ASTM E1673-21

Standard Test Method for Percent Suspensibility

SIGNIFICANCE AND USE
4.1 This test method is designed specifically for dry formulations, but need not be restricted to these materials.  
4.2 Either option of this test method (see Section 8) may be used to determine the percent suspensibility.  
4.3 This test method may not be applicable to all dry formulations such as those containing liquid or soluble technical/pesticides or ingredients that rise to the top upon separation.  
4.4 This test method may not be applicable to formulations containing ingredients that decompose under the test conditions.  
4.5 This test method may not give reproducible results if flocculation occurs.  
4.6 This test method should be run in duplicate.  
4.7 Products containing water soluble or volatile components may result in errors.
SCOPE
1.1 This test method is used to determine the percent suspensibility of dry pesticide formulations.  
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For specific precautionary statements see Section 7.  
1.4 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-Sep-2021
• ICS: 65.100.01 - Pesticides and other agrochemicals in general
• Technical Committee: E35 - Pesticides, Antimicrobials, and Alternative Control Agents
• Drafting Committee: E35.22 - Pesticide Formulations and Delivery Systems

Relations

• Refers: ASTM D1126-12 - Standard Test Method for Hardness in Water
• Effective Date: 01-Mar-2012
• Refers: ASTM D1126-02(2007)e1 - Standard Test Method for Hardness in Water
• Effective Date: 01-Aug-2007
• Refers: ASTM D1193-06 - Standard Specification for Reagent Water
• Effective Date: 01-Mar-2006
• Refers: ASTM D1126-02 - Standard Test Method for Hardness in Water
• Effective Date: 10-May-2002
• 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 E1673-21 is the international standard test method for determining the percent suspensibility of dry pesticide formulations. Developed by ASTM, this method is vital for assessing the dispersion stability of products such as wettable powders, water-dispersible granules, and similar materials. Percent suspensibility indicates how well a solid pesticide formulation remains suspended in water and is critical for ensuring the efficacy and safety of pesticide applications.

The standard outlines precise laboratory procedures for sample preparation, mixing, settling, and evaluation. It is designed for use by quality assurance laboratories, formulation chemists, and regulatory agencies, providing a reliable basis for comparing products and ensuring compliance with industry requirements.

Key Topics

• Purpose and Scope

  • Specifically applies to dry pesticide formulations, though it can be used with other materials if suitable.
  • Not recommended for formulations with soluble or volatile components, liquids, or ingredients that rise to the surface or decompose under test conditions.
  • Stipulates use only with SI units.

• Test Procedure

  • Involves mixing a weighed dry sample into standardized water, agitation, settling, and analysis of the remaining suspended solids.
  • Two options for measurement: evaporation and centrifuge/evaporation.
  • Results reported as percent suspensibility.

• Apparatus and Materials

  • Top-loading balance, specific beakers and mixing cylinders, magnetic stirrer, centrifuge, vacuum apparatus, and oven.
  • Rigorously defined reagent water and synthetic waters for reproducibility.

• Repeatability and Reproducibility

  • Duplicate samples are mandatory for accuracy.
  • Results from different laboratories or analysts considered suspect if differing by more than 3% absolute.

• Safety Considerations

  • Users must review MSDS and product labeling for proper personal protective equipment and risk mitigation.
  • Disposal of test materials must conform to safety and environmental standards.

Applications

• Quality Control: Central for manufacturers of pesticides and agrochemicals to verify formulation stability and performance before market release.
• Product Development: Used during R&D to optimize formulations for better dispersion and field application.
• Regulatory Compliance: Meets the requirements of national and international agencies for pesticide registration and approval.
• Comparative Analysis: Enables benchmarking against competitors and aids in troubleshooting formulation issues.

This method is essential wherever consistent performance of dry, water-dispersible pesticide formulations is required, both in laboratory and industrial environments.

Related Standards

• ASTM D1126: Standard Test Method for Hardness in Water - referenced for checking water hardness in sample preparation.
• ASTM D1193: Specification for Reagent Water - used for establishing standard water quality in testing.
• CIPAC MT-73: For auxiliary methods in hardness titration.
• ISO Standards for Pesticide Formulation Testing: Related international protocols for evaluating similar physical-chemical properties.

