ASTM D3919-15

Standard Practice for Measuring Trace Elements in Water by Graphite Furnace Atomic Absorption Spectrophotometry

SIGNIFICANCE AND USE
5.1 Elemental constituents in potable water, receiving water, and wastewater need to be identified for support of effective pollution control programs. Currently, one of the most sensitive and practical means for measuring low concentrations of trace elements is by graphite furnace atomic absorption spectrophotometry. ICP-MS may also be appropriate but at a higher instrument cost. See Test Method D5673.
SCOPE
1.1 This practice covers the general considerations for the quantitative determination of trace elements in water and wastewater by graphite furnace atomic absorption spectrophotometry. Furnace atomizers are a most useful means of extending detection limits; however, the practice should only be used at concentration levels below the optimum range of direct flame aspiration atomic absorption spectrophotometry. Because of differences between various makes and models of satisfactory instruments, no detailed operating instructions can be provided for each instrument. Instead, the analyst should follow the instructions provided by the manufacturer of a particular instrument.  
1.2 Wavelengths, estimated detection limits, and optimum concentration ranges are given in the individual methods. Ranges may be increased or decreased by varying the volume of sample injected or the instrumental settings or by the use of a secondary wavelength. Samples containing concentrations higher than those given in the optimum range may be diluted or analyzed by other techniques.  
1.3 This technique is generally not applicable to brines and seawater. Special techniques such as separation of the trace elements from the salt, careful temperature control through ramping techniques, or matrix modification may be useful for these samples.  
1.4 The analyst is encouraged to consult the literature as provided by the instrument manufacturer as well as various trade journals and scientific publications.  
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.6 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.

General Information

• Status: Published
• Publication Date: 31-Jan-2015
• ICS: 13.060.50 - Examination of water for chemical substances
• Technical Committee: D19 - Water
• Drafting Committee: D19.05 - Inorganic Constituents in Water

Relations

• Refers: ASTM D1129-13(2020)e2 - Standard Terminology Relating to Water
• Effective Date: 01-May-2020
• Refers: ASTM D5673-15 - Standard Test Method for Elements in Water by Inductively Coupled Plasma—Mass Spectrometry
• Effective Date: 01-Jul-2015
• Refers: ASTM D4841-88(2013) - Standard Practice for Estimation of Holding Time for Water Samples Containing Organic and Inorganic Constituents
• Effective Date: 01-Jan-2013
• Refers: ASTM D4841-88(2013)e1 - Standard Practice for Estimation of Holding Time for Water Samples Containing Organic and Inorganic Constituents
• Effective Date: 01-Jan-2013
• Refers: ASTM D2777-12 - Standard Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
• Effective Date: 15-Jun-2012
• Refers: ASTM D5810-96(2011) - Standard Guide for Spiking into Aqueous Samples
• Effective Date: 01-May-2011
• Refers: ASTM D3370-10 - Standard Practices for Sampling Water from Closed Conduits
• Effective Date: 01-Dec-2010
• Refers: ASTM D5673-10 - Standard Test Method for Elements in Water by Inductively Coupled Plasma-Mass Spectrometry
• Effective Date: 01-Aug-2010
• Refers: ASTM D1129-10 - Standard Terminology Relating to Water
• Effective Date: 01-Mar-2010
• Refers: ASTM D3370-08 - Standard Practices for Sampling Water from Closed Conduits
• Effective Date: 01-Oct-2008
• Refers: ASTM D4841-88(2008) - Standard Practice for Estimation of Holding Time for Water Samples Containing Organic and Inorganic Constituents
• Effective Date: 15-Jul-2008
• Refers: ASTM D2777-08 - Standard Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
• Effective Date: 15-Jan-2008
• Refers: ASTM D3370-07 - Standard Practices for Sampling Water from Closed Conduits
• Effective Date: 01-Dec-2007
• Refers: ASTM D1129-06ae1 - Standard Terminology Relating to Water
• Effective Date: 01-Sep-2006
• Refers: ASTM D1129-06a - Standard Terminology Relating to Water
• Effective Date: 01-Sep-2006

Overview

ASTM D3919-15 – Standard Practice for Measuring Trace Elements in Water by Graphite Furnace Atomic Absorption Spectrophotometry is a widely recognized standard from ASTM International. This practice offers guidelines for the quantitative determination of trace elements in water and wastewater using graphite furnace atomic absorption spectrophotometry (GFAAS). With increasing demands for accurate environmental analyses, especially for pollution control programs, this standard provides one of the most sensitive and practical approaches for measuring very low concentrations of trace metals.

GFAAS significantly extends detection capabilities over standard flame atomic absorption, making it essential for analysis of elements at trace levels. The practice is typically applied to potable water, receiving water, and wastewater samples and is especially useful when lower detection limits are required.

Key Topics

• Trace Element Quantification: Guidance for measuring low-level elemental concentrations in aqueous matrices, essential for regulatory and environmental monitoring.
• Instrument Use: Emphasis on following manufacturer’s instructions for different makes and models of atomic absorption spectrophotometers.
• Detection Limits & Range: Recommendations for selecting wavelength, optimizing detection limits, and adjusting sample or instrumental parameters.
• Matrix Interferences: Identification and mitigation strategies for background absorption, chemical and spectral interference, and matrix effects.
• Quality Assurance: Procedures for calibration, calibration verification, quality control samples, method blanks, and matrix spike recoveries.
• Sample Handling: Detailed protocols to avoid contamination, preserve sample integrity, and select proper materials for sampling and storage.
• Applicability: This technique is recommended for water and wastewater but not generally for brines and seawater due to potential matrix interferences without further treatment.

