ASTM D3557-17

Standard Test Methods for Cadmium in Water

SIGNIFICANCE AND USE
4.1 The test for cadmium is necessary because it is a toxicant and because there is a limit specified for cadmium in potable water in the National Interim Primary Drinking Water Regulations. This test serves to determine whether the cadmium content of potable water is above or below the acceptable limit.
SCOPE
1.1 These test methods cover the determination of dissolved and total recoverable cadmium in water and wastewater by atomic-absorption spectrophotometry and differential pulse anodic stripping voltammetry.2 Section 44 on Quality Control pertains to these test methods. Four test methods are included as follows:    
Concentration
Range  
Sections  
Test Method A—Atomic Absorption,
Direct  
0.05 to 2.0 mg/L  
7 to 15  
Test Method B—Atomic Absorption,
Chelation-Extraction  
5 to 200 μg/L  
16 to 24  
Test Method C—Differential Pulse
Anodic Stripping Voltammetry  
1 to 100 μg/L  
25 to 34  
Test Method D—Atomic Absorption,
Graphite Furnace  
2 to 10 μg/L  
35 to 43  
1.2 Test Method B can be used to determine cadmium in brines. It is the user's responsibility to ensure the validity of these test methods for waters of untested matrices.  
1.3 ICP-MS or ICP-AES may also be appropriate but at a higher instrument cost. See Test Methods D5673 and D1976.  
1.4 The values stated in SI units are to be regarded as standard. The values given in parentheses are mathematical conversion to inch-pound units that are provided for information only and are not considered standard.  
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.  
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-May-2017
• ICS: 13.060.50 - Examination of water for chemical substances
• Technical Committee: D19 - Water
• Drafting Committee: D19.05 - Inorganic Constituents in Water

Relations

• Replaces: ASTM D3557-12 - Standard Test Methods for Cadmium in Water
• Effective Date: 01-Jun-2017
• Refers: ASTM D3558-15(2023) - Standard Test Methods for Cobalt in Water
• Effective Date: 01-Dec-2023
• Refers: ASTM D1129-13(2020)e2 - Standard Terminology Relating to Water
• Effective Date: 01-May-2020
• Refers: ASTM D1976-20 - Standard Test Method for Elements in Water by Inductively-Coupled Plasma Atomic Emission Spectroscopy
• Effective Date: 01-May-2020
• Refers: ASTM D1066-18 - Standard Practice for Sampling Steam
• Effective Date: 01-Aug-2018
• Refers: ASTM D1066-18e1 - Standard Practice for Sampling Steam
• Effective Date: 01-Aug-2018
• Refers: ASTM D1976-18 - Standard Test Method for Elements in Water by Inductively-Coupled Plasma Atomic Emission Spectroscopy
• Effective Date: 01-Jul-2018
• Refers: ASTM D1691-17 - Standard Test Methods for Zinc in Water
• Effective Date: 01-Jun-2017
• Refers: ASTM D5673-15 - Standard Test Method for Elements in Water by Inductively Coupled Plasma—Mass Spectrometry
• Effective Date: 01-Jul-2015
• Refers: ASTM D3558-15 - Standard Test Methods for Cobalt in Water
• Effective Date: 01-Feb-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 D858-12 - Standard Test Methods for Manganese in Water
• Effective Date: 01-Sep-2012
• Refers: ASTM D1691-12 - Standard Test Methods for Zinc in Water
• Effective Date: 01-Sep-2012
• 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

Overview

ASTM D3557-17: Standard Test Methods for Cadmium in Water is a critical international standard developed by ASTM International. This standard defines reliable test methods for the determination of dissolved and total recoverable cadmium in water and wastewater. Recognizing cadmium as a significant toxicant, ASTM D3557-17 ensures compliance with regulatory limits required by drinking water and environmental protection agencies. It specifies techniques primarily based on atomic absorption spectrophotometry and differential pulse anodic stripping voltammetry, covering a wide range of concentration levels and types of water matrices.

Key Topics

• Scope of Methods:
  The standard includes four test methods for cadmium analysis:

  • Test Method A: Atomic absorption, direct (0.05 to 2.0 mg/L)
  • Test Method B: Atomic absorption, chelation-extraction (5 to 200 μg/L)
  • Test Method C: Differential pulse anodic stripping voltammetry (1 to 100 μg/L)
  • Test Method D: Atomic absorption, graphite furnace (2 to 10 μg/L)

• Applicability:
  Applicable to potable water, wastewater, brines (for Test Method B), and various natural and treated waters. Each method addresses different detection ranges for flexibility in water quality monitoring.

• Quality Control:
  Section 44 and referenced quality control practices ensure reliable and standardized results, with specific guidance on calibration, reagent purity, and analysis procedures.

• Matrix Considerations:
  Users must validate methods when applied to new or untested sample matrices to ensure accuracy and reliability.

• Safety and Regulatory Compliance:
  The document emphasizes adhering to safety protocols and regulatory limitations, particularly concerning hazardous materials and appropriate laboratory practices.

Applications

ASTM D3557-17 serves multiple industries and sectors, providing practical value in the following areas:

• Drinking Water Compliance:
  Used by water utilities and public health agencies to monitor cadmium levels and meet regulatory standards, such as those set in the National Interim Primary Drinking Water Regulations.

• Environmental Monitoring:
  Applied in environmental laboratories for routine assessment of cadmium pollution in surface waters, groundwaters, and industrial discharges.

• Wastewater Treatment:
  Essential for wastewater treatment plants to test for cadmium prior to discharge, ensuring environmental protection and liability avoidance.

• Industrial Process Control:
  Beneficial for manufacturers and process industries, especially where cadmium compounds are used or generated, to ensure effluent compliance and workplace safety.

• Brine and Specialized Waters:
  Test Method B’s applicability to brines supports industries such as oil and gas, chemical processing, and desalination.

Related Standards

ASTM D3557-17 is frequently utilized alongside several other ASTM standards to provide comprehensive analysis of inorganic constituents in water. Key related standards include:

• ASTM D5673: Inductively Coupled Plasma–Mass Spectrometry for Element Determination in Water
• ASTM D1976: Inductively Coupled Plasma Atomic Emission Spectroscopy for Element Analysis
• ASTM D858: Test Methods for Manganese in Water
• ASTM D1129: Terminology Relating to Water
• ASTM D1886: Test Methods for Nickel in Water
• ASTM D3558, D1688, D1068, D3559, D1687, D1691: Test methods for other metals (cobalt, copper, iron, lead, chromium, zinc)
• ASTM D1193: Specification for Reagent Water
• ASTM D3370 and D1066: Practices for Sampling Water and Steam