Keywords

percent suspensibility, suspension, dry pesticide formulations, water dispersible granules, wettable powders, dispersion, ASTM E1673, product quality, pesticide testing, formulation stability, analytical chemistry, laboratory standards

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ASTM E1673-21 is a foundational test method within the agrochemical industry, supporting product integrity and regulatory acceptance worldwide. For official use, always refer to the current standard as issued by ASTM International.

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: E1673 − 21
Standard Test Method for
Percent Suspensibility
This standard is issued under the fixed designation E1673; 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 isdrawnoffandtheremainingsuspensionisdried.Theresidue
weight will determine the percent suspensibility.
1.1 This test method is used to determine the percent
suspensibility of dry pesticide formulations.
4. Significance and Use
1.2 The values stated in SI units are to be regarded as
4.1 This test method is designed specifically for dry
standard. No other units of measurement are included in this
formulations, but need not be restricted to these materials.
standard.
4.2 Either option of this test method (see Section 8) may be
1.3 This standard does not purport to address all of the
used to determine the percent suspensibility.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
4.3 This test method may not be applicable to all dry
priate safety, health, and environmental practices and deter-
formulations such as those containing liquid or soluble
mine the applicability of regulatory limitations prior to use.
technical/pesticides or ingredients that rise to the top upon
For specific precautionary statements see Section 7.
separation.
1.4 This international standard was developed in accor-
4.4 This test method may not be applicable to formulations
dance with internationally recognized principles on standard-
containing ingredients that decompose under the test condi-
ization established in the Decision on Principles for the
tions.
Development of International Standards, Guides and Recom-
4.5 This test method may not give reproducible results if
mendations issued by the World Trade Organization Technical
flocculation occurs.
Barriers to Trade (TBT) Committee.
4.6 This test method should be run in duplicate.
2. Referenced Documents
4.7 Products containing water soluble or volatile compo-
2.1 ASTM Standards:
nents may result in errors.
D1126Test Method for Hardness in Water
D1193Specification for Reagent Water
5. Apparatus
5.1 Balance, top loading, with an accuracy of 60.01 g or
3. Summary of Test Method
better.
3.1 Aknownquantityofdrypesticideisslurriedinto50mL
5.2 Beaker, 100 mL.
of test water in a 100mL beaker. The slurry is quantitatively
transferred to a 250mL mixing cylinder using additional test
5.3 Mixing Cylinder, stoppered, 250 mL, flat bottom, KI-
water to rinse the beaker. The 250mL mixing cylinder is then
MAX series 20039 or equivalent.
filled to volume with test water. The mixing cylinder is
5.4 Timer, adjustable, with an accuracy of 6 min.
stoppered and inverted 15 complete cycles. The mixing cylin-
derisallowedtostandfor30min.After30minthetop225mL 5.5 Magnetic Stirrer, 120 rpm to 1200 rpm, or equivalent.
5.6 Stir Bar, magnetic 1 in. in length and ⁄8 in. in diameter
(2.5 cm×1 cm).
This test method is under the jurisdiction of ASTM Committee E35 on