Applications

• Environmental Compliance: Widely used by laboratories supporting pollution control and regulatory reporting for trace metals in municipal and industrial wastewater, drinking water, and surface water.
• Analytical Services: Essential for laboratories offering services in trace element detection, environmental risk assessment, and compliance monitoring.
• Research and Development: Serves as a reference point for research into new methodologies or the impact of trace element contamination.
• Operational Efficiencies: The automated sampling requirements and sensitivity make GFAAS suited for high-throughput laboratory settings.
• Limitations: While highly sensitive, GFAAS is not well suited for high-salt matrices like seawater; additional sample preparation or alternative techniques (e.g., ICP-MS) may be necessary.

Related Standards

• ASTM D1129: Terminology Relating to Water, for consistent usage of key terms.
• ASTM D1193: Specification for Reagent Water, ensuring reagent purity.
• ASTM D3370: Practices for Sampling Water from Closed Conduits, for standardized sampling methods.
• ASTM D5673: Test Method for Elements in Water by Inductively Coupled Plasma–Mass Spectrometry (ICP-MS), a complementary high-sensitivity technique.
• ASTM D2777: Practice for Determination of Precision and Bias of Applicable Test Methods.
• ASTM D4841: Practice for Estimation of Holding Time for Water Samples.
• ASTM D5810: Guide for Spiking into Aqueous Samples.
• ASTM D5847: Practice for Writing Quality Control Specifications for Standard Test Methods for Water Analysis.

Conclusion

Adherence to ASTM D3919-15 provides laboratories with robust procedures for measuring trace elements in water and wastewater by graphite furnace atomic absorption spectrophotometry. Following this standard ensures high sensitivity, reliability, and comparability of analytical results, supporting water quality monitoring, regulatory compliance, and environmental protection initiatives. By following the best practices outlined and referencing related ASTM standards, organizations can achieve precise, accurate, and trustworthy trace element data for decision-making and compliance.

Standards Content (Sample)

