ASTM D2668-07(2021)

Standard Test Method for 2,6-<emph type="bold"><emph type="ital">di-tert</emph></emph >-Butyl-<emph type="bold"><emph type="ital"> p</emph></emph>-Cresol and 2,6-<emph type="bold"><emph type="ital">di-tert</emph></emph>-Butyl Phenol in Electrical Insulating Oil by Infrared Absorption

SIGNIFICANCE AND USE
3.1 The quantitative determination of 2,6-ditertiary-butyl paracresol and 2,6-ditertiary-butyl phenol in a new electrical insulating oil measures the amount of this material that has been added to the oil as protection against oxidation. In a used oil it measures the amount remaining after oxidation has reduced its concentration. The test is also suitable for manufacturing control and specification acceptance.  
3.2 When an infrared spectrum is obtained of an electrical insulating oil inhibited with either of these compounds there is an increase in absorbance of the spectrum at several wavelengths (or wavenumbers). 2,6 ditertiary-butyl paracresol produces pronounced increases in absorbance at 2.72 μm (3650 cm−1), and 11.63 μm (860 cm−1 ). 2,6 ditertiary-butyl phenol produces pronounced increases in absorbance at 2.72 μm (3650 cm−1) and 13.42 μm (745 cm −1).  
3.3 When making this test on other than a highly oxidized oil or when using a double-beam spectrophotometer, it has been found convenient to obtain the spectrum between 2.5 μm (4000 cm−1) and 2.9 μm (3450 cm−1) because the instrument is compensated for the presence of moisture and the band is not influenced by intermolecular forces (associations). However, when testing a highly oxidized oil or when using a single-beam instrument better results may be obtained if the scan is made between 10.90 μm (918 cm−1) and 14.00 μm (714 cm−1).  
3.4 Increased absorption at 11.63 μm (860 cm −1) or 13.42 μm (745 cm−1) or both, will identify the inhibitor as 2,6-ditertiary-butyl paracresol or 2,6-ditertiary-butyl phenol respectively (Note 1).
Note 1: The absorbance at 745 cm−1 for 2,6-ditertiary-butyl phenol and at 860 cm−1 for 2,6-ditertiary-butyl paracresol for equal concentrations will be in the approximate ratio of 2.6 to 1.
SCOPE
1.1 This test method covers the determination of the weight percent of 2,6-ditertiary-butyl paracresol (DBPC) and 2,6-ditertiary-butyl phenol (DBP) in new or used electrical insulating oil in concentrations up to 0.5 % by measuring its absorbance at the specified wavelengths in the infrared spectrum.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.4 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: 30-Nov-2021
• ICS: 29.040.10 - Insulating oils
• Technical Committee: D27 - Electrical Insulating Liquids and Gases
• Drafting Committee: D27.03 - Analytical Tests

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: D2668 − 07 (Reapproved 2021)
Standard Test Method for
2,6-di-tert-Butyl- p-Cresol and 2,6-di-tert-Butyl Phenol in
1
Electrical Insulating Oil by Infrared Absorption
This standard is issued under the fixed designation D2668; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope insulating oil measures the amount of this material that has
been added to the oil as protection against oxidation. In a used
1.1 This test method covers the determination of the weight
oil it measures the amount remaining after oxidation has
percent of 2,6-ditertiary-butyl paracresol (DBPC) and 2,6-
reduced its concentration. The test is also suitable for manu-
ditertiary-butyl phenol (DBP) in new or used electrical insu-
facturing control and specification acceptance.
lating oil in concentrations up to 0.5% by measuring its
absorbance at the specified wavelengths in the infrared spec-
3.2 When an infrared spectrum is obtained of an electrical
trum.
insulating oil inhibited with either of these compounds there is
1.2 The values stated in SI units are to be regarded as
an increase in absorbance of the spectrum at several wave-
standard. No other units of measurement are included in this
lengths (or wavenumbers). 2,6 ditertiary-butyl paracresol pro-
standard.
duces pronounced increases in absorbance at 2.72 µm (3650
−1 −1
cm ), and 11.63 µm (860 cm ). 2,6 ditertiary-butyl phenol
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the producespronouncedincreasesinabsorbanceat2.72µm(3650
−1 −1
cm ) and 13.42 µm (745 cm ).
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
3.3 When making this test on other than a highly oxidized
mine the applicability of regulatory limitations prior to use.
oil or when using a double-beam spectrophotometer, it has
1.4 This international standard was developed in accor-
been found convenient to obtain the spectrum between 2.5 µm
dance with internationally recognized principles on standard-
−1 −1
(4000cm )and2.9µm(3450cm )becausetheinstrumentis
ization established in the Decision on Principles for the
compensated for the presence of moisture and the band is not
Development of International Standards, Guides and Recom-
influenced by intermolecular forces (associations). However,
mendations issued by the World Trade Organization Technical
whentestingahighlyoxidizedoilorwhenusingasingle-beam
Barriers to Trade (TBT) Committee.
instrument better results may be obtained if the scan is made
−1 −1
2. Referenced Documents
between 10.90 µm (918 cm ) and 14.00 µm (714 cm ).
2
2.1 ASTM Standards: −1
3.4 Increased absorption at 11.63 µm (860 cm ) or 13.42
D923Practices for Sampling Electrical Insulating Liquids
−1
µm (745 cm ) or both, will identify the inhibitor as 2,6-
D2144Practices for Examination of Electrical Insulating
ditertiary-butyl paracresol or 2,6-ditertiary-butyl phenol re-
Oils by Infrared Absorption
spectively (Note 1).
D3487Specification for Mineral Insulating Oil Used in
−1
Electrical Apparatus
NOTE 1—The absorbance at 745 cm for 2,6-ditertiary-butyl phenol
−1
and at 860 cm for 2,6-ditertiary-butyl paracresol for equal concentra-
3. Significance and Use
tions will be in the approximate ratio of 2.6 to 1.
3.1 The quantitative determination of 2,6-ditertiary-butyl
4. Apparatus
paracresol and 2,6-ditertiary-butyl phenol in a new electrical
4.1 Withequipmentdescriptionreferringtocompliance,the
1
This test method is under the jurisdiction of ASTM Committee D27 on
equipment shall be in accordance with Section 6 of Practices
Electrical Insulating Liquids and Gases and is the direct responsibility of Subcom-
D2144. Accordingly, the use of Fourier-transform rapid scan
mittee D27.03 on Analytical Tests.
Current edition approved Dec. 1, 2021. Published January 2022. Originally
infrared (FTIR) spectrophotometers is permitted by reference
approved in 1967. Last previous edition approved in 2013 as D2668–07(2013).
to that test method.
DOI: 10.1520/D2668-07R21.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM 5. Sampling
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. 5.1 Obtain the sample in accordance with Practices D923.
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