ASTM D3598-89(2016)

Standard Test Method for Citrate in Synthetic Detergents

ABSTRACT
This test method covers the enzymatic determination of citrate in both liquid and solid synthetic detergents. The test method is applicable to most detergents containing citrate at a minimum concentration of approximately 5 %. The apparatus to be used in the determination of citrate shall includes interval timer, micropipet, and spectrophotometer. An enzyme system that is based upon the selective cleavage of citrate by citrate lyase (citrate oxaloacetate-lyase; EC 4.1.3.6) shall be employed. One of the products, oxaloacetate, shall be reduced to malate by malic dehydrogenase (L-malate: NAD oxidoreductase; EC 1.1.1.37) with the simultaneous oxidation of reduced (beta)-nicotinamide adenine dinucleotide to (beta)-nicotinamide adenine dinucleotide, oxidized form. The course of the reaction shall be measured spectrophotometrically. The decrease in absorbance at 340 nm caused by the formation of (beta)-nicotinamide adenine dinucleotide, oxidized form, is directly proportional to the concentration of citrate.
SCOPE
1.1 This test method covers the enzymatic determination of citrate in both liquid and solid synthetic detergents. The test method is applicable to most detergents containing citrate at a minimum concentration of approximately 5 % (1-8).2  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.3 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. Material Safety Data Sheets are available for reagents and materials. Review them for hazards prior to usage.

General Information

• Status: Published
• Publication Date: 30-Jun-2016
• ICS: 71.100.40 - Surface active agents
• Technical Committee: D12 - Soaps and Other Detergents
• Drafting Committee: D12.12 - Analysis and Specifications of Soaps, Synthetics, Detergents and their Components

Relations

• Replaces: ASTM D3598-89(2009) - Standard Test Method for Citrate in Synthetic Detergents
• Effective Date: 01-Jul-2016
• Refers: ASTM D501-03(2009) - Standard Test Methods of Sampling and Chemical Analysis of Alkaline Detergents
• Effective Date: 01-Oct-2009
• Refers: ASTM D1193-06 - Standard Specification for Reagent Water
• Effective Date: 01-Mar-2006
• Refers: ASTM D501-03 - Standard Test Methods of Sampling and Chemical Analysis of Alkaline Detergents
• Effective Date: 01-Oct-2003
• 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

Overview

ASTM D3598-89(2016): Standard Test Method for Citrate in Synthetic Detergents is an internationally recognized method developed by ASTM International. This standard specifies a precise enzymatic procedure for the determination of citrate content in both liquid and solid synthetic detergents. Applicable to detergents with citrate concentrations of at least 5%, this method uses selective enzyme systems and spectrophotometric measurements for accurate and reliable analysis.

This standard is widely used by laboratories, manufacturers, and quality control professionals in the cleaning and detergent industry to ensure product consistency, regulatory compliance, and accurate labeling of citrate content.

Key Topics

• Enzymatic Determination: Employs enzyme-based reactions for specific and sensitive citrate analysis.
• Applicable Sample Types: Valid for both liquid and solid synthetic detergent formulations with citrate levels above 5%.
• Required Equipment: Uses readily available laboratory instruments, including an interval timer, micropipet (e.g., Eppendorf pipets), and a spectrophotometer capable of measuring absorbance at 340 nm.
• Specificity of the Method: Highly specific to citrate, with minimal interference from other organic acids such as isocitric, aconitic, oxalic, or tartaric acids.
• Standard Reagents: Relies on citrate lyase and malic dehydrogenase enzymatic systems, with NADH as a spectrophotometric indicator.

Applications

• Product Quality Control: Enables detergent manufacturers to verify the citrate content in their products, supporting compliance with product specifications and industry regulations.
• Research and Development: Facilitates formulation optimization by accurately measuring citrate, which may impact performance attributes like cleaning efficiency and environmental friendliness.
• Regulatory Compliance: Assists in meeting national and international standards for ingredient disclosure and labeling in synthetic detergents.
• Routine Laboratory Analysis: Provides a reliable and repeatable protocol for ongoing evaluation of detergent batches or new formulations.

