ASTM D7260-06
(Practice)Standard Practice for Optimization, Calibration, and Validation of Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) for Elemental Analysis of Petroleum Products and Lubricants
Standard Practice for Optimization, Calibration, and Validation of Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) for Elemental Analysis of Petroleum Products and Lubricants
SCOPE
1.1 This practice covers information on the calibration and operational guidance for the multi-element measurements using inductively coupled plasma-atomic emission spectrometry (ICP-AES).
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.
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Designation:D7260–06
Standard Practice for
Optimization, Calibration, and Validation of Inductively
Coupled Plasma-Atomic Emission Spectrometry (ICP-AES)
for Elemental Analysis of Petroleum Products and
Lubricants
This standard is issued under the fixed designation D7260; 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.
1. Scope inLubricatingOilsbyInductivelyCoupledPlasmaAtomic
Emission Spectrometry
1.1 This practice covers information on the calibration and
D5184 Test Methods for Determination of Aluminum and
operational guidance for the multi-element measurements us-
Silicon in Fuel Oils by Ashing, Fusion, Inductively
ing inductively coupled plasma-atomic emission spectrometry
Coupled Plasma Atomic Emission Spectrometry, and
(ICP-AES).
Atomic Absorption Spectrometry
1.2 This standard does not purport to address all of the
D5185 Test Method for Determination of Additive Ele-
safety concerns, if any, associated with its use. It is the
ments, Wear Metals, and Contaminants in Used Lubricat-
responsibility of the user of this standard to establish appro-
ing Oils and Determination of Selected Elements in Base
priate safety and health practices and determine the applica-
Oils by Inductively Coupled Plasma Atomic Emission
bility of regulatory limitations prior to use.
Spectrometry (ICP-AES)
2. Referenced Documents D5600 Test Method for Trace Metals in Petroleum Coke by
Inductively Coupled Plasma Atomic Emission Spectrom-
2.1 ASTM Standards:
etry (ICP-AES)
D4057 Practice for Manual Sampling of Petroleum and
D5708 Test Methods for Determination of Nickel, Vana-
Petroleum Products
dium, and Iron in Crude Oils and Residual Fuels by
D4307 Practice for Preparation of Liquid Blends for Use as
Inductively Coupled Plasma (ICP)Atomic Emission Spec-
Analytical Standards
trometry
D6299 Practice for Applying Statistical Quality Assurance
D6130 Test Method for Determination of Silicon and Other
and Control Charting Techniques to Evaluate Analytical
Elements in Engine Coolant by Inductively Coupled
Measurement System Performance
Plasma-Atomic Emission Spectroscopy
D6792 Practice for Quality System in Petroleum Products
D6349 Test Method for Determination of Major and Minor
and Lubricants Testing Laboratories
Elements in Coal, Coke, and Solid Residues from Com-
2.2 ICP-AES Related Standards:
bustion of Coal and Coke by Inductively Coupled
C1111 Test Method for Determining Elements in Waste
Plasma—Atomic Emission Spectrometry
Streams by Inductively Coupled Plasma-Atomic Emission
D6357 Test Methods for Determination of Trace Elements
Spectroscopy
in Coal, Coke, and Combustion Residues from Coal
C1109 Practice for Analysis of Aqueous Leachates from
Utilization Processes by Inductively Coupled Plasma
Nuclear Waste Materials Using Inductively Coupled
Atomic Emission Spectrometry, Inductively Coupled
Plasma-Atomic Emission Spectroscopy
Plasma Mass Spectrometry, and Graphite Furnace Atomic
D1976 Test Method for Elements in Water by Inductively-
Ab
Coupled Argon Plasma Atomic Emission Spectroscopy
D7040 Test Method for Determination of Low Levels of
D4951 TestMethodforDeterminationofAdditiveElements
PhosphorusinILSACGF4andSimilarGradeEngineOils
by Inductively Coupled Plasma Atomic Emission Spec-
This practice is under the jurisdiction ofASTM Committee D02 on Petroleum
trometry
Products and Lubricants and is the direct responsibility of Subcommittee D02.03 on
D7111 Test Method for Determination of Trace Elements in
Elemental Analysis.
Middle Distillate Fuels by Inductively Coupled Plasma
Current edition approved May 1, 2006. Published June 2006. DOI: 10.1520/
D7260-06.