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: D3919 − 15
Standard Practice for
Measuring Trace Elements in Water by Graphite Furnace
Atomic Absorption Spectrophotometry
This standard is issued under the fixed designation D3919; 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* priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
1.1 This practice covers the general considerations for the
quantitative determination of trace elements in water and
2. Referenced Documents
wastewater by graphite furnace atomic absorption spectropho-
2.1 ASTM Standards:
tometry. Furnace atomizers are a most useful means of extend-
D1129 Terminology Relating to Water
ing detection limits; however, the practice should only be used
D1193 Specification for Reagent Water
at concentration levels below the optimum range of direct
D2777 Practice for Determination of Precision and Bias of
flame aspiration atomic absorption spectrophotometry. Be-
Applicable Test Methods of Committee D19 on Water
cause of differences between various makes and models of
D3370 Practices for Sampling Water from Closed Conduits
satisfactory instruments, no detailed operating instructions can
D4841 Practice for Estimation of Holding Time for Water
be provided for each instrument. Instead, the analyst should
Samples Containing Organic and Inorganic Constituents
follow the instructions provided by the manufacturer of a
D5673 Test Method for Elements in Water by Inductively
particular instrument.
Coupled Plasma—Mass Spectrometry
1.2 Wavelengths, estimated detection limits, and optimum
D5810 Guide for Spiking into Aqueous Samples
concentration ranges are given in the individual methods.
D5847 Practice for Writing Quality Control Specifications
Ranges may be increased or decreased by varying the volume
for Standard Test Methods for Water Analysis
of sample injected or the instrumental settings or by the use of
a secondary wavelength. Samples containing concentrations
3. Terminology
higher than those given in the optimum range may be diluted
3.1 Definitions—For definitions of terms used in this
or analyzed by other techniques.
practice, refer to Terminology D1129.
1.3 This technique is generally not applicable to brines and
3.2 Definitions of Terms Specific to This Standard:
seawater. Special techniques such as separation of the trace
3.2.1 graphite furnace, n—an electrothermal graphite de-
elements from the salt, careful temperature control through
vicecapableofreachingthespecifiedtemperaturesrequiredby
ramping techniques, or matrix modification may be useful for
the element being determined.
these samples.
3.2.2 platform or similar device, n— a flat, grooved or
1.4 The analyst is encouraged to consult the literature as
ungrooved piece of pyrolytic graphite (which is inserted in the
provided by the instrument manufacturer as well as various
graphite tube) on which the sample is placed (1).
trade journals and scientific publications.
1.5 The values stated in SI units are to be regarded as
4. Summary of Practice
standard. No other units of measurement are included in this
4.1 The element is determined by an atomic absorption
standard.
spectrophotometerusedinconjunctionwithagraphitefurnace.
1.6 This standard does not purport to address all of the
The principle is essentially the same as with direct flame
safety concerns, if any, associated with its use. It is the
aspiration atomic absorption except a furnace, rather than a
responsibility of the user of this standard to establish appro-
flame,isusedtoatomizethesample.Theelementalatomstobe
1 2
This practice is under the jurisdiction ofASTM Committee D19 on Water and For referenced ASTM standards, visit the ASTM website, www.astm.org, or
is the direct responsibility of Subcommittee D19.05 on Inorganic Constituents in contactASTM Customer Service at [e-mail]. ForAnnual Book ofASTM
Water. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Feb. 1, 2015. Published March 2015. Originally the ASTM website.
approved in 1980. Last previous edition approved in 2008 as D3919 – 08. DOI: The boldface numbers in parentheses refer to the list of references at the end of
10.1520/D3919-15. this standard.
*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
D3919 − 15
measured are placed in the beam of radiation by increasing the absorbed only by the background, so that interspersing periods
temperature of the furnace, thereby causing the injected speci- of high and low source current permit correction of the
men to be volatilized. Radiation from a given excited element background.
is passed through the vapor containing ground-state atoms of
6.2 Some types of interference problems encountered in
that element. The decrease in intensity of the transmitted
direct aspiration atomic absorption spectrophotometry can be
radiation is a measure of the amount of the ground-state
observed with the furnace technique. Although quite rare,
element in the vapor.Amonochromator isolates the character-
spectral interference may be encountered. When this occurs,
istic radiation from the hollow-cathode lamp and a photosen-
the use of another wavelength is suggested. Additionally, the
sitive device measures the attenuated transmitted radiation.
furnace technique is subject to chemical and matrix interfer-
4.2 Dissolved elements are determined on a filtered sample ence and the composition of the sample matrix can have a
major effect on the analysis. Therefore, for each different
with no pretreatment. See 9.5.
matrix encountered, the possibility of these interferences
4.3 Total recoverable elements are determined following
should be considered.
acid digestion and filtration. If suspended material is not
6.3 Gases generated in the furnace during the atomization
present, this digestion and filtration may be omitted.
may have molecular absorption bands encompassing the ana-
lytical wavelength. When this occurs, either using background
5. Significance and Use
correction or choosing an alternative wavelength outside the
5.1 Elementalconstituentsinpotablewater,receivingwater,
absorptionbandshouldeliminatethisinterference.Nonspecific
and wastewater need to be identified for support of effective
broadband absorption interference can also be compensated by
pollutioncontrolprograms.Currently,oneofthemostsensitive
background correction.
and practical means for measuring low concentrations of trace
6.4 Memory effects occur if, during atomization, all the
elements is by graphite furnace atomic absorption spectropho-
analyte is not volatilized and removed from the furnace. This
tometry. ICP-MS may also be appropriate but at a higher
condition is dependent on several factors, such as the volatility
instrument cost. See Test Method D5673.
of the element and its chemical form, whether pyrolytic
graphite is used, the rate of atomization, and furnace design. If
6. Interferences
this situation is detected through blank burns, the tube must be
6.1 Background absorption is caused by the formation of
cleaned by operating the furnace at full power for the required