Related Standards

• ASTM D501 - Test Methods of Sampling and Chemical Analysis of Alkaline Detergents: Offers guidance on detergent sampling and general chemical analysis procedures.
• ASTM D1193 - Specification for Reagent Water: Specifies standards for water purity used in the analytical process, ensuring accuracy and consistency in results.
• General Laboratory Standards: Methods for enzymatic analysis, as referenced in related ASTM documents and authoritative publications, align with broadly accepted scientific practices.

Practical Value

Implementing ASTM D3598-89(2016) in laboratory or manufacturing operations delivers several benefits:

• Accuracy and Reliability: The enzymatic method's high specificity minimizes interference, yielding trustworthy citrate measurements in most synthetic detergents.
• Standardization: Ensures comparability of test results across different laboratories and production runs, fostering confidence in quality assurance processes.
• Ease of Integration: Utilizes standard lab equipment and readily available reagents, making it accessible for most quality control and chemical testing laboratories.
• Risk Minimization: Enables early detection of formulation inconsistencies or deviations, helping prevent costly product recalls or non-compliance issues.

By adhering to this ASTM standard, organizations demonstrate their commitment to product excellence and regulatory adherence within the detergent industry.

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Keywords: ASTM D3598, citrate determination, synthetic detergents, enzymatic test method, spectrophotometric analysis, detergent quality control, laboratory testing standards

