AATCC TM168-2023 聚氨基多羧酸及其盐类螯合值测试法：PAN 铜

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AATCC Manual of International Test Methods and Procedures/2025 AATCC TM168-2023 317

1. Foreword

This test method is an alternate to

AATCC TM149, Test Method for Chela-

tion Value of Aminopolycarboxylic Ac-

ids and Their Salts: Calcium Oxalate. Ti-

tration with a calcium salt using either

oxalate or a dye indicator, as in AATCC

TM149, yields a value that includes par-

tially-substituted EDTA, HEDTA, DTPA,

nitrilotriacetic acid (NTA), iminodiacetic

acid (IDA), glycolate and other weak

chelating agents found in some commer-

cial products. This alternative procedure

excludes the effect of the partially-substi-

tuted products, providing a more strin-

gent value.

2. Purpose and Scope

2.1 The active ingredient content of

ethylenediaminetetraacetic acid (EDTA),

N-hydroxyethylethylenediaminetriacetic

acid (HEDTA) and diethylenetriamine-

pentaacetic acid (DTPA) and their salts is

usually expressed by the calcium chela-

tion value (CaCV). This value indicates

the amount of calcium (as calcium car-

bonate) which will be chelated by a

known weight of chelating agent. This

method excludes the effect of partially-

substituted products.

3. Principle

3.1 Calcium chelation value is deter-

mined experimentally by titrating a

weighed specimen of chelating agent

with a copper nitrate solution of known

concentration in the presence of PAN (1-

(2-pyridylazo)-2-naphthol). Initially, the

color of the solution is yellow-green due

to free indicator. When all of the chelat-

ing agent has reacted with copper nitrate,

the color of the solution changes to a per-

manent purple which is the end point.

3.2 The CaCV indicates the amount of

calcium (as calcium carbonate) that will

be sequestered by a known weight of

chelating agent and is expressed as milli-

grams of calcium carbonate (CaCO3) per

gram of chelating agent (mg calcium car-

bonate/g chelating agent).

4. Referenced Documents

NOTE: Use current versions of all

publications unless otherwise specified.

4.1 AATCC 149 Test Method for Che-

lation Value of Aminopolycarboxylic Ac-

ids and Their Salts: Calcium Oxalate

5. Terminology

5.1 chelating agent, n.—in textile

chemistry, a chemical capable of deacti-

vating metal ions by formation of a wa-

ter-soluble complex. SYN: sequestering

agent.

6. Safety Precautions

6.1 The safety precautions specified in

the method/procedure are ancillary to the

testing procedures and are not intended to

be all inclusive.

6.2 It is the user’s responsibility to ref-

erence applicable safety data sheets, use

safe and proper techniques, and wear ap-

propriate personal protective equipment

in handling materials in this standard.

7. Reagents

7.1 Acetic acid, 1.0N (CH3COOH)

7.2 Cupric nitrate 2.5 hydrate

(Cu(NO3)2 · 2.5H2O)

7.3 Ethylene diaminetetraacetic acid

(free acid) (EDTA) (C10H16O8N2)

7.4 Methanol

7.5 1-(2-Pyridylazo)-2-naphthol, (PAN)

(C15H11ON3)

7.6 Sodium acetate trihydrate

(CH3COONa · 3H2O)

7.7 Sodium hydroxide, 1.0N (NaOH)

8. Sampling

8.1 Conduct the test in triplicate; i.e.,

analyze 3 test specimens from a sample.

9. Specimens

9.1 Do not use aluminum or metallic

weighing pans.

9.2 If solid chelating agent is being

evaluated, dry a 2-g sample at the appro-

priate temperature for at least 2 h and

cool in a desiccator before weighing

specimens.

9.2.1 Dry free acid forms of chelating

agents at 120°C.

9.2.2 Dry salt forms of chelating agents

at 80°C.

9.3 For analysis of solid EDTA,

HEDTA, and DTPA (either free acid or

salt forms) weigh a 0.24-0.26 g specimen

of the dried chelating agent to an accu-

racy of 0.01 g.

9.4 For analysis of commercial solu-

tion, of salts of the chelating agents,

weigh a 0.49