ASTM D8301-21

Standard Test Method for Determination of the Content of Nitroxide Radical (4-Hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl) in Butadiene, Styrene and Isoprene by Cyclic Voltammetry Method

SIGNIFICANCE AND USE
4.1 Nitroxide radicals (H-Tempo, O-Tempo (4-oxo-2,2,6,6-tetramethylpiperidine-1-oxyl), etc.) are widely used as inhibitors of thermopolymerization in the processes of transportation, storage, and separation of monomers (isoprene, butadiene, styrene, etc.). This test method provides a procedure for assaying nitroxide radicals in monomers.  
4.2 This procedure can be used for determination of the content of nitroxide radicals (H-Tempo, O-Tempo, etc.) in other solvents (dimethyl formamide, DMSO etc.).
SCOPE
1.1 This test method is designed to determine the content of nitroxide radical 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (H-Tempo) in butadiene, isoprene, and styrene.  
1.2 This test method is applicable to samples with nitroxide radical 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (H-Tempo) with concentrations to 100 mg⁄kg. The limit of detection (LOD) is 0.47 mg/kg for nitroxide radical 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (H-Tempo) and the limit of quantitation (LOQ) is 1.6 mg/kg nitroxide radical 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (H-Tempo).  
1.3 The following applies for the purposes of determining the conformance of the test results using this test method to applicable specifications, results shall be rounded of in accordance with the rounding-off method of Practice E29.  
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this 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 establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-May-2021
• ICS: 83.140.01 - Rubber and plastics products in general
• Technical Committee: D16 - Aromatic, Industrial, Specialty and Related Chemicals
• Drafting Committee: D16.07 - Styrene, Ethylbenzene and C9 and C10 Aromatic Hydrocarbons

Relations

• Refers: ASTM E29-08 - Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
• Effective Date: 01-Oct-2008
• Refers: ASTM E29-06b - Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
• Effective Date: 15-Nov-2006
• Refers: ASTM E29-06a - Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
• Effective Date: 15-Sep-2006
• Refers: ASTM E29-06 - Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
• Effective Date: 01-May-2006
• Refers: ASTM D1193-06 - Standard Specification for Reagent Water
• Effective Date: 01-Mar-2006
• Refers: ASTM E29-04 - Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
• Effective Date: 01-Dec-2004
• Refers: ASTM E29-02e1 - Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
• Effective Date: 10-May-2002
• Refers: ASTM E29-93a(1999) - Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
• Effective Date: 10-May-1999
• Refers: ASTM D1193-99e1 - Standard Specification for Reagent Water
• Effective Date: 10-Feb-1999
• Refers: ASTM D1193-99 - Standard Specification for Reagent Water
• Effective Date: 10-Feb-1999

Overview

ASTM D8301-21 establishes a standard test method for the determination of the content of nitroxide radical-specifically 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (H-TEMPO)-in butadiene, styrene, and isoprene using the cyclic voltammetry method. Nitroxide radicals, such as H-TEMPO and O-TEMPO, are essential inhibitors of thermopolymerization, aiding in the safe storage, transportation, and handling of monomers. This method provides laboratories and chemical manufacturers with a reliable, reproducible, and sensitive process for quantifying nitroxide radical concentrations, helping to maintain the stability and safety of monomer supplies.

Key Topics

• Scope and Applicability

  • Measures H-TEMPO content in butadiene, isoprene, and styrene monomers.
  • Applicable to samples with H-TEMPO concentrations up to 100 mg/kg.
  • Offers a limit of detection (LOD) as low as 0.47 mg/kg and limit of quantitation (LOQ) of 1.6 mg/kg.
  • Adaptable for other solvents, such as dimethyl formamide and DMSO.

• Method Highlights

  • Utilizes cyclic voltammetry, a potent electrochemical technique, for sensitive detection of nitroxide radicals.
  • Standardizes sample preparation, calibration, and calculation steps to ensure repeatable results.
  • Ensures that results conform to significant digits and rounding procedures as per ASTM E29.

