ASTM D4927-20

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D4927 − 15 (Reapproved 2020) D4927 − 20
Standard Test Methods for
Elemental Analysis of Lubricant and Additive Components—
Barium, Calcium, Phosphorus, Sulfur, and Zinc by
Wavelength-Dispersive X-Ray Fluorescence Spectroscopy
This standard is issued under the fixed designation D4927; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope Scope*
1.1 These test methods cover the determination of barium, calcium, phosphorus, sulfur, and zinc in unused lubricating oils at
element concentration ranges shown in Table 1. The range can be extended to higher concentrations by dilution of sample
specimens. Additives can also be determined after dilution. Two different methods are presented in these test methods.
1.2 Test Method A (Internal Standard Procedure)—Internal standards are used to compensate for interelement effects of X-ray
excitation and fluorescence (see Sections 8 through 13).
1.3 Test Method B (Mathematical Correction Procedure)—The measured X-ray fluorescence intensity for a given element is
mathematically corrected for potential interference from other elements present in the sample (see Sections 14 through 19).
1.4 The preferred concentration units are mass % barium, calcium, phosphorus, sulfur, or zinc.
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.
2. Referenced Documents
2.1 ASTM Standards:
D6299 Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measure-
ment System Performance
3. Summary of the Test Methods
3.1 A sample specimen is placed in the X-ray beam and the intensity of the appropriate fluorescence lines of barium, calcium,
These test methods are under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and are the direct responsibility of
Subcommittee D02.03 on Elemental Analysis.
Current edition approved May 1, 2020Dec. 1, 2020. Published June 2020January 2021. Originally approved in 1989. Last previous edition approved in 20152020 as
D4927 – 15.D4927 – 15 (2020). DOI: 10.1520/D4927-15R20.10.1520/D4927-20.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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TABLE 1 Range of Applicability
Element Range, Mass %
Barium 0.04-8.5
Calcium 0.01-1.0
Phosphorus 0.01-0.5
Sulfur 0.1-4.0
Zinc 0.01-0.6
phosphorus, sulfur, and zinc are measured. Instrument response factors related to the concentration of standards enable the
determination of the concentration of elements in the tested sample specimens. Enhancement or depressionabsorption of the X-ray
fluorescence of a given element by an interfering element in the sample may occur. Two test methods (A and B) are described for
compensating any interference effect.
3.2 Test Method A (Internal Standard Procedure)—Internal standards are used with the standards and sample specimens to
compensate for the potential interelement effects.
3.2.1 Barium, Calcium, Phosphorus, and Zinc—A sample specimen that has been blended with a single internal standard solution
(containing tin or titanium for barium and calcium, zirconium for phosphorus, and nickel for zinc) is poured into an X-ray cell.
Total net counts (peak intensity—background) intensity – background) for each element and its respective internal standard are
collected at their appropriate wavelengths. The ratios between elemental and internal standard counts are calculated and converted
into barium, calcium, phosphorus, or zinc concentrations, or a combination thereof, from calibration curves.
3.2.2 Sulfur—A sample specimen is mixed with a lead internal standard solution and analyzed as described in 3.2.1.
3.3 Test Method B (Mathematical Correction Procedure)—The measured intensity for a given element is mathematically corrected
for the interference from other elements in the sample specimen. This requires that intensities from all elements in the specimen
be obtained.
3.3.1 The sampletest specimen is placed in the X-ray beam and the intensities of the fluorescence lines ofbeam. Total net counts
or intensities (peak intensity – background) for barium, calcium, phosphorus, sulfur, and zinc are measured. A similar measurement
is made away from the fluorescence lines in order to obtain a background correction. measured at their appropriate wavelengths.
Concentrations of the elements of interest are determined by comparison of net signals against appropriate interelement correction
factors calibration curves developed from responses of calibration standards. The calibration procedure includes interelement
corrections.
3.3.2 The X-ray fluorescence spectrometer is initially calibrated with a suite of standards in order to determine by regression
analysis, interelement correction factors and instrument response factors.
3.3.3 Subsequent calibration is achieved using a smaller number of standards since only the instrument response factors need to
be redetermined. One of these standards (or an optional synthetic pellet) can be used to monitor instrumental drift when performing
a high volume of analyses.
3.4 Additives and additive packages can be determined after dilution with base oil to place the elemental concentrations in the
range described in 1.1.
4. Significance and Use
4.1 Some oils are formulated with organo-metallic additives which act as detergents, antioxidants, antiwear agents, and so forth.
Some of these additives contain one or more of these elements: barium, calcium, phosphorus, sulfur, and zinc. These test methods
provide a means of determining the concentration of these elements which in turn provides an indication of the additive content
of these oils.
