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: E1251 − 24

Standard Test Method for

Analysis of Aluminum and Aluminum Alloys by Spark
Atomic Emission Spectrometry1
This standard is issued under the fixed designation E1251; 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. Analysis of Hg in aluminum by Spark-AES is not

1.1 This test method describes the analysis of aluminum and recommended. Accurate analysis of Hg using this technique is
its alloys by spark-atomic emission spectrometry (Spark-AES). compromised by the presence of an intense iron interference.
The aluminum specimen to be analyzed may be in the form of Inaccurate reporting of Hg due to these interference effects can
a chill cast disk, casting, foil, sheet, plate, extrusion, or some jeopardize the current designation of aluminum production as
other wrought form or shape. The elements covered in the a mercury-free process. To demonstrate compliance with
scope of this method are listed as follows. legislated Hg content limits, use of an alternate method capable
of analysis with a minimum reporting limit of 0.0001% or
Tested Mass Fraction Range
Element
(Wt %) lower is recommended. Suitable techniques include but are not
Antimony 0.001 to 0.003 limited to GD-MS, XRF, cold vapor AA, and ICP-MS.
Arsenic 0.001 to 0.006
Beryllium 0.0004 to 0.24 1.2 This test method is suitable primarily for the analysis of
Bismuth 0.03 to 0.6 chill cast disks as defined in Practices E716. Other forms may
Boron 0.0006 to 0.009
Calcium 0.0002 to 0.04
be analyzed, provided that: (1) they are sufficiently massive to
Chromium 0.001 to 0.23 prevent undue heating, (2) they allow machining to provide a
Cobalt 0.4 to 1.60 clean, flat surface, which creates a seal between the specimen
Copper 0.001 to 5.5
Gallium 0.02 to 0.11
and the spark stand, and (3) reference materials of a similar
Iron 0.2 to 0.5 metallurgical condition and chemical composition are avail-
Lead 0.04 to 0.6 able.
Lithium 0.0003 to 2.1
Magnesium 0.03 to 5.4 1.3 This standard does not purport to address all of the
Manganese 0.001 to 1.2 safety concerns, if any, associated with its use. It is the
Nickel 0.005 to 2.6
Phosphorus 0.003 to 0.017
responsibility of the user of this standard to establish appro-
Silicon 0.07 to 16 priate safety, health, and environmental practices and deter-
Sodium 0.003 to 0.02 mine the applicability of regulatory limitations prior to use.
Strontium 0.03 to 11.0
Tin 0.03 to 21.0
Specific safety and health statements are given in Section 10.
Titanium 0.001 to 0.12 1.4 This international standard was developed in accor-
Vanadium 0.002 to 0.022 dance with internationally recognized principles on standard-
Zinc 0.002 to 5.7
Zirconium 0.001 to 0.12 ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
NOTE 1—The mass fraction ranges given in the scope were established
through cooperative testing (ILS) of selected reference materials. The
mendations issued by the World Trade Organization Technical
range shown for each element does not demonstrate the actual usable Barriers to Trade (TBT) Committee.
analytical range for that element. The usable analytical range may be
extended higher or lower based on individual instrument capability, 2. Referenced Documents
spectral characteristics of the specific element wavelength being used, and
the availability of appropriate reference materials.
2.1 ASTM Standards:2
Warning—Mercury (Hg) is intentionally not included in the B985 Practice for Sampling Aluminum Ingots, Billets, Cast-
ings and Finished or Semi-Finished Wrought Aluminum
Products for Compositional Analysis
1
This test method is under the jurisdiction of ASTM Committee E01 on
Analytical Chemistry for Metals, Ores, and Related Materials and is the direct
2
responsibility of Subcommittee E01.04 on Aluminum and Magnesium. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Dec. 15, 2024. Published January 2025. Originally contact ASTM Customer Service at www.astm.org/contact. For Annual Book of
approved in 1988. Last previous edition approved in 2017 as E1251 – 17a. DOI: ASTM Standards volume information, refer to the standard’s Document Summary
10.1520/E1251-24. page on the ASTM website.

Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States

1
 E1251 − 24
E29 Practice for Using Significant Digits in Test Data to particular alloy being analyzed. For best results, the reference
Determine Conformance with Specifications material being used should be within 610 % of the composi-
E135 Terminology Relating to Analytical Chemistry for tion (for each respective element) of the material being
Metals, Ores, and Related Materials analyzed.
E305 Practice for Establishing and Controlling Spark
Atomic Emission Spectrochemical Analytical Curves 4. Summary of Test Method
E406 Practice for Using Controlled Atmospheres in Atomic
4.1 A controlled electrical discharge is produced in an argon
Emission Spectrometry
atmosphere between the prepared flat surface of a specimen
E691 Practice for Conducting an Interlaboratory Study to
and the tip of a counter electrode. The energy of the discharge
Determine the Precision of a Test Method
is sufficient to ablate material from the surface of the specimen,
E716 Practices for Sampling and Sample Preparation of
break the chemical or physical bonds, and cause the resulting
Aluminum and Aluminum Alloys for Determination of
atoms or ions to emit radiant energy. The radiant energies of
Chemical Composition by Spark Atomic Emission Spec-
the selected analytical wavelengths and the internal standard
trometry
wavelength(s) are converted into electrical signals by either
E826 Practice for Testing Homogeneity of a Metal Lot or
photomultiplier tubes (PMTs) or a suitable solid state detector.
Batch in Solid Form by Spark Atomic Emission Spec-
The detector signals are electrically integrated and converted to
trometry (Withdrawn 2023)3
a digitized value. The signals are ratioed to the proper internal
E1329 Practice for Verification and Use of Control Charts in
standard signal and converted into mass fractions.
Spectrochemical Analysis (Withdrawn 2019)3
E1507 Guide for Describing and Specifying the Spectrom- 4.2 Three different methods of calibration defined in 3.2.1,
eter of an Optical Emission Direct-Reading Instrument 3.2.2, and 3.2.3 are capable of giving the same precision,
E2972 Guide for Production, Testing, and Value Assignment accuracy, and detection limit.
of In-House Reference Materials for Metals, Ores, and 4.2.1 Binary calibration employs calibration curves that are
Other Related Materials determined using a large number of high-purity binary calibra-
2.2 ANSI Standard:4 tion materials. This approach is used when there is a need to
ANSI H35.1/H35.1M American National Standard Alloy analyze almost the entire range of aluminum alloys. Because
and Temper Designation Systems for Aluminum binary calibration materials may respond differently from alloy
calibration materials, thus the latter are used to improve
3. Terminology accuracy by applying a slope or intercept correction, or both, to
3.1 Definitions—For definitions of terms used in this the observed readings.
Standard, refer to Terminology E135. 4.2.2 Global calibration employs calibration curves that are
determined using many different alloy calibration materials
3.2 Definitions of Terms Specific to This Standard: with a wide variety of compositions. Mathematical calculations
3.2.1 alloy-type calibration—calibration curves determined correct for both alloy difference and inter-element effects. Like
using calibration materials from alloys with similar composi- 4.2.1, specific alloy calibration materials may be used to apply
tions. a slope or intercept correction, or both, to the observed
3.2.2 binary-type calibration—calibration curves deter- readings.
mined using binary calibration materials (primary aluminum to 4.2.3 Alloy calibration employs calibration curves that are
which has been added one specific element). determined using different alloy calibration materials that have
3.2.3 global-type calibration—calibration curves deter- similar compositions. Again, specific alloy calibration materi-
mined using calibration materials from many different alloys als may be used to apply a slope or intercept correction, or
with considerable compositional differences. both, to the observed readings.
3.2.4 two-point drift correction—the practice of analyzing
high and low drift correction materials for each calibration 5. Significance and Use
curve and adjusting the intensities obtained back to the values 5.1 The metallurgical properties of aluminum and its alloys
obtained on those particular drift correction materials during are highly dependent on chemical composition. Precise and
the collection of the calibration data. The corrections are accurate analyses are essential to obtaining desired properties,
calculated mathematically and are applied to both the slope and meeting customer specifications, and minimizing scrap due to
intercept. Improved precision may be obtained by using a off-grade material.
multi-point drift correction as described in Practice E1329. 5.2 This test method is applicable to chill cast specimens as
3.2.5 type standardization—mathematical adjustment of the defined in Practices E716 and can also be applied to other types
calibration curve’s slope or intercept using a single reference of samples provided that suitable reference materials are
material at or close to the nominal composition for the available. Also, other sample forms can be melted and cast into
a disk, using an appropriate mold, as described in Practices
3
E716. However, some elements (for example, magnesium)
The last approved version of this historical standard is referenced on
readily form oxides, while others (for example, sodium,
www.astm.org.
4
Available from American National Standards Institute (ANSI), 25 W. 43rd St., lithium, calcium, and strontium) are volatile, and may be lost to
4th Floor, New York, NY 10036, http://www.ansi.org. varying degrees during the melting process.