5.7 Weighing Dish, aluminum (57mm×18 mm) or petri
Pesticides, Antimicrobials, and Alternative Control Agents and is the direct
responsibility of Subcommittee E35.22 on Pesticide Formulations and Delivery
dish, or equivalent.
Systems.
Current edition approved Oct. 1, 2021. Published November 2021. Originally 5.8 Vacuum Apparatus, see Fig. 1, equipped with a vented
approved in 1995. Last previous edition approved in 2017 as E1673–96 (2017).
stopper to prevent the formation of a vacuum.
DOI: 10.1520/E1673-21.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 5.9 Filtering Flask, heavy wall, 500 mL, KIMAX Series
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
27060 or equivalent.
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. 5.10 Gravity Oven.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1673 − 21
flask. Dissolve the reagents with approximately 750 mL of
water and equilibrate to 20°C. Dilute the solution to 1000 mL
total volume with water at 20°C, stopper the flask and mix the
solution thoroughly. This mixture is equivalent to 13680 ppm
ascalciumcarbonate(CaCO )andisbasedonacompositional
ratio of 4:1 calcium carbonate to magnesium carbonate.
6.3.1 Soft Water—Equivalenttoatotalhardnessof34.2ppm
as calcium carbonate (CaCO ). Transfer 2.50 mL of synthetic
hardwaterstockbypipettoa1000mLvolumetricflask.Dilute
to the 1000mL mark with water at 20°C. Mix solution
thoroughly.
NOTE 2—It is recommended that total hardness be checked in accor-
dance with Test Method MT-73, CIPAC 1, EDTA titration. An alternate
method is provided in Test Method D1126 where the value is represented
as CaCO . A value within 6% of the nominal hardness value is
acceptable.
6.3.2 Hard Water—Equivalent to a total hardness of 342
ppm as calcium carbonate (CaCO ). Transfer 25 mL of
synthetic hard water stock by buret to a 1000mL volumetric
flask.Dilutetothe1000mLmarkwithwaterat20°C.Mixthis
solution thoroughly (see Note 2).
6.3.3 Extra-Hard Water—Equivalent to a total hardness of
1000 ppm as calcium carbonate (CaCO ).Transfer 73.1 mLof
synthetic hard water stock by buret to a 1000mL volumetric
flask.Dilutetothe1000mLmarkwithwaterat20°C.Mixthis
solution thoroughly (see Note 2).
6.3.4 Other Test Waters—Other synthetic waters can be
prepared by using the following calculation:
DesiredWaterHardness÷13.6805 (1)
millilitresofsynthetichardwaterstockat20 °Ctobe
@
FIG. 1 Vacuum Apparatus
dilutedvolumetricallyto1000mLwithwaterat20 °C#
5.11 Centrifuge, any centrifuge capable of holding a 50 mL 6.4 Other Carriers—Carriers other than water may be used
or larger tube and maintaining a minimum speed of 1500 rpm. when appropriate.
5.12 Centrifuge Tube, plastic or glass, 50 mL or larger.
7. Safety Precautions
6. Reagents (Test Water)
7.1 Before testing, read the precautionary statements on the
product label or the Material Safety Data Sheet (MSDS), or
6.1 Purity of Reagents—Reagent grade chemicals shall be
both. Take proper precautions to prevent skin contact and
used in all tests. Unless otherwise indicated, it is intended that
inhalation of the fines or vapors, or both. Take care to prevent
all reagents shall conform to the specifications of the Commit-
contamination of the surrounding area. Always wear the
tee onAnalytical Reagents of theAmerican Chemical Society
appropriatesafetyequipmentand,whereindicated,wearrespi-
where such specifications are available.
ratory devices approved by the National Institute of Occupa-
6.2 Purity of Water—Unless otherwise indicated, re
...