4.2 Several additive elements and their compounds are added to the lubricating oils to give beneficial performance (see Table 2).
5. Interferences
5.1 The additive elements found in lubricating oils will affect the measured intensities from the elements of interest to a varying
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TABLE 2 Lubricants and Additive Materials
Element Compounds Purpose/Application
Barium Sulfonates, Phenates Detergent inhibitors, corrosion inhibitors, detergents, rust inhibitors,
automatic transmission fluids
Calcium Sulfonates, Phenates Detergent inhibitors, dispersants
Phosphorus Dithiophosphates, Phosphates phosphites Anti-rusting agents, extreme pressure additives, anti-wear
Sulfur Base oils, sulfonates, thiophosphates, polysulfides Detergents, extreme pressure additives, anti-wear
and other sulfurized components
Zinc Dialkyldithiophosphates, Dithiocarbamates, Anti-oxidant, corrosion inhibitors, anti-wear additives, detergents,
Phenolates, Carboxylates crankcase oils, hypoid gear lubricants, aircraft piston engine oils, turbine
oils, automatic transmission fluids, railroad diesel engine oils, brake
lubricants
degree. In general for lubricating oils, the X-radiation emitted by the element of interest is absorbed by the other elements in the
sample matrix. Also, the X-radiation emitted from one element can further excite another element. element; this is further referred
to as “enhancement.” These effects are significant at concentrations varying from 0.03 % by mass due to the heavier elements to
1 % by mass for the lighter elements. The measured intensity for a given element can be mathematically corrected for the
absorption and enhancement of the emitted radiation by the other elements present in the sample specimen. Suitable internal
standards can also compensate for X-ray inter-element effects. If an element is present at significant concentrations and an
interelement correction for that element is not employed, the results can be low due to absorption or high due to enhancement.
6. Apparatus
6.1 Wavelength Dispersive X-Ray Spectrometer, equipped for soft X-ray detection of radiation soft X-ray in the range from 1
0.1 nm to 1.0 nm (1 A˚ to 10 10 A˚.). For optimum sensitivity, the spectrometer is equipped with the following:
6.1.1 X-Ray Generating Tube, with chromium, rhodium, or scandium target. Other targets can also be employed.
6.1.2 Helium, purgeable optical path.
6.1.3 Interchangeable Crystals, germanium, lithium fluoride (LiF(LiF200), ), graphite, or pentaerythritol (PET), or a
combination thereof. Other crystals can also be used.
6.1.4 Pulse-Height Analyzer, or other means of energy discrimination.
6.1.5 Detector, flow proportional, or scintillation, or flow proportional and scintillation counter.
6.2 Shaker, Mechanical Stirrer, or Ultrasonic Bath, capable of handling from 30 mL to 1 L bottles.
6.3 X-Ray Disposable Plastic Cells, with suitable film window. Suitable films include Mylar, polypropylene, or polyimid with
film thicknesses between 0.25 mil to 0.35 mil (6.3 μm to 8.8 μm).
NOTE 1—Some films contain contamination of the elements of interest (Mylar in particular). The magnitude of the contamination is assessed and the same
film batch used throughout the entire analysis.
7. Purity of Reagents
7.1 Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all reagents shall conform
to the specifications of the Committee on Analytical Reagents of the American Chemical Society, where such specifications are
available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use
without lessening the accuracy of the determination.
A registered trademark of E. I. du Pont de Nemours and Co.DuPont Teijin Films, LP.
ACS Reagent Chemicals, Specifications and Procedures for Reagents and Standard-Grade Reference Materials, American Chemical Society, Washington, DC. For
suggestions on the testing of reagents not listed by the American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and
the United States Pharmacopeia and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.
D4927 − 20
TEST METHOD A (INTERNAL STANDARD PROCEDURE)
8. Reagents and Materials
8.1 Helium, for optical path of spectrometer.
8.2 P-10 Ionization Gas, 90 % by volume argon and 10 % by volume methane for the flow proportional counter.
8.3 Diluent Solvent, a suitable solvent free of metals, sulfur, and phosphorus (for example, kerosene, white oil, or xylenes).
8.4 Internal Standard Materials:
8.4.1 Nickel Octoate, preferably containing 5.0 % by mass 6 0.1 % by mass nickel. If the nickel concentration is higher or lower
(minimum concentration that can be used is 2.5 % by mass 6 0.1 % by mass nickel), the laboratory needs to adjust the amount
of sample taken in 9.1 to yield an equivalent nickel concentration level in the internal standard. Other nickel-containing organic
matrices (free of other metals, sulfur, and phosphorus) may be substituted provided the nickel is stable in solution, the
concentration is known (≥2.5 % by mass 6 0.1 % by mass nickel), and the laboratory can adjust the amount of sample taken in
9.1 to yield an equivalent nickel concentration level in the internal standard if the nickel concentration does not initially contain
5.0 % by mass 6 0.1 % by mass nickel.