2
 E1251 − 24
6. Recommended Analytical Wavelengths and Potential equipped with an exhaust system that will safely dispose of the
Interferences argon gas and the metal dust created during the excitation
6.1 Table 1 lists the analytical wavelengths commonly used cycle. Considering health and cleanliness, the exhausted gas
for aluminum analysis. Other lines may be used if they give and dust should not be vented directly into the laboratory.
comparable results. Also listed are recommended mass fraction Manufacturers have designed their instruments with some type
ranges, background equivalent mass fractions, detection limits, of exhaust/filter system to minimize this problem. The exhaust
useful linear ranges, and potential interferences. The values can then be vented into an efficient hood system.
given in this table are typical; actual values obtained are 7.4 Gas Flow System, will be designed so that it can deliver
dependent on instrument design. pure argon gas to the excitation chamber. The purity of the
NOTE 2—The background equivalent mass fraction and detection limits argon gas will affect the precision of the results. Argon gas with
listed in Table 1 have been attained with a spectrometer that has a a minimum purity of 99.995 % has been found acceptable. The
reciprocal dispersion of 54 nm/mm and a working resolution of 3.5 nm,
using an entrance slit width of 25 µm and exit slit widths of 50 µm.
gas shall be delivered by a flow system as described in Practice
E406. The argon gas source can be from high-purity com-
7. Apparatus pressed gas cylinders, a cryogenic-type tank that contains
liquid argon or possibly from a central supply (liquid only). It
7.1 Specimen Preparation Equipment: is essential that only argon gas meeting the minimum purity of
7.1.1 Sampling Molds, for aluminum, the techniques of 99.995 % be used. A lower purity grade of argon, such as a
pouring a sample disk are described in Practices E716. Chill “welding grade,” should not be used. The delivery system shall
cast samples, poured and cast as described within Practices be composed of a two-stage type (high/low pressure) regulator
E716, shall be the recommended form in this test method. of all-metal construction with two pressure gages. Delivery
7.1.2 Lathe, capable of machining a smooth, flat surface on tubing must not introduce any contamination of the argon
the reference materials and samples. A variable speed cutter, a stream. Refrigerant-grade copper tubing is recommended. The
cemented carbide or polycrystalline diamond tool bit, and an gages on the regulator will allow for the adjustment of the gas
automatic cross feed are highly recommended. Proper depth of pressure to the instrument. Delivery pressure specifications
cut and desired surface finish are described in Practices E716. will vary with instrument manufacturer. Please note that the
7.1.3 Milling Machine, a milling machine can be used as an delivery tube connections should be made with all metal seals
alternative to a lathe. and the delivery tubing should be kept as short as possible. All
7.1.4 It is strongly recommended that the same preparation metal connections are strongly recommended because the
machinery used to prepare the reference materials is also used discharge is adversely affected by organic contamination, or by
to prepare the samples. Differences in surface characteristics as little as 2 ug ⁄g of oxygen or a few ug/g of water vapor.
may influence the analysis. Argon supply shall be sufficient to support the required flow
7.2 Excitation Source—In today’s instrumentation, the ex- during analysis and bleed during idle periods. All connections
citation source is computer controlled and is normally pro- must be leak-free.
grammed to produce: (1) a high-energy pre-spark (of some 7.5 Measuring and Control System of the instrument con-
preset duration), (2) a spark-type discharge (of some preset sists of either photomultiplier and integrating electronics or
duration), (3) an arc-type discharge (of some preset duration), solid-state photosensitive arrays (CCD or CID) that convert
and (4) a spark-type discharge, during which, time-resolved observed light intensities to a digitizable signal. A dedicated
measurements are made for improved detection limits (this computer or microprocessor is used to control burn conditions,
may be optional on some instruments). source operation, data acquisition, and the conversion of
7.2.1 Typical parameters and times are given in Table 2. intensity data to mass fractions. Data should be accessible to
Note that the information presented is given as an example the operator throughout all steps of the calculation process. The
only and parameters may vary with respect to instrument instrument’s control software should include functions for drift
model and manufacturer. correction (standardization), type standardization, and the ap-
7.3 Excitation Chamber, shall be designed with an upper plication of these functions to subsequent analyses.
plate that is smooth and flat so that it will seal tightly with the
prepared surface of the sample specimen. The seal that is 8. Materials
formed between the two will prevent atmosphere from entering 8.1 Counter Electrode—The counter electrode and speci-
the discharge chamber. The excitation chamber will contain a men surface are the two terminus points of the spark discharge.
mounting clamp to hold the counter electrode. The excitation The counter electrode should be made from tungsten or other
stand assembly will also have some type of clamp or device suitable material and have a pointed end. The gap distance
designed to hold the sample firmly against the top plate. Some between the specimen surface and the tip of the counter
manufacturers may provide liquid cooling for the top plate to electrode is specified by the manufacturer. The diameter and
minimize sample heating during the excitation cycle. The geometry of the counter electrode is also application and
excitation chamber will also be constructed so that it is flushed manufacturer dependent. If different designs or configurations
automatically with argon gas during the analytical burn cycle. are offered, it is recommended that the prospective purchaser
The excitation chamber’s design should allow for a flow of test each design to determine which performs best for the
argon gas to prevent the deposition of ablated metal dust on the intended analytical task. The counter electrode configuration
inner-chamber window(s). The excitation chamber will be and auxiliary gap distance must not be altered subsequent to

3
 E1251 − 24
TABLE 1 Recommended Analytical Lines
Wavelength Recommended Background Calculated High
Interferences
Element in Air Mass Fraction Equivalent, Detection Mass Fraction
Element, λ(nm) and k, %F
(nm)A Range, % %B Limit, %C,D Index, %E
Aluminum 256.799 I 70-100
266.039 I 70-100
237.208 I 70-100
Antimony 231.147 I 0.001-0.5 0.17 0.0002 Co 231.166 0.6
259.806 I 0.001-0.5 0.0002 Fe 259.837
Mn 259.817 0.01
Arsenic 234.984 I 0.005-0.1
Beryllium 234.861 I 0.0001-0.05 0.001 0.00003
313.042 II 0.0001-0.05 0.0035 0.00001
332.134 I 0.0001-0.05 0.00001
Bismuth 306.772 I 0.001-0.7 0.04 0.0002
Boron 249.773 I 0.0001-0.05 0.002 0.0001* Fe 249.782 0.001
Mn 249.778 0.007
249.678 I 0.0001-0.05
208.959 I 0.0001-0.05 Mo 208.952 0.13
Cadmium 228.802 I 0.001-1 0.05 <0.0001 As 228.812
479.992 I 0.005-2 0.15 0.003
Calcium 393.367 IIG 0.001-0.05 0.001 0.00005 Fe 393.361
Chromium 425.435 I 0.001-1 0.015 <0.0001
267.716 II 0.001-1 0.004 0.0005*
276.654 IIG 0.005-1
Cobalt 345.351 I 0.0001-2 <0.0001
Copper 327.396 I 0.001-1.5 0.005 <0.0001 0.7
324.754 I 0.001-0.5
296.117 I 0.05-20 0.40 0.01* >20 Fe 296.128
224.700 II 0.01-5 0.03 0.0005* 5
510.554 I 0.05-20 0.32 0.01* >20
Gallium 294.364 I 0.001-0.05 0.015 <0.0001
417.206 IG 0.001-0.05 Fe 417.213
Ti 417.190
Cr 417.167
Iron 238.204 II 0.001-1.5 0.015 0.0008 1.0
259.940 II 0.001-1.5 0.005 0.0004
259.957 I
273.955 II 0.01-3.5
374.949 IG 0.001-3.5 0.0001
441.512 I 0.01-3.5 0.0004
438.355 I 0.005-3.5
Lead 405.782 I 0.002-0.7 0.04 0.0001 Mn 405.792 0.01
Mg 405.763 0.001
283.306 I 0.002-0.7 0.07 0.002
Lithium 610.364 I 0.0001-3
670.784 I 0.0001-0.02 0.0005 <0.0005
323.261 I 0.01-3 Fe 323.279
Sb 323.250
Magnesium 279.553 II 0.0005-0.3 0.0006 0.00003 0.04
285.213 I 0.0005-0.3 0.008 <0.0001 0.25
277.669 I 0.05-11 0.08 0.01 >11
383.231 IG 0.01-11 0.015 0.002* >11
383.826 I 0.1-11
518.362 I 0.01-11 0.02 0.002* >11
Manganese 403.076 IG 0.001-0.1 0.028 0.0001*
259.373 II 0.0005-0.5 0.004 0.00005 0.2
293.306 II 0.001-2 0.006 0.0002* >1.1
346.033 II 0.01-2
Nickel 341.476 I 0.001-2 0.02 <0.0001 >2.5 Zr 341.466 0.01
310.188 I 0.005-4 0.05 0.001* >5
231.604 II 0.001-2 0.015 0.0005* <2.5
Phosphorus 178.231 IH 0.0001-0.1 0.084 0.0001
Silicon 288.158 I 0.001-1.5 0.01 0.0001 1.5 Cr 288.123
251.612 I 0.001-1.5 0.006 0.0001 1.5
390.553 IG 0.05-24 0.25 0.01 >24 Cr 390.566 0.09
212.415 I 0.05-24 0.5 0.05 >24
Silver 328.068 I 0.0005-0.1
338.289 I 0.0001-0.1 >10
466.848 I 0.05-1.5
Sodium 588.995 I 0.0001-0.05 0.0015 <0.0001
Strontium 421.552 IIG 0.0001-0.1 0.0004 0.0001
460.733 I 0.0005-0.06
Tin 317.502 I 0.001-7.5 0.04 0.0001 >10
Titanium 334.904 II 0.0005-0.5 0.004 <0.0001
337.280 II 0.001-0.5 0.002 <0.00010
363.545 I 0.0005-0.05 0.030 0.003*

