ASTM E1479-99(2005)
(Practice)Standard Practice for Describing and Specifying Inductively-Coupled Plasma Atomic Emission Spectrometers
Standard Practice for Describing and Specifying Inductively-Coupled Plasma Atomic Emission Spectrometers
SIGNIFICANCE AND USE
This practice describes the essential components of an inductively-coupled plasma atomic emission spectrometer (ICP-AES). The components include excitation/radio-frequency generators, sample introduction systems, spectrometers, detectors, and signal processing and displays. This description allows the user or potential user to gain a cursory understanding of an ICP-AES system. This practice also provides a means for comparing and evaluating various systems, as well as understanding the capabilities and limitations of each instrument.
Training—The vendor should provide training in safety, basic theory of ICP spectrochemical analysis, operations of hardware and software, and routine maintenance for at least one operator. Training ideally should consist of the basic operation of the instrument at the time of installation, followed by an in-depth course one or two months later. Advanced courses are also offered at several of the important spectroscopy meetings that occur throughout the year as well as by independent training institutes. Furthermore, several independent consultants are available who can provide training, in most cases at the user’site.
SCOPE
1.1 This practice describes the components of an inductively-coupled plasma atomic emission spectrometer (ICP-AES) that are basic to its operation and to the quality of its performance. This practice identifies critical factors affecting accuracy, precision, and sensitivity. It is not the intent of this practice to specify component tolerances or performance criteria, since these are unique for each instrument. A prospective user should consult with the vendor before placing an order, to design a testing protocol to demonstrate that the instrument meets all anticipated needs.
1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.3This 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. Specific safety hazard statements are given in Section 13.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:E1479–99(Reapproved2005)
Standard Practice for
Describing and Specifying Inductively-Coupled Plasma
Atomic Emission Spectrometers
This standard is issued under the fixed designation E1479; 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 E520 Practice for Describing Photomultiplier Detectors in
Emission and Absorption Spectrometry
1.1 This practice describes the components of an
inductively-coupled plasma atomic emission spectrometer
3. Terminology
(ICP-AES) that are basic to its operation and to the quality of
3.1 Definitions—For terminology relating to emission spec-
its performance. This practice identifies critical factors affect-
trometry, refer to Terminology E135.
ing accuracy, precision, and sensitivity. It is not the intent of
this practice to specify component tolerances or performance
4. Summary of Practice
criteria, since these are unique for each instrument.Aprospec-
4.1 AnICP-AESisaninstrumentusedtodetermineelemen-
tive user should consult with the vendor before placing an
tal composition. It typically is comprised of several assemblies
order, to design a testing protocol to demonstrate that the
including a radio-frequency (RF) generator, an impedance
instrument meets all anticipated needs.
matchingnetwork(whererequired),aninductioncoil,aplasma
1.2 The values stated in SI units are to be regarded as
torch, a plasma ignitor system, a sample introduction system, a
standard. The values given in parentheses are for information
light gathering optic, an entrance slit and dispersing element to
only.
sample and isolate wavelengths of light emitted from the
1.3 This standard does not purport to address all of the
plasma, one or more devices for converting the emitted light
safety concerns, if any, associated with its use. It is the
into an electrical current or voltage, one or more analog
responsibility of the user of this standard to establish appro-
preamplifiers, one or more analog-to-digital converter(s), and a
priate safety and health practices and determine the applica-
dedicated computer with printer (see Fig. 1 ).
bility of regulatory limitations prior to use. Specific safety
4.1.1 The sample is introduced into a high-temperature
hazard statements are given in Section 13.
(>6000 K) plasma that is formed from the ionization of the gas
stream contained in the torch. The torch is inserted through
2. Referenced Documents
2 metal tubing formed into a helix, which is called the load coil.
2.1 ASTM Standards:
Energy is applied to the load coil by means of an RF generator.
E135 Terminology Relating to Analytical Chemistry for
4.1.2 Theterminductively-coupledreferstothefactthatthe
Metals, Ores, and Related Materials
physical phenomenon of induction creates a plasma by trans-
E158 Practice for Fundamental Calculations to Convert
ferringenergyfromtheloadcoiltothegasstreamthathasbeen
Intensities into Concentrations in Optical Emission Spec-
3 momentarilypreionizedbyahighvoltageignitorelectrodethat
trochemical Analysis
functions only during plasma ignition.