• Precision and Safety

  • Designed with high reproducibility, emphasizing strict repeatability criteria.
  • Requires compliance with relevant safety, health, and environmental practices.
  • Details use of SI units as the mandatory measurement system.

Applications

The ASTM D8301-21 standard is widely applicable to industries involved in:

• Monomer Production and Supply

  • Essential for producers and distributors of butadiene, isoprene, and styrene to ensure safe handling and storage by monitoring inhibitor levels.
  • Helps prevent spontaneous polymerization reactions during transportation and storage by verifying sufficient inhibitor (nitroxide radical) content.

• Quality Control Laboratories

  • Provides a standardized quality assurance test for verifying the consistency and safety of raw monomer batches.
  • Supports compliance with safety data sheets and regulatory requirements by offering traceable, reliable inhibitor quantification.

• Research and Development

  • Useful for R&D teams developing new processes or inhibitors involving nitroxide radicals.
  • Supports studies into the behavior of inhibitors in various solvents and under different storage conditions.

• Regulatory Compliance

  • Assists companies in maintaining compliance with global safety regulations such as OSHA for air contaminants and hazard communication.
  • Aligns with internationally recognized principles as outlined by the WTO TBT Committee.

Related Standards

Familiarity with the following related ASTM standards and reference documents will enhance the effective implementation of ASTM D8301-21:

• ASTM D1193 - Specification for Reagent Water, defining reagent water types for test purposes.
• ASTM E29 - Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications.
• OSHA Regulations, 29 CFR 1910.1000 - Air Contaminants, and 1910.1200 - Hazard Communication, establishing safety practices for laboratory environments.
• World Trade Organization TBT Committee Documents - Covers principles for the development of international standards, guides, and recommendations.