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: D3598 − 89 (Reapproved 2016)
Standard Test Method for
Citrate in Synthetic Detergents
This standard is issued under the fixed designation D3598; 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 formation of β-nicotinamide adenine dinucleotide, oxidized
form, is directly proportional to the concentration of citrate.
1.1 This test method covers the enzymatic determination of
citrate in both liquid and solid synthetic detergents. The test
4. Interferences
method is applicable to most detergents containing citrate at a
4.1 The test method is highly specific for citrate. Other
minimum concentration of approximately 5 % (1-8).
organic acids, for example, cisand trans-aconitic, d,l-isocitric,
1.2 The values stated in SI units are to be regarded as
α-ketoglutaric, oxalic, succinic, or tartaric acids, do not inter-
standard. No other units of measurement are included in this
fere.
standard.
4.2 Although low levels of zinc or magnesium, or both, are
1.3 This standard does not purport to address all of the
required as an activator for the enzyme citrate lyase, exces-
safety concerns, if any, associated with its use. It is the
sively high levels of divalent metallic ions including zinc and
responsibility of the user of this standard to establish appro-
magnesium will cause inactivation of the enzyme and poten-
priate safety and health practices and determine the applica-
tially interfere with the test method (7).
bility of regulatory limitations prior to use. Material Safety
4.3 The test method is not applicable to those detergents
Data Sheets are available for reagents and materials. Review
containing components with excessive absorptivity at 340 nm
them for hazards prior to usage.
such that ultraviolet measurements are inappropriate at 340 nm
2. Referenced Documents
under test conditions.
2.1 ASTM Standards:
5. Apparatus
D501 Test Methods of Sampling and Chemical Analysis of
5.1 Interval Timer.
Alkaline Detergents
D1193 Specification for Reagent Water
5.2 Micropipet, suitable Eppendorf pipets for dispensing 10
and 100-µL volumes and with disposable tips.
3. Summary of Test Method
5.3 Spectrophotometer, suitable for measuring ultraviolet
3.1 This test method employs an enzyme system that is
absorbance at 340 nm and equipped with 1-cm matched quartz
based upon the selective cleavage of citrate by citrate lyase
cells with tapered TFE-fluorocarbon stoppers and a minimum
(citrate oxaloacetate-lyase; EC 4.1.3.6) (1). One of the
volume of 4 mL.
products, oxaloacetate, is reduced to malate by malic dehydro-
genase (L-malate: NAD oxidoreductase; EC 1.1.1.37) with the
6. Reagents
simultaneous oxidation of reduced β-nicotinamide adenine
6.1 Purity of Reagents—Reagent grade chemicals shall be
dinucleotide to β-nicotinamide adenine dinucleotide, oxidized
used in all tests. Unless otherwise indicated, it is intended that
form. The course of the reaction is measured spectrophoto-
all reagents shall conform to the specifications of the Commit-
metrically.Thedecreaseinabsorbanceat340nmcausedbythe
tee onAnalytical Reagents of theAmerican Chemical Society,
where such specifications are available. Other grades may be
This test method is under the jurisdiction of ASTM Committee D12 on Soaps
used, provided it is first ascertained that the reagent is of
and Other Detergents and is the direct responsibility of Subcommittee D12.12 on
sufficiently high purity to permit its use without lessening the
Analysis and Specifications of Soaps, Synthetics, Detergents and their Components.
accuracy of the determination.
Current edition approved July 1, 2016. Published August 2016. Originally
approved in 1977 as D3598 – 77 T. Last previous edition approved in 2009 as
D3598 – 89 (2009). DOI: 10.1520/D3598-89R16.
2 4
The boldface numbers in parentheses refer to the references at the end of this Reagent Chemicals, American Chemical Society Specifications, American
test method. Chemical Society, Washington, DC. For suggestions on the testing of reagents not
For referenced ASTM standards, visit the ASTM website, www.astm.org, or listed by the American Chemical Society, see Analar Standards for Laboratory
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
Standards volume information, refer to the standard’s Document Summary page on and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
the ASTM website. MD.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D3598 − 89 (2016)
6.2 Purity of Water—Unless otherwise indicated, references S 3 V
C 5 (1)
I,II
to water shall be understood to mean Type II reagent water 10
conforming to Specification D1193.
where:
6.3 Citrate Lyase Solution (40 units/mL)—Add sufficient
C = concentration of trisodium citrate dihydrate in the
I,II
cold water to a vial of citrate lyase containing a premeasured
standard Solutions I or II,µ g/mL,
weight of enzyme protein such that the resulting solution will
S = standard weight of TSC, mg, and
contain 40 units/mL; for example, 2.0 mL of water is added to
V = volume taken for the final dilution, mL.
a vial containing 5 mg of enzyme protein with an activity of 16
Prepare all solutions fresh daily.
units/mg of enzyme protein. One unit of activity will convert
6.10 Zinc Chloride Solution (0.003 M)—Dissolve 41 mg of
1.0 µmol of citrate to oxaloacetate per minute at pH 7.6 at
zinc chloride in 100 mL of water.
25°C. The citrate lyase solution should be maintained in an ice
bath for the duration of the analyses and can be used for 5 days
7. Sampling
if refrigerated. Citrate lyase (EC 4.1.3.6) from Aerobacter
7.1 Collect the sample in accordance with Test Methods
aerogenes is commercially available as a lyophilized powder
D501.
containing approximately 24 % citrate lyase, 24 % albumin,
48 % saccharose and 4 % magnesium sulfate (MgSO ·7H O).
4 2
8. Procedure
The citrate lyase powder should be stored as specified by the
8.1 Dissolve an accurately weighed detergent sample
supplier.
equivalent to approximately 300 mg of trisodium citrate
6.4 Disodium β-Nicotinamide Adenine Dinucleotide, Re-
dihydrate in distilled water and dilute to 200 mL. Dilute a 3.0
duced Form Solution (0.0032 M)—Dissolve 10 mg of
mL aliquot of this solution to 100 mL with water. This is the
disodiumβ -nicotinamide adenine dinucleotide, reduced form,
sample test solution.
(β-NADH) in 4.0 m
...