molecularspeciesfromthesamplematrixthatabsorborscatter
time period at regular intervals in the analytical scheme.
the light emitted by the hollow cathode or electrodeless
6.5 Interferencefromasmoke-producingsamplematrixcan
discharge line source. Without correction, this will cause the
sometimes be reduced by extending the charring time at a
analytical results to be erroneously high. Three approaches
higher temperature. Also, some instruments utilize an ashing
exist for simultaneous background correction: continuum
cycle in the presence of air.Take care, however, to prevent loss
source, Zeeman, and Smith-Hieftje.
of analyte.
6.1.1 Continuum Source—The continuum source procedure
involves the use of a deuterium arc source for the ultraviolet or 6.6 Samples containing large amounts of organic material
a tungsten halide lamp for the visible region of the spectrum.
should be oxidized by conventional acid digestion prior to
Light from the primary spectral source and the appropriate being placed in the furnace. In this way, broadband absorption
continuum source are alternately passed through the graphite
willbeminimized.Theuseofexpendable-typelaboratoryware
furnace. Narrow-band emission of the primary source is should be considered to limit contamination.
affected by the scatter and background absorption from the
6.7 Carbide formation, resulting from the chemical environ-
matrix as well as the absorption of light by analyte atoms. The
ment of the furnace, has been observed with certain elements
broadband emission of the continuum source is affected only
that form carbides at high temperatures. Barium, molybdenum,
by the background absorption. The effect of the background is
nickel, titanium, and vanadium may be cited as examples.
removed by taking a ratio of the energy of the two sources.
Whenthistakesplace,theelementwillbereleasedveryslowly
6.1.2 Zeeman Correction—The Zeeman correction system
from the carbide and longer atomization times may be required
involves the use of an external magnetic field to split the
before the signal returns to baseline levels. This problem is
atomic spectral line. When the magnetic field is off, both
greatly reduced and sensitivity increases with the use of
sampleandbackgroundaremeasured.Whenthemagneticfield
pyrolytically coated graphite.
is applied, the absorption line is shifted and only the back-
6.8 Ionization interferences have to date not been reported
ground absorption is measured. Background correction is
with furnace techniques.
performed by electronically comparing the field-off and field-
on measurements, yielding an analyte-only absorption re- 6.9 Contamination of the sample can be a major source of
sponse.
error because of the extreme sensitivities achieved with the
6.1.3 Smith-Hieftje System—This system involves cycling furnace. Keep the sample preparation work area scrupulously
theatomiclinesourceathighcurrentsforbriefintervals.These clean (see 9.1). Clean all glassware with dilute HNO (1 + 1).
intervals cause nonexcited atoms of the source element to Pipette tips have been known to be a source of contamination.
undergo the process of self-reversal by emitting light at If suspected, acid soak them with HNO (1 + 1) and rinse
wavelengths other than those of the analyte. This light is thoroughlywithwater.Theuseofonlyhigh-qualitypipettetips
D3919 − 15
greatly reduces this problem. It is very important that special during the charring/ashing process. The use of ammonium
attentionbegiventoreagentblanksinboththeanalysisandthe dihydrogen phosphate or phosphoric acid results in higher
correction of analytical results. Lastly, pyrolytic graphite, volatilization temperatures for many elements, thus permitting
because of the production process and handling, can become the use of higher charring/ashing temperatures to remove or
contaminated. As many as five, to possibly ten, high- reduce matrix interferences. Nickel nitrate has been shown to
temperatureburnsmayberequiredtocleanthetubebeforeuse. perform the same role for arsenic and selenium by forming
high temperature arsenides and selenides. An alternate ap-
6.10 Oxide formation is greatly reduced because atomiza-
proach to the same problem is to reduce the temperature at
tion occurs in an inert atmosphere.
which the matrix volatilizes, permitting it to be removed at a
6.11 Several investigators who have studied interferences in
lower charring/ashing temperature. Sodium chloride in seawa-
thegraphitefurnacehaveconcludedthatnitrateisthepreferred ter can be volatilized by adding ammonium nitrate as a matrix
anion of the matrix. Therefore, nitric acid is preferable for any
modifier. The sodium nitrate and ammonium chloride formed
digestion or solubilization step. If the situation absolutely are more volatile than the sodium chloride and can be
requires the use of another acid in addition to HNO,orin
volatilized at much lower charring/ashing temperatures. Other
place of HNO (for example, tin), use the minimum amount of
matrix modifiers include various organic acids such as citric
acid. This applies particularly to hydrochloric and perchloric and ascorbic acid. These acids are believed to reduce matrix
acids, but also to sulfuric and phosphoric acids to a lesser
interferences by preventing the formation of large salt crystals
extent. that can occlude the analyte. A table of additional matrix
modifiers is given in Appendix X1. See also the literature
6.12 The tests as outlined in 6.12.1 – 6.12.5 are recom-
(2-18).
mended prior to reporting analytical data. These tests will
6.12.4 Platform Furnaces—The pseudo-constant tempera-
provide indication whether positive or negative interference
ture furnace design suggested by L’Vov (1) has minimized
effects are operative in any way on the analyte elements
matrix and gas phase interference problems. L’Vov placed a
thereby distorting the accuracy of the reported values.
graphite platform inside the graphite tube furnace to approxi-
6.12.1 Spiking Verification—Whenthesampleabsorbanceis
mate a constant temperature design. Since the platform is
40 % or less of the absorbance of the highest standard on the
heated by radiation, it lags behind the tube walls in
standardcurve,theamountofspikeaddedtothesampleshould
temperature, and delays the atomization of the analyte until the
result in a net increase equal to 50 % of the highest standard
tubeatmosphereisatahigher,moreconstanttemperature.This
concentration. The purpose of adding a large spike is to
results in reduced vapor-phase condensation and reduces the
differentiate between matrix interferences and random errors.
effectofthesamplematrixontheanalytesignal.Theintegrated
The recovery of the spike must be between 90 and 110 % for
absorbancesignalisproportionaltothenumberofatomsinthe
verification of the original determination. If the result of the
sample, independent of the rate at which atomization occurs.
originaldeterminationisabove40 %onthecurve,twoaliquots
This type of furnace is commercially available or the modifi-