Keywords: nitroxide radical determination, H-TEMPO, cyclic voltammetry, butadiene, isoprene, styrene, monomer inhibitors, ASTM D8301, inhibitor analysis, polymerization inhibitor quantification.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D8301 − 21
Standard Test Method for
Determination of the Content of Nitroxide Radical (4-
Hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl) in Butadiene,
Styrene and Isoprene by Cyclic Voltammetry Method
This standard is issued under the fixed designation D8301; 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.
1. Scope 2. Referenced Documents
2.1 ASTM Standards:
1.1 This test method is designed to determine the content of
D1193 Specification for Reagent Water
nitroxide radical 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-
E29 Practice for Using Significant Digits in Test Data to
oxyl (H-Tempo) in butadiene, isoprene, and styrene.
Determine Conformance with Specifications
1.2 This test method is applicable to samples with nitroxide
2.2 Other Documents:
radical 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (H-
OSHARegulations, 29 CFR, paragraph 1910.1000 Air Con-
Tempo) with concentrations to 100 mg⁄kg. The limit of
taminants
detection(LOD)is0.47mg/kgfornitroxideradical4-hydroxy-
OSHA Regulations, 29 CFR, paragraph 1910.1200 Hazard
2,2,6,6-tetramethylpiperidine-1-oxyl (H-Tempo) and the limit
Communication
of quantitation (LOQ) is 1.6 mg/kg nitroxide radical
4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (H-Tempo).
3. Summary of Test Method
1.3 The following applies for the purposes of determining
3.1 A sample of butadiene is dissolved in acetonitrile.
the conformance of the test results using this test method to
Butadiene is separated by evaporation. The intensity of the
applicable specifications, results shall be rounded of in accor-
cathode current signal is compared in the cyclic voltammetry
dance with the rounding-off method of Practice E29.
(CV) with that produced by the known concentration of the
1.4 The values stated in SI units are to be regarded as
H-Tempo.
standard. No other units of measurement are included in this
3.2 A sample of isoprene and styrene is dissolved in
standard.
acetonitrile. The intensity of the cathode current signal is
1.5 This standard does not purport to address all of the compared in the cyclic voltammetry (CV) with that produced
by the known concentration of the H-Tempo.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter- 4. Significance and Use
mine the applicability of regulatory limitations prior to use.
4.1 Nitroxide radicals (H-Tempo, O-Tempo (4-oxo-2,2,6,6-
1.6 This international standard was developed in accor-
tetramethylpiperidine-1-oxyl), etc.) are widely used as inhibi-
dance with internationally recognized principles on standard-
tors of thermopolymerization in the processes of
ization established in the Decision on Principles for the
transportation, storage, and separation of monomers (isoprene,
Development of International Standards, Guides and Recom-
butadiene,styrene,etc.).Thistestmethodprovidesaprocedure
mendations issued by the World Trade Organization Technical
for assaying nitroxide radicals in monomers.
Barriers to Trade (TBT) Committee.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
This test method is under the jurisdiction of ASTM Committee D16 on contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Aromatic, Industrial, Specialty and Related Chemicals and is the direct responsi- Standards volume information, refer to the standard’s Document Summary page on
bility of Subcommittee D16.07 on Styrene, Ethylbenzene and C9 and C10Aromatic the ASTM website.
Hydrocarbons. Available from U.S. Government Printing Office, Superintendent of
Current edition approved June 1, 2021. Published June 2021. DOI: 10.1520/ Documents, 732 N. Capitol St., NW, Washington, DC 20401-0001, http://
D8301-21. www.access.gpo.gov.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D8301 − 21
NOTE 1—Commercially available solutions of the same concentration
4.2 This procedure can be used for determination of the
can be used instead.
content of nitroxide radicals (H-Tempo, O-Tempo, etc.) in
other solvents (dimethyl formamide, DMSO etc.). 9.2 Preparation of Sodium Perchlorate Solution in Acetoni-
trile (с=0.1 mol/dm NaClO ):
5. Interferences
9.2.1 Weigh 3.06 6 0.01 g of sodium perchlorate (NaClO )
5.1 The N-phenyl-p-phenylenediamine derivatives in con-
with an accuracy to 0.0001 g; transfer quantitively to the
3 3
centrations of 1 mg/kg interfere with the determination of the
volumetric flask with a capacity of 250 cm . Add 200 cm of
nitroxide radical concentration by this procedure.
acetonitrile and stir thoroughly; make up the volume to
250 cm with acetonitrile and stir it.