4
 E1251 − 24
TABLE 1 Continued
Wavelength Recommended Background Calculated High
Interferences
Element in Air Mass Fraction Equivalent, Detection Mass Fraction
Element, λ(nm) and k, %F
(nm)A Range, % %B Limit, %C,D Index, %E
Vanadium 318.341 I 0.001-0.15 0.06 0.0003*
437.924 I 0.001-0.25
310.230 II 0.001-0.15 0.014 <0.0001
Zinc 213.856 I 0.0005-0.1 0.035 0.0001* 0.05
334.502 I 0.001-10.0 0.065 0.0004 >8
481.053 I 0.01-10 0.07 0.001* >10
472.216 I 0.01-10 0.26 0.0015 >10
Zirconium 339.198 II 0.001-1 0.02 0.001*
349.621 IIG 0.001-1 0.006 <0.0001
A
I = atom line, II = ion line.
B
Background Equivalent Mass Fraction—The mass fraction at which the signal due to the element is equal to the signal due to the background.
C
In this test method, the calculated detection limit was measured by calculating the standard deviation of ten consecutive burns on a specimen with element mass
fraction(s) at levels below ten times the expected detection limit.
D
See footnote C. For values marked with an asterisk (*) the available data were for a mass fraction greater than ten (10) times but less than a hundred (100) times the
expected detection limit.
E
High Mass Fraction Index—The mass fraction at which the slope of the calibration curve drops below 0.75.
F
Interference Factor, k—The apparent increase in the mass fraction of the element being determined, expressed in percent, due to the presence of 1.0 % of the interfering
element.
G
Useful analytical wavelengths with improved signal to background ratios due to the complete removal of C-N background by the argon atmosphere.
H
If phosphorus is determined, the most sensitive wavelength appears to be the 178.231 nm in the second order which requires either a vacuum or a gas filled
spectrometer. The vacuum spectrometer should be operated at a pressure of 25 microtorr or less. The gas filled spectrometer will be charged with nitrogen to a positive
pressure of slightly over one atmosphere (101 k pa). Optimum results are obtained by using a background channel that has been profiled “off peak” of the first order 178.231
nm phosphorus line as the internal standard. The ratio of P 178.231 nm (2nd) / background near the 178.231 nm (1st) is plotted against % phosphorus. Even with this
compensation for variability in background, alloys with highly different compositions of major alloying elements, particularly silicon, require separate reference materials
and analytical curves.

TABLE 2 Typical Excitation Source Electrical Parameters available from the National Institute of Standards and Tech-
Parameter
High Energy
Spark Arc
nology (NIST). Also, there are other commercial sources for
Pre-spark aluminum reference materials.
Resistance, Ω 1 1 15 9.1.2 For trace elements, reference materials that contain
Inductance, µH 30 130 30
Volts, V 400 400 400 variable mass fractions of the trace element in a typical alloy of
Frequency, Hz 300 300 300 constant or nearly constant composition are available. These
Capacitance, µF 12 3 5
reference materials can be used for establishing the analytical
Time, s 10 5 5
curve, but will not reveal potential interferences from nearby
wavelengths of other elements, or matrix effects that change
spectrometer calibration or calibration adjustments. Electrode instrument response or background. For optimum usefulness,
maintenance (frequent brushing of the counter electrode) to several of the calibration materials should have mass fractions
maintain its configuration, gap distance, and minimize surface for the other elements that vary over the expected ranges in the
contamination are critical to accurate, precise analytical results. specimen to be analyzed.
It is recommended that the instrument purchaser order several 9.1.3 Atomic emission analysis is a comparative technique
spare counter electrodes so that they can be replaced when that requires a close match of the metallurgy, structure, and
necessary. composition between the reference material and the test
material. Differences in structure, such as result from the
9. Reference Materials sodium modification of high silicon alloys, or differences in
9.1 Calibration Materials—All calibration materials shall metallurgical history, due to extruding, rolling, or heat treating,
be homogeneous and free of cracks or porosity. These materials induce a variety of effects that can influence the analytical
should also possess a metallurgical condition that is similar to results. To ensure analytical accuracy, care must be taken to
the material(s) that are being analyzed. The calibration mate- match the characteristics of the reference material to that of the
rials shall be used to produce the analytical curves for the test material or suitable corrections to adjust for these influ-
various elements being determined. ences must be established.
9.1.1 It is recommended that a calibration curve for any 9.2 Drift Correction (Standardization) Materials:
particular element be composed of a minimum of four calibra- 9.2.1 Materials for Drift Correction—Both high and low
tion materials. The mass fractions of these calibration materials mass fraction materials are available from several commercial
should be fairly evenly spaced over the calibrated analytical sources or may be developed in-house. The low material is
range so that a mathematically valid calibration curve can be usually high-purity aluminum. The high material(s) should
established using all of the points. have mass fractions near or above the median mass fraction for
9.1.1.1 The calibration materials used shall be of sufficient the calibrated range of each wavelength. The commercially
quality, purchased from a recognized reputable source, and available materials are tested for homogeneity and reproduc-
have certified values to the required accuracy for the antici- ibility of spectral response but are not necessarily certified for
pated analytical tasks to be performed. A few SRMs are composition of individual elements. Composition certification