Atomic Emission Spectrometry (ICP-AES)
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
E1479 Practice for Describing and Specifying Inductively-
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Coupled Plasma Atomic Emission Spectrometers
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. 2.3 Other Standards:
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D7260–06
IP 437 Determination of Additive Elements in Unused slit and dispersing element to separate and measure the
Lubricating Oils and Additive Packages by Inductively intensity of the wavelengths of light emitted from the plasma,
Coupled Plasma-Atomic Emission Spectrometry one or more devices for converting the emitted light into an
ISO/TC 17/SC 1 N 883 Guidelines for the Preparation of electrical current or voltage, one or more analog preamplifiers,
Standard Methods ofAnalysis Using Inductively Coupled one or more analog-to-digital converter(s), and a dedicated
Plasma-Atomic Emission Spectrometry and for Use of computer with printer. Solid state CCD or CID detectors if
ICP Spectrometry for the Determination of Chemical used may not require extra analog-to-digital components.
Composition (1991) Recently modern camera-type instruments have been supplant-
ing the photomultiplier tube type detectors. Cameras may not
3. Summary of Practice
have high resolution, but they offer greater wavelength choice.
3.1 AnInductivelyCoupledPlasma-AtomicEmissionSpec- 5.2.1 Plasmacanbemonitoredeitheraxiallyversusradially.
trometry(ICP-AES)instrumentisonethatisusedtodetermine
Potential for improved sensitivity as much as tenfold is often
elemental composition of various liquid matrices. Details of realized with axial monitoring. However, the increased inter-
the instrument components are given in Practice E1479. This
ference from molecular background may compromise these
practice summarizes the protocols to be followed during gains depending on the wavelength monitored and matrix used
calibration and verification of the instrument performance.
(especially for organics versus aqueous).
5.2.2 Echelle Spectrometers—More recently echelle grat-
4. Significance and Use
ings are being increasingly used in several commercial plasma
4.1 Accurate elemental analysis of petroleum products and
spectrometers. A prism is used as an order-sorter to improve
lubricants is necessary for the determination of chemical
sensitivity. To measure widely separated lines with useful
properties, which are used to establish compliance with com-
efficiency, echelle instruments have to be operated in many
mercial and regulatory specifications.
different orders. This involves complex wavelength scanning
4.2 Inductively Coupled Plasma-Atomic Emission Spec-
programs for computer controlled echelle monochromators.
trometry is one of the more widely used analytical techniques
While the resolution of a grating monochromator is relatively
in the oil industry for multi-element analysis as evident from at
constant across its working range, practical resolution of an
least twelve standard test methods (for example, Test Methods
echelle monochromator can vary considerably with wave-
C1111,D1976,D4951,D5184,D5185,D5600,D5708,D6130,
length. Inherently higher theoretical resolving power of the
D6349, D6357, D7040, and D7111) published for the analysis
echelle when used in high order, relative to the diffraction
of fossil fuels and related materials. These have been briefly
grating used in the first order, allows a relatively compact
summarized by Nadkarni.
echelle instrument to achieve high resolving power. The
4.3 The advantages of using an ICP-AES analysis include
detectionlimitsobtainedwithechelleplasmaspectrometersare
high sensitivity for many elements of interest in the oil
comparable to those achieved by grating spectrometers.
industry, relative freedom from interferences, linear calibration
5.3 Spectrometer Environment:
over a wide dynamic concentration range, single or multi-
5.3.1 Temperature fluctuations affect the instrument stabil-
elementcapability,andabilitytocalibratetheinstrumentbased
ity. Some manufacturers provide systems for maintaining a
on elemental standards irrespective of their elemental chemical
constant internal temperature within the optical compartment
forms, within limits described below such as solubility and
and sample introduction area that assumes changes in the
volatilityassumingdirectliquidaspiration.Thus,thetechnique
outside temperature are not being controlled within the neces-
has become a method of choice in most of the oil industry
saryspecifiedrangeandrateofchangetoinsurestability.Other
laboratories for metal analyses of petroleum products and
manufacturers design their spectrometers to be stable over a
lubricants.
specified temperature range without attempting to control the
spectrometer’s internal temperature.