By following the methodologies outlined in ASTM D3557-17, laboratories, regulatory bodies, and industries can achieve accurate, traceable, and internationally recognized measurements of cadmium in water, supporting public health, environmental integrity, and regulatory 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: D3557 − 17
Standard Test Methods for
Cadmium in Water
This standard is issued under the fixed designation D3557; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* 2. Referenced Documents
1.1 Thesetestmethodscoverthedeterminationofdissolved 2.1 ASTM Standards:
and total recoverable cadmium in water and wastewater by D858Test Methods for Manganese in Water
atomic-absorption spectrophotometry and differential pulse D1066Practice for Sampling Steam
anodic stripping voltammetry. Section 44 on Quality Control D1068Test Methods for Iron in Water
pertains to these test methods. Four test methods are included D1129Terminology Relating to Water
as follows: D1193Specification for Reagent Water
D1687Test Methods for Chromium in Water
Concentration
Sections
Range
D1688Test Methods for Copper in Water
Test Method A—Atomic Absorption, 0.05 to 2.0 7 to 15
D1691Test Methods for Zinc in Water
Direct mg/L
D1886Test Methods for Nickel in Water
Test Method B—Atomic Absorption, 5 to 200 µg/L 16 to 24
Chelation-Extraction
D1976Test Method for Elements in Water by Inductively-
Test Method C—Differential Pulse 1 to 100 µg/L 25 to 34
Coupled Argon Plasma Atomic Emission Spectroscopy
Anodic Stripping Voltammetry
D2777Practice for Determination of Precision and Bias of
Test Method D—Atomic Absorption, 2to10µg/L 35 to 43
Graphite Furnace
Applicable Test Methods of Committee D19 on Water
D3370Practices for Sampling Water from Closed Conduits
1.2 Test Method B can be used to determine cadmium in
brines. It is the user’s responsibility to ensure the validity of D3558Test Methods for Cobalt in Water
D3559Test Methods for Lead in Water
these test methods for waters of untested matrices.
D3919Practice for Measuring Trace Elements in Water by
1.3 ICP-MS or ICP-AES may also be appropriate but at a
Graphite Furnace Atomic Absorption Spectrophotometry
higher instrument cost. See Test Methods D5673 and D1976.
D4841Practice for Estimation of Holding Time for Water
1.4 The values stated in SI units are to be regarded as
Samples Containing Organic and Inorganic Constituents
standard. The values given in parentheses are mathematical
D5673Test Method for Elements in Water by Inductively
conversion to inch-pound units that are provided for informa-
Coupled Plasma—Mass Spectrometry
tion only and are not considered standard.
D5810Guide for Spiking into Aqueous Samples
1.5 This standard does not purport to address all of the D5847Practice for Writing Quality Control Specifications
safety concerns, if any, associated with its use. It is the for Standard Test Methods for Water Analysis
responsibility of the user of this standard to establish appro-
3. Terminology
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
3.1 Definitions:
1.6 This international standard was developed in accor-
3.1.1 For definitions of terms used in this standard, refer to
dance with internationally recognized principles on standard-
Terminology D1129.
ization established in the Decision on Principles for the
3.2 Definitions of Terms Specific to This Standard:
Development of International Standards, Guides and Recom-
3.2.1 continuing calibration blank, n—asolutioncontaining
mendations issued by the World Trade Organization Technical
no analytes (of interest) which is used to verify blank response
Barriers to Trade (TBT) Committee.
and freedom from carryover.
3.2.2 continuing calibration verification, n—a solution (or
These test methods are under the jurisdiction of ASTM Committee D19 on
setofsolutions)ofknownconcentrationusedtoverifyfreedom
Water and are the direct responsibility of Subcommittee D19.05 on Inorganic
Constituents in Water.
Current edition approved June 1, 2017. Published June 2017. Originally
approved in 1977. Last previous edition approved in 2012 as D3557– 12. DOI: For referenced ASTM standards, visit the ASTM website, www.astm.org, or
10.1520/D3557-17. contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Platte,J.A.,andMarcy,V.M.,“ANewToolfortheWaterChemist,”Industrial Standards volume information, refer to the standard’s Document Summary page on
Water Engineering, May 1965. 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
D3557 − 17
This could reduce hazards of working with acids in the field when
fromexcessiveinstrumentaldrift;theconcentrationistocover
appropriate.
the range of calibration curve.
3.2.3 SCE, n—saturated calomel electrode.
TEST METHOD A—ATOMIC ABSORPTION, DIRECT
3.2.4 spikingsolution,n—thestandardsolutionaddedtothe
7. Scope
polarographic cell that is used to quantitate the sample.
3.2.5 stripping peak potential, n—the applied potential ver- 7.1 This test method covers the determination of dissolved
sus SCE at which the stripping peak current is a maximum.
and total recoverable cadmium in most waters and wastewa-
ters.
3.2.6 stripping peak signal, n—the current measured at the
stripping peak maximum for a metal.
7.2 This test method is applicable in the range from 0.05 to
2.0 mg/L of cadmium. The range may be extended to concen-
3.2.7 total recoverable metal, n—a descriptive term relating
to the metal forms of cadmium recovered in the acid-digestion trations greater than 2.0 mg/L by dilution of the sample.
procedure specified in these test standards.
7.3 This test method has been used successfully with
reagentgradewater,riverwater,wastewater,groundwater,tap
4. Significance and Use
water, lake water, and refinery effluent. The information on
4.1 The test for cadmium is necessary because it is a
precisionandbiasmaynotapplytootherwater.Itistheuser’s
toxicant and because there is a limit specified for cadmium in
responsibility to ensure the validity of this test method for
potable water in the National Interim Primary Drinking Water
waters of other matrices.
Regulations. This test serves to determine whether the cad-
mium content of potable water is above or below the accept-
8. Summary of Test Method
able limit.
8.1 Cadmium is determined by atomic absorption spectro-
photometry. Dissolved cadmium is determined by aspirating a
5. Purity of Reagents
portion of the filtered sample directly with no pretreatment.
5.1 Reagent grade chemicals shall be used in all tests.
Total recoverable cadmium is determined by aspirating the
Unlessotherwiseindicated,itisintendedthatallreagentsshall
sample following hydrochloric-nitric acid digestion and filtra-
conform to the specifications of the Committee on Analytical
tion. The same digestion procedure may be used to determine
Reagents of the American Chemical Society. Other grades
total recoverable nickel (Test Methods D1886), chromium
may be used, provided it is first ascertained that the reagent is
(Test Methods D1687), cobalt (Test Methods D3558), copper
of sufficiently high purity to permit its use without lessening
(Test Methods D1688), iron (Test Methods D1068), lead (Test
the accuracy of the determination.
Methods D3559), manganese (Test Methods D858), and zinc
5.2 Unless otherwise indicated, references to water shall be (Test Methods D1691).
understood to mean reagent water conforming to Specification
D1193, Type I. Other reagent water types may be used,
9. Interferences
provided it is first ascertained that the water is of sufficiently
9.1 Calcium concentrations above 1000 mg/L suppress the
high purity to permit its use without adversely affecting the
cadmiumabsorption.At2000mg/Lofcalciumthesuppression
bias and precision of the test method. Type II water was
is 19%.
specified at the time of round-robin testing of this test method.
9.2 Sodium, potassium, sulfate, and chloride (9000 mg/L
6. Sampling each),magnesium(4500mg/L),iron(4000mg/L),nitrate(100
mg/L), and nickel, lead, copper, zinc, cobalt, and chromium
6.1 Collect the samples in accordance with the applicable
(10 mg/L each), do not interfere.
ASTM standard as follows: Practices D3370 and D1066.
9.3 Background correction or a chelation-extraction proce-
6.2 Samples shall be preserved with HNO (sp gr 1.42) to a
dure (see Test Method B) may be necessary to determine low
pH of 2 or less immediately at the time of collection, normally
levels of cadmium in some waters.
about 2 mL/L of HNO . If only dissolved cadmium is to be
determined,thesampleshallbefilteredthrougha0.45-µm(No.
NOTE 2—Instrument manufacturer’s instructions for use of the specific
325)membranefilterbeforeacidification.Theholdingtimefor
correction technique should be followed.
samplesmaybecalculatedinaccordancewithPracticeD4841.
10. Apparatus
NOTE1—Alternatively,thepHmaybeadjustedinthelaboratorywithin
14 days of collection. However, acid must be added at least 24 hours
10.1 Atomic Absorption Spectrophotometer, for use at
before analysis to dissolve any metals that adsorb to the container walls.
228.8 nm.
NOTE 3—The manufacturer’s instructions shall be followed for all
4 instrumental parameters.Awavelength other than 228.8 nm may be used
Reagent Chemicals, American Chemical Society Specifications, American
if it has been determined to be equally suitable.
Chemical Society, Washington, DC. For Suggestions on the testing of reagents not
listed by the American Chemical Society, see Annual Standards for Laboratory
10.2 Cadmium Light Source—Either cadmium hollow-
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
cathode lamps or multielement hollow-cathode lamps, or
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
MD. electrodeless-discharge lamps.
D3557 − 17
10.3 Pressure-Reducing Valves—The supplies of fuel and 12.2 When determining total recoverable cadmium, add 0.5
oxidant shall be maintained at pressures somewhat higher than mL of HNO (sp gr 1.42) to each blank and standard solution
the controlled operating pressure of the instrument by suitable and proceed as directed in 13.3 through 13.5. After the
valves. digestion of the blank and standard solutions has been com-
pleted in 13.5, return to 12.3 to complete the standardization
11. Reagents and Materials for total recoverable determinations. When determining dis-
solved cadmium, proceed with 12.3.
11.1 Cadmium Solution, Stock (1 mL=1.0 mg Cd)—
Dissolve 1.000 g of cadmium metal in a minimum quantity of
12.3 Aspirate the blank and standards and record the instru-
HNO (sp gr 1.42) and dilute to 1 L. A purchased cadmium
3 ment readings. Aspirate HNO (1+499) between each stan-
stock solution of appropriate known purity is also acceptable.
dard.
11.2 Cadmium Solution, Standard (1 mL=0.1 mg Cd)—
12.4 Read directly in concentration if this capability is
Dilute 100.0 mL of the cadmium stock solution and 1 mL of
provided with the instrument or measure the absorbance of the
HNO (sp gr 1.42) to 1000 mL with water.