NOTE 2—Many X-ray tubes emit copper X rays which increase in intensity with age. This does not present a problem when using copper as an internal
standard for zinc providing that frequent calibrations are performed. No problem exists when using nickel as internal for zinc and nickel is the preferred
internal standard material. The use of a primary beam filter (such as, for example, 100 micron Al) when measuring Cu is recommended to fully avoid
problems with the tube contamination.
8.4.2 Titanium 2-Ethylhexoide or Tin Octoate, preferably containing 8.0 % by mass 6 0.1 % by mass titanium or tin. If the
titanium or tin concentration is higher or lower (minimum concentration that can be used is 4.0 % by mass 6 0.1 % by mass
titanium or tin), the laboratory needs to adjust the amount of sample taken in 9.1 to yield an equivalent titanium or tin concentration
level in the internal standard. Other titanium or tin containing organic matrices (free of other metals, sulfur, and phosphorus) may
be substituted, provided the titanium or tin is stable in solution, the concentration is known (≥4.0 % by mass 6 0.1 % by mass
titanium or tin), and the laboratory can adjust the amount of sample taken in 9.1 to yield an equivalent titanium or tin concentration
level in the internal standard if the titanium or tin concentration does not initially contain 8.0 % by mass 6 0.1 % by mass titanium
or tin.
8.4.3 Zirconium Octoate, preferably containing 12.0 % by mass 6 0.1 % by mass zirconium. If the laboratory uses zirconium
octoate with a lower mass % zirconium concentration level, the laboratory needs to evaporate away the petroleum solvent to yield
a solution that contains 12.0 % by mass 6 0.1 % by mass zirconium. Other zirconium containing organic matrices (free of other
metals, sulfur, and phosphorus) may be substituted, provided the zirconium is stable in solution and the concentration is known
and does not exceed 12.0 % by mass 6 0.1 % by mass zirconium. If the zirconium concentration is <12.0 % by mass 6 0.1 %
by mass , mass, the laboratory needs to evaporate away the petroleum solvent to yield a solution that contains 12.0 % by mass 6
0.1 % by mass zirconium.
8.4.4 Lead Naphthenate, containing 24.0 % by mass 6 0.1 % by mass lead.
8.5 Calibration Standard Materials:
NOTE 3—In addition to calibration standards identified in 8.5.1 – 8.5.5, single-element or multielement calibration standards may also be prepared from
materials similar to the samples being analyzed, provided the calibration standards to be used have previously been characterized by independent primary
(for example, gravimetric or volumetric) analytical techniques to establish the elemental concentration mass percent levels.
8.5.1 Barium 2-Ethylhexoide or Sulfonate, with concentrations ≥4 mass % ≥4 % by mass barium and certified to better than
60.1 % absolute (95 % confidence limit), so that calibration standards can be prepared as stated in 10.1.1 and 10.1.2.
8.5.2 Calcium Octoate or Sulfonate, with concentrations ≥ 4 mass % ≥4 % by mass calcium and certified to better than 60.1 %
absolute (95 % confidence limit), so that calibration standards can be prepared as stated in 10.1.1 and 10.1.2.
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8.5.3 Bis(2-Ethylhexyl)Hydrogen Phosphate, 97 % purity (9.62 % by mass phosphorus). Other phosphorus containing organic
matrices (free of other metals) may be substituted provided the phosphorus is stable in solution and the concentration is ≥4 mass %
≥4 % by mass phosphorus and certified to better than 60.1 % absolute (95 % confidence limit), so that calibration standards can
be prepared as stated in 10.1.1 and 10.1.2.
8.5.4 Zinc Sulfonate or Octoate, with concentration ≥4 mass % ≥4 % by mass zinc and certified to better than 60.1 % absolute
(95 % confidence limit), so that calibration standards can be prepared as stated in 10.1.1 and 10.1.2.
8.5.5 Di-n-Butyl Sulfide, 97 % purity, (21.9 % by mass sulfur). Other sulfur containing organic matrices (free of metals) may be
substituted, provided the sulfur is stable in solution and the concentration is ≥2 % by mass sulfur and certified to better than
60.1 % absolute (95 % confidence limit), so that calibration standards can be prepared as stated in 10.1.2.
8.6 Quality Control (QC) Samples, preferably are portions of one or more lubricating oils or additives that are stable and
representative of the samples of interest. These QC samples can be used to check the validity of the testing process and
performance of the instrument as described in Section 12.