should be withdrawn and diluted at least 1 + 1. One of the
cation can be made by the user (19).
aliquots should be spiked before dilution with an amount
6.12.5 Standard Additions—Analyze the sample by method
resulting in a net increase over the unspiked aliquot equivalent
of standard additions while noting the precautions and limita-
to 50 % of the highest standard concentration. The reported
tions of its use. See 12.4.
result should be based on the analysis of the diluted aliquot.
For verification of this result, the spike recovery must be 7. Apparatus
between 90 and 110 %. For spiking verification to be valid in
7.1 Atomic Absorption Spectrophotometer—Single- or dual-
either situation in the presence of nonspecific absorbance,
channel, single- or double-beam instrument having a grating
simultaneous background correction must be used during
monochromator, photomultiplier detector, adjustable slits,
analysis. If the result of the determination cannot be verified,
wavelength range from 190 to 800 nm, and simultaneous
the sample should be treated in one or more of the following
background correction.
ways:
7.2 Hollow-Cathode Lamps—Single-element lamps are pre-
6.12.2 Serial Dilution—Successively dilute and reanalyze
ferred but multi-element lamps may be used. Electrodeless
the sample using spiking verifications to determine if the
discharge lamps may also be used when available, and are
interference can be eliminated. This assumes that the analyte
preferred for elements such as As, Se, Sb.
occurs at a sufficiently high concentration.
7.3 Graphite Tubes—Graphite tubes should be compatible
6.12.3 Matrix Modification—Matrix modifiers are fre-
with furnace device. Pyrolytically coated graphite tubes are
quently used to stabilize volatile or moderately volatile analyte
recommended.
metals such as lead, cadmium, chromium, and nickel. Metals
such as these begin to volatilize at very low temperatures and 7.4 Data System—Data are collected using internal micro-
requirethatthecharring/ashingtemperaturebelowered.Lower processor or external desktop computer systems. Data can be
charring/ashing temperatures reduce the chance of removing stored on disks, transmitted to central servers, or printed in
potential interferents from the matrix during the charring/ hard copy. Data may be evaluated and processed using the
ashing step. Adding certain chemical compounds or combina- instrument’s dedicated systems to determine analyte concen-
tions of chemical compounds will reduce the volatility of trations. Users of this practice may use a strip chart recorder to
selected metals by the formation of less volatile compounds obtain sample and calibration data, if desired.
D3919 − 15
7.5 Automatic sampling should be used. Studies have rities on laboratory apparatus that the sample contacts are all
shown that the coefficient of variation for aqueous samples sources of potential contamination. Sample containers can
varies from 0.4 to 1.6 %, depending upon the metal and introduce either positive or negative errors in the measurement
concentration (20). of trace elements by: (a) contributing contaminants through
leaching or surface desorption, and (b) by depleting concen-
8. Reagents and Materials
trations through absorption. Thus, the collection and treatment
of the sample prior to analysis requires particular attention (see
8.1 Purity of Reagents—It is intended that all reagents
6.8).
conform to the specifications of the Committee on Analytical
Reagents of the American Chemical Society as a minimum
9.2 Sample Collection—Collect all samples in accordance
when such specifications are available. The high sensitivity of
with Practices D3370.
graphite furnace atomic absorption spectrophotometry may
9.3 Sample Containers—Store the sample in a clean glass,
requirereagentsofahigherpurity.Stockstandardsolutionsare
linear polyethylene, polypropylene, or TFE-fluorocarbon con-
prepared from high-purity metals, oxides, or nonhydroscopic
tainer.
reagent grade salts using water and ultrapure nitric acid.
9.4 SampleSize—Samplesizemustbesufficienttoallowfor
Sulfuric, hydrochloric, and phosphoric acids are to be avoided
wherever possible as they produce an adverse effect on many the determination. In general, use microliter sample aliquots
for the analysis. However, when sample processing or multiple
elements. A lesser grade of nitric acid and reagents may be
used, provided it is first ascertained that the reagent is of analyses, or both, are required, larger sample volumes may be
necessary.
sufficiently high purity to permit its use without lessening the
accuracy of the determination.
9.5 Sample Preservation—In most cases, samples are pre-
served by adding HNO to a pH of less than 2. However,
8.2 Purity of Water—Unless otherwise indicated, references
towatershallbeunderstoodtomeanreagentwaterconforming certain metals may require a different type of preservation.The
analystshouldrefertothespecificmethodforguidance.Ifonly
to Type I of Specification D1193. Other reagent water types
may be used, provided it is first ascertained that the water is of dissolved elements are to be determined, filter the sample
through a 0.45-µm membrane filter before adding acid. Filter
sufficiently high purity to permit its use without lessening the
bias and precision of the determination. and preserve as soon as possible, preferably at the time of
collection.
8.3 Filter Paper—Purchase suitable filter paper. Typically
the filter papers have a pore size of 0.45-µm membrane.
NOTE 1—Alternatively, the filtration and pH may be adjusted in the
laboratoryifthesampleisreturnedwithin14days.However,acidmustbe
Material such as fine-textured, acid-washed, ashless paper, or
added at least 24 hours before analysis to dissolve any metals that adsorb
glass fiber paper are acceptable. The user must first ascertain
to the container walls.This could reduce hazards of working with acids in
that the filter paper is of sufficient purity to use without
the field when appropriate.
adversely affecting the bias and precision of the test method.
9.6 Sample Storage—Analyze samples containing trace
8.4 Nitric Acid (sp gr 1.42)—Distilled ultrapure concen-
concentrations of analyte as soon as possible, preferable at the
trated nitric acid (HNO ).
time of collection. The holding time for the samples may be
calculated in accordance with Practice D4841.
8.5 Standard Solution, Stock (1 mL = 1 mg element)—
Prepare each stock solution at a concentration of 1000 mg of
10. Preparation of Atomic Absorption Spectrophotometer
the element per liter. Commercially available standard solu-
10.1 Furnace Device—Mount the furnace device in accor-
tions of appropriate known purity may also be used.
dance with the instructions provided by the instrument manu-
8.6 Argon,standard,weldersgrade,commerciallyavailable.
facturer.
Nitrogen, argon with 5 % hydrogen, and hydrogen may also be
used if recommended by the instrument manufacturer. The 10.2 Turn on the instrument and allow the warm-up as
instructed by the instrument manufacturer.
...

