ASTM D6481-99(2004)
(Test Method)Standard Test Method for Determination of Phosphorus, Sulfur, Calcium, and Zinc in Lubrication Oils by Energy Dispersive X-ray Fluorescence Spectroscopy
Standard Test Method for Determination of Phosphorus, Sulfur, Calcium, and Zinc in Lubrication Oils by Energy Dispersive X-ray Fluorescence Spectroscopy
SIGNIFICANCE AND USE
Some oils are formulated with organo-metallic additives, which act, for example, as detergents, antioxidants, and antiwear agents. Some of these additives contain one or more of these elements: calcium, phosphorus, sulfur, and zinc. This test method provides a means of determining the concentrations of these elements, which in turn provides an indication of the additive content of these oils.
This test method is primarily intended to be used at a manufacturing location for monitoring of additive elements in lubricating oils. It can also be used in central and research laboratories.
SCOPE
1.1 This test method covers the quantitative determination of additive elements in unused lubricating oils, as shown in .
1.2 This test method is limited to the use of energy dispersive X-ray fluorescence (EDXRF) spectrometers employing an X-ray tube for excitation in conjunction with the ability to separate the signals of adjacent elements.
1.3 This test method uses interelement correction factors calculated from empirical calibration data.
1.4 This test method is not suitable for the determination of magnesium and copper at the concentrations present in lubricating oils.
1.5 This test method excludes lubricating oils that contain chlorine or barium as an additive element.
1.6 This test method can be used by persons who are not skilled in X-ray spectrometry. It is intended to be used as a routine test method for production control analysis.
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 to use.
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Designation:D6481–99 (Reapproved 2004)
Standard Test Method for
Determination of Phosphorus, Sulfur, Calcium, and Zinc in
Lubrication Oils by Energy Dispersive X-ray Fluorescence
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Spectroscopy
This standard is issued under the fixed designation D6481; 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.
TABLE 1 Elements and Range of Concentrations Determined
1. Scope
Element Concentration Range
1.1 This test method covers the quantitative determination
Phosphorus 0.02 to 0.3 mass %
of additive elements in unused lubricating oils, as shown in
Sulfur 0.05 to 1.0 mass %
Table 1.
Calcium 0.02 to 1.0 mass %
1.2 This test method is limited to the use of energy
Zinc 0.01 to 0.3 mass %
dispersive X-ray fluorescence (EDXRF) spectrometers em-
ploying an X-ray tube for excitation in conjunction with the
ability to separate the signals of adjacent elements.
are determined by comparison of these intensities against a
1.3 This test method uses interelement correction factors
calibration curve using empirical interelement correction fac-
calculated from empirical calibration data.
tors and ratio to backscatter.
1.4 This test method is not suitable for the determination of
2.2 The EDXRF spectrometer is initially calibrated using a
magnesium and copper at the concentrations present in lubri-
setofpreparedstandardstocollectthenecessaryintensitydata.
cating oils.
Each calibration line and any correction coefficient are ob-
1.5 This test method excludes lubricating oils that contain
tained by a regression of this data, using the program supplied
chlorine or barium as an additive element.
with the spectrometer.
1.6 This test method can be used by persons who are not
3. Significance and Use
skilled in X-ray spectrometry. It is intended to be used as a
routine test method for production control analysis.
3.1 Some oils are formulated with organo-metallic addi-
1.7 This standard does not purport to address all of the
tives, which act, for example, as detergents, antioxidants, and
safety concerns, if any, associated with its use. It is the
antiwear agents. Some of these additives contain one or more
responsibility of the user of this standard to establish appro-
of these elements: calcium, phosphorus, sulfur, and zinc. This
priate safety and health practices and determine the applica-
test method provides a means of determining the concentra-
bility of regulatory limitations to use.
tions of these elements, which in turn provides an indication of
the additive content of these oils.
2. Summary of Test Method
3.2 This test method is primarily intended to be used at a
2.1 A specimen is placed in the X-ray beam, and the
manufacturing location for monitoring of additive elements in
appropriate regions of its spectrum are measured to give the
lubricating oils. It can also be used in central and research
fluorescent intensities of phosphorus, sulfur, calcium, and zinc.
laboratories.
Other regions of the spectrum are measured to compensate for
4. Interferences
varying background. If the detector does not completely
resolve all the elements in a single measurement, then to
4.1 The additive elements found in lubricating oils will
improve selectivity, there is a combination of sequential and
affect the measured intensities from the elements of interest to
simultaneous measurements employing primary and secondary
a varying degree. In general, for lubricating oils, the
beam filters. There can be correction of measured intensities
X-radiation emitted by the element of interest can be absorbed
for spectral overlap. Concentrations of the elements of interest
by itself (self-absorption) or by the other elements present in
the sample matrix. Also the X-radiation emitted from one
element can further excite (enhance) another element. These
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interelement effects are significant at concentrations varying
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
from 0.03 mass %, due to the heavier elements, to 1 mass %,
D02.03 on Elemental Analysis.
forthelighterelements.Enhancementeffectscanbeminimised
Current edition approved May 1, 2004. Published May 2004. Originally
byselectiveexcitation.Themeasuredconcentrationforagiven
approved in 1999. Last previous edition approved in 1999 as D6481 - 99. DOI:
10.1520/D6481-99R04. element can be mathematically corrected for self-absorption
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D6481–
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