standards and prepare an analytical curve by plotting the
11.3 Hydrochloric Acid (sp gr 1.19)—Concentrated hydro-
absorbance versus the concentration for each standard on the
chloric acid (HCl).
instrument software.
NOTE 4—If the reagent blank concentration is greater than the method
13. Procedure
detection limit, distill the HCl or use spectrograde acid.
(Warning—When HCl is distilled, an azeotropic mixture is
13.1 An effective way to clean all glassware to be used for
obtained (approximately 6 N HCl). Therefore, whenever con-
preparation of standard solutions or in the digestion step, or
centratedHClisspecifiedforthepreparationofareagentorin
both,isbysoakingtheglasswareovernightwithHNO (1+1)
the procedure, use double the volume specified if distilled acid
and then rinse with reagent.
is used.)
13.2 Measure 100.0 mL of a well-mixed acidified sample
11.4 Nitric Acid (sp gr 1.42)—Concentrated nitric acid
into a 125-mL beaker or flask.
(HNO ).
NOTE 6—If only dissolved cadmium is to be determined, start with
NOTE 5—If the reagent blank concentration is greater than the method
13.6.
detection limit, distill the HNO or use a spectrograde acid.
13.3 Add 5 mL of HCl (sp gr 1.19) to each sample.
11.5 Nitric Acid (1+499)—Add 1 volume of HNO (sp gr
1.42) to 499 volumes of water.
13.4 Heatthesamples(between65°Cand95°C)onasteam
bath or hotplate below boiling in a well-ventilated hood until
11.6 Oxidant:
the volume has been reduced to 15 to 20 mL, making certain
11.6.1 Air,whichhasbeenpassedthroughasuitablefilterto
that the samples do not boil.
remove oil, water, and other foreign substances is the usual
oxidant.
NOTE 7—For samples containing appreciable amounts of suspended
11.7 Fuel: matterordissolvedsolids,theamountofreductioninvolumeislefttothe
discretion of the analyst.
11.7.1 Acetylene—Standard, commercially available acety-
NOTE 8—Many laboratories have found block digestion systems a
lene is the usual fuel. Acetone, always present in acetylene
useful way to digest samples for trace metals analysis. Systems typically
cylinders, can affect analytical results. The cylinder should be
consist of either a metal or graphite block with wells to hold digestion
replaced at 345 kPa (50 psi). (Warning—“Purified” grade
tubes. The block temperature controller must be able to maintain unifor-
acetylene containing a special proprietary solvent rather than
mity of temperature across all positions of the block. The digestion block
must be capable of maintaining a temperature between 65°C and 95°C.
acetone should not be used with poly(vinyl chloride) tubing as
For trace metals analysis, the digestion tubes should be constructed of
weakening of the tubing walls can cause a potentially hazard-
polypropylene and have a volume accuracy of at least 0.5 %. All lots of
ous situation.)
tubes should come with a certificate of analysis to demonstrate suitability
for their intended purpose.
11.8 Paper Filter—Purchase suitable filter paper. Typically
the filter papers have a pore size of 0.45-µm membrane.
13.5 Cool and filter the samples through a suitable filter
Material such as fine-textured, acid-washed, ashless paper, or
(11.8) such as fine-textured, acid-washed, ashless, paper into
glass fiber paper are acceptable. The user must first ascertain
100-mL volumetric flasks. Wash the filter paper two or three
that the filter paper is of sufficient purity to use without
times with water and adjust to volume.
adversely affecting the bias and precision of the test method.
13.6 Aspirate each filtered and acidified sample and deter-
mine its absorbance or concentration at 228.8 nm. Aspirate
12. Standardization
HNO (1+499) between each sample.
12.1 Prepare 100 mL each of a blank and at least four
standard solutions to bracket the expected cadmium concen-
14. Calculation
tration range of the samples to be analyzed by diluting the
standard cadmium solution (11.2) with HNO (1+499). Pre- 14.1 Calculate the concentration of cadmium in the sample,
pare the standards each time the test is to be performed or as in milligrams per litre, using the analytical curve prepared in
determined by Practice D4841. 12.4.
D3557 − 17
15. Precision and Bias hydrochloricacid,anddilutedtoaspecifiedvolumewithwater.
A portion of the resulting solution is then aspirated into the
15.1 The precision of this test method was tested by 17
air-acetylene flame of the spectrophotometer. The digestion
laboratories in reagent water, river water, wastewater, ground
procedure summarized in 8.1 is used to determine total
water, tap water, lake water, and refinery effluent. The overall
recoverable cadmium. The same chelation-extraction proce-
bias and precision of this test method, within its designated
dure may be used to determine nickel (Test Methods D1886),
range, varies with the quantity being measured in accordance
cobalt (Test Methods D3558), copper (Test Methods D1688),
with Table 1.
iron (Test Methods D1068), lead (Test Methods D3559), and
15.2 These data may not apply to waters of the matrices,
zinc (Test Methods D1691).
therefore, it is the responsibility of the analyst to ensure the
18. Interferences
validity of the test method in other matrices.
15.3 Precision and bias for this test method conforms to 18.1 See Section 9.
Practice D2777–77, which was in place at the time of
19. Apparatus
collaborative testing. Under the allowances made in 1.4 of
Practice D2777–13, these precision and bias data meet 19.1 All items of apparatus described in Section 10 are
existing requirements for interlaboratory studies of Committee required.
D19 test methods.
20. Reagents and Materials
TEST METHOD B—ATOMIC ABSORPTION,
20.1 BromphenolBlueIndicatorSolution(1g/L)—Dissolve
CHELATION-EXTRACTION
0.1 g of bromphenol blue in 100 mL of 50% ethanol or
isopropanol.
16. Scope
20.2 Cadmium Solution, Stock (1.0 mL=1.0 mg Cd)—See
16.1 Thistestmethodcoversthedeterminationofdissolved
11.1.
and total recoverable cadmium in most waters and brines.
20.3 Cadmium Solution, Intermediate (1.0 mL=50 µg
16.2 This test method is applicable in the range from 5 to
Cd)—Dilute 50.0 mL of stock cadmium solution and 1 mL of
200 µg/L of cadmium. The range may be extended to concen-
HNO (sp gr 1.42) to 1 L with water.
trations greater than 200 µg/L by dilution of the sample.
20.4 Cadmium Solution, Standard (1.0 mL=0.5 µg Cd)—
16.3 This test method has been used successfully with
Dilute 10 mL of cadmium intermediate solution and 1 mL of
reagentgradewater,riverwater,wastewater,groundwater,tap
HNO (sp gr 1.42) to 1 L with water.
water, lake water, and refinery effluent. The information on
20.5 Chloroform (CHCl ).
precision and bias may not apply to other water.
20.6 Hydrochloric Acid (sp gr 1.19)—Concentrated hydro-
16.4 It is the responsibility of the analyst to determine the
chloric acid (HCl) (see Note 4).
acceptability of this test method when analyzing other matri-
ces.
20.7 Hydrochloric Acid(1+2)—Add 1 volume of HCl (sp
gr 1.19) to 2 volumes of water.
17. Summary of Test Method
20.8 HydrochloricAcid(1+49)—Add1volumeofHCl(sp
17.1 Cadmium is determined by atomic absorption spectro-
gr 1.19) to 49 volumes of water.
photometry.The element, either dissolved or total recoverable,
20.9 Nitric Acid (sp gr 1.42)—Concentrated nitric acid
is chelated with pyrrolidine dithiocarbamic acid and extracted
(HNO ) (see Note 5).
with chloroform. The extract is evaporated to dryness, treated
with hot nitric acid to destroy organic matter, dissolved in
20.10 Pyrrolidine Dithiocarbamic Acid-Chloroform
Reagent—Add36mLofpyrrolidineto1LofCHCl .Coolthe
solution and add 30 mL of CS in small portions, swirling
Supporting data have been filed atASTM International Headquarters and may
between additions. Dilute to 2 Lwith CHCl .The reagent can
beobtainedbyrequestingResearchReportRR:D19-1030.ContactASTMCustomer
be used for several months if stored in a cool, dark place.
Service at [e-mail].
(Warning—All components of this reagent are highly toxic.
Carbon disulfide is also highly flammable. Prepare and use in
TABLE 1 Determination of Bias and Precision for Cadmium by
a well-ventilated hood. Avoid inhalation and direct contact.)
Atomic Absorption, Direct
20.11 Sodium Hydroxide Solution (100 g/L)—Dissolve 100
Statistically
Amount Added, Amount
S , mg/L S , mg/L % Bias Significant,
T O g of sodium hydroxide (NaOH) in water, cool, and dilute to 1
mg/L Found, mg/L
95 % Level
L.
Reagent Water
0.20 0.200 0.033 0.033 0.0 No
20.12 Materials—Use materials from 11.6, 11.7, and 11.8.
0.60 0.592 0.034 0.026 −1.3 No
1.60 1.521 0.111 0.061 −4.9 Yes
21. Standardization
Water of Choice
0.20 0.200 0.033 0.033 0.0 No
21.1 Prepareablankandsufficientstandardcontainingfrom
0.60 0.589 0.040 0.026 −1.8 No
0.0to20µgofcadmiumbydiluting0.0to40.0-mLportionsof
1.60 1.511 0.114 0.061 −5.6 Yes
cadmium standard solution to 100 mL with water.
D3557 − 17
21.2 When determining total recoverable cadmium use 22.9 Plugthetipoftheseparatoryfunnelwithcotton,allow
125-mLbeakersorflasks,add0.5mLofHNO (spgr1.42)and the phases to separate, and drain the CHCl phase into a
3 3
proceed as directed in 22.3 through 22.16. When determining 100-mL beaker.
dissolved cadmium, use 250-mL separatory funnels and pro-
22.10 Repeattheextractionwith10mLofCHCl anddrain
ceed as directed in 22.6 through 22.16.
the CHCl layer into the same beaker.
21.3 Read directly in concentration if this capability is
NOTE 13—If color still remains in the CHCl extract, reextract the
provided with the instrument or measure the absorbance of the
aqueous phase until the CHCl layer is colorless.
standards and construct an analytical curve by reading absor-
22.11 Place the beaker on a hotplate set at low heat or on a
bances from the instrument software.
steam bath, and evaporate to near dryness. Remove beaker
from heat and allow residual solvent to evaporate without
22. Procedure
further heating. (Warning—Perform in a well-ventilated
22.1 An effective way to clean all glassware to be used for
hood.)
preparation of standard solutions or in the digestion step, or
22.12 Hold the beaker at a 45° angle, and slowly add
both,isbysoakingtheglasswareovernightwithHNO (1+1)
dropwise 2 mL of HNO (sp gr 1.42), rotating the beaker to
and then rinse with reagent.
effect thorough contact of the acid with the residue.
22.2 Measure a volume of a well-mixed acidified sample 22.12.1 If acid is added to the beaker in a vertical position,
containing less than 20.0 µg of cadmium (100-mL maximum)
a violent reaction will occur, accompanied by high heat and
intoa125-mLbeakerorflaskandadjustthevolumeto100mL spattering.
with water.
22.13 Place the beaker on a hotplate set at low heat or on a
steam bath, and evaporate to near dryness. Remove beaker
NOTE 9—If only dissolved cadmium is to be determined, measure a
volume of filtered and acidified sample containing less than 20 µg of
from heat and allow residual solvent to evaporate without
cadmium(100-mLmaximum)intoa250-mLseparatoryfunnel,andbegin