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: D3919 − 08 D3919 − 15
Standard Practice for
Measuring Trace Elements in Water by Graphite Furnace
Atomic Absorption Spectrophotometry
This standard is issued under the fixed designation D3919; 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 Scope*
1.1 This practice covers the general considerations for the quantitative determination of trace elements in water and wastewater
by graphite furnace atomic absorption spectrophotometry. Furnace atomizers are a most useful means of extending detection limits;
however, the practice should only be used at concentration levels below the optimum range of direct flame aspiration atomic
absorption spectrophotometry. Because of differences between various makes and models of satisfactory instruments, no detailed
operating instructions can be provided for each instrument. Instead, the analyst should follow the instructions provided by the
manufacturer of a particular instrument.
1.2 Wavelengths, estimated detection limits, and optimum concentration ranges are given in the individual methods. Ranges
may be increased or decreased by varying the volume of sample injected or the instrumental settings or by the use of a secondary
wavelength. Samples containing concentrations higher than those given in the optimum range may be diluted or analyzed by other
techniques.
1.3 This technique is generally not applicable to brines and seawater. Special techniques such as separation of the trace elements
from the salt, careful temperature control through ramping techniques, or matrix modification may be useful for these samples.
1.4 The analyst is encouraged to consult the literature as provided by the instrument manufacturer as well as various trade
journals and scientific publications.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 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.
2. Referenced Documents
2.1 ASTM Standards:
D1129 Terminology Relating to Water
D1193 Specification for Reagent Water
D2777 Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
D3370 Practices for Sampling Water from Closed Conduits
D4841 Practice for Estimation of Holding Time for Water Samples Containing Organic and Inorganic Constituents
D5673 Test Method for Elements in Water by Inductively Coupled Plasma—Mass Spectrometry
D5810 Guide for Spiking into Aqueous Samples
D5847 Practice for Writing Quality Control Specifications for Standard Test Methods for Water Analysis
3. Terminology
3.1 Definitions—For definitions of terms used in this practice, refer to Terminology D1129.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 graphite furnace—furnace, n—an electrothermal graphite device capable of reaching the specified temperatures required
by the element being determined.
This practice is under the jurisdiction of ASTM Committee D19 on Water and is the direct responsibility of Subcommittee D19.05 on Inorganic Constituents in Water.
Current edition approved Nov. 15, 2008Feb. 1, 2015. Published November 2008March 2015. Originally approved in 1980. Last previous edition approved in 20042008
as D3919 – 04.D3919 – 08. DOI: 10.1520/D3919-08.10.1520/D3919-15.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. 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
D3919 − 15
3.2.2 platform or similar device—device, n— a flat, grooved or ungrooved piece of pyrolytic graphite (which is inserted in the
graphite tubetube) on which the sample is placed (1).
4. Summary of Practice
4.1 The element is determined by an atomic absorption spectrophotometer used in conjunction with a graphite furnace. The
principle is essentially the same as with direct flame aspiration atomic absorption except a furnace, rather than a flame, is used to
atomize the sample. The elemental atoms to be measured are placed in the beam of radiation by increasing the temperature of the
furnace, thereby causing the injected specimen to be volatilized. Radiation from a given excited element is passed through the
vapor containing ground-state atoms of that element. The decrease in intensity of the transmitted radiation is a measure of the
amount of the ground-state element in the vapor. A monochromator isolates the characteristic radiation from the hollow-cathode
lamp and a photosensitive device measures the attenuated transmitted radiation.
4.2 Dissolved elements are determined on a filtered sample with no pretreatment. See 9.5.
4.3 Total recoverable elements are determined following acid digestion and filtration. If suspended material is not present, this
digestion and filtration may be omitted.
5. Significance and Use
5.1 Elemental constituents in potable water, receiving water, and wastewater need to be identified for support of effective
pollution control programs. Currently, one of the most sensitive and practical means for measuring low concentrations of trace
elements is by graphite furnace atomic absorption spectrophotometry. ICP-MS may also be appropriate but at a higher instrument
cost. See Test Method D5673.
6. Interferences
6.1 Background absorption is caused by the formation of molecular species from the sample matrix that absorb or scatter the
light emitted by the hollow cathode or electrodeless discharge line source. Without correction, this will cause the analytical results
to be erroneously high. Three approaches exist for simultaneous background correction: continuum source, Zeeman, and
Smith-Hieftje.
6.1.1 Continuum Source—The continuum source procedure involves the use of a deuterium arc source for the ultraviolet or a
tungsten halide lamp for the visible region of the spectrum. Light from the primary spectral source and the appropriate continuum
source are alternately passed through the graphite furnace. Narrow-band emission of the primary source is affected by the scatter
and background absorption from the matrix as well as the absorption of light by analyte atoms. The broadband emission of the
continuum source is affected only by the background absorption. The effect of the background is removed by taking a ratio of the
energy of the two sources.
6.1.2 Zeeman Correction—The Zeeman correction system involves the use of an external magnetic field to split the atomic
spectral line. When the magnetic field is off, both sample and background are measured. When the magnetic field is applied, the
absorption line is shifted and only the background absorption is measured. Background correction is performed by electronically
comparing the field-off and field-on measurements, yielding an analyte-only absorption response.
6.1.3 Smith-Hieftje System—This system involves cycling the atomic line source at high currents for brief intervals. These
intervals cause nonexcited atoms of the source element to undergo the process of self-reversal by emitting light at wavelengths
other than those of the analyte. This light is absorbed only by the background, so that interspersing periods of high and low source
current permit correction of the background.
6.2 Some types of interference problems encountered in direct aspiration atomic absorption spectrophotometry can be observed
with the furnace technique. Although quite rare, spectral interference may be encountered. When this occurs, the use of another
wavelength is suggested. Additionally, the furnace technique is subject to chemical and matrix interference and the composition
of the sample matrix can have a major effect on the analysis. Therefore, for each different matrix encountered, the possibility of
these interferences should be considered.
6.3 Gases generated in the furnace during the atomization may have molecular absorption bands encompassing the analytical
wavelength. When this occurs, either using background correction or choosing an alternative wavelength outside the absorption
band should eliminate this interference. Nonspecific broadband absorption interference can also be compensated by background