5
 E1251 − 24
is not required because these materials are only used to adjust 12. Preparation of Reference Materials and Specimen
intensity ratios back to those obtained during the initial 12.1 Preparation of Reference Materials—All reference
calibration of the instrument. Care should be exercised when materials shall have their surfaces prepared for analysis ac-
replacing depleted materials with new ones that are from cording to Practices E716 with the cutting depth usually
different heats or lots, since the actual mass fraction of the limited to that required to produce a fresh surface (about 0.010
individual element(s) may be different from the material in. or 250 µm). The surfaces of the reference materials and the
currently in use. Whenever materials are replaced, appropriate surfaces of the test specimens shall be prepared in the same
procedures must be followed to reference the intensities manner. See Practices E716 for details.
obtained from the new material to the intensities obtained from
the material being replaced. See 14.3 for details. 12.2 Preparation of Specimens—For techniques to select
9.2.2 High-Purity Drift Correction Materials—These shall and prepare both chill cast samples and other forms of
be homogeneous and shall consist of aluminum with the lowest aluminum, such as sheet, plate, extrusions, and castings refer to
available mass fraction of the elements being determined. Practices E716.
These materials are used to establish the background readings 12.3 To achieve the best analytical results, both reference
of the spectrometer for most elements. Their exact composi- materials and sample specimens should have fresh surfaces.
tions need not be known. Surfaces should not be tested that: (1) are freshly prepared, (2)
9.2.3 Blank Drift Correction Materials—These materials appear oxidixed, (3) have porosity, inclusions or other foreign
shall be homogeneous and of similar composition to the alloy substances, or (4) have been contaminated by handling.
type calibration materials as described in 9.1 but will contain
the lowest available mass fractions of the trace elements being 13. Preparation of Apparatus
determined. They may be used if the lowest mass fraction of 13.1 Prepare the spectrometer for operation in accordance
the element being determined is within ten times the detection with the manufacturer’s instructions.
limit of that element.
NOTE 3—It is not within the scope of this method to prescribe all of the
9.2.4 Type Standardization Materials—These should be ref- details that are associated with the correct operation of any spectrometer.
erence materials or equivalent materials that closely match the The reader is referred to the manufacturer’s manual. Additionally, it is
metallurgical history and composition of the unknown(s). recommended that the purchaser of the spectrometer determine if training
These usually provide a nominal mass fraction reference point courses are offered by the manufacturer. Frequently manufacturer’s will
offer specific spectrometer training courses several times yearly.
which the instrument’s computer software can use to calculate
a slope or intercept correction to the observed readings to 13.1.1 Instrument Configuration—Instruments are usually
fine-tune the instrument’s calculated response for each element pre-configured for the analytical program (elements), mass
of interest. This correction is then applied to each subsequent fraction ranges, and alloy families according to specifications
analysis. When using this approach it is assumed that the that have been requested by the purchaser. Optionally, the
composition(s) of the unknown(s) will be essentially similar to purchaser may also choose to specify that the instrument is
the composition of this material. completely pre-calibrated for all alloys and all intended ana-
lytical tasks. The purchaser also has the option of completely
10. Hazards configuring and calibrating the instrument. When this is done,
10.1 The spark discharge presents a potential electrical careful attention is required in the selection of the correct
shock hazard. The spark stand or the sample clamping device, analytical conditions, analytical channels, internal standard
or both, shall be provided with a safety interlock system to channels, calibration ranges, and calibration materials to meet
prevent energizing the electrode whenever contact can be made the specific analytical tasks. Whether the manufacturer or the
with the electrode. The instrument should be designed so end user calibrates an instrument, it is the responsibility of the
access to the power supply is restricted by the use of safety end user to verify that the instrument is performing according
interlocks. to the specifications that have been defined in the initial
agreement or according to the performance as stated by the
10.2 Fumes of the fine metallic powder that are exhausted manufacturer. It is beyond the scope of this test method to
from the excitation chamber can be poisonous if the sample describe the intricacies of complete instrument configuration.
specimens contain significant levels of hazardous elements. The user should consult the manufacturer’s hardware and
Therefore, the instrument shall be designed with an internal software manuals for specific configuration requirements.
exhaust system that is equipped with its own set of filters. 13.1.2 Profiling the Instrument—Profile the instrument ac-
Additionally, the instrument exhaust (after being filtered), may cording to the manufacturer’s instructions. If the instrument is
be vented directly to a safe area. The filters should be cleaned newly installed, it is recommended that the profile be checked
or changed according to the manufacturer’s recommendations several times during the first few weeks of operation to
to enable correct instrument operation. determine the stability of the unit. Compare the differences in
the settings to the tolerance variability allowed by the manu-
11. Sampling facturer.
11.1 Chill Cast Disks and Other Aluminum Forms—For the 13.1.3 Checking Optical Alignment—Position or test the
techniques used to sample, melt, and cast molten aluminum position of the spectrometer exit slits, secondary mirrors (if
metal into a chill cast disk suitable for analysis, refer to used) or refractor plates (if used), and photomultipliers to
Practices E716. ensure that the peak radiation passes through each slit and