further heating.
with 22.6.
22.14 Add 2 mL of HCl (1+2) to the beaker, and heat,
22.3 Add 5 mL of HCl (sp gr 1.19) to each sample.
while swirling for 1 min.
22.4 Heatthesamples(between65°Cand95°C)onasteam
22.15 Cool and quantitatively transfer the solution to a
bath or hotplate below boiling in a well-ventilated hood until
10-mL volumetric flask and adjust to volume with water.
the volume has been reduced to 15 to 20 mL, making certain
22.16 Aspirateeachsampleandrecordthescalereadingsor
that the samples do not boil.
concentrations at 228.8 nm.
NOTE 10—When analyzing brine samples and samples containing
appreciable amounts of suspended matter or dissolved solids, the amount
23. Calculation
of reduction in volume is left to the discretion of the analyst.
NOTE 11—Many laboratories have found block digestion systems a
23.1 Determine the weight of cadmium in each sample by
useful way to digest samples for trace metals analysis. Systems typically
referringtotheanalyticalcurve.Calculatetheconcentrationof
consist of either a metal or graphite block with wells to hold digestion
cadmium in micrograms per litre as follows:
tubes. The block temperature controller must be able to maintain unifor-
mity of temperature of across all positions of the block. The digestion
Cadmium, µg/L 5 1000/A 3B (1)
~ !
block must be capable of maintaining a temperature between 65°C and
95°C. For trace metals analysis, the digestion tubes should be constructed where:
of polypropylene and have a volume accuracy of at least 0.5 %. All lots
1000 = 1000 mL / L,
of tubes should come with a certificate of analysis to demonstrate
A = volume of original sample, mL, and
suitability for their intended purpose.
B = weight of cadmium in sample, µg.
22.5 Cool and filter the samples through a suitable filter
(11.8), such as fine-textured, acid-washed, ashless paper, into
24. Precision and Bias
250-mL separatory funnels. Wash the filter paper two or three
24.1 The precision of this test method was tested by seven
times with water and adjust the volume to approximately 100
laboratories in reagent water, river water, waste water, ground
mL.
water, tap water, lake water, and refinery effluent. The overall
22.6 Add2dropsofbromphenolblueindicatorsolutionand
precisionofthistestmethod,withinitsdesignatedrange,varies
mix.
with the quantity being measured according to Table 2.
22.7 Adjust the pH by addition of NaOH (100 g/L) solution
24.2 These data may not apply to waters of other matrices,
until a blue color persists.Add HCl (1+49) by drops until the
therefore, it is the responsibility of the analyst to ensure the
blue color just disappears; then add 2.5 mLof HCl (1+49) in
validity of the test method in a particular matrix.
excess. The pH at this point should be 2.3.
24.3 Precision and bias for this test method conforms to
NOTE 12—The pH adjustment of 22.7 may be made with a pH meter
Practice D2777–77, which was in place at the time of
instead of using an indicator.
collaborative testing. Under the allowances made in 1.4 of
22.8 Add 10 mL of pyrrolidine dithiocarbamic acid- Practice D2777– 13, these precision and bias data meet
chloroform reagent and shake vigorously for 2 min. existing requirements for interlaboratory studies of Committee
(Warning—See Note 12.) D19 test methods.
D3557 − 17
TABLE 2 Determination of Bias and Precision for Cadmium by
26.4 The stripping peak height is proportional to the con-
Atomic Absorption, Chelation-Extraction
centration of the cadmium, and the stripping peak potential is
Statistically
a qualitative measure of the cadmium in solution.
Amount Added, Amount
S , µg/L S , µg/L % Bias Significant,
T O
µg/L Found, µg/L
95 % Level
27. Interferences
Reagent Water
30 30.6 4.3 3.3 +2.1 No
27.1 Selenium does not interfere up to 50 µg/L. Interfer-
80 76.9 9.9 6.2 −3.9 No
160 151.0 21.3 3.9 −5.6 No
ences from selenium concentration up to 1000 µg/L may be
Water of Choice
overcome by adding ascorbic acid which reduces selenium
30 28.9 7.0 4.5 −3.6 No
(IV) to selenium metal and eliminates the interference.
80 76.9 10.5 3.6 −3.9 No
160 152.7 19.7 9.1 −4.6 No
27.2 When ferric ions are present at levels greater than
cadmium,interferencemayoccurfromoxidizingthedeposited
metal out of the amalgam. Interference by ferric iron at
TEST METHOD C—DIFFERENTIAL
concentrations as high as 20 mg/L is eliminated by warming
PULSE ANODIC STRIPPING VOLTAMMETRY
with hydroxylamine. Ferric ions are reduced to ferrous ions by
thehydroxylamine,andtheinterferencecausedbythepresence
25. Scope
of iron is eliminated.
25.1 This test method describes the determination of cad-
27.3 The presence of a neighboring stripping peak which is
mium in water and wastewaters using differential pulse anodic
<100 mV from that of cadmium will interfere.
stripping voltammetry.
25.2 This test method is applicable up to a concentration of
28. Apparatus
100 µg/L cadmium. Higher concentrations can be determined
28.1 Polarographic Instrumentation capable of performing
by dilution.
differential pulse work.
25.3 The lower limit of detection for cadmium is 1.0 µg/L.
28.2 Hanging Mercury Drop Electrode.
NOTE 14—The lower limit of detection for differential pulse anodic
stripping voltammetry is not absolute and can easily be lowered by 28.3 Reagent Purifier System.
changing the experimental parameters as described in Appendix X1.
28.4 Counter Electrode, platinum.
However, these variations have not been interlaboratory tested.
28.5 Salt Bridge, with slow leakage fritted glass tip, to
25.4 It is the responsibility of the analyst to determine the
isolate saturated calomel electrode from the test solution.
acceptability of this test method when analyzing other matri-
ces. 28.6 MagneticStirrer—Themagneticstirrerusedmusthave
a separate On/Off switch, so that uniform rotational speed can
26. Summary of Test Method
be maintained. A0.5-in. (13-mm) magnetic stirring bar is also
26.1 This test method determines the total recoverable required.
concentration of cadmium in water and wastewater. The same
28.7 pH Meter.
digestion, sample preparation, and analysis procedure may be
28.8 Hot Plate or Hot Block Digestion System.
usedtodeterminetotalrecoverablelead(TestMethodsD3559)
simultaneously with cadmium. 28.9 Micropipettes incorporating disposable plastic tips are
used. The sizes required are 10, 20, 50, and 100 µL.
26.2 The sample is digested with nitric acid in a polaro-
graphiccell:0.2Mammoniumcitratebuffer(pH3.0)and10%
29. Reagents and Materials
hydroxylamine solution are added. The solution is warmed to
dissolve the cadmium. Warming with hydroxylamine elimi- 29.1 Purity of Reagents—The ammonium citrate solution
nates interference from ferric iron by reducing it to ferrous.
and redistilled nitric acid are purified or purchased to contain
less than 1 µg/L of cadmium.
26.3 After cooling, this sample is de-aerated, and the
cadmium is deposited into a hanging mercury drop electrode
with a surface area of 1.5 to 3.0 mm at a constant potential
of−0.80 V versus saturated calomel electrode (SCE). The Two instruments that have been found satisfactory for this purpose are the
polarographic analyzer with mechanical drop timer, Model 174A, and the Houston
cadmium is then stripped back into solution using the differ-
Omnigraphic X-Y Recorder, Model 2200-3-3, available from Princeton Applied
entialpulsescanningmode,andthecurrentismeasuredduring
Research, Princeton, NJ.Another instrument, the Charge TransferAnalyzer, Model
the stripping step. (Warning—Mercury has been designated
3040, available from Environmental SciencesAssociates (ESA), Bedford, MA, has
also been found satisfactory for this purpose. For settings on ESA Model 3040
by many regulatory agencies as a hazardous material that can
equivalent to those in 33.10, see ESAApplication Note CTA-AN-1.
cause serious medical issues. Mercury, or its vapor, has been
The hanging mercury drop electrode, Model 9323, or the automated hanging
demonstrated to be hazardous to health and corrosive to
mercury drop electrode, Model 314, manufactured by PrincetonApplied Research,
materials.Cautionshouldbetakenwhenhandlingmercuryand
have been found satisfactory for this purpose.
BoththeElectrolytePurificationSystem,Model9500,availablefromPrinceton
mercurycontainingproducts.SeetheapplicableproductSafety
Applied Research, and the PM Reagent Cleaning System, Model 2014, available
Data Sheet (SDS) for additional information. Users should be
from ESA, have been found satisfactory for this purpose.
awarethatsellingmercuryand/ormercurycontainingproducts
AVycortip,availablefromCorningGlassWorks,Corning,NY,hasbeenfound
into your state or country may be prohibited by law.) satisfactory for this purpose.
D3557 − 17
29.2 AmmoniumCitrateBuffer—Dissolve42gofcitricacid 30. Hazards
in 800 mL of water and add enough ammonium hydroxide to
30.1 The liquid mercury used for the hanging mercury drop
bring the pH to 3.0 6 0.2. Dilute to 1000 mL with water and
electrode forms a toxic vapor, and the liquid itself is toxic.
place in the cell of the reagent purifier system. Purify for a
Handle with gloves in a ventilated hood. (Warning—Mercury
minimum of 36 h at a potential of−1.3 V versus SCE at a
has been designated by many regulatory agencies as a hazard-
mercury pool working electrode. De-aerate the supporting
ousmaterialthatcancauseseriousmedicalissues.Mercury,or
electrolyte during the purification process. If the buffer con-
its vapor, has been demonstrated to be hazardous to health and
tainslessthan1µg/Lofcadmium,thepurificationstepmaybe
corrosive to materials. Caution should be taken when handling
omitted, providing new buffer is prepared every 2 weeks. The
mercury and mercury containing products. See the applicable
electrolyzedbufferisstableagainstbacterialgrowthforatleast
product Safety Data Sheet (SDS) for additional information.
1 month.
Users should be aware that selling mercury and/or mercury
NOTE 15—To prevent bacterial growth in the unpurified buffer for a containing products into your state or country may be prohib-
month, sterilize by autoclaving for 15 min at 121°C and 103.4 kPa (15
ited by law.)
psi).
29.3 AquaRegia(1+1)—Add1volumeofnitricacid(spgr
31. Calibration
1.42) to 4 volumes of water. Then add 3 volumes of hydro-
31.1 After a differential pulse anodic stripping curve is run
chloric acid (sp gr 1.19). (Warning—Toxic fumes may be
on the sample solution, the anodic stripping curve is quanti-
released. Prepare and use in a ventilated hood.)
tated using the technique of standard additions.
29.4 Ascorbic Acid (100 g/L)—Dissolve 10.0 g of
31.2 Prepare 100 mg/Lstock solutions by diluting 5.00 mL
L-ascorbic acid in reagent water and dilute to 100 mL.
of the cadmium standard solutions to 50.0 mL with HNO
29.5 Hydrochloric Acid (sp gr 1.19)—Concentrated hydro-
(1+160). These can be stored for several weeks if kept in a
chloric acid (HCl).
plastic bottle.
29.6 HydroxylamineS
...