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: E1673 − 96 (Reapproved 2017) E1673 − 21
Standard Test Method for
Percent Suspensibility
This standard is issued under the fixed designation E1673; 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 is used to determine the percent suspensibility of dry pesticide formulations.
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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use. For specific precautionary statements see Section 7.
1.4 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:
D1126 Test Method for Hardness in Water
D1193 Specification for Reagent Water
3. Summary of Test Method
3.1 A known quantity of dry pesticide is slurried into 50 mL of test water in a 100-mL100 mL beaker. The slurry is quantitatively
transferred to a 250-mL250 mL mixing cylinder using additional test water to rinse the beaker. The 250-mL250 mL mixing
cylinder is then filled to volume with test water. The mixing cylinder is stoppered and inverted 15 complete cycles. The mixing
cylinder is allowed to stand for 30 min. After 30 min the top 225 mL is drawn off and the remaining suspension is dried. The residue
weight will determine the percent suspensibility.
4. Significance and Use
4.1 This test method is designed specifically for dry formulations, but need not be restricted to these materials.
4.2 Either option of this test method (see Section 8) may be used to determine the percent suspensibility.
This test method is under the jurisdiction of ASTM Committee E35 on Pesticides, Antimicrobials, and Alternative Control Agents and is the direct responsibility of
Subcommittee E35.22 on Pesticide Formulations and Delivery Systems.
Current edition approved April 1, 2017Oct. 1, 2021. Published April 2017November 2021. Originally approved in 1995. Last previous edition approved in 20122017 as
E1673 – 96 (2012).(2017). DOI: 10.1520/E1673-96R17.10.1520/E1673-21.
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.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1673 − 21
4.3 This test method may not be applicable to all dry formulations such as those containing either liquids or liquid or soluble
technical/pesticides or ingredients that rise to the top upon separation.
4.4 This test method may not be applicable to formulations containing ingredients that decompose under the test conditions.
4.5 This test method may not give reproducible results if flocculation occurs.
4.6 This test method should be run in duplicate.
4.7 Products containing water soluble or volatile components may result in errors.
5. Apparatus
5.1 Balance, top loading, with an accuracy of 60.01 g or better.
5.2 Beaker, 100 mL.
5.3 Mixing Cylinder, stoppered, 250 mL, flat bottom, KIMAX series 20039 or equivalent.
5.4 Timer, adjustable, with an accuracy of 6 min.
5.5 Magnetic Stirrer, 120 rpm to 1200 rpm, or equivalent.
5.6 Stir Bar, magnetic 1 in. in length and ⁄8 in. in diameter (2.5 cm × 1 cm).
5.7 Weighing Dish, aluminum (57 × 18(57 mm × 18 mm) or petri dish, or equivalent.
5.8 Vacuum Apparatus, see Fig. 1, equipped with a vented stopper to prevent the formation of a vacuum.
5.9 Filtering Flask, heavy wall, 500 mL, KIMAX Series 27060 or equivalent.
5.10 Gravity Oven.
5.11 Centrifuge, any centrifuge capable of holding a 50 mL or larger tube and maintaining a minimum speed of 1500 rpm.
5.12 Centrifuge Tube, plastic or glass, 50 mL or larger.
6. Reagents (Test Water)
6.1 Purity of Reagents—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 where
such specifications are available.
6.2 Purity of Water—Unless otherwise indicated, reference to water shall be understood to mean reagent water, Type IV, as defined
by Specification D1193.
NOTE 1—Type IV grade reagent water may be prepared by distillation, ion exchange, reverse osmosis, electrodialysis, or a combination thereof.
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. (USPC), Rockville, MD.
E1673 − 21
FIG. 1 Vacuum Apparatus
6.3 Synthetic Hard Water Stock—Transfer 12.14 g of anhydrous calcium chloride (CaCl ) and 5.55 g of magnesium chloride
hexahydrate (MgCl ·6H O) to a 1000-mL1000 mL volumetric flask. Dissolve the reagents with approximately 750 mL of water
2 2
and equilibrate to 20°C.20 °C. Dilute the solution to 1000 mL total volume with water at 20°C,20 °C, stopper the flask and mix
the solution thoroughly. This mixture is equivalent to 13 680 ppm as calcium carbonate (CaCO ) and is based on a compositional
ratio of 4:1 calcium carbonate to magnesium carbonate.
6.3.1 Soft Water—Equivalent to a total hardness of 34.2 ppm as calcium carbonate (CaCO ). Transfer 2.50 mL of synthetic hard
water stock by pipet to a 1000-mL volumetric flask and dilute to volume 1000 mL volumetric flask. Dilute to the 1000 mL mark
with water at 20°C.20 °C. Mix solution thoroughly.
NOTE 2—It is recommended that total hardness be checked in accordance with Test Method MT-73, CIPAC 1, EDTA titration. An alternate method is
provided in Test Method D1126 where the value is represented as CaCO . A value within 6% of the nominal hardness value is acceptable.
6.3.2 Hard Water—Equivalent to a total hardness of 342 ppm as calcium carbonate (CaCO ). Transfer 25 mL of synthetic hard
water stock by buret to a 1000-mL volumetric flask and dilute to volume 1000 mL volumetric flask. Dilute to the 1000 mL mark
with water at 20°C.20 °C. Mix this solution thoroughly (see Note 2).
6.3.3 Extra-Hard Water—Equivalent to a total hardness of 1000 ppm as calcium carbonate (CaCO ). Transfer 73.1 mL of synthetic
hard
...