 The additive extraction procedure is made effective by
3.1 Abbreviations:Abbreviations:
the insolubility of the polymer sample in solvents generally
3.1.1 BHEB—2,6-di-t-butyl-4-ethyl-hydroxybenzene or bu-
used for liquid chromatographic analysis.
tylated hydroxyethylbenzene.
5.3 Under optimum conditions, the lowest level of detection
3.1.2 BHT—2,6-di-t-butyl-4-methyl hydroxybenzene or bu-
for a phenolic antioxidant is approximately 2 ppm.
tylated hydroxytoluene.
3.1.3 Irganox 1010—tetrakis[methylene(3,5-di-t-butyl-4-
6. Interferences
hydroxyhydrocinnamate)].
6.1 Any material eluting at or near the same retention times
as the additive or as the internal standard can cause erroneous
This test method is under the jurisdiction of ASTM Committee D-20 on Plastics results. A polymer solvent extract solution containing no
and is the direct responsibility of Subcommittee D20.15 on Thermoplastic Materi-
internal standard should be examined to minimize the possi-
als.
bility of interferences.
Current edition approved April 10, 1997. Published May 1998. Originally
6.2 A major source of interferences can be from solvent
published as D 1996 – 92. Last previous edition D 1996 – 92.
Annual Book of ASTM Standards, Vol 14.02.
impurities; therefore, the solvents should be examined prior to
Annual Book of ASTM Standards, Vol 08.03.
use.
Annual Book of ASTM Standards, Vol 14.01.
*A Summary of Changes section appears at the end of this standard.
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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 1996
7. Apparatus 10.1.11 Column—Reverse phase C-18, 5 micron, 15 by 4.6
mm.
7.1 Liquid Chromatograph, equipped with a variable wave-
10.1.12 Temperature—Column set at 60°C.
length ultraviolet detector, heated column, and gradient elution
10.1.13 Sample Size—10 μL.
capabilities. The liquid chromatograph should be equipped
with a means for a 10-microliter sample solution injection such
11. Calibration by Internal Standard
as a sample loop.
11.1 Weigh accurately into a 125-mL flat bottom flask 50 6
7.2 Chromatographic Column, RP-18, 5 micron spherical
1 mg of the desired additive. Weigh 51.8 mg of Tinuvin-P into
particle, 15 by 4.6 mm; Vydac 201TP5415, Separations Group
the flask. Dissolve the components in 5 to 10 mL of warm
or equivalent.
2-propanol. Transfer the solution mixture to a 1000-mL volu-
7.3 Computer System or Integrator coupled with the chro-
metric flask and dilute to volume with 2-propanol.
matograph is recommended to measure peak area.
11.2 Standardize the liquid chromatograph detector re-
7.4 Wiley Mill, equipped with a 20-mesh screen and water
sponse by injection of 10 μL of the solution at the conditions
cooled jacket to prevent thermodegradation of antioxidants
listed in 10.1.
such as BHT and BHEB.
11.3 Measure the peak areas using a computer or an
7.5 Recorder, mv scale dependent upon the output of the
integrator and calculate the relative response factor R as
detector.
follows:
7.6 Reflux Extraction Apparatus, consisting of a condenser
conc. ~mg/L! additive 3 area Tinuvin2P
(24/40 ground glass joint), a flat bottom 125-mL flask having
R 5 (1)
conc. ~mg/L! Tinuvin2P 3 area additive
a 24/40 ground glass joint, and a hot plate. (See Appendix X1,
11.4 Average the response factors for three replicate injec-
Fig. X1.1.)
7.7 Filter Systems (PTFE), for non-aqueous solutions (pore tions of the calibration mixture.
size of 0.22 microns).
NOTE 2—Tinuvin-P cannot be used as an internal standard when this
7.8 Analytical Balance, capable of weighing to 6 0.0001 g.
compound is expected as an additive in samples being analyzed.
12. Sample Preparation
8. Reagents and Materials
12.1 Grind the sample to a particle size of 20-mesh using a
8.1 Tinuvin P, 2(28hydroxy-58-methyl phenyl)benzotriazole.
8.2 2-Propanol: water cooled Wiley mill.
8.2.1 2-Propanol T-P, HPLC grade, spectroquality or chro-
NOTE 3—Grind 7 to8gofthe sample to run the analysis. It is important
matography quality reagent 2-Propanol with 51.8 mg/L
to minimize the time of grinding to prevent any thermodegradation of the
Tinuvin-P added as an internal standard.
additives in the polymer.
8.2.2 2-Propanol, HPLC grade, spectroquality or chroma-
12.2 Weigh 5 6 0.01 g of the sample into the flask, add a
tography quality reagent.
stirring bar, add by pipet 50.0 mL of 2-propanol solvent
8.3 Water, HPLC or UV quality reagent, degassed by
containing the internal standard, and boil for 1 h (with stirring)
sparging with high purity helium or by filtration under vacuum.
using the reflux apparatus.
8.4 Acetonitrile, HPLC, spectroquality or chromatography
NOTE 4—The internal standard is present in the extraction 2-propanol
quality reagent, a reagent whose UV cut-off is about 190 nm.
extraction solvent (51.8 μg/mL).
9. Hazards
12.3 Cool the solution to room temperature by raising the
flask off the hot plate while still attached to the condenser.
9.1 2-Propanol is flammable. This extraction procedure
12.4 Attach a filter disk assembly to a 5-mL Luer-Lok tip
should be carried out in a fume hood.
hypodermic syringe. (See Appendix X1, Fig. X1.2.)
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