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: D3557 − 12 D3557 − 17
Standard Test Methods for
Cadmium in Water
This standard is issued under the fixed designation D3557; 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*
1.1 These test methods cover the determination of dissolved and total recoverable cadmium in water and wastewater by
atomic-absorption spectrophotometry and differential pulse anodic stripping voltammetry. Section 44 on Quality Control pertains
to these test methods. Four test methods are included as follows:
Concentration
Sections
Range
Test Method A—Atomic Absorption, 0.05 to 2.0 7 to 15
Direct mg/L
Test Method B—Atomic Absorption, 5 to 200 μg/L 16 to 24
Chelation-Extraction
Test Method C—Differential Pulse 1 to 100 μg/L 25 to 34
Anodic Stripping Voltammetry
Test Method D—Atomic Absorption, 2 to 10 μg/L 35 to 43
Graphite Furnace
Concentration
Sections
Range
Test Method A—Atomic Absorption, 0.05 to 2.0 7 to 15
Direct mg/L
Test Method B—Atomic Absorption, 5 to 200 μg/L 16 to 24
Chelation-Extraction
Test Method C—Differential Pulse 1 to 100 μg/L 25 to 34
Anodic Stripping Voltammetry
Test Method D—Atomic Absorption, 2 to 10 μg/L 35 to 43
Graphite Furnace
1.2 Test Method B can be used to determine cadmium in brines. It is the user’s responsibility to ensure the validity of these test
methods for waters of untested matrices.
1.3 ICP-MS or ICP-AES may also be appropriate but at a higher instrument cost. See Test Methods D5673 and D1976.
1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values statedgiven
in each system are mathematical conversions and may not be exact equivalents; therefore, each system shall be used independently
of the other.parentheses are mathematical conversion to inch-pound units that are provided for information only and are not
considered standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D858 Test Methods for Manganese in Water
These test methods are under the jurisdiction of ASTM Committee D19 on Water and are the direct responsibility of Subcommittee D19.05 on Inorganic Constituents
in Water.
Current edition approved Sept. 1, 2012June 1, 2017. Published September 2012June 2017. Originally approved in 1977. Last previous edition approved in 20072012 as
ɛ1
D3557 – 02 (2007)D3557 . – 12. DOI: 10.1520/D3557-12.10.1520/D3557-17.
Platte, J. A., and Marcy, V. M., “A New Tool for the Water Chemist,” Industrial Water Engineering, May 1965.
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
D3557 − 17
D1066 Practice for Sampling Steam
D1068 Test Methods for Iron in Water
D1129 Terminology Relating to Water
D1193 Specification for Reagent Water
D1687 Test Methods for Chromium in Water
D1688 Test Methods for Copper in Water
D1691 Test Methods for Zinc in Water
D1886 Test Methods for Nickel in Water
D1976 Test Method for Elements in Water by Inductively-Coupled Argon Plasma Atomic Emission Spectroscopy
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
D3558 Test Methods for Cobalt in Water
D3559 Test Methods for Lead in Water
D3919 Practice for Measuring Trace Elements in Water by Graphite Furnace Atomic Absorption Spectrophotometry
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—Definitions: For definitions of terms used in these test methods, refer to Terminology D1129.
3.1.1 For definitions of terms used in this standard, refer to Terminology D1129.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 continuing calibration blank, n—a solution containing no analytes (of interest) which is used to verify blank response and
freedom from carryover.
3.2.2 continuing calibration verification, n—a solution (or set of solutions) of known concentration used to verify freedom from
excessive instrumental drift; the concentration is to cover the range of calibration curve.
3.2.3 SCE, n—saturated calomel electrode.
3.2.4 spiking solution, n—the standard solution added to the polarographic cell that is used to quantitate the sample.
3.2.5 stripping peak potential, n—the applied potential versus SCE at which the stripping peak current is a maximum.
3.2.3 SCE, n—saturated calomel electrode.
3.2.6 stripping peak signal, n—the current measured at the stripping peak maximum for a metal.
3.2.7 total recoverable metal, n—a descriptive term relating to the metal forms of cadmium recovered in the acid-digestion
procedure specified in these test standards.
4. Significance and Use
4.1 The test for cadmium is necessary because it is a toxicant and because there is a limit specified for cadmium in potable water
in the National Interim Primary Drinking Water Regulations. This test serves to determine whether the cadmium content of potable
water is above or below the acceptable limit.
5. Purity of Reagents
5.1 Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all reagents shall conform
to the specifications of the Committee on Analytical Reagents of the American Chemical Society. Other grades may be used,
provided it is first ascertained that the reagent is of sufficiently high purity to permit its use without lessening the accuracy of the
determination.
5.2 Unless otherwise indicated, references to water shall be understood to mean reagent water conforming to Specification
D1193, Type I. 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 adversely affecting the bias and precision of the test method. Type II water was specified at the time of
round-robin testing of this test method.
6. Sampling
6.1 Collect the samples in accordance with the applicable ASTM standard as follows: Practices D3370 and D1066.
Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For Suggestions on the testing of reagents not listed by
the American Chemical Society, see Annual Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National
Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.
D3557 − 17
6.2 Samples shall be preserved with HNO (sp gr 1.42) to a pH of 2 or less immediately at the time of collection, normally about
2 mL/L of HNO . If only dissolved cadmium is to be determined, the sample shall be filtered through a 0.45-μm (No. 325)
membrane filter before acidification. The holding time for samples may be calculated in accordance with Practice D4841.
NOTE 1—Alternatively, the pH may be adjusted in the laboratory if the sample is returned within 14 days. within 14 days of collection. However, acid
must be added at least 24 hours before analysis to dissolve any metals that adsorb to the container walls. This could reduce hazards of working with acids
in the field when appropriate.
TEST METHOD A—ATOMIC ABSORPTION, DIRECT
7. Scope
7.1 This test method covers the determination of dissolved and total recoverable cadmium in most waters and wastewaters.
7.2 This test method is applicable in the range from 0.05 to 2.0 mg/L of cadmium. The range may be extended to concentrations
greater than 2.0 mg/L by dilution of the sample.
7.3 This test method has been used successfully with reagent grade water, river water, wastewater, ground water, tap water, lake
water, and refinery effluent. The information on precision and bias may not apply to other water. It is the user’s responsibility to
ensure the validity of this test method for waters of other matrices.
7. Scope
7.1 This test method covers the determination of dissolved and total recoverable cadmium in most waters and wastewaters.
7.2 This test method is applicable in the range from 0.05 to 2.0 mg/L of cadmium. The range may be extended to concentrations
greater than 2.0 mg/L by dilution of the sample.
7.3 This test method has been used successfully with reagent grade water, river water, wastewater, ground water, tap water, lake
water, and refinery effluent. The information on precision and bias may not apply to other water. It is the user’s responsibility to
ensure the validity of this test method for waters of other matrices.
8. Summary of Test Method
8.1 Cadmium is determined by atomic absorption spectrophotometry. Dissolved cadmium is determined by aspirating a portion
of the filtered sample directly with no pretreatment. Total recoverable cadmium is determined by aspirating the sample following
hydrochloric-nitric acid digestion and filtration. The same digestion procedure may be used to determine total recoverable nickel
(Test Methods D1886), chromium (Test Methods D1687), cobalt (Test Methods D3558), copper (Test Methods D1688), iron (Test
Methods D1068), lead (Test Methods D3559), manganese (Test Methods D858), and zinc (Test Methods D1691).
9. Interferences
9.1 Calcium concentrations above 1000 mg/L suppress the cadmium absorption. At 2000 mg/L of calcium the suppression is
19 %.
9.2 Sodium, potassium, sulfate, and chloride (9000 mg/L each), magnesium (4500 mg/L), iron (4000 mg/L), nitrate (100 mg/L),
and nickel, lead, copper, zinc, cobalt, and chromium (10 mg/L each), do not interfere.
9.3 Background correction or a chelation-extraction procedure (see Test Method B) may be necessary to determine low levels
of cadmium in some waters.
NOTE 2—Instrument manufacturer’s instructions for use of the specific correction technique should be followed.
10. Apparatus
10.1 Atomic Absorption Spectrophotometer, for use at 228.8 nm.
NOTE 3—The manufacturer’s instructions shall be followed for all instrumental parameters. A wavelength other than 228.8 nm may be used if it has
been determined to be equally suitable.
10.2 Cadmium Light Source—Either cadmium hollow-cathode lamps or multielement hollow-cathode lamps, or electrodeless-
discharge lamps.
10.3 Pressure-Reducing Valves—The supplies of fuel and oxidant shall be maintained at pressures somewhat higher than the
controlled operating pressure of the instrument by suitable valves.
11. Reagents and Materials
11.1 Cadmium Solution, Stock (1 mL = 1.0 mg Cd)—Dissolve 1.000 g of cadmium metal in a minimum quantity of HNO (sp
gr 1.42) and dilute to 1 L. A purchased cadmium stock solution of appropriate known purity is also acceptable.
11.2 Cadmium Solution, Standard (1 mL = 0.1 mg Cd)—Dilute 100.0 mL of the cadmium stock solution and 1 mL of HNO
(sp gr 1.42) to 1000 mL with water.
D3557 − 17
11.3 Hydrochloric Acid (sp gr 1.19)—Concentrated hydrochloric acid (HCl).
NOTE 4—If the reagent blank concentration is greater than the method detection limit, distill the HCl or use spectrograde acid. (Warning—When HCl
is distilled, an azeotropic mixture is obtained (approximately 6 N HCl.) Therefore, whenever concentrated HCl is specified for the preparation of a reagent