correction.
6.4 Memory effects occur if, during atomization, all the analyte is not volatilized and removed from the furnace. This condition
is dependent on several factors, such as the volatility of the element and its chemical form, whether pyrolytic graphite is used, the
rate of atomization, and furnace design. If this situation is detected through blank burns, the tube must be cleaned by operating
the furnace at full power for the required time period at regular intervals in the analytical scheme.
The boldface numbers in parentheses refer to the list of references at the end of this standard.
D3919 − 15
6.5 Interference from a smoke-producing sample matrix can sometimes be reduced by extending the charring time at a higher
temperature. Also, some instruments utilize an ashing cycle in the presence of air. Take care, however, to prevent loss of analyte.
6.6 Samples containing large amounts of organic material should be oxidized by conventional acid digestion prior to being
placed in the furnace. In this way, broadband absorption will be minimized. The use of expendable-type laboratory ware should
be considered to limit contamination.
6.7 Carbide formation, resulting from the chemical environment of the furnace, has been observed with certain elements that
form carbides at high temperatures. Barium, molybdenum, nickel, titanium, and vanadium may be cited as examples. When this
takes place, the element will be released very slowly from the carbide and longer atomization times may be required before the
signal returns to baseline levels. This problem is greatly reduced and sensitivity increases with the use of pyrolytically coated
graphite.
6.8 Ionization interferences have to date not been reported with furnace techniques.
6.9 Contamination of the sample can be a major source of error because of the extreme sensitivities achieved with the furnace.
Keep the sample preparation work area scrupulously clean (see 9.1). Clean all glassware with dilute HNO (1 + 1). Pipette tips
have been known to be a source of contamination. If suspected, acid soak them with HNO (1 + 1) and rinse thoroughly with water.
The use of only high-quality pipette tips greatly reduces this problem. It is very important that special attention be given to reagent
blanks in both the analysis and the correction of analytical results. Lastly, pyrolytic graphite, because of the production process
and handling, can become contaminated. As many as five, to possibly ten, high-temperature burns may be required to clean the
tube before use.
6.10 Oxide formation is greatly reduced because atomization occurs in an inert atmosphere.
6.11 Several investigators who have studied interferences in the graphite furnace have concluded that nitrate is the preferred
anion of the matrix. Therefore, nitric acid is preferable for any digestion or solubilization step. If the situation absolutely requires
the use of another acid in addition to HNO , or in place of HNO (for example, tin), use the minimum amount of acid. This applies
3 3
particularly to hydrochloric and perchloric acids, but also to sulfuric and phosphoric acids to a lesser extent.
6.12 Some types of interference problems encountered in direct aspiration atomic absorption spectrophotometry can be
observed with the furnace technique. Although quite rare, spectral interference may be encountered. When this occurs, the use of
another wavelength is suggested. Additionally, the furnace technique is subject to chemical and matrix interference and the
composition of the sample matrix can have a major effect on the analysis. Therefore, for each different matrix encountered, the
possibility of these interferences should be considered. The tests as outlined in 6.2.16.12.1 – 6.2.56.12.5 are recommended prior
to reporting analytical data. These tests will provide indication whether positive or negative interference effects are operative in
any way on the analyte elements thereby distorting the accuracy of the reported values.
6.12.1 Spiking Verification—When the sample absorbance is 40 % or less of the absorbance of the highest standard on the
standard curve, the amount of spike added to the sample should result in a net increase equal to 50 % of the highest standard
concentration. The purpose of adding a large spike is to differentiate between matrix interferences and random errors. The recovery
of the spike must be between 90 and 110 % for verification of the original determination. If the result of the original determination
is above 40 % on the curve, two aliquots should be withdrawn and diluted at least 1 + 1. One of the aliquots should be spiked before
dilution with an amount resulting in a net increase over the unspiked aliquot equivalent to 50 % of the highest standard
concentration. The reported result should be based on the analysis of the diluted aliquot. For verification of this result, the spike
recovery must be between 90 and 110 %. For spiking verification to be valid in either situation in the presence of nonspecific
absorbance, simultaneous background correction must be used during analysis. If the result of the determination cannot be verified,
the sample should be treated in one or more of the following ways:
6.12.2 Serial Dilution—Successively dilute and reanalyze the sample using spiking verifications to determine if the interference
can be eliminated. This assumes that the analyte occurs at a sufficiently high concentration.
6.12.3 Matrix Modification—Matrix modifiers are frequently used to stabilize volatile or moderately volatile analyte metals such
as lead, cadmium, chromium, and nickel. Metals such as these begin to volatilize at very low temperatures and require that the
charring/ashing temperature be lowered. Lower charring/ashing temperatures reduce the chance of removing potential interferents
from the matrix during the charring/ashing step. Adding certain chemical compounds or combinations of chemical compounds will
reduce the volatility of selected metals by the formation of less volatile compounds during the charring/ashing process. The use
of ammonium dihydrogen phosphate or phosphoric acid results in higher volatilization temperatures for many elements, thus
permitting the use of higher charring/ashing temperatures to remove or reduce matrix interferences. Nickel nitrate has been shown
to perform the same role for arsenic and selenium by forming high temperature arsenides and selenides. An alternate approach to
the same problem is to reduce the temperature at which the matrix volatilizes, permitting it to be removed at a lower
charring/ashing temperature. Sodium chloride in seawater can be volatilized by adding ammonium nitrate as a matrix modifier. The
sodium nitrate and ammonium chloride formed are more volatile than the sodium chloride and can be volatilized at much lower
charring/ashing temperatures. Other matrix modifiers include various organic acids such as citric and ascorbic acid. These acids
are believed to reduce matrix interferences by preventing the formation of large salt crystals that can occlude the analyte. A table
of additional matrix modifiers is given in Appendix X1. See also the literature (22-18–3).
D3919 − 15
6.12.4 Platform Furnaces—The pseudo-constant temperature furnace design suggested by L’Vov (1) has minimized matrix and
gas phase interference problems. L’Vov placed a graphite platform inside the graphite tube furnace to approximate a constant
temperature design. Since the platform is heated by radiation, it lags behind the tube walls in temperature, and delays the
atomization of the analyte until the tube atmosphere is at a higher, more constant temperature. This results in reduced vapor-phase
condensation and reduces the effect of the sample matrix on the analyte signal. The integrated absorbance signal is proportional
to the number of atoms in the sample, independent of the rate at which atomization occurs. This type of furnace is commercially