E172 Practice for Describing and Specifying the Excitation
3 4.2 When material passes through the plasma, it is vapor-
Source in Emission Spectrochemical Analysis
ized, atomized, and many elements are almost completely
E416 Practice for Planning and Safe Operation of a Spec-
3 ionized.Freeatomsandionsareexcitedbycollisionfromtheir
trochemical Laboratory
ground states. When the excited atoms or ions subsequently
decay to a lower energy state, they emit photons, some of
which pass through the entrance slit of a spectrometer. Each
This practice is under the jurisdiction of ASTM Committee E01 on Analytical
Chemistry of Metals, Ores, and Related Materials and is the direct responsibility of
element emits a unique set of emission lines. Photons of a
Subcommittee E01.20 on Fundamental Practices.
desired wavelength may be selected from the ultraviolet and
Current edition approved May 1, 2005. Published June 2005. Originally
visible spectra by means of a dispersing element.
approved in 1992. Last previous edition approved in 1999 as E1479 – 99. DOI:
10.1520/E1479-99R05. 4.2.1 Instruments may determine elements either simultane-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
ously or sequentially. The output of the detector generally is
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
directed to a preamplifier, an analog-to-digital converter, and a
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
Withdrawn. The last approved version of this historical standard is referenced
on www.astm.org. Courtesy of PerkinElmer, Inc., 761 Main Ave., Norwalk, CT 06859.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E1479–99 (2005)
FIG. 1 Components of Inductively Coupled Plasma
computer which measures and stores a value proportional to provides a means for comparing and evaluating various sys-
the electrical current or voltage generated by the detector(s). tems, as well as understanding the capabilities and limitations
Using blank and known calibration solutions, a calibration of each instrument.
curve is generated for each element of interest.
5.2 Training—The vendor should provide training in safety,
4.2.2 The computer compares the signals arising from the basic theory of ICP spectrochemical analysis, operations of
various elements in the sample to the appropriate calibration
hardware and software, and routine maintenance for at least
curve. The concentrations of more than 70 elements may be one operator. Training ideally should consist of the basic
determined.
operation of the instrument at the time of installation, followed
by an in-depth course one or two months later. Advanced
4.3 Sensitivities (see 12.3) in a simple aqueous solution are
less than one part per million (ppm) for all of these elements, courses are also offered at several of the important spectros-
copy meetings that occur throughout the year as well as by
generally less than 10 parts per billion (ppb) for most, and may
even be below 1 ppb for some. independent training institutes. Furthermore, several indepen-
dent consultants are available who can provide training, in
4.3.1 Organic liquids may also be used as solvents yielding
most cases at the user’s site.
sensitivities that are within an order of magnitude of aqueous
limits for many common organic solvents. Some organic
6. Excitation/Radio Frequency Generators
solvents may afford detection limits similar or even superior to
those obtained using aqueous solutions.
6.1 Excitation—A specimen is converted into an aerosol
4.3.2 Direct sampling of solid materials has been performed
entrained in a stream of argon gas and transported through a
successfully by such techniques as spark or laser ablation and
high temperature plasma. The plasma produces excited neutral
slurry nebulization. However, these require greater care in the
atoms and excited ions. The photons emitted when excited
choice of reference materials and the operation of the sampling
atoms or ions return to their ground states or lower energy
devices. Solid materials, therefore, are usually dissolved prior
levels are measured and compared to emissions from reference
to analysis.
materials of similar composition. For further details see Prac-
tice E172.
5. Significance and Use
6.2 Radio-Frequency Generator:
5.1 This practice describes the essential components of an 6.2.1 An RF generator is used to initiate and sustain the
inductively-coupled plasma atomic emission spectrometer argon plasma. Commercial generators operate at 27.12 and
(ICP-AES). The components include excitation/radio- 40.68 MHz since these frequencies are designated as clear
frequency generators, sample introduction systems, spectrom- frequencies by U.S. Federal Communications Committee
eters, detectors, and signal processing and displays. This (FCC) regulations. Generators typically are capable of produc-
description allows the user or potential user to gain a cursory ing 1.0 to 2.0 kW for the 27.12 MHz generator and 1.0 to 2.3
understanding of an ICP-AES system. This practice also kW for the 40.68 MHz system.
E1479–99 (2005)
7.2.1 Samples generally are presented to the instrument as
aqueous or organic solutions. A nebulizer is employed to
convert the solution to an aerosol suitable for transport into the
plasma where vaporization, atomization, excitation, and emis-
sion occur.
7.2.2 Some nebulizers, designated as self-aspirating pneu-
matic nebulizers, operating on the Venturi principle, create a
partial vacuum to force liquid up a capillary tube into the
nebulizer. Precision of operation may be improved if a peri-
staltic pump controls the solution flow rate.