or in the procedure, use double the volume specified if distilled acid is used.)
(Warning—When HCl is distilled, an azeotropic mixture is obtained (approximately 6 N HCl). Therefore, whenever
concentrated HCl is specified for the preparation of a reagent or in the procedure, use double the volume specified if distilled acid
is used.)
11.4 Nitric Acid (sp gr 1.42)—Concentrated nitric acid (HNO ).
NOTE 5—If the reagent blank concentration is greater than the method detection limit, distill the HNO or use a spectrograde acid.
11.5 Nitric Acid (1 + 499)—Add 1 volume of HNO (sp gr 1.42) to 499 volumes of water.
11.6 Oxidant:
11.6.1 Air, which has been passed through a suitable filter to remove oil, water, and other foreign substances is the usual oxidant.
11.7 Fuel:
11.7.1 Acetylene—Standard, commercially available acetylene is the usual fuel. Acetone, always present in acetylene cylinders,
can affect analytical results. The cylinder should be replaced at 345 kPa (50 psi). (Warning—“Purified” grade acetylene containing
a special proprietary solvent rather than acetone should not be used with poly(vinyl chloride) tubing as weakening of the tubing
walls can cause a potentially hazardous situation.)
11.8 Paper Filter—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.
12. Standardization
12.1 Prepare 100 mL each of a blank and at least four standard solutions to bracket the expected cadmium concentration range
of the samples to be analyzed by diluting the standard cadmium solution (11.2) with HNO (1 + 499). Prepare the standards each
time the test is to be performed.performed or as determined by Practice D4841.
12.2 When determining total recoverable cadmium, add 0.5 mL of HNO (sp gr 1.42) to each blank and standard solution and
proceed as directed in 13.213.3 through 13.413.5. After the digestion of the blank and standard solutions has been completed in
13.413.5, return to 12.3 to complete the standardization for total recoverable determinations. When determining dissolved
cadmium, proceed with 12.3.
12.3 Aspirate the blank and standards and record the instrument readings. Aspirate HNO (1 + 499) between each standard.
12.4 Prepare Read directly in concentration if this capability is provided with the instrument or measure the absorbance of the
standards and prepare an analytical curve by plotting the absorbance versus the concentration for each standard on the instrument
software. Alternatively, read directly in concentration if this capability is provided with the instrument.
13. Procedure
13.1 An effective way to clean all glassware to be used for preparation of standard solutions or in the digestion step, or both,
is by soaking the glassware overnight with HNO (1 + 1) and then rinse with reagent.
13.2 Measure 100.0 mL of a well-mixed acidified sample into a 125-mL beaker or flask.
NOTE 6—If only dissolved cadmium is to be determined, start with 13.513.6.
13.3 Add 5 mL of HCl (sp gr 1.19) to each sample.
13.4 Heat the samples (between 65°C and 95°C) on a steam bath or hotplate below boiling in a well-ventilated hood until the
volume has been reduced to 15 to 20 mL, making certain that the samples do not boil.
NOTE 7—For samples containing appreciable amounts of suspended matter or dissolved solids, the amount of reduction in volume is left to the
discretion of the analyst.
NOTE 8—Many laboratories have found block digestion systems a useful way to digest samples for trace metals analysis. Systems typically consist of
either a metal or graphite block with wells to hold digestion tubes. The block temperature controller must be able to maintain uniformity of temperature
across all positions of the block. The digestion block must be capable of maintaining a temperature between 65°C and 95°C. For trace metals analysis,
the digestion tubes should be constructed of polypropylene and have a volume accuracy of at least 0.5 %. All lots of tubes should come with a certificate
of analysis to demonstrate suitability for their intended purpose.
13.5 Cool and filter the samples through a suitable filter (11.8) such as fine-textured, acid-washed, ashless, paper into 100-mL
volumetric flasks. Wash the filter paper two or three times with water and adjust to volume.
13.6 Aspirate each filtered and acidified sample and determine its absorbance or concentration at 228.8 nm. Aspirate HNO
(1 + 499) between each sample.
D3557 − 17
14. Calculation
14.1 Calculate the concentration of cadmium in the sample, in milligrams per litre, using the analytical curve prepared in 12.4.
15. Precision and Bias
15.1 The precision of this test method was tested by 17 laboratories in reagent water, river water, wastewater, ground water, tap
water, lake water, and refinery effluent. The overall bias and precision of this test method, within its designated range, varies with
the quantity being measured in accordance with Table 1.
15.2 These data may not apply to waters of the matrices, therefore, it is the responsibility of the analyst to ensure the validity
of the test method in other matrices.
D2777 – 77, which was in place at the time of collaborative
15.3 Precision and bias for this test method conforms to Practice
testing. Under the allowances made in 1.4 of Practice D2777 – 08, – 13, these precision and bias data meet existing requirements
for interlaboratory studies of Committee D19 test methods.
TEST METHOD B—ATOMIC ABSORPTION, CHELATION-EXTRACTION
16. Scope
16.1 This test method covers the determination of dissolved and total recoverable cadmium in most waters and brines.
16.2 This test method is applicable in the range from 5 to 200 μg/L of cadmium. The range may be extended to concentrations
greater than 200 μg/L by dilution of the sample.
16.3 This test method has been used successfully with reagent grade water, river water, wastewater, ground water, tap water,
lake water, and refinery effluent. The information on precision and bias may not apply to other water.
16.4 It is the responsibility of the analyst to determine the acceptability of this test method when analyzing other matrices.
16. Scope
16.1 This test method covers the determination of dissolved and total recoverable cadmium in most waters and brines.
16.2 This test method is applicable in the range from 5 to 200 μg/L of cadmium. The range may be extended to concentrations
greater than 200 μg/L by dilution of the sample.
16.3 This test method has been used successfully with reagent grade water, river water, wastewater, ground water, tap water,
lake water, and refinery effluent. The information on precision and bias may not apply to other water.
16.4 It is the responsibility of the analyst to determine the acceptability of this test method when analyzing other matrices.
17. Summary of Test Method
17.1 Cadmium is determined by atomic absorption spectrophotometry. The element, either dissolved or total recoverable, is
chelated with pyrrolidine dithiocarbamic acid and extracted with chloroform. The extract is evaporated to dryness, treated with hot
nitric acid to destroy organic matter, dissolved in hydrochloric acid, and diluted to a specified volume with water. A portion of the
resulting solution is then aspirated into the air-acetylene flame of the spectrophotometer. The digestion procedure summarized in
8.1 is used to determine total recoverable cadmium. The same chelation-extraction procedure may be used to determine nickel (Test
Methods D1886), cobalt (Test Methods D3558), copper (Test Methods D1688), iron (Test Methods D1068), lead (Test Methods
D3559), and zinc (Test Methods D1691).
Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D19-1030. Contact ASTM Customer
Service at [e-mail].
TABLE 1 Determination of Bias and Precision for Cadmium by
Atomic Absorption, Direct
Statistically
Amount Added, Amount
S , mg/L S , mg/L % Bias Significant,
T O
mg/L Found, mg/L
95 % Level
Reagent Water
0.20 0.200 0.033 0.033 0.0 No
0.60 0.592 0.034 0.026 −1.3 No
1.60 1.521 0.111 0.061 −4.9 Yes
Water of Choice
0.20 0.200 0.033 0.033 0.0 No
0.60 0.589 0.040 0.026 −1.8 No
1.60 1.511 0.114 0.061 −5.6 Yes
D3557 − 17
18. Interferences
18.1 See Section 9.
19. Apparatus
19.1 All items of apparatus described in Section 10 are required.
20. Reagents and Materials
20.1 Bromphenol Blue Indicator Solution (1 g/L)—Dissolve 0.1 g of bromphenol blue in 100 mL of 50 % ethanol or
isopropanol.
20.2 Cadmium Solution, Stock (1.0 mL = 1.0 mg Cd)—See 11.1.
20.3 Cadmium Solution, Intermediate (1.0 mL = 50 μg Cd)—Dilute 50.0 mL of stock cadmium solution and 1 mL of HNO (sp
gr 1.42) to 1 L with water.
20.4 Cadmium Solution, Standard (1.0 mL = 0.5 μg Cd)—Dilute 10 mL of cadmium intermediate solution and 1 mL of HNO
(sp gr 1.42) to 1 L with water.
20.5 Chloroform (CHCl ).
20.6 Hydrochloric Acid (sp gr 1.19)—Concentrated hydrochloric acid (HCl) (see Note 4).
20.7 Hydrochloric Acid (1 + 2)—Add 1 volume of HCl (sp gr 1.19) to 2 volumes of water.
20.8 Hydrochloric Acid (1 + 49)—Add 1 volume of HCl (sp gr 1.19) to 49 volumes of water.
20.9 Nitric Acid (sp gr 1.42)—Concentrated nitric acid (HNO ) (see Note 5).
20.10 Pyrrolidine Dithiocarbamic Acid-Chloroform Reagent—Add 36 mL of pyrrolidine to 1 L of CHCl . Cool the solution and
add 30 mL of CS in small portions, swirling between additions. Dilute to 2 L with CHCl . The reagent can be used for several
2 3
months if stored in a cool, dark place. (Warning—All components of this reagent are highly toxic. Carbon disulfide is also highly
flammable. Prepare and use in a well-ventilated hood. Avoid inhalation and direct contact.)
20.11 Sodium Hydroxide Solution (100 g/L)—Dissolve 100 g of sodium hydroxide (NaOH) in water, cool, and dilute to 1 L.
20.12 Materials—Use materials from 11.6, 11.7and , and 11.711.8.
21. Standardization
21.1 Prepare a blank and sufficient standard containing from 0.0 to 20 μg of cadmium by diluting 0.0 to 40.0-mL portions of
cadmium standard solution to 100 mL with water.
21.2 When determining total recoverable cadmium use 125-mL beakers or flasks, add 0.5 mL of HNO (sp gr 1.42) and proceed
as directed in 22.222.3 through 22.1522.16. When determining dissolved cadmium, use 250-mL separatory funnels and proceed
as directed in 22.522.6 through 22.1522.16.
21.3 Construct an analytical curve by reading concentrations from the instrument software. Alternatively, read directly in
concentration if this capability is provided with the instruments.Read directly in concentration if this capability is provided with
the instrument or measure the absorbance of the standards and construct an analytical curve by reading absorbances from the
instrument software.
22. Procedure
22.1 An effective way to clean all glassware to be used for preparation of standard solutions or in the digestion step, or both,
is by soaking the glassware overnight with HNO (1 + 1) and then rinse with reagent.
22.2 Measure a volume of a well-mixed acidified sample containing less than 20.0 μg of cadmium (100-mL maximum) into a
125-mL beaker or flask and adjust the volume to 100 mL with water.
NOTE 9—If only dissolved cadmium is to be determined, measure a volume of filtered and acidified sample containing less than 20 μg of cadmium
(100-mL maximum) into a 250-mL separatory funnel, and begin with 22.522.6.
22.3 Add 5 mL of HCl (sp gr 1.19) to each sample.
22.4 Heat the samples (between 65°C and 95°C) on a steam bath or hotplate below boiling in a well-ventilated hood until the
volume has been reduced to 15 to 20 mL, making certain that the samples do not boil.
NOTE 10—When analyzing brine samples and samples containing appreciable amounts of suspended matter or dissolved solids, the amount of reduction
in volume is left to the discretion of the analyst.
NOTE 11—Many laboratories have found block digestion systems a useful way to digest samples for trace metals analysis. Systems typically consist
of either a metal or graphite block with wells to hold digestion tubes. The block temperature controller must be able to maintain uniformity of temperature
of across all positions of the block. The digestion block must be capable of maintaining a temperature between 65°C and 95°C. For trace metals analysis,
the digestion tubes should be constructed of polypropylene and have a volume accuracy of at least 0.5 %. All lots of tubes should come with a certificate
D3557 − 17
of analysis to demonstrate suitability for their intended purpose.
22.5 Cool and filter the samples through a suitable filter, filter (11.8), such as fine-textured, acid-washed, ashless paper, into
250-mL separatory funnels. Wash the filter paper two or three times with water and adjust the volume to approximately 100 mL.
22.6 Add 2 drops of bromphenol blue indicator solution and mix.
22.7 Adjust the pH by addition of NaOH (100 g/L) solution until a blue color persists. Add HCl (1 + 49) by drops until the blue
color just disappears; then add 2.5 mL of HCl (1 + 49) in excess. The pH at this point should be 2.3.
NOTE 12—The pH adjustment of 22.622.7 may be made with a pH meter instead of using an indicator.
22.8 Add 10 mL of pyrrolidine dithiocarbamic acid-chloroform reagent and shake vigorously for 2 min. (Warning—See Note
12.Warning)—see Note 12.)
22.9 Plug the tip of the separatory funnel with cotton, allow the phases to separate, and drain the CHCl phase into a 100-mL
beaker.
22.10 Repeat the extraction with 10 mL of CHCl and drain the CHCl layer into the same beaker.
3 3
NOTE 13—If color still remains in the CHCl extract, reextract the aqueous phase until the CHCl layer is colorless.
3 3
22.11 Place the beaker on a hotplate set at low heat or on a steam bath, and evaporate to near dryness. Remove beaker from
heat and allow residual solvent to evaporate without further heating. (Warning—Perform in a well-ventilated hood.Warning)—
Perform in a well-ventilated hood.)
22.12 Hold the beaker at a 45° angle, and slowly add dropwise 2 mL of HNO (sp gr 1.42), rotating the beaker to effect thorough
contact of the acid with the residue.
22.12.1 If acid is added to the beaker in a vertical position, a violent reaction will occur, accompanied by high heat and
spattering.
22.13 Place the beaker on a hotplate set at low heat or on a steam bath, and evaporate to near dryness. Remove beaker from
heat and allow residual solvent to evaporate without further heating.
22.14 Add 2 mL of HCl (1 + 2) to the beaker, and heat, while swirling for 1 min.
22.15 Cool and quantitatively transfer the solution to a 10-mL volumetric flask and adjust to volume with water.
22.16 Aspirate each sample and record the scale readings or concentrations at 228.8 nm.
23. Calculation
23.1 Determine the weight of cadmium in each sample by referring to the analytical curve. Calculate the concentration of
cadmium in micrograms per litre as follows:
Cadmium, µg/L5 ~1000/A! 3B (1)
where:
1000 = 1000 mL / Liter
1000 = 1000 mL / L,
A = volume of original sample, mL, and
B = weight of cadmium in sample, μg.
24. Precision and Bias
24.1 The precision of this test method was tested by seven laboratories in reagent water, river water, waste water, ground water,
tap water, lake water, and refinery effluent. The overall precision of this test method, within its designated range, varies with the
quantity being measured according to Table 2.
TABLE 2 Determination of Bias and Precision for Cadmium by
Atomic Absorption, Chelation-Extraction
Statistically
Amount Added, Amount
S , μg/L S , μg/L % Bias Significant,
T O
μg/L Found, μg/L
95 % Level
Reagent Water
30 30.6 4.3 3.3 +2.1 No
80 76.9 9.9 6.2 −3.9 No
160 151.0 21.3 3.9 −5.6 No
Water of Choice
30 28.9 7.0 4.5 −3.6 No
80 76.9 10.5 3.6 −3.9 No
160 152.7 19.7 9.1 −4.6 No
D3557 − 17
24.2 These data may not apply to waters of other matrices, therefore, it is the responsibility of the analyst to ensure the validity
of the test method in a particular matrix.
24.3 Precision and bias for this test method conforms to Practice D2777 – 77, which was in place at the time of collaborative
testing. Under the allowances made in 1.4 of Practice D2777 – 08, – 13, these precision and bias data meet existing requirements
for interlaboratory studies of Committee D19 test methods.
TEST METHOD C—DIFFERENTIAL PULSE ANODIC STRIPPING VOLTAMMETRY
25. Scope
25.1 This test method describes the determination of cadmium in water and wastewaters using differential pulse anodic stripping
voltammetry.
25.2 This test method is applicable up to a concentration of 100 μg/L cadmium. Higher concentrations can be determined by
dilution.
25.3 The lower limit of detection for cadmium is 1.0 μg/L.
NOTE 14—The lower limit of detection for differential pulse anodic stripping voltammetry is not absolute and can easily be lowered by changing the
experimental parameters as described in Appendix X1. However, these variations have not been interlaboratory tested.
25.4 It is the responsibility of the analyst to determine the acceptability of this test method when analyzing other matrices.
25. Scope
25.1 This test method describes the determination of cadmium in water and wastewaters using differential pulse anodic stripping
voltammetry.
25.2 This test method is applicable up to a concentration of 100 μg/L cadmium. Higher concentrations can be determined by
dilution.
25.3 The lower limit of detection for cadmium is 1.0 μg/L.
NOTE 14—The lower limit of detection for differential pulse anodic stripping voltammetry is not absolute and can easily be lowered by changing the
experimental parameters as described in Appendix X1. However, these variations have not been interlaboratory tested.
25.4 It is the responsibility of the analyst to determine the acceptability of this test method when analyzing other matrices.
26. Summary of Test Method
26.1 This test method determines the total recoverable concentration of cadmium in water and wastewater. The same digestion,
sample preparation, and analysis procedure may be used to determine total recoverable lead (Test Methods D3559) simultaneously
with cadmium.
26.2 The sample is digested with nitric acid in a polarographic cell: 0.2 M ammonium citrate buffer (pH 3.0) and 10 %
hydroxylamine solution are added. The solution is warmed to dissolve the cadmium. Warming with hydroxylamine eliminates
interference from ferric iron by reducing it to ferrous.
26.3 After cooling, this sample is de-aerated, and the cadmium is deposited into a hanging mercury drop electrode with a surface
area of 1.5 to 3.0 mm at a constant potential of − 0.80 V versus saturated calomel electrode (SCE). The cadmium is then stripped
back into solution using the differential pulse scanning mode, and the current is measured during the stripping step.
(Warning—Mercury has been designated by many regulatory agencies as a hazardous material that can cause serious medical
issues. Mercury, or its vapor, has been demonstrated to be hazardous to health and corrosive to materials. Caution should be taken
when handling mercury and mercury containing products. See the applicable product Safety Data Sheet (SDS) for additional
information. Users should be aware that selling mercury and/or mercury containing products into your state or country may be
prohibited by law.)
26.4 The stripping peak height is proportional to the concentration of the cadmium, and the stripping peak potential is a
qualitative measure of the cadmium in solution.
27. Interferences
27.1 Selenium does not interfere up to 50 μg/L. Interferences from selenium concentration up to 1000 μg/L may be overcome
by adding ascorbic acid which reduces selenium (IV) to selenium metal and eliminates the interference.
27.2 When ferric ions are present at levels greater than cadmium, interference may occur from oxidizing the deposited metal
out of the amalgam. Interference by ferric iron at concentrations as high as 20 mg/L is eliminated by warming with hydroxylamine.
Ferric ions are reduced to ferrous ions by the hydroxylamine, and the interference caused by the presence of iron is eliminated.
27.3 The presence of a neighboring stripping peak which is <100 mV from that of cadmium will interfere.
D3557 − 17
28. Apparatus
28.1 Polarographic Instrumentation capable of performing differential pulse work.
28.2 Hanging Mercury Drop Electrode.
28.3 Reagent Purifier System.
28.4 Counter Electrode, platinum.
28.5 Salt Bridge, with slow leakage fritted glass tip, to isolate saturated calomel electrode from the test solution.
28.6 Magnetic Stirrer—The magnetic stirrer used must have a separate On/Off switch, so that uniform rotational speed can be
maintained. A0.5-in. (13-mm) magnetic stirring bar is also required.
28.7 pH Meter.
28.8 Hot Plate. Plate or Hot Block Digestion System.
28.9 Micropipettes incorporating disposable plastic tips are used. The sizes required are 10, 20, 50, and 100 μL.