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 E1251 − 24
illuminates the centers of the phototubes. This shall be done by faster and the gap should be checked more frequently and the
a trained expert initially and as often as necessary thereafter to electrode may need replaced more frequently.
ensure proper alignment. 13.6 Reference Material/Sample Placement—Reference
13.1.4 Modern direct reading spectrometers should show materials and samples should be placed on the spark stand so
little drift in the response channels with time. However, if at that the hole in the top plate is completely covered. Completely
any time the gain adjustment of any channel drops below 0.5 or covering the hole will prevent air leaks into the discharge area.
increases above 2, or if the background changes by more than Air can cause “bad” burns and adversely affect precision and
0.5 to 2 times, that channel should be checked for alignment or accuracy. The hole should be covered during idle periods for
deterioration of components. the same reason. Samples and reference materials should be
13.2 Electrical Parameters—Various sets of electrical pa- sparked approximately 7 mm to 10 mm from their outer edge.
rameters in a rectified-capacitor discharge source produce This can be best accomplished by placing them so that the
somewhat similar high-frequency oscillatory unidirectional outer edge of the machined surface just covers the hole in the
waveforms. These have been found to produce comparable top plate. Overlapping the burns may adversely affect precision
analytical performance. Refer to 7.2 for typical parameters. and accuracy.
13.7 It is essential that operators learn the difference be-
13.3 Spark Conditions—These conditions vary with the
tween a “good” burn and a “bad” burn. Bad burns can be
manufacturer of the equipment and may require selection by
caused by an air leak between the sample and the top plate, a
the user. A longer integration may result in better precision and
poor quality sample, poor quality argon, and various other
accuracy with less sample through-put, while a shorter inte-
reasons. A “good” burn will have a deeply pitted area in the
gration will increase sample through-put but may decrease
center surrounded by a blackish ring. The actual appearance of
precision and accuracy. Typical time ranges are:
a burn will vary with source conditions and alloy. A “bad” burn
Flush period, s 2 to 7 will tend to have shallow pits surrounded by a white or silver
Pre-burn period, s 2 to 20
Integration (spark) period, s 2 to 10 colored ring. Usually the intensity of the aluminum internal
Integration (arc) period, s 2 to 10 standard channel for a “bad” burn will be considerably lower
13.4 Gas Flow—Argon flow rate requirements may vary than a good burn. All “bad” burns should be rejected and
between manufacturers and between laboratories. The follow- replaced.
ing ranges are presented as a guide. 13.8 Warm-Up—After any prolonged interval of instrument
Standby, L/min 0.03 to 0.5 non-use, several warm-up burns should be taken. Generally
During Integration, L/m 3.0 to 10 two to four burns are sufficient to check for proper gas flow and
13.4.1 The high-pressure compressed gas cylinder should consistency of results.
be changed when the pressure falls below 7 kg/cm2 (100 kPa).
If the gas is supplied from a cryogenic tank, caution should be 14. Drift Correction
exercised so that the tank is not allowed to completely empty. 14.1 Need for Drift Correction—Spark Atomic emission
Consult with the gas supplier for their recommendation regard- spectrometric analyses depend upon relative measurements
ing cryogenic tank changes. See Practice E406 for precautions that are subject to drift over time. To correct for drift, a suite of
when handling gases. reference materials that includes both high and low mass
13.5 Electrode System—The sample specimen serves as one fractions of the elements is used to drift correct the intensities
electrode, the cathode. The tungsten or other suitable electrode whenever a correction is required. Failure to routinely correct
serves as the counter electrode. Since the discharge is essen- for instrument drift will adversely affect analysis results. The
tially unidirectional, the counter electrode is not attacked and frequency for drift correction should be determined by statis-
therefore can be used for many burns. Because the electrode is tical process control methods based on periodic measurement
moveable, continual adjustment of the analytical gap is re- of a control sample.
quired. It is recommended that this gap be checked periodi- 14.2 Drift Correction—Select a suite of reference materials
cally. The adjustment frequency is dependent on the number of that will cover the analytical array and anticipated element
burns. Consult the manufacturer to determine the optimum mass fraction ranges of the instrument to be drift corrected. It
adjustment frequency for each instrument type. However, is highly recommended that the purchaser of a new instrument
material ablated from the sample surface tends to accumulate specify that the appropriate drift correction materials be
on the tip of some types of electrodes, and can change the gap included with the purchase of the spectrometer. If the instru-
and may adversely affect results. Therefore the counter elec- ment comes pre-calibrated, then these materials should auto-
trode should be cleaned (brushed) with a wire brush that is matically be included with the instrument. It is the responsi-
normally supplied with the instrument. For best performance it bility of the purchaser to ensure that the correct drift correction
is strongly recommended that the counter electrode be cleaned materials are included with the instrument. Follow the manu-
after every burn. Also, with continued use the shape of the facturer’s instructions when drift correcting. The spectrom-
electrode may change due to this buildup of material. Frequent eter’s software should have a program that will guide the
close inspection of the electrode is recommended. Some operator through the drift correction process. If the instrument
instruments use pin type electrodes that are not affected by an is newly installed, give the unit sufficient time to stabilize in its
accumulation of ablated material. Pin electrodes tend to erode new environment before proceeding with a drift correction. It