5. Apparatus
5.3.2 Since temperature and humidity changes may also
5.1 Spectrometer—Aninductivelycoupledplasmaemission
affect the sample introduction system, detectors, and electronic
spectrometer with a spectral bandpass of 0.05 nm or less is
readout as well as the spectrometer alignment, some manufac-
required. The spectrometer may be of the simultaneous multi-
turers specify that care be used in selecting a location for the
elemental or sequential scanning type. The spectrometer may
spectrometerthatexperiencesminimalvariationintemperature
be of the air path, inert gas path, or vacuum type, with spectral
and relative humidity. The user needs to provide a controlled
lines selected appropriately for use with specific instrument.
environment as specified by the manufacturer. This is a very
Either an analog or digital readout system may be used.
important factor in optimum performance of an ICP-AES
5.2 An ICP-AES instrument system is typically comprised
system.
of several assemblies including a radio-frequency (RF) gen-
5.3.3 The generator output power and the plasma gas flow
erator, an impedance matching network (where required), an
determine the plasma temperature and thus significantly influ-
induction coil, a plasma torch, a plasma igniter system, a
ence the emission signal and the background. Thus, the power
sampleintroductionsystem,alightgatheringoptic,anentrance
applied and gas flow adjustments may be used to control the
signal to background ratio and, matrix, and some spectral
interferences.
Nadkarni, R.A., “Use of ICP-AES for MetalAnalysis in the Oil Industry,” ICP
Information Newsletter, Vol 30(10), 2005, pp. 1059–1061. 5.4 Optical Path:
D7260–06
5.4.1 Since oxygen exhibits increasing absorbance with 5.9 Safety—The ICP-AES instrument is not normally con-
decreasing wavelengths below 200 nm, the performance of an sidered as a hazardous instrument. However, appropriate pre-
air path instrument degrades below that wavelength and is cautions should be taken regarding the fumes, heat, and
generally not useful below approximately 190 nm. UV/visible light radiation as well as appropriate RF shielding.
The equipment should always be used according to the
5.4.2 Purging the optical path with nitrogen or argon, or
manufacturer’s operating instructions. No attempt should be
another gas with low absorption in this ultraviolet region may
made to bypass the interlocks.Adequate cooling times must be
extend the spectral region to wavelengths below 167 nm. Use
allowed before handling any hot components. Any safety
of these purge gases is in general less expensive to maintain
covers must be in position.
thanthevacuumpathsystems.Sealedopticsfilledwithaninert
5.9.1 Fumes from the plasma and any ozone generated by
gas is also available for such work.
the UV radiation must be removed by means of a suitable heat
5.5 Wavelength Selection:
and acid resistant (acids can be formed from halogens or
5.5.1 When selecting the fixed position wavelengths to be
sulfate and nitrates in the solution) chimney fitted with an
utilized in a Paschen-Runge polychromator for particular
exhaust fan of sufficient capacity.
applications, close collaboration between user and instrument
5.9.2 A UV/visible light absorbing viewing window (with
manufacturer is critical. Camera instruments do not have this
RF shielding) must always be in place to protect the eyes and
problem.
skin of the operator from radiation.
5.5.2 If possible, use the peak and background wavelengths
5.9.3 Often the organic samples and solvents used in or-
suggested in the methods. When there is a choice such as with
ganic ICP-AES analysis are toxic and hazardous.All appropri-
the sequential instruments, choose the wavelength that will
ate precautions must be taken in handling such materials to
yield signals of 100 to 10003 the detection limit sought.Also,
protect the operators. Consult MSDS and other safety infor-
ensure that the chosen wavelength will not be interfered with
mation before handling these chemicals.
from unexpected elements. See Section 6.
5.5.3 Often ion lines may be chosen for use over atom lines
6. Interferences
to avoid interelement interference and sensitivity of detection.
6.1 Several types of interference effects may contribute to
This choice will be dependent on the analyte of interest and the
inaccuracies in the elemental determination using ICP-AES.
sample matrix being analyzed.
Principally these interferences can be classifies as spectral,
5.6 Peristaltic Pump—Differences in the viscosities of the
physical, and chemical.
test specimen solutions and standard solutions can cause
6.2 Spectral Interferences:
differences in the uptake rates adversely affecting the accuracy
of the analysis. These effects can be minimized by using a
NOTE 1—An empirical method for correcting spectral interferences is
peristaltic pump (or an internal standard). If a peristaltic pump
detailed in Test Method D5185.
is used, inspect the pump tubing and replace it, if necessary,
6.2.1 Spectral interferences can be categorized as (1) unre-
before starting each day. Verify the solution uptake rate daily
solved overlap of a spectral line from another element, (2)
and adjust to the desired rate. Compatibility of the solution
unresolved overlap of molecular band spectra, (3) background
with the peristaltic pump tubing must also be confirmed to
contribution from continuous or recombination phenomena,
prevent premature pump failure. A variety of polymeric mate-
and (4) background contribution from stray light from line
rial options are available for pump tubing to address this
emission of high concentration of elements. With echelle
concern by simple empirical testing with the given solvent/
spectrometers it may be possible to look at two or more lines
sample matrix used. Generally speaking, the selected tubing
to identify interference.
soake
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