available or the modification can be made by the user (419).
6.12.5 Standard Additions—Analyze the sample by method of standard additions while noting the precautions and limitations
of its use. See 12.4.
6.3 Gases generated in the furnace during the atomization may have molecular absorption bands encompassing the analytical
wavelength. When this occurs, either using background correction or choosing an alternative wavelength outside the absorption
band should eliminate this interference. Nonspecific broadband absorption interference can also be compensated by background
correction.
6.4 Memory effects occur if, during atomization, all the analyte is not volatilized and removed from the furnace. This condition
is dependent on several factors, such as the volatility of the element and its chemical form, whether pyrolytic graphite is used, the
rate of atomization, and furnace design. If this situation is detected through blank burns, the tube must be cleaned by operating
the furnace at full power for the required time period at regular intervals in the analytical scheme.
6.5 Interference from a smoke-producing sample matrix can sometimes be reduced by extending the charring time at a higher
temperature. Also, some instruments utilize an ashing cycle in the presence of air. Take care, however, to prevent loss of analyte.
6.6 Samples containing large amounts of organic material should be oxidized by conventional acid digestion prior to being
placed in the furnace. In this way, broadband absorption will be minimized. The use of expendable-type laboratory ware should
be considered to limit contamination.
6.7 Carbide formation, resulting from the chemical environment of the furnace, has been observed with certain elements that
form carbides at high temperatures. Barium, molybdenum, nickel, titanium, and vanadium may be cited as examples. When this
takes place, the element will be released very slowly from the carbide and longer atomization times may be required before the
signal returns to baseline levels. This problem is greatly reduced and sensitivity increases with the use of pyrolytically coated
graphite.
6.8 Ionization interferences have to date not been reported with furnace techniques.
6.9 Contamination of the sample can be a major source of error because of the extreme sensitivities achieved with the furnace.
Keep the sample preparation work area scrupulously clean (see 9.1). Clean all glassware with dilute HNO (1 + 1). Pipette tips
have been known to be a source of contamination. If suspected, acid soak them with HNO (1 + 1) and rinse thoroughly with water.
The use of only high-quality pipette tips greatly reduces this problem. It is very important that special attention be given to reagent
blanks in both the analysis and the correction of analytical results. Lastly, pyrolytic graphite, because of the production process
and handling, can become contaminated. As many as five, to possibly ten, high-temperature burns may be required to clean the
tube before use.
6.10 Oxide formation is greatly reduced because atomization occurs in an inert atmosphere.
6.11 Several investigators who have studied interferences in the graphite furnace have concluded that nitrate is the preferred
anion of the matrix. Therefore, nitric acid is preferable for any digestion or solubilization step. If the situation absolutely requires
the use of another acid in addition to HNO , or in place of HNO (for example, tin), use the minimum amount of acid. This applies
3 3
particularly to hydrochloric and perchloric acids, but also to sulfuric and phosphoric acids to a lesser extent.
7. Apparatus
7.1 Atomic Absorption Spectrophotometer—Single- or dual-channel, single- or double-beam instrument having a grating
monochromator, photomultiplier detector, adjustable slits, wavelength range from 190 to 800 nm, and simultaneous background
correction.
7.2 Hollow-Cathode Lamps—Single-element lamps are preferred but multi-element lamps may be used. Electrodeless discharge
lamps may also be used when available, and are preferred for elements such as As, Se, Sb.
7.3 Graphite Tubes—Graphite tubes should be compatible with furnace device. Pyrolytically coated graphite tubes are
recommended.
7.4 Data System—Data are collected using internal microprocessor or external desktop computer systems. Data can be stored
on disks, transmitted to central servers, or printed in hard copy. Data may be evaluated and processed using the instrument’s
dedicated systems to determine analyte concentrations. Users of this practice may use a strip chart recorder to obtain sample and
calibration data, if desired.
D3919 − 15
7.5 Automatic sampling should be used. Studies have shown that the coefficient of variation for aqueous samples varies from
0.4 to 1.61.6 %, depending upon the metal and concentration (520).
8. Reagents and Materials
8.1 Purity of Reagents—It is intended that all reagents conform to the specifications of the Committee on Analytical Reagents
of the American Chemical Society as a minimum when such specifications are available. The high sensitivity of graphite furnace
atomic absorption spectrophotometry may require reagents of a higher purity. Stock standard solutions are prepared from
high-purity metals, oxides, or nonhydroscopic reagent grade salts using water and ultrapure nitric acid. Sulfuric, hydrochloric, and
phosphoric acids are to be avoided wherever possible as they produce an adverse effect on many elements. A lesser grade of nitric
acid and reagents 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.
8.2 Purity of Water—Unless otherwise indicated, references to water shall be understood to mean reagent water conforming to
Type I of Specification D1193. Other reagent water types may be used, provided it is first ascertained that the water is of sufficiently
high purity to permit its use without lessening the bias and precision of the determination.
8.3 Filter Paper—Purchase suitable filter paper. Typically the filter papers have a pore size of 0.45-μm membrane. Material such
as fine-textured, acid-washed, ashless paper, or glass fiber paper are acceptable. The user must first ascertain that the filter paper
is of sufficient purity to use without adversely affecting the bias and precision of the test method.
8.4 Nitric Acid (sp gr 1.42)—Distilled ultrapure concentrated nitric acid (HNO ).
8.5 Standard Solution, Stock (1 mL = 1 mg element)—Prepare each stock solution at a concentration of 1000 mg of the element
per liter. Commercially available standard solutions of appropriate known purity may also be used.
8.6 Argon, standard, welders grade, commercially available. Nitrogen, argon with 5 % hydrogen, and hydrogen may also be
used if recommended by the instrument manufacturer. The analyst should be aware that moisture present in some grades of inert
gas may cause interference. The use of dry or moisture-free inert gas is suggested.
9. Samples and Sampling Procedures
9.1 Sample Handling—For the determination of trace elements, contamination and loss are of prime concern. Dust in the
laboratory environment, impurities in reagents, and impurities on laboratory apparatus that the sample contacts are all sources of
potential contamination. Sample containers can introduce either positive or negative errors in the measurement of trace elements
by: (a) contributing contaminants through leaching or surface desorption, and (b) by depleting concentrations through absorption.
Thus, the collection and treatment of the sample prior to analysis requires particular attention (see 6.8).
9.2 Sample Collection—Collect all samples in accordance with Practices D3370.
9.3 Sample Containers—Store the sample in a clean glass, linear polyethylene, polypropylene, or TFE-fluorocarbon container.
9.4 Sample Size—Sample size must be sufficient to allow for the determination. I
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