ASTM D2668-07(2013)

Standard Test Method for 2,6-<i>di-tert</i>-Butyl-<i> p</i>-Cresol and 2,6-<ital>di-tert</ital>-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 and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 31-Oct-2013
• ICS: 29.040.10 - Insulating oils
• Technical Committee: D27 - Electrical Insulating Liquids and Gases
• Drafting Committee: D27.03 - Analytical Tests

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D2668 − 07 (Reapproved 2013)
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 3.2 When an infrared spectrum is obtained of an electrical
insulating oil inhibited with either of these compounds there is
1.1 This test method covers the determination of the weight
an increase in absorbance of the spectrum at several wave-
percent of 2,6-ditertiary-butyl paracresol (DBPC) and 2,6-
lengths (or wavenumbers). 2,6 ditertiary-butyl paracresol pro-
ditertiary-butyl phenol (DBP) in new or used electrical insu-
duces pronounced increases in absorbance at 2.72 µm (3650
lating oil in concentrations up to 0.5% by measuring its
−1 −1
cm ), and 11.63 µm (860 cm ). 2,6 ditertiary-butyl phenol
absorbance at the specified wavelengths in the infrared spec-
producespronouncedincreasesinabsorbanceat2.72µm(3650
trum.
−1 −1
cm ) and 13.42 µm (745 cm ).
1.2 The values stated in SI units are to be regarded as
3.3 When making this test on other than a highly oxidized
standard. No other units of measurement are included in this
oil or when using a double-beam spectrophotometer, it has
standard.
been found convenient to obtain the spectrum between 2.5 µm
1.3 This standard does not purport to address all of the −1 −1
(4000cm )and2.9µm(3450cm )becausetheinstrumentis
safety concerns, if any, associated with its use. It is the
compensated for the presence of moisture and the band is not
responsibility of the user of this standard to establish appro-
influenced by intermolecular forces (associations). However,
priate safety and health practices and determine the applica-
whentestingahighlyoxidizedoilorwhenusingasingle-beam
bility of regulatory limitations prior to use.
instrument better results may be obtained if the scan is made
−1 −1
between 10.90 µm (918 cm ) and 14.00 µm (714 cm ).
2. Referenced Documents
−1
2 3.4 Increased absorption at 11.63 µm (860 cm ) or 13.42
2.1 ASTM Standards:
−1
µm (745 cm ) or both, will identify the inhibitor as 2,6-
D923Practices for Sampling Electrical Insulating Liquids
ditertiary-butyl paracresol or 2,6-ditertiary-butyl phenol re-
D2144Practices for Examination of Electrical Insulating
spectively (Note 1).
Oils by Infrared Absorption
−1
D3487Specification for Mineral Insulating Oil Used in 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-
Electrical Apparatus
tions will be in the approximate ratio of 2.6 to 1.
3. Significance and Use
4. Apparatus
3.1 The quantitative determination of 2,6-ditertiary-butyl
4.1 Withequipmentdescriptionreferringtocompliance,the
paracresol and 2,6-ditertiary-butyl phenol in a new electrical
equipment shall be in accordance with Section 6 of Practices
insulating oil measures the amount of this material that has
D2144. Accordingly, the use of Fourier-transform rapid scan
been added to the oil as protection against oxidation. In a used
infrared (FTIR) spectrophotometers is permitted by reference
oil it measures the amount remaining after oxidation has
to that test method.
reduced its concentration. The test is also suitable for manu-
facturing control and specification acceptance.
5. Sampling
5.1 Obtain the sample in accordance with Practices D923.
1
This test method is under the jurisdiction of ASTM Committee D27 on
6. Calibration and Standardization
Electrical Insulating Liquids and Gases and is the direct responsibility of Subcom-
mittee D27.03 on Analytical Tests.
6.1 When the manufacturer of the oil is known and the base
Current edition approved Nov. 1, 2013. Published December 2013. Originally
oil is available, use it to prepare the standards. For oils of
approved in 1967. Last previous edition approved in 2007 as D2668–07. DOI:
10.1520/D2668-07R13.
unknown origin, use base oils which meet the requirements of
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Specification D3487. Some base oils may provide a better
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
match than others and therefore it is desirable to have several
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. available.
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