5.2 Do not use rubber stoppers as antioxidants on the
surface of the rubber contaminate acetonitrile solution. These
9.3 Preparation of a Filler for a Bridge Electrolyte:
antioxidants at concentrations of 1 mg/kg interfere with deter-
9.3.1 Add5gof powdered agar-agar a little at a time to
mination of the nitroxide radical concentration.
100 cm of a potassium chloride solution at 100 °C (water
bath); make sure that the solution does not foam and boil. The
6. Apparatus
solution is aged at 100 °C until all the agar-agar is dissolved,
6.1 Laboratory balances with maximum weighing capacity
and then add 10 g to 15 g of solid potassium chloride to create
of 200 g and 500 g, capable of determining 0.0001 g and
an excess of the solid phase.
0.01 g.
9.4 Preparation of a Salt Bridge:
6.2 Potentiostat-galvanostat capable of providing the device
9.4.1 A U-shaped glass tube is filled with a hot solution
parameters for the experiment noted in Annex A2.
prepared according to 9.3, with a syringe.
6.3 PC with the operating system set up and potentiostat
NOTE 2—Store the electrode junction in a water solution of potassium
control program.
chloride with tube branches downwards.
NOTE 3—Other bridging electrolytes can be used.
6.4 Electrochemical Cell:
9.5 Preparation of a Nitroxide Radical Solution at a Con-
6.4.1 Working Electrode—Platinum electrode, standard
type, ID-3mm. centration of 100 mg⁄kg:
9.5.1 Weigh a conical flask with a capacity of 250 cm with
6.4.2 Reference Electrode—Ag/AgCl/KCl, E = 207 mV
(25 °C). an accuracy to 0.01 g; weigh 0.01 6 0.001 g of nitroxide
radical with an accuracy to 0.0001 g and quantitatively transfer
6.4.3 Auxiliary (counter) Electrode—Platinum rod, dia.
3 3
0.5 mm, 50 mm long. it to a flask with a capacity of 250 cm . Add 100 cm of
acetonitrile and stir thoroughly, make up the solution to a
6.4.4 SaltBridge (U-form tube filled with electrolytic saline
filler). weight of 1 000 000 times greater than the weight of the
nitroxide radical (100.0 6 10 g) with acetonitrile and stir it;
7. Reagents and Materials
close the flask.
7.1 Potassium Chloride (KCl, CAS 7447-40-7)—Analytical
9.6 Preparation of Calibration Solutions with Nitroxide
reagent grade.
Radical Concentration of 2 mg⁄kg,5mg⁄kg, 10 mg⁄kg,
7.2 Acetonitrile (CH CN, CAS 75-05-8)—Analytical re-
20 mg⁄kg, 30 mg⁄kg, 40 mg⁄kg, 50 mg⁄kg, 60 mg⁄kg, 80 mg⁄kg,
agent grade.
90 mg/kg:
9.6.1 Pipette 0.2 cm of the solution obtained in accordance
7.3 Water—Shall be understood to mean Type I or Type II
with 9.5 and put it into a container with a ground glass stopper;
reagent water conforming to Specification D1193.
pipette 9.8 cm of acetonitrile into the same container. Stir the
7.4 Sodium Perchlorate (NaClO , CAS 7601-89-0)—
obtained solution with a concentration of 2 mg⁄kg.
Analytical reagent grade.
9.6.2 Prepare other solutions as described above by taking
7.5 Nitroxide Radical Standard (4-Hydroxy-2,2,6,6-
the appropriate amount of the solution obtained according to
tetramethylpiperidine-l-oxyl, min. 98 %, CAS 2226-96-2).
9.5 and the amount of acetonitrile.
9.6.3 It is acceptable to prepare solutions of nitroxide
7.6 Powdered Agar-agar.
radical using other volumetric apparatus or other final volumes
7.7 U-shaped Glass Tube.
of solutions, or combinations thereof.
8. Hazards
NOTE 4—Prepared solutions with nitroxide radical should be kept in
tightly closed containers to avoid concentration changes of the obtained
8.1 Consult current OSHA regulations, suppliers’ Safety
solutions, due to the evaporation of acetonitrile.
Data Sheets, and local regulations for all materials used in this
9.7 Butadiene Sample Preparation:
test method.
9.7.1 Put 10 cm of acetonitrile into the cylinder with a
9. Sampling, Test Specimens, and Test Units
well-ground stopper previously pre-weighed with an accuracy
9.1 Preparation of Potassium Chloride Solution to 0.01 g, and reweigh the cylinder with an accuracy to 0.01 g.
(c=3 mol/dm KCl): Cool the cylinder with acetonitrile to -10 °C in the cryostat or
9.1.1 Transfer 111.8 6 0.5 g of potassium chloride (KCl) to cooling mixture. Pipette 30 cm of butadiene into the cylinder
a volumetric flask with a capacity of 500 cm . Add distilled with acetonitrile. Stir and weigh the flask with an accuracy to
water to the volume. 0.01 g. Evaporate the butadiene slowly by adjusting the
D8301 − 21
cylinder temperature to the standard temperature. The evapo- 11.2 Prepare a test specimen (see 9.9) and prepare electro-
ration time shall not be less than 1 h under standard conditions lytic cell (see 10.1 – 10.3).
(or up to the mass of the flask, less than the mass of the flask
11.3 Check in the software that there are no discontinuities
with acetonitrile). At the end of evaporation, weigh the flask
in the system.The indicator of the absence of discontin
...