9. Preparation of Internal Standards
9.1 Barium, Calcium, Phosphorus, and Zinc—Dispense 240 g 6 0.5 g of nickel octoate (5.0 % 6 0.1 % by mass nickel), 30 g 6
0.1 g of titanium 2-ethylhexoide (8.0 % 6 0.1 % by mass titanium) or 30 g 6 0.1 g of tin octoate (8.0 % 6 0.1 % by mass tin),
and 450 g 6 1 g of diluent solvent into a 1 L bottle. Shake or stir the bottle for a minimum of 10 min. If the laboratory uses internal
materials that have different elemental concentrations than those explicitly stated in 8.4.1 and 8.4.2, it will be necessary for the
laboratory to adjust the amount of sample taken in order to obtain an equivalent elemental concentration in the internal standard
blend that is prepared according to the following equations:
A 5 240 3 5/x (1)
~ !
B 5 30 3 8/y (2)
~ !
C 5 720 2 @A1B# (3)
where:
A = nickel containing material in blend, g,
B = titanium or tin containing material in blend, g,
C = diluent to add to blend, g,
x = nickel in material chosen as an internal standard, mass %, and
y = titanium or tin in material chosen as an internal standard, mass %.
9.2 Sulfur—Lead naphthenate, 24 % by mass lead, serves as a suitable internal standard. (Warning—Hazardous. Lead
naphthenate is toxic and precautions should be taken to avoid inhalation of vapors, ingestion, or skin contact.) No further treatment
of this compound is necessary.
10. Preparation of Calibration Standards
10.1 Barium, Calcium, Phosphorus, and Zinc:
10.1.1 For concentrations less than 0.1 % by mass, prepare standards containing 0.00 % by mass, 0.01 % by mass, 0.025 % by
mass, 0.050 % by mass, 0.075 % by mass, and 0.10 % by mass of each respective element in the diluent solvent.
10.1.2 For concentrations greater than 0.1 % by mass, prepare standards containing 0.00 % by mass, 0.10 % by mass, 0.25 % by
mass, 0.50 % by mass, 0.75 % by mass, and 1.00 % by mass of each respective element in the diluent solvent.
10.1.3 Dispense 1.000 g 6 0.001 g of the zirconium internal standard solution described in 8.4.3 into a 30 mL bottle. Prepare an
individual bottle for each of the calibration standards.
10.1.4 Dispense 1.000 g 6 0.001 g of the internal standard solution described in 9.1 into a 30 mL bottle. Repeat for all of the
calibration-standard bottles.
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10.1.5 Add 8.00 g 6 0.001 g of each standard to a respective bottle containing the internal standards and shake or stir well
(minimum of 10 min) to mix the constituents.
10.2 Sulfur:
10.2.1 Prepare five standards covering the range from 0.00 % by mass to 2.00 % by mass sulfur in the diluent solvent.
10.2.2 Dispense 1.000 g 6 0.001 g of lead internal standard into 30 mL bottles (one bottle for each standard).
10.2.3 Add 9.000 g 6 0.001 g of each standard to each respective bottle containing internal standard. Shake or stir contents for
a minimum of 10 min using apparatus defined in 6.2.
11. Instrument Calibration for Barium, Calcium, Phosphorus, Sulfur, and Zinc
11.1 Fill respective X-ray cups at least half full with the calibration standard solutions. Make sure that no wrinkles or bulges are
present in the film. The film must be flat.
11.2 Place the sample cups in the X-ray beam in order to measure and record the net intensity (peak intensity—background
intensity minus background intensity) for both the analyte signal and the internal standard signal accordingsignal. Table 3 to the
wavelengths and conditions suggested in provides suggested crystal parameters. Table 3. Up to 60 s counting periods may be used
at each wavelength position. Do this for each of the calibration standards for each of the elements.
NOTE 4—The parameters indicated in Table 3 are presented for guidance only and they will vary according to the instrument used.
11.3 Calculate the ratio, R, of the net element counts to their corresponding net internal standard counts for all of the net elements
and standards as follows:
R 5 E/I (4)
where:
E = net element counts, and
I = net internal standard counts.
NOTE 5—Many modern X-ray spectrometer instruments will calculate this ratio automatically and store the information in the instrument computer
system.
NOTE 6—Many modern X-ray spectrometer instruments use count rate (intensity, expressed in kcps) instead of counts collected in a given measuring time.
11.4 Perform regression analyses for each calibration element by ratioing the net element counts to the net internal standard counts
versus the element concentration (mass %) on linear graph paper or by way of the instrument computer system. It is r
...