ASTM E1615-22

Standard Test Method for Determination of Trace Quantities of Iron by Visible Spectrophotometry

SIGNIFICANCE AND USE
4.1 This test method is suitable for determining trace concentrations of iron in a wide variety of products, provided that appropriate sample preparation has rendered the iron and sample matrix soluble in water or other suitable solvent. Each sample matrix must be investigated for suitability using this test method.  
4.2 This test method assumes that the amount of color developed is proportional to the amount of iron in the test solution. The calibration curve is linear over the specified range.
SCOPE
1.1 This test method covers the determination of iron in aromatic hydrocarbons, their derivatives, and related chemicals in the range from 0.01 to 0.2 μg/g using [3-(2-pyridyl)-5,6-bis(4-phenylsulfonic acid)-1,2,4-triazine, monosodium salt, monohydrate] (PDTS)2 reagent solution. The range may be extended through the use of a 5- or 10-cm cell or by suitable dilution of the sample solution.  
1.2 The limit of detection (LOD) is 0.01 µg/kg for iron and the limit of quantitation (LOQ) is 0.04 µg/kg.
Note 1: The LOD and LOQ were calculated using data from the ILS.  
1.3 This test method is intended to be general for the final steps in the determination of iron and does not include procedures for sample preparation.  
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.5 Review the current Safety Data Sheets (SDS) for detailed information concerning toxicity, first-aid procedures, and safety precautions.  
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For specific warning statements, see Section 8.  
1.7 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: 30-Apr-2022
• ICS: 77.120.99 - Other non-ferrous metals and their alloys
• Technical Committee: D16 - Aromatic, Industrial, Specialty and Related Chemicals
• Drafting Committee: D16.04 - Instrumental Analysis

Relations

• Refers: ASTM D6809-02(2016) - Standard Guide for Quality Control and Quality Assurance Procedures for Aromatic Hydrocarbons and Related Materials
• Effective Date: 01-Nov-2016
• Refers: ASTM D6143-13 - Standard Test Method for Iron Content of Bisphenol A (4,4<emph type="bdit">&prime;</emph > - Isopropylidenediphenol)
• Effective Date: 01-Jun-2013
• Refers: ASTM D6143-09 - Standard Test Method for Iron Content of Bisphenol A (4,4&#180; - Isopropylidenediphenol)
• Effective Date: 01-Dec-2009
• Refers: ASTM E275-08 - Describing and Measuring Performance of Ultraviolet and Visible Spectrophotometers
• Effective Date: 15-Oct-2008
• Refers: ASTM D6809-02(2007) - Standard Guide for Quality Control and Quality Assurance Procedures for Aromatic Hydrocarbons and Related Materials
• Effective Date: 01-Jun-2007
• Refers: ASTM D1193-06 - Standard Specification for Reagent Water
• Effective Date: 01-Mar-2006
• Refers: ASTM D6143-05 - Standard Test Method for Iron Content of Bisphenol A (4,4&#180; - Isopropylidenediphenol)
• Effective Date: 01-Jul-2005
• Refers: ASTM E60-98(2004) - Standard Practice for Analysis of Metals, Ores, and Related Materials by Molecular Absorption Spectrometry
• Effective Date: 01-May-2004
• Refers: ASTM D6809-02 - Standard Guide for Quality Control and Quality Assurance Procedures for Aromatic Hydrocarbons and Related Materials
• Effective Date: 10-Jun-2002
• Refers: ASTM E275-01 - Standard Practice for Describing and Measuring Performance of Ultraviolet, Visible, and Near-Infrared Spectrophotometers
• Effective Date: 10-Feb-2001
• Refers: ASTM E275-93 - Standard Practice for Describing and Measuring Performance of Ultraviolet, Visible, and Near-Infrared Spectrophotometers
• Effective Date: 10-Feb-2001
• Refers: ASTM D1193-99e1 - Standard Specification for Reagent Water
• Effective Date: 10-Feb-1999
• Refers: ASTM D1193-99 - Standard Specification for Reagent Water
• Effective Date: 10-Feb-1999
• Refers: ASTM E60-98 - Standard Practice for Analysis of Metals, Ores, and Related Materials by Molecular Absorption Spectrometry
• Effective Date: 10-May-1998
• Refers: ASTM D6143-97 - Standard Test Method for Iron Content of Bisphenol A (4,4&#180 - Isopropylidenediphenol)
• Effective Date: 10-Jun-1997

Overview

ASTM E1615-22 establishes a standard test method for the determination of trace quantities of iron using visible spectrophotometry. This internationally recognized standard is essential for laboratories and industry professionals needing reliable, quantitative analysis of iron content, especially at very low concentration levels. The test is applicable across a broad spectrum of aromatic hydrocarbons, their derivatives, and related chemicals. It utilizes the [3-(2-pyridyl)-5,6-bis(4-phenylsulfonic acid)-1,2,4-triazine, monosodium salt, monohydrate] (PDTS) reagent solution for colorimetric detection of iron.

This spectrophotometric method is especially valued for its sensitivity, offering a limit of detection (LOD) of 0.01 µg/kg and a limit of quantitation (LOQ) of 0.04 µg/kg, making it well-suited for environments where iron contamination at sub-ppm levels must be strictly controlled.

Key Topics

• Scope of Application

  • Designed for aromatic hydrocarbons, their derivatives, and related chemicals.
  • Trace iron detection in the range 0.01 to 0.2 μg/g, extendable by cell length or sample dilution.

• Scientific Basis

  • Iron reacts with PDTS reagent forming a magenta-colored complex.
  • The intensity of coloring, measured at 560 nm, reflects the iron concentration through Beer-Lambert law linearity.

• Accuracy and Precision

  • High sensitivity and selectivity with proven repeatability and reproducibility from interlaboratory studies.
  • Quality assurance supported by precision statements and control chart recommendations.

• Sample Preparation

  • The method applies to samples where iron and matrix are fully soluble in water or suitable solvents.
  • Complete procedures for analysis, including calibration and absorbance measurement, are specified but do not cover initial sample preparation.

• Interferences and Limitations

  • Ions absorbing at 560 nm and certain heavy metals can interfere.
  • The pH of the final solution should remain between 4 and 9 for optimal results.
  • All glassware must be free of iron, and sample matrices should be validated for method suitability.

• Safety and Regulatory Considerations

  • Emphasizes adherence to current Safety Data Sheets (SDS) and local regulations.
  • Special handling of reagents, especially those containing thiols, is mandated.

Applications

ASTM E1615-22 is widely applied in:

• Quality Assurance & Control:

  • Monitoring iron contamination in manufacturing processes, particularly in the chemical and petrochemical sectors.
  • Routine determination of trace iron in industrial products to ensure compliance with specifications.

• Research & Development:

  • Supporting new product development where trace elemental analysis is critical.

• Environmental & Regulatory Testing:

  • Assessing contamination and ensuring regulatory compliance for chemical products.

• Process Troubleshooting:

  • Identifying sources of iron contamination in process streams and end products.

• Batch Certification:

  • Offering documented assurance of iron concentrations for supply chain transparency and customer requirements.

Related Standards

Professionals working with ASTM E1615-22 may also reference these related ASTM and industry standards:

• ASTM D1193 - Specification for Reagent Water
• ASTM D6143 - Test Method for Iron Content in Bisphenol A
• ASTM D6809 - Guide for Quality Control Procedures in Aromatic Hydrocarbons
• ASTM E60 - Practice for Analysis of Metals/Ores by Spectrophotometry
• ASTM E180 - Practice for Determining Precision of ASTM Methods for Industrial and Specialty Chemicals
• ASTM E200 - Practice for Preparation, Standardization, and Storage of Reagent Solutions
• ASTM E275 - Practice for Measuring Performance of UV and Visible Spectrophotometers

Adherence to ASTM E1615-22 in conjunction with these supporting documents promotes consistent, high-quality results and confidence in iron determinations by visible spectrophotometry in the chemical industry and analytical laboratories.

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: E1615 − 22
Standard Test Method for
Determination of Trace Quantities of Iron by Visible
Spectrophotometry
This standard is issued under the fixed designation E1615; 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* 2. Referenced Documents
1.1 This test method covers the determination of iron in 2.1 ASTM Standards:
aromatichydrocarbons,theirderivatives,andrelatedchemicals D1193 Specification for Reagent Water
in the range from 0.01 to 0.2 µg/g using [3-(2-pyridyl)-5,6- D6143 Test Method for Iron Content of Bisphenol A (4,4' -
bis(4-phenylsulfonic acid)-1,2,4-triazine, monosodium salt, Isopropylidenediphenol)
monohydrate] (PDTS) reagent solution. The range may be D6809 Guide for Quality Control and Quality Assurance
extended through the use of a 5- or 10-cm cell or by suitable Procedures for Aromatic Hydrocarbons and Related Ma-
dilution of the sample solution. terials
E60 Practice for Analysis of Metals, Ores, and Related
1.2 The limit of detection (LOD) is 0.01 µg/kg for iron and
Materials by Spectrophotometry
the limit of quantitation (LOQ) is 0.04 µg/kg.
E180 Practice for Determining the Precision of ASTM
NOTE 1—The LOD and LOQ were calculated using data from the ILS.
Methods for Analysis and Testing of Industrial and Spe-
1.3 This test method is intended to be general for the final cialty Chemicals (Withdrawn 2009)
E200 Practice for Preparation, Standardization, and Storage
steps in the determination of iron and does not include
procedures for sample preparation. of Standard and Reagent Solutions for ChemicalAnalysis
E275 Practice for Describing and Measuring Performance of
1.4 The values stated in SI units are to be regarded as
Ultraviolet and Visible Spectrophotometers
standard. No other units of measurement are included in this
standard.
3. Summary of Test Method
1.5 Review the current Safety Data Sheets (SDS) for de-
3.1 Certain molecules like PDTS which contains the ferroin
tailedinformationconcerningtoxicity,first-aidprocedures,and
group -N=C-C=N- react as a bidentate ligands with ferrous
safety precautions.
metal ions forming a colored complex species.
1.6 This standard does not purport to address all of the
3.2 This test method is based upon a photometric determi-
safety concerns, if any, associated with its use. It is the
2,5
nation of the ferroin PDTS complex with the iron (II) ion.
responsibility of the user of this standard to establish appro-
The sample is dissolved in a suitable solvent, any ferric iron is
priate safety, health, and environmental practices and deter-
reduced to ferrous iron when the iron is reacted with PDTS
mine the applicability of regulatory limitations prior to use.
reagent solution which will also convert the dissolved iron
For specific warning statements, see Section 8.
compoundstoformamagentacoloriron(II)complex.Theiron
1.7 This international standard was developed in accor-
content of the sample solution is determined by measurement
dance with internationally recognized principles on standard-
of the magenta color at 560 nm using a suitable photometer.
ization established in the Decision on Principles for the
3.3 Quantitation of the iron content in the sample is accom-
Development of International Standards, Guides and Recom-
plished by measuring the intensity of the color produced by the
mendations issued by the World Trade Organization Technical
magenta complex described above. The Beer-Lambert law is
Barriers to Trade (TBT) Committee.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
This test method is under the jurisdiction of ASTM Committee D16 on contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Aromatic, Industrial, Specialty and Related Chemicals and is the direct responsi- Standards volume information, refer to the standard’s Document Summary page on
bility of Subcommittee D16.04 on Instrumental Analysis. the ASTM website.
Current edition approved May 1, 2022. Published June 2022. Originally The last approved version of this historical standard is referenced on
approved in 1994. Last previous edition approved in 2016 as E1615 – 16. DOI: www.astm.org.
10.1520/E1615-22. Gibbs, C. R., “Characterization and Application of FerroZine Iron Reagent as
Stookey, L. L., “FerroZine—A New Spectrophotometric Reagent for Iron,” a Ferrous Iron Indicator,” Analytical Chemistry, Vol 48, No. 8, July 1976, pp.
Analytical Chemistry, Vol 42, No. 7, June 1970, pp. 779 – 781. 1197–1201.
*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
E1615 − 22
NOTE3—Adiscussionofphotometersandphotometricpracticeisgiven
obeyed in this system at low concentrations of the colored
in Practices E60 and E275.
complex. The Beer-Lambert law establishes a relationship
amongtheabsorbance,samplethickness,andtheconcentration
7. Reagents
of the absorbing specie as follows:
7.1 Unless otherwise indicated, it is intended that all re-
A 5 abc (1)
agents shall conform to the specifications of the Committee on
where: Analytical Reagents of theAmerican Chemical Society, where
such specifications are available. Other grades may be used,
A = absorbance = log (I /I = –log (T) T = I/I ; transmittance
0 0
provided it is first ascertained that the reagent is of sufficiently
= light exit cell/light to cell;
high purity to permit its use without lessening the accuracy of
a = microgram Fe absorptivity, (slope), liter/(mole cm) or
the determination.
mL/(mg cm);
b = pathlength through sample, cm; and
7.2 Purity of Solvents:
c = concentration of solute in µg Fe in sol’n, moles/liter or
7.2.1 Water—Unless otherwise indicated, references to wa-
mg/mL.
ter shall be understood to mean Type I reagent water conform-
NOTE 2—This method plots Abs vs. Conc;b=1cm; Slope (a) is
ing to Specification D1193.
rise/run or a = A/c; therefore c = A/a.
7.2.2 Methanol—Use iron-free methanol such as HPLC
4. Significance and Use grade methanol.
4.1 This test method is suitable for determining trace 7.3 Iron, Standard Solution, 1 mL = 1 µg Fe (see Notes 4
concentrations of iron in a wide variety of products, provided and 5)—Dissolve 0.1000 g of iron wire in 10 mL of hydro-
that appropriate sample preparation has rendered the iron and chloric acid (HCl, 1 + 1) and 1 mL of saturated bromine water
sample matrix soluble in water or other suitable solvent. Each (400 mL water + 20 mL bromine). Boil until the excess
sample matrix must be investigated for suitability using this bromine is removed. Add 200 mL of HCl, cool, and dilute to
test method. 1 L in a volumetric flask. Dilute 10 mL of this solution to 1 L.
4.2 This test method assumes that the amount of color
NOTE 4—The preparation of this reagent is also described in Practice
developed is proportional to the amount of iron in the test E200.
NOTE 5—As an alternative, the standard iron solution may be prepared
solution. The calibration curve is linear over the specified
by diluting 1.00 mL of commercially available iron standard stock
range.
solution (1000 mg iron/L) to 1 L with water.
NOTE 6—When the solvent is methanol, use the reagent grade iron-free
5. Interferences
methanol.
5.1 Any ion that absorbs light at 560 nm will interfere with
7.4 PDTS Reagent Solution—Contains color reagent [3-(2-
the determination. Anionic interferences include oxalate in
pyridyl)-5,6-bis(4-phenylsulfonic acid)-1,2,4-triazine, mono-
concentrations over 500 µg/g, cyanide, and nitrate.
sodium salt, monohydrate] or PDTS, buffer, and a reducing
agent like thioglycolic acid or hydroxylamine hydrochloric
5.2 Copper, cobalt, calcium, magnesium, lead, silver,
acid.
molybdenum, aluminum, nickel, zinc, arsenic, manganese,
7.4.1 Alternatively, the PDTS and PDTZ (2,4,6-tris(2-
hexavalent chromium, trivalent chromium, divalent cobalt, and
pyridyl)-1,3,5-triazine) reagent solution is available
monovalent copper are the only metals other than iron that
commercially, or the reagents may be prepared as described
form colored species with PDTS reagent solution under test
below.
conditions. At least 1000 mg/L of the alkali metals and the
7.4.1.1 Reducing Agent—Hydroxylamine hydrochloride,
alkaline earths had no effect on the determination. Many heavy
10 % by weight solution in hydrochloric acid: Dissolve 10 g of
metals will react with PDTS reagent solution in competition
reagent grade hydroxylamine hydrochloride (NH OH.HCL) in
with iron, but with the excess reagent used in the test there is
30 g of Type I water in a plastic bottle; add 50 mL of reagent
no effect on the results.
grade concentrated hydrochloric acid and mix well. Prepare
5.3 The pH range of the final solution should be from 4 to
this solution fresh daily.
2,5
9 to give the best test results.
7.4.1.2 Color Reagent, 0.514 weight percent solution: Dis-
5.4 All glassware used in this test method must be iron-free
solve 0.514 g of PDTS reagent solution in 100 g of Type I
and scrupulously clean by precleaning with dilute hydrochloric
waterinaplasticbottle,andmixwell.Discardthereagentafter
acid and PDTS reagent solution followed by a water rinse.
seven days.
7.4.1.3 Buffer Reagent-pH 10.0 Buffer—Dissolve 200 g of
6. Apparatus
reagent grade ammonium acetate in a minimum of Type I
6.1 Photometer, capable of measuring light absorption at
water, add 175 mL of concentrated ammonium hydroxide and
560 nm and holding a 5-cm or 10-cm cell. Check the
performanceofthephotometeratregularintervalsaccordingto
ACS Reagent Chemicals, Specifications and Procedures for Reagents and
the guidelines given in Practice E275 and the manufacturer’s
Standard-Grade Reference Materials, American Chemical Society, Washington,
manual.
DC. For suggestions on the testing of reagents not listed by theAmerican Chemical
Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset,
6.2 Absorption Cells, 5-cm or 10-cm light path.
U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharma-
copeial Convention, Inc. (USPC), Rockville, MD.
E1615 − 22
dilute to 500 mLin a volumetric flask. Mix well. Check the pH 10.3 Construct a calibration graph by plotting the absor-
of the buffer to verify that it is pH 10 6 0.5. If it is not in the bancesagainstthecorrespondingmicrogramsofironpresentin
required pH range, remake the buffer. Store the buffer in a the calibration solutions, including the blank. Obtain the best
plastic bottle. Discard after four weeks. straight line through the points (calibration function) by
applying simple linear regression. Determine the slope (S) of
8. Hazards
the linear calibration function.
8.1 Consult current OSHA regulations, suppliers’ Safety
10.3.1 Evaluate and verify the obtained calibration graph
Data Sheets, and local regulations for all materials used in this
and function by checking for a random scatter of the
test method.
y-residuals around an average of zero, and by preparing and
analyzing a control solution.
8.2 PDTS Reagent Solution—This solution may contain
thiols as the reducing agent. Wear butyl rubber or neoprene
NOTE 7—Many spectrophotometers have the ability to calculate a
gloves when handling the solution and avoid inhalation of the calibration graph automatically after measuring the calibration solutions
and subsequently to show the concentration of the component being
vapors.
measureddirectlyonadisplay.Insuchcasesnomanualcalibrationgraphs
need to be constructed. It is, however, recommended to verify the
9. Sample Preparation
calculation procedure of the instrument and to establish the characteristics
9.1 Because this is a general test method for the final steps
of the calibration graph according to suitable regression analysis software.
in determining iron, specific procedures for sample preparation
NOTE 8—As the calibration function has been derived from a single
prepared calibration standard, verify the accuracy of the calibration
are not included (see 4.1 and 4.2). Most Committee D16
function by preparing and analyzing a control solution containing an
chemicals are finished liquid products which do not need
accurately known amount of approximately 5 µg of iron. If reasonably
sample preparation before running this analysis.
possible this control solution should be completely independent, that is,
prepared by a different operator, different batches of chemicals etc. The
9.2 Appropriate sample preparation has rendered the iron
difference between the known value and the measured value should be
and sample matrix soluble in water or an other suitable solvent
within the confidence limits for the control solution, as derived from the
such as methanol. Some sample preparation may include
confidence limits of intercept and slope of the calibration function.
microwave sample digestion or heating samples in acid.
11. Procedure
9.3 Iron III in the sample has been reduced to Iron II.
9.4 A sample containing 0.5 to 10 µg of iron is used. 11.1 PDTS Reagent Solution Method (7.4):
Dilutions are made for dark samples (11.2.5). 11.1.1 Weightothreesignificantfiguresasamplecontaining
0.5 to 10 µg of iron into a clean, dry 50-mL, glass-stoppered,
9.5 The pH range of the final solution should be 4 to 9 to
volumetric flask (see Note 6). Add sufficient water to dissolve
give the best results.
the sample but do not exceed 40 mL total volume.
10. Calibration
NOTE 9—Preliminary tests must be made to determine if the sample or
10.1 PDTS Reagent Solution Method (7.4):
any impurities in the sample interfere in any way with the analysis.
10.1.1 By means of suitable pipets or a burette, transfer 0
11.1.2 To prepare a reagent blank, add about 20 mL
...

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: E1615 − 16 E1615 − 22
Standard Test Method for
Iron inDetermination of Trace Quantities Using the
FerroZine Methodof Iron by Visible Spectrophotometry
This standard is issued under the fixed designation E1615; 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 This test method covers the determination of iron in aromatic hydrocarbons, their derivatives, and related chemicals in the
range from 0.01 to 0.2 μg/g using FerroZine[3-(2-pyridyl)-5,6-bis(4-phenylsulfonic acid)-1,2,4-triazine, monosodium salt,
monohydrate] (PDTS) reagent solution. The range may be extended through the use of a 5- or 10-cm cell or by suitable dilution
of the sample solution.
1.2 The limit of detection (LOD) is 0.01 μg/kg for iron and the limit of quantitation (LOQ) is 0.04 μg/kg.
NOTE 1—The LOD and LOQ were calculated using data from the ILS.
1.3 This test method is intended to be general for the final steps in the determination of iron and does not include procedures for
sample preparation.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 Review the current Safety Data Sheets (SDS) for detailed information concerning toxicity, first-aid procedures, and safety
precautions.
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, health, and environmental practices and determine the applicability of
regulatory limitations prior to use. For specific warning statements, see Section 7.48.
1.7 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:
D1193 Specification for Reagent Water
This test method is under the jurisdiction of ASTM Committee D16 on Aromatic, Industrial, Specialty and Related Chemicals and is the direct responsibility of
Subcommittee D16.04 on Instrumental Analysis.
Current edition approved April 1, 2016May 1, 2022. Published May 2016June 2022. Originally approved in 1994. Last previous edition approved in 20082016 as E1615–
08. – 16. DOI: 10.1520/E1615-16.10.1520/E1615-22.
FerroZine is a trademark of Hach Chemical Company.Stookey, L. L., “FerroZine—A New Spectrophotometric Reagent for Iron,” Analytical Chemistry, Vol 42, No. 7,
June 1970, pp. 779 – 781.
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
E1615 − 22
D6143 Test Method for Iron Content of Bisphenol A (4,4' - Isopropylidenediphenol)
D6809 Guide for Quality Control and Quality Assurance Procedures for Aromatic Hydrocarbons and Related Materials
E60 Practice for Analysis of Metals, Ores, and Related Materials by Spectrophotometry
E180 Practice for Determining the Precision of ASTM Methods for Analysis and Testing of Industrial and Specialty Chemicals
(Withdrawn 2009)
E200 Practice for Preparation, Standardization, and Storage of Standard and Reagent Solutions for Chemical Analysis
E275 Practice for Describing and Measuring Performance of Ultraviolet and Visible Spectrophotometers
3. Summary of Test Method
3.1 Certain molecules like PDTS which contains the ferroin group -N=C-C=N- react as a bidentate ligands with ferrous metal ions
forming a colored complex species.
2,5
3.2 This test method is based upon a photometric determination of the FerroZineferroin PDTS complex with the iron (II) ion.
The sample is dissolved in a suitable solvent and solvent, any ferric iron is reduced to ferrous iron when the iron is reacted with
FerroZinePDTS reagent solution which will also convert the dissolved iron compounds to form a magenta color iron (II) complex.
The iron content of the sample solution is determined by measurement of the magenta color at 560 nm using a suitable photometer.
3.3 Quantitation of the iron content in the sample is accomplished by measuring the intensity of the color produced by the magenta
complex described above. The Beer-Lambert law is obeyed in this system at low concentrations of the colored complex. The
Beer-Lambert law establishes a relationship among the absorbance, sample thickness, and the concentration of the absorbing specie
as follows:
A5 abc (1)
where:
A = absorbance = log (I /I = –log (T) T = I/I ; transmittance = light exit cell/light to cell;
0 0
a = microgram Fe absorptivity, (slope), liter/(mole cm) or mL/(mg cm);
b = pathlength through sample, cm; and
c = concentration of solute in μg Fe in sol’n, moles/liter or mg/mL.
NOTE 2—This method plots Abs vs. Conc; b = 1 cm; Slope (a) is rise/run or a = A/c; therefore c = A/a.
4. Significance and Use
4.1 This test method is suitable for determining trace concentrations of iron in a wide variety of products, provided that appropriate
sample preparation has rendered the iron and sample matrix soluble in water or other suitable solvent. Each sample matrix must
be investigated for suitability using this test method.
4.2 This test method assumes that the amount of color developed is proportional to the amount of iron in the test solution. The
calibration curve is linear over the specified range.
5. Interferences
5.1 Any ion that absorbs light at 560 nm will interfere with the determination. Anionic interferences include oxalate in
concentrations over 500 μg/g, cyanide, and nitrate.
5.2 Of copper, Copper, cobalt, calcium, magnesium, lead, silver, molybdenum, aluminum, nickel, zinc, arsenic, manganese,
hexavalent chromium, trivalent chromium, divalent cobalt, and monovalent copper are the only metals other than iron that form
colored species with FerroZine PDTS reagent solution under test conditions. At least 1000 mg/L of the alkali metals and the
alkaline earths had no effect on the determination. Many heavy metals will react with FerroZine PDTS reagent solution in
competition with iron, but with the excess reagent used in the test there is no effect on the results.
2,5
5.3 The pH range of the final solution should be from 4 to 9 to give the best test results.
The last approved version of this historical standard is referenced on www.astm.org.
Gibbs, C. R., “Characterization and Application of FerroZine Iron Reagent as a Ferrous Iron Indicator,” Analytical Chemistry, Vol 48, No. 8, July 1976, pp. 1197–1201.
E1615 − 22
5.4 All glassware used in this test method must be iron-free and scrupulously clean by precleaning with dilute hydrochloric acid
and FerroZinePDTS reagent solution followed by a water rinse.
6. Apparatus
6.1 Photometer, capable of measuring light absorption at 560 nm and holding a 5-cm or 10-cm cell. Check the performance of
the photometer at regular intervals according to the guidelines given in Practice E275 and the manufacturer’s manual.
6.2 Absorption Cells, 5-cm or 10-cm light path.
E1615 − 22
NOTE 3—A discussion of photometers and photometric practice is given in PracticePractices E60 and E275.
7. Reagents
7.1 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, where such specifications are available. 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.
7.2 Purity of Water—Solvents: Unless otherwise indicated, references to water shall be understood to mean Type II or Type III
reagent water conforming to Specification D1193.
7.2.1 Water—Unless otherwise indicated, references to water shall be understood to mean Type I reagent water conforming to
Specification D1193.
7.2.2 Methanol—Use iron-free methanol such as HPLC grade methanol.
7.3 Iron, Standard Solution, 1 mL = 1 μg Fe (see Notes 24 and 35)—Dissolve 0.1000 g of iron wire in 10 mL of hydrochloric acid
(HCl, 1 + 1) and 1 mL of saturated bromine water (400 mL water + 20 mL bromine). Boil until the excess bromine is removed.
Add 200 mL of HCl, cool, and dilute to 1 L in a volumetric flask. Dilute 10 mL of this solution to 1 L.
NOTE 4—The preparation of this reagent is also described in Practice E200.
NOTE 5—As an alternative, the standard iron solution may be prepared by diluting 1.00 mL of commercially available iron standard stock solution (1000
mg iron/L) to 1 L with water.
NOTE 6—When the solvent is methanol, use the reagent grade iron-free methanol.
7.4 FerroZinePDTS Reagent Solution—Contains FerroZine color reagent [3-(2-pyridyl)-5,6-bis(4-phenylsulfonic acid)-1,2,4-
triazine, monosodium salt, monohydrate], monohydrate] or PDTS, buffer, and a reducing agent. (agent likeWarning—This
solution contains thiols as reducing agents. Wear butyl rubber or neoprene gloves when handling the solution and avoid inhalation
of the vapors.) thioglycolic acid or hydroxylamine hydrochloric acid.
7.4.1 Alternatively, the individual solutions can PDTS and PDTZ (2,4,6-tris(2-pyridyl)-1,3,5-triazine) reagent solution is available
commercially, or the reagents may be prepared as described below.
7.4.1.1 Reducing Agent—Hydroxylamine hydrochloride, 10 percent 10 % by weight solution in hydrochloric acid: Dissolve 10 g
of reagent grade hydroxylamine hydrochloride (NH OH.HCL) in 30 g of deionized Type I water in a plastic bottle; add 50 mL
of reagent grade concentrated hydrochloric acid and mix well. Prepare this solution fresh daily.
7.4.1.2 Color Reagent—Reagent, FerroZine, 0.514 weight percent solution: Dissolve 0.514 g of FerroZinePDTS reagent solution
in 100 g of deionized Type I water in a plastic bottle, and mix well. Discard the reagent after seven days.
7.4.1.3 Buffer Reagent-pH 10.0 Buffer—Dissolve 200 g of reagent grade ammonium acetate in a minimum of deionized Type I
water, add 175 mL of concentrated ammonium hydroxide and dilute to 500 mL in a volumetric flask. Mix well. Check the pH of
the buffer to verify that it is pH 10 6 0.5. If it is not in the required pH range, remake the buffer. Store the buffer in a plastic bottle.
Discard after four weeks.
8. Hazards
8.1 Consult current OSHA regulations, suppliers’ Safety Data Sheets, and local regulations for all materials used in this test
method.
Reagent Chemicals, American Chemical Society Specifications,ACS Reagent Chemicals, Specifications and Procedures for Reagents and Standard-Grade Reference
Materials, American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed by the American Chemical Society, see Analar Standards for
Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharmacopeial Convention, Inc. (USP),(USPC),
Rockville, MD.
E1615 − 22
8.2 PDTS Reagent Solution—This solution may contain thiols as the reducing agent. Wear butyl rubber or neoprene gloves when
handling the solution and avoid inhalation of the vapors.
9. SamplingSample Preparation
9.1 Because this is a general test method for the final steps in determining iron, specific procedures for sample preparation are not
included (see 4.1 and 4.2). Most Committee D16 chemicals are finished liquid products which do not need sample preparation
before running this analysis.
9.2 Appropriate sample preparation has rendered the iron and sample matrix soluble in water or an other suitable solvent such as
methanol. Some sample preparation may include microwave sample digestion or heating samples in acid.
9.3 Iron III in the sample has been reduced to Iron II.
9.4 A sample containing 0.5 to 10 μg of iron is used. Dilutions are made for dark samples (11.2.5).
9.5 The pH range of the final solution should be 4 to 9 to give the best results.
10. Calibration
10.1 FerroZinePDTS Reagent Solution Method (7.4):
10.1.1 By means of suitable pipets or a buret,burette, transfer 0 (reagent blank), 2.0, 4.0, 6.0, 8.0, and 10.0 mL, respectively, of
the standard iron solution and approximately 20 mL of water to each of six clean, dry, 50-mL, glass-stoppered volumetric flasks.
These flasks represent 0, 2.0, 4.0, 6.0, 8.0, and 10.0 μg of iron. Add 2.0 mL of FerroZinePDTS reagent solution to each flask, dilute
the contents of each flask to volume with water, stopper, and mix well by inverting the flasks several times. Let the solutions stand
for a minimum of 5 min but not more than 10 min to develop the magenta color. Measure the absorbance of each calibration
standard in accordance with 10.311.3 and 11.4.
10.2 Individual Solution Method (7.4.1):
10.2.1 By means of suitable pipets or a buret,burette, transfer 0 (reagent blank), 2.0, 4.0, 6.0, 8.0, and 10.0 mL, respectively, of
the standard iron solution and approximately 40 mL of water to each of six clean, dry, 100-mL, glass-stoppered volumetric flasks.
These flasks represent 0, 2.0, 4.0, 6.0, 8.0, and 10.0 μg of iron. Add 2 mL each of the individual reagents (reducing reagent, color
reagent and buffer reagent) as described in 10.27.4 and 10.3to each flask, dilute the contents of each flask to volume with water,
stopper, and mix well by inverting the flasks several times. Let the solutions stand for a minimum of 5 min but not more than 20
min to develop the magenta color. Measure the absorbance of each calibration standard in accordance with 10.3.
10.3 Construct a calibration graph by plotting the absorbances against the corresponding micrograms of iron present in the
calibration solutions, including the blank. Obtain the best straight line through the points (calibration function) by applying simple
linear regression. Determine the slope (S) of the linear calibration function.
10.3.1 Evaluate and verify the obtained calibration graph and function by checking for a random scatter of the y-residuals around
an average of zero, and by preparing and analyzing a control solution.
NOTE 7—Many spectrophotometers have the ability to calculate a calibration graph automatically after measuring the calibration solutions and
subsequently to show the concentration of the component being measured directly on a display. In such cases no manual calibration graphs need to be
constructed. It is, however, recommended to verify the calculation procedure of the instrument and to establish the characteristics of the calibration graph
according to suitable regression analysis software.
NOTE 8—As the calibration function has been derived from a single prepared calibration standard, verify the accuracy of th
...