7.2.3 Other nebulizers require an auxiliary device, such as a
peristaltic pump, to drive solution to the nebulizer. Generally,
FIG. 2 Concentric Glass Nebulizer (CGN)
pump-fed nebulizers are more tolerant of high levels of
dissolved solids and much less affected by suspended solids
6.2.2 Generators more powerful than 2.5 kW are of limited
and viscosity variations.
practical analytical utility and are not commercially marketed
7.2.4 If fluoride is present in solutions to be analyzed, it is
with ICPspectrometers. The power requirements are related to
necessary to employ a nebulizer fabricated from hydrofluoric
torch geometry and types of samples to be analyzed. Refer to
acid (HF)-resistant materials (see 7.4.1.). It is possible to use
Practice E172 for details. More power (typically 1.5 to 2 kW
theHF-resistantnebulizerformostothertypesofsolutions,but
for a 27.12 MHz system utilizing a 20-mm outside diameter
sensitivity and precision may be degraded. An HF-resistant
torch and 1.2 to 1.7 kWfor a 40.68 MHz generator) is required
nebulizer may be more expensive to acquire and repair, and
for analyzing samples dissolved in organic solvents than is
require greater operator proficiency and training than other
needed for aqueous solutions (approximately 1.0 kW). Less
nebulizers.
power is required for small diameter torches (for example, 650
7.3 Self-Aspirating or Non-Pump-Fed Nebulizers:
to 750 W for a 13-mm outside diameter torch).
7.3.1 Concentric Glass Nebulizers (CGN):
6.3 Load Coil:
7.3.1.1 CGNs consist of a fine capillary through which the
6.3.1 Acoil made from copper (or another metal or an alloy
sample solution flows surrounded by a larger tube drawn to a
with similar electrical properties) is used to transmit power
fine orifice (concentric) slightly beyond the end of the central
from the generator to the plasma torch (see 7.6). A typical
capillary (see Fig. 2). Minor variations in capillary diameter
designconsistsofatwo-tosix-turncoilofabout1-in.(25-mm)
and placement affect optimal operating pressure for the sample
diameter, made from ⁄8-in. (3-mm) outside diameter and
gas flow and change the sample solution uptake rate. Uptake
⁄16-in. (1.6-mm) inside diameter copper tubing (though larger
rates of liquid are typically 0.5 to 3 mL/min.
tubing is used with two-turn coils). The tubing is fitted with
7.3.1.2 CGNs exhibit somewhat degraded sensitivity and
ferrules or similar devices to provide a leak-free connection to
precision for solutions that approach saturation or concentra-
a coolant, either recirculated by a pump or fed from a
tions of more that a few tenths of a percent of dissolved solids.
municipal water supply.Argon gas blown through the coil has
This problem can be greatly reduced by using an inner argon
been used to cool other load coils.
stream that has been bubbled through water in order to
6.3.2 Thehighpowerconductedbythecoilcanleadtorapid
humidify the sample gas argon. Furthermore, since suspended
oxidation, surface metal vaporization, RF arc-over and even
solids may clog the tip, it is desirable to include a piece of
melting if the coil is not cooled continuously.
capillary tubing of even smaller diameter in the sample
6.3.3 Asafety interlock must be included to turn off the RF
solution uptake line. This action will isolate a potential
generator in case of loss of coolant flow.
clogging problem prior to clogging at the nebulizer tip.
6.4 Impedance Matching:
7.3.2 Micro-Concentric Nebulizer (MCN):
6.4.1 To optimize power transfer from the generator to the
7.3.2.1 To some extent, the MCN mimics the concept and
inducedplasma,theoutputimpedanceofthegeneratormustbe
function of the CGN but the MCN employs a thinner-walled
matched to the input impedance of the load coil. Some
poly-ether-imide capillary and TFE-fluorocarbon (or other
instruments include an operator-adjustable capacitor for im-
polymer)outerbodytominimizeoreliminateundesirablelarge
,
4 5
pedance matching.
drop formation and facilitate HF tolerance (see Fig. 3 ). A
6.4.2 Alternately, RF frequency may be automatically tuned
true aerosol, as opposed to a mist, is produced consisting of
or varied in free-running fashion against a fixed capacitor-
only the desired smallest size droplets. Liquid uptake rates to
inductor network. Most modern instruments, however, incor-
produce similar sensitivity to CGNs are sharply reduced with
porate an automatic impedance matching network to simplify
the MCN. The MCN utilizes typical uptake rates of <0.1
ignition, to reduce incidence of plasma extinction when intro-
mL/min and is HF tolerant. Unusually small sample size, low
ducing sample solutions, and to optimize power transfer.
uptake rates, fast washout times, and very low drain rates
characterize this nebulizer. The low uptake rate is particularly
7. Sample Introduction
7.1 The sample introduction system of an ICP instrument
consists of a nebulizer, a spray chamber, and a torch.
Courtesy of CETAC Technologies, a division of Transgenomic Inc., 5600 S.
7.2 Nebulizers: 42nd St., Omaha, NE.
E1479–99 (2005)
facturer and is known as a fixed cross-flow nebulizer. It
requires little maintenance and is very durable. Problems with
high levels of dissolved and suspended solids are similar to
those of the concentric glass nebulizer.
7.4 Pump-Fed Pneumatic Nebulizers:
7.4.1 Grid Nebulizer—constructed from a fine-mesh screen
of acid and solvent resistant material, such as platinum,
mounted vertically in an inert housing. Sample solution is
pumped over the surface of the mesh. A high-velocity gas
stream is directed through the openings in the screen, shearing
the liqu
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