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 E1251 − 24
is recommended that the spectrometer be allowed to stabilize when using third and fourth order regressions that enough
under vacuum (if so equipped) and to adapt to the final calibration materials are available to adequately cover the
controlled environment surroundings for at least two days entire range.
before a drift correction is performed. Note, the instrument 15.3 Verifying the Accuracy of Calibration—After complet-
must be profiled before performing a drift correction. Refer to ing a calibration, re-burn several of the calibration materials as
Practice E1329 for further details. unknowns and compare the measured mass fractions for each
14.3 Number of Burns—It is recommended that four burns element with the certified values. Check for clerical errors,
be taken on each of the drift correction materials during the elemental interferences, or biases if results do not compare
drift correction process. favorably.
14.4 Checking Homogeneity of Candidate Drift Correction 15.3.1 If individual calibration materials give consistently
Materials—If the homogeneity of the material(s) being used is high readings for an element, check for possible interferences
questionable; the material(s) can be tested for homogeneity. from other elements. Manually calculate or, using the instru-
ment’s software, have the software calculate the appropriate
14.5 Recording the Drift Correction Readings: factors for the interference(s).
14.5.1 Instruments that come pre-calibrated will have the
initial drift corrected response factors entered into the instru- 16. Procedure for Analyzing Specimens
ment’s software. 16.1 Excitation—Burn the specimens using the parameters
14.5.2 If the instrument does not come pre-calibrated, then and conditions in 13.2, 13.3, 13.4, and 13.5.
follow the manufacturer’s instructions regarding establishing
the initial drift correction responses/factors. Initial drift correc- 16.2 Replicate Burns—Burn the specimens from one to
tion responses should be established immediately after calibra- eight times, depending on the complexity of the alloy, speci-
tion. men homogeneity, and the level of confidence required. A
14.5.3 If one of the drift correction materials must be single burn is frequently employed for qualitative analysis of
replaced because it has become unusable (too thin), follow the primary aluminum to detect major changes in the composition
instructions listed in the instrument’s manual regarding the of aluminum from individual Hall cells to assess performance.
replacement and recording of the new drift correction materi- A single burn shall not be used for determining compliance
al’s responses. Failure to properly replace drift correction with composition specifications. Two to four burns are recom-
materials may adversely affect analysis accuracy. mended for most alloys where homogeneity is acceptable and
accuracy becomes important. In very complex alloys or in
15. Calibration alloy systems that are noted for their segregation, additional
15.1 Obtaining Calibration Data—The following procedure burns may be required.
is designed to allow the user to collect accurate data for the 16.2.1 The determinations from all burns should be aver-
purpose of generating calibration curves. For details on estab- aged unless a burn produces a very abnormal internal standard
lishing and controlling spectrochemical calibration curves, intensity or appears visually to be bad (see 13.7). When a burn
refer to Practice E305. Any recently installed, laboratory-grade is rejected, it should be replaced in order to maintain the
spectrometer should show minimal drift over an 8-h to 24-h normal number of burns to be averaged.
time period when placed in a laboratory with a carefully
17. Calculation of Results
controlled environment.
15.1.1 Select the reference materials for use as the calibra- 17.1 After performing the test material analyses, the instru-
tion materials. ment software will calculate the mass fractions of the elements
15.1.2 Follow the manufacturer’s operating manual and use based on the calibration curves. Further manipulation of the
the instrument’s software to design, and name the analytical data should not be necessary.
program. Using the software, enter the identities of the selected 17.2 Rounding of test results obtained using this test method
calibration materials and their associated mass fractions for the shall be performed as directed in Practice E29, Rounding
elements to be calibrated in this calibration. Method, unless an alternative rounding method is specified by
15.1.3 Before starting the collection of calibration data, the customer or applicable material specification.
thoroughly clean the excitation chamber and check the analyti-
cal gap or replace the electrode as needed. Prepare fresh 18. Data Reporting
surfaces on the selected calibration materials. 18.1 Number of Significant Figures—The composition of
15.1.4 Profile the instrument. alloys shall not be reported with more significant figures or
15.1.5 Burn the calibration materials and collect the data. higher precision than that of the materials used to calibrate the
15.2 Refer to Practice E305 and calibrate the instrument spectrometer. As a general guideline, labs should report results
using the instrument’s software, following the instructions in at least to the number of decimal places given in ANSI
the manufacturer’s manual. Use the appropriate program that H35.1/H35.1M if possible. Footnote 3 in Section 2 of ANSI
allows for the calculation of the calibration curves. Take care H35.1/H35.1M provides the following:

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 E1251 − 24
TABLE 3 Summary of Interlaboratory Tests
Mass Fraction
Test Sample ST SR R 2R
Certified Observed
Antimony
WA1199 0.0013 0.0012 0.00041 0.00041 0.0011 0.0022
SS1075 0.0033 0.0036 0.00024 0.00024 0.00067 0.0013
Arsenic
L1 0.0014 0.0012 0.00021 0.00021 0.00059 0.0012
L5 0.0064 0.0055 0.00083 0.00083 0.0023 0.0046
Beryllium
3004-3 0.0004(4) 0.00046 0.000010 0.000040 0.00011 0.0002
5056 0.004 0.0037 0.000011 0.00037 0.0010 0.002
358 0.24 0.237 0.0021 0.0034 0.0095 0.02
Bismuth
1000 0.034 0.0335 0.0005 0.0010 0.0029 0.006
2011 0.56 0.567 0.0048 0.021 0.058 0.12
Boron
1075 0.0006 0.00055 0.000024 0.00006 0.00016 0.0003
18 0.009 0.0107 0.00026 0.0012 0.0033 0.007
Calcium
3004-3 0.0002(5) 0.00027 0.000012 0.000072 0.0002 0.0004A
Chromium
3003 0.001 0.00146 0.00009 0.0023 0.0064 0.013
1000 0.036 0.0347 0.00025 0.0033 0.0092 0.018
5056 0.12 0.1208 0.00093 0.0050 0.0140 0.028
7075 0.23 0.2264 0.0036 0.0067 0.0189 0.038
Cobalt
7091 0.44 0.4423 0.0054 0.0054 0.015 0.030
Copper
1075 0.001 0.00084 0.00014 0.00061 0.0017 0.0034
1000 0.030 0.0306 0.00027 0.00123 0.0035 0.007
3003 0.15 0.154 0.00074 0.00435 0.0122 0.024
7075 1.58 1.564 0.0179 0.0388 0.109 0.22
2011 5.49 5.492 0.0231 0.0538 0.151 0.30
Gallium
1075 0.022 0.0219 0.00030 0.00053 0.0015 0.0030
Iron
5056 0.20 0.195 0.00532 0.01655 0.046 0.09
2011 0.53 0.530 0.00264 0.01275 0.036 0.07
Lead
1000 0.036 0.035 0.0003 0.0009 0.003 0.005
2011 0.56 0.580 0.0060 0.0461 0.129 0.26
Lithium
3004-3 0.0003(4) 0.00034 0.000006 0.000025 0.00007 0.00014
2090 2.14 2.13 0.023 0.041 0.114 0.23
Magnesium
1000 0.030 0.0317 0.00044 0.00158 0.0044 0.009
356 0.36 0.354 0.00426 0.00860 0.024 0.05
7075 2.61 2.596 0.0219 0.0283 0.079 0.16
5056 5.36 5.364 0.0400 0.0441 0.123 0.25
Manganese
1075 0.001 0.00102 0.00008 0.00024 0.001 0.013A
1000 0.032 0.0316 0.00022 0.00131 0.0037 0.007
5056 0.10 0.1006 0.00044 0.0039 0.0109 0.022
3003 1.21 1.208 0.00850 0.0139 0.039 0.08
Nickel
3003 0.005 0.00474 0.00007 0.00028 0.0008 0.0016
1000 0.031 0.0299 0.00028 0.00177 0.0050 0.0099
850 1.21 1.219 0.0044 0.0082 0.023 0.048
336 2.60 2.596 0.0216 0.0247 0.069 0.139
Phosphorus
AP-4 0.003 0.00269 0.00016 0.00028 0.0008 0.0016
Silicon
1075 0.068 0.0699 0.0004 0.00266 0.0074 0.015
2011 0.28 0.288 0.00194 0.00784 0.022 0.044
356 7.18 7.16 0.0414 0.0811 0.23 0.45
390A 16.36 16.29 0.13 0.242 0.68 1.35
Sodium
3004-3 0.0002(9) 0.00026 0.000011 0.000017 0.00005 0.00010
18 0.021 0.024 0.0016 0.0036 0.010 0.020
StrontiumB
336 0.027 0.0271 0.0005 0.0008 0.00229 0.00458
356 0.028 0.0277 0.0003 0.0016 0.00435 0.00870
Tin
1000 0.028 0.0287 0.0002 0.0011 0.003 0.006
Titanium
1075 0.001 0.00083 0.000031 0.000341 0.0010 0.0019A

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TABLE 3 Continued
Mass Fraction
Test Sample ST SR R 2R
Certified Observed
2011 0.003 0.00321 0.000041 0.000185 0.0005 0.0010A
1000 0.031 0.0318 0.000161 0.000799 0.0022 0.0045
356 0.12 0.1176 0.00058 0.00353 0.010 0.020
Vanadium
1075 0.002 0.00195 0.000055 0.00016 0.0005 0.0009
1000 0.022 0.0218 0.000237 0.00058 0.0016 0.0033
Zinc
1075 0.002 0.00229 0.00040 0.00069 0.0019 0.004
1000 0.030 0.0302 0.00065 0.00071 0.0020 0.004
356 0.01 0.1001 0.00059 0.00111 0.0031 0.006
7075 5.74 5.741 0.0285 0.0927 0.26 0.52
Zirconium
1075 0.001 0.00093 0.00007 0.00017 0.0005 0.0009
2090 0.12 0.120 0.012 0.0023 0.006 0.013
A
Values are below minimum quantifiable limit calculated based on the data in this ILS.
B
Supporting data for strontium have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:E01-1113.

Standard limits for alloying elements and impurities are expressed to the 19. Precision and Bias5
following places:
19.1 Precision—Eight laboratories cooperated in the inter-
Less than 0.001 % 0.000X laboratory study using either the binary calibration approach or
the alloy-type calibration technique. Since an attempt was
0.001 but less than 0.01 % 0.00X
made to include all general alloy types, not all laboratories
0.01 but less than 0.10 % unalloyed aluminum 0.0XX could analyze all materials or all mass fraction ranges. Testing
made by a refining process
was done in accordance with Practice E691. A summary of the
Alloys and unalloyed aluminum not made by a 0.0X inter-laboratory test is shown in Table 3.
refining process
19.2 Bias—There is no evidence of bias since all acceptable
0.10 through 0.55 percent 0.XX individual test results are within one R of the assumed mass
(It is customary to express limits of 0.30 % through fractions.
0.55 % as 0.X0 or 0.X5)

Over 0.55 % 0.X, X.X, etc.

20. Keywords
(Except that combined Si + Fe limits for 1XXX 20.1 aluminum; aluminum alloys; Spark Atomic Emission
designations must be expressed as 0.XX or 1.XX)
Spectrometry (Spark-AES)

5
Supporting data have been filed at ASTM International Headquarters and may
be obtained by requesting Research Report RR:E01-1113. Contact ASTM Customer
Service at www.astm.org/contact.

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