29. Reagents and Materials
29.1 Purity of Reagents—The ammonium citrate solution and redistilled nitric acid are purified or purchased to contain less than
1 μg/L of cadmium.
29.2 Ammonium Citrate Buffer—Dissolve 42 g of citric acid in 800 mL of water and add enough ammonium hydroxide to bring
the pH to 3.0 6 0.2. Dilute to 1000 mL with water and place in the cell of the reagent purifier system. Purify for a minimum of
36 h at a potential of − 1.3 V versus SCE at a mercury pool working electrode. De-aerate the supporting electrolyte during the
purification process. If the buffer contains less than 1 μg/L of cadmium, the purification step may be omitted, providing new buffer
is prepared every 2 weeks. The electrolyzed buffer is stable against bacterial growth for at least 1 month.
NOTE 15—To prevent bacterial growth in the unpurified buffer for a month, sterilize by autoclaving for 15 min at 121°C and 1.03 × 10103.4 PakPa
(15 psi).
29.3 Aqua Regia (1 + 1)—Add 1 volume of nitric acid (sp gr 1.42) to 4 volumes of water. Then add 3 volumes of hydrochloric
acid (sp gr 1.19). (Warning—Toxic fumes may be released. Prepare and use in a ventilated hood.Warning)—Toxic fumes may be
released. Prepare and use in a ventilated hood.)
29.4 Ascorbic Acid (100 g/L)—Dissolve 10.0 g of L-ascorbic acid in reagent water and dilute to 100 mL.
29.5 Hydrochloric Acid (sp gr 1.19)—Concentrated hydrochloric acid (HCl).
29.6 Hydroxylamine Solution (100 g/L)—Dissolve 5.00 g of hydroxylamine hydrochloride (NH OH·HCl) in reagent water and
dilute to 50 mL.
29.7 Nitric Acid (sp gr 1.42) —Redistilled concentrated nitric acid (HNO ).
29.8 Nitric Acid (sp gr 1.42)—Concentrated nitric acid (HNO ).
29.9 Nitric Acid (1 + 160)—Add 1 volume of nitric acid to 160 volumes of water.
29.10 Nitric Acid (2 + 3)—Add 2 volumes of nitric acid, reagent grade, to 3 volumes of water.
29.11 Purified Nitrogen—Nitrogen employed for de-oxygenation must be sufficiently oxygen-free so that a differential pulse
polarographic scan from − 0.20 to − 0.80 V versus SCE of the ammonium citrate buffer solution, after 10-min de-aeration at 10
mm /min, gives a signal no more than 0.1 μA. See Appendix X2 to learn methods of gas purification.
29.12 Standard Solutions—Obtain standard 100 mg/L reference solution for cadmium or prepare from cadmium metal.
29.12.1 Cadmium Solution, Stock (1 mL = 1.0 mg Cd)—Dissolve 1.000 g cadmium metal in a minimum quantity of HNO (sp
gr 1.42) and dilute to 1000 mL. A purchased cadmium stock solution of appropriate known purity is also acceptable.
29.12.2 Cadmium Solution, Standard (1 mL = 0.1 mg Cd)—Dilute 100.0 mL of cadmium stock solution and 1 mL of HNO (sp
gr 1.42) to 1000 mL with water.
Two instruments that have been found satisfactory for this purpose are the polarographic analyzer with mechanical drop timer, Model 174A, and the Houston
Omnigraphic X-Y Recorder, Model 2200-3-3, available from Princeton Applied Research, Princeton, NJ. Another instrument, the Charge Transfer Analyzer, Model 3040,
available from Environmental Sciences Associates (ESA), Bedford, MA, has also been found satisfactory for this purpose. For settings on ESA Model 3040 equivalent to
those in 33.10, see ESA Application Note CTA-AN-1.
The hanging mercury drop electrode, Model 9323, or the automated hanging mercury drop electrode, Model 314, manufactured by Princeton Applied Research, have
been found satisfactory for this purpose.
Both the Electrolyte Purification System, Model 9500, available from Princeton Applied Research, and the PM Reagent Cleaning System, Model 2014, available from
ESA, have been found satisfactory for this purpose.
A Vycor tip, available from Corning Glass Works, Corning, NY, has been found satisfactory for this purpose.
Acids that may contain suitably low levels of cadmium (and lead) are the redistilled reagents or equivalent available from G. Frederick Smith Chemical Co., 867
McKinley Ave., Columbus, OH 43223.
Certified Atomic Absorption Standards, (Fisher Scientific Co., Fairlawn, NJ) have been found satisfactory for this purpose.
D3557 − 17
30. Hazards
30.1 The liquid mercury used for the hanging mercury drop electrode forms a toxic vapor, and the liquid itself is toxic. Handle
with gloves in a ventilated hood. (Warning—Mercury has been designated by many regulatory agencies as a hazardous material
that can cause serious medical issues. Mercury, or its vapor, has been demonstrated to be hazardous to health and corrosive to
materials. Caution should be taken when handling mercury and mercury containing products. See the applicable product Safety
Data Sheet (SDS) for additional information. Users should be aware that selling mercury and/or mercury containing products into
your state or country may be prohibited by law.)
31. Calibration
31.1 After a differential pulse anodic stripping curve is run on the sample solution, the anodic stripping curve is quantitated
using the technique of standard additions.
31.2 Prepare 100 mg/L stock solutions by diluting 5.00 mL of the cadmium standard solutions to 50.0 mL with HNO (1 + 160).
These can be stored for several weeks if kept in a plastic bottle.
31.3 Prepare spiking solution by diluting 5.00 mL of the cadmium stock solution to 50.0 mL with HNO (1 + 160). Prepare fresh
daily. Alternatively, if lead is to be quantified too, both metals may be added to a single spiking solution. The best procedure here
is to prepare the spiking solution with each metal in the ratio expected in the sample. (Example: If lead is expected to be 5 times
the cadmium, prepare a spiking solution with lead and cadmium in a 5 to 1 ratio).
5 3
31.4 Add an appropriate aliquot of the cadmium spiking solution to the sample in the cell. De-aerate for 5 min at 10 mm /min
to mix the solution and remove oxygen added with the spike.
31.5 Repeat the analysis procedure beginning with 32.8.
32. Procedure
32.1 Soak voltammetric cells (or digestion vessels) overnight in concentrated HNO , and verify that the reagent blank is less
than 1 μg/L for cadmium. Omit the soaking step if the reagent blank of the unsoaked cells is less than 1 μg/L. Clean other glassware
with HNO (2 + 3). See Annex A1 for a procedure to clean glassware.
NOTE 16—Soaking the cells of digestion vessels in aqua regia (1 + 1) for 1 h improves blank values.
32.2 Place exactly 10.0 mL of a well-mixed sample containing less than 100 μg/L of cadmium into the cell.
NOTE 17—Concentrations greater than 100 μg/L of cadmium may be determined by dilution.
32.3 Add 2.0 mL of redistilled HNO to each sample.
32.4 Evaporate the samples without boiling (between 65°C and 95°C) on a hot plate or steam bath below boiling in a
well-ventilated hood until the sample just reaches dryness (do not “bake” as this may cause losses due to volatilization). 32.3 and
32.4 may be repeated if necessary for samples containing large amounts of organic matter.
32.5 Cool, add 5.0 mL of ammonium citrate buffer, and 100 μL of hydroxylamine solution. Warm the solution 15 min to reduce
the ferric iron and to effect dissolution of the metals in the buffer.
32.6 Bring to volume of 10 to 12 mL with ammonium citrate buffer (pH 3.0). The exact volume need not be known because
the standard additions method will be used to quantitate.
32.6.1 To overcome selenium at levels up to 1000 μg/L, add 1 mL of ascorbic acid.
5 3
32.7 De-aerate for 10 min at 10 mm /min with an oxygen-free stream of nitrogen.
32.8 After de-aeration is complete, extrude with the hanging mercury drop electrode a mercury droplet whose area is 1.5 to 3
2 12
mm , as determined in Annex A2. Turn on the magnetic stirrer and adjust the stirring rate so that the solution beneath the mercury
droplet is well stirred but there is no visible movement of the mercury droplet. The stirrer is turned on 15 s prior to deposition to
assure uniform rotational speed. (Warning—Mercury has been designated by many regulatory agencies as a hazardous material
that can cause serious medical issues. Mercury, or its vapor, has been demonstrated to be hazardous to health and corrosive to
materials. Caution should be taken when handling mercury and mercury containing products. See the applicable product Safety
Data Sheet (SDS) for additional information. Users should be aware that selling mercury and/or mercury containing products into
your state or country may be prohibited by law.)
32.9 Connect the cell. Deposit at − 0.80 V versus SCE for exactly 2 min, switch off stirrer, and wait exactly 30 s before
beginning the scan. The quiescent period between deposition and scan allows convection to cease.
32.9.1 Annex A3 gives typical stripping curve shapes, peak potential, and sensitivities (in μA/5 μg/L) for cadmium deposited
into a mercury droplet with a 2.9-mm area for 2 min with stirring plus 30 s without stirring.
With the Model 9323 hanging mercury drop electrode manufactured by Princeton Applied Research, a mercury droplet with suitable surface area is formed by rotating
the micrometer six small vertical divisions.
D3557 − 17
32.10 The following typical settings are for polarographic instrumentation capable of performing differential pulse work:
electrode, hanging mercury drop electrode (area 1.5 to 3 mm ); initial potential, − 0.80 V versus SCE; scan rate, 5 mV/s; scan
direction, “ + ”; modulation amplitude, 25 mV; current range, 1 to 20 μA; drop time, 0.5 s; display direction,“−” ; direction, “ −
”; low pass filter, off; mode, differential pulse; deposition time, 2 min with stirring plus 30 s quiescent; scan range, stop − 0.20 V.
32.10.1 The linearity of this test method has been tested up to currents of 20 μA. If the sample gives stripping peaks with
currents larger than 20 μA, one may decrease the deposition time (see Appendix X1), although this technique has not been
interlaboratory tested. The recommended procedure is to dilute the sample and proceed as in 32.2 through 32.10.
32.11 To obtain a blank, place exactly 10.0 mL of Type IV water into the cell and proceed as in 32.2 through 32.10.
33. Calculation
33.1 Calculate the concentration of cadmium determined by the standard addition procedure as follows:
i vC
1 s
C 5 (2)
u
i v1~i 2 i !V
1 2 1
where:
i = stripping peak height for the sample,
i = stripping height for the sample plus standard,
v = volume of standard taken for spiking,
V = volume of sample before digestion,
C = concentration of standar
...