ASTM D4608-89(2017)

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: D4608 − 89 (Reapproved 2017)
Standard Test Method for
Citrate in Detergents
This standard is issued under the fixed designation D4608; 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 4. Significance and Use
4.1 This test method is suitable in research, development,
1.1 This test method covers a potentiometric titration pro-
and manufacturing control to monitor the level of citrate, a
cedure for the determination of citrate in liquid and powder
sequestering agent, in powder and liquid detergents.
detergents.
4.2 Accurate determination of sequestering agent is impor-
1.2 The values stated in SI units are to be regarded as
tant in evaluating cost and performance of detergent products.
standard. No other units of measurement are included in this
standard.
5. Interferences
1.3 This standard does not purport to address all of the
5.1 Other complexing agents such as nitrilotriacetic acid
safety concerns, if any, associated with its use. It is the
(NTA), ethylenedinitrilotetraacetic acid (EDTA), phosphates,
responsibility of the user of this standard to establish appro-
etc. will titrate as citrate in this method. For accurate citrate
priate safety and health practices and determine the applica-
determinations, such complexing agents must be absent.
bility of regulatory limitations prior to use. Material Safety
Data Sheets are available for reagents and materials. Review
6. Apparatus
them for hazards prior to usage. Specific safety precautions are
6.1 pH Meter, with millivolt capability.
given in Section 8.
6.2 Copper Ion Selective Electrode.
2. Referenced Documents
6.3 Calomel Reference Electrode.
2 7
2.1 ASTM Standards: 6.4 Glass Electrode Triple Purpose.
E70 Test Method for pH of Aqueous Solutions With the
6.5 Buret, semi-micro, 25 mL capacity with 0.1 mL gradu-
Glass Electrode
ations.
E180 Practice for Determining the Precision of ASTM
6.6 Magnetic Stirrer, and TFE-fluorocarbon-coated mag-
Methods for Analysis and Testing of Industrial and Spe-
netic stirring bars.
cialty Chemicals (Withdrawn 2009)
7. Reagents
3. Summary of Test Method
7.1 Purity of Reagents—Reagent grade chemicals shall be
3.1 The sample is titrated in an aqueous solution buffered at
used in all tests. Unless otherwise indicated, it is intended that
pH 8.5, with standard copper sulfate solution. The endpoint is
all reagents shall conform to specifications of the Committee
detected potentiometrically using a copper ion selective elec-
on Analytical Reagents of the American Chemical Society,
trode. The citrate content is calculated from the amount of
where such specifications are available. Other grades may be
standard copper sulfate solution consumed.
used, provided it is first ascertained that the reagent is of
An automatic titrator may be used.
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This test method is under the jurisdiction of ASTM Committee D12 on Soaps Orion Model 94-29A or equivalent has been found suitable for this purpose.
and Other Detergents and is the direct responsibility of Subcommittee D12.12 on Available from Orion Inc.
Analysis and Specifications of Soaps, Synthetics, Detergents and their Components. Orion Model 90-22 or equivalent has been found suitable for this purpose.
Current edition approved Jan. 1, 2017. Published February 2017. Originally Available from Orion Inc.
approved in 1986. Last previous edition approved in 2009 as D4608 – 89(2009). Corning Model No. 476022 or equivalent has been found suitable for this
DOI: 10.1520/D4608-89R17. purpose. Available from Corning Inc.
2 8
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Reagent Chemicals, American Chemical Society Specifications, American
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Chemical Society, Washington, DC. For suggestions on the testing of reagents not
Standards volume information, refer to the standard’s Document Summary page on listed by the American Chemical Society, see Analar Standards for Laboratory
the ASTM website. Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
The last approved version of this historical standard is referenced on and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
www.astm.org. MD.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4608 − 89 (2017)
sufficiently high purity to permit its use without lessening the
N = normality of Na S O solution, and
2 2 3
accuracy of the determination.
25.0 = aliquot of CuSO solution titrated.
7.2 Purity of Water—Unless otherwise indicated, reference
7.10 Citric Acid—(C H O ).
6 8 7
to water shall be understood to mean distilled water or water of
8. Safety Precautions
equal purity.
8.1 All reagents and chemicals should be handled with care.
7.3 Hydrochloric Acid Solution (1 + 1)—Slowly mix 1 vol-
Before using any chemical, read and follow all safety precau-
ume of concentrated hydrochloric acid (sp gr 1.19) with 1
tions and instructions on the manufacturer label. Clean up any
volume of water.
spillimmediately.Forinformationoncleaningupspillsreferto
7.4 Sodium Hydroxide Solution (20 %)—Prepare a 20 %
the Laboratory Disposal Manual, Manufacturing Chemists
aqueous solution of sodium hydroxide.
Association, Washington, DC.
7.5 Sodium Hydroxide Solution (0.1 N)—Prepare a 0.1 N
9. Procedure
aqueous solution of sodium hydroxide.
9.1 Accuratelyweigh(tothenearest0.1mg)enoughsample
7.6 Hydrochloric Acid Solution (0.1 N)—Prepare a 0.1 N
to contain about 150 mg citrate as sodium citrate or 100 mg as
aqueous solution of hydrochloric acid.
citric acid. Quantitatively transfer to a 400-mL beaker with
7.7 Borate Buffer Solution (pH 8.5)—Dissolve 12.8 g of
water and bring the volume to about 200 mL. While stirring
sodium borate (Na B O ·10H O) and 16.6 g of boric acid
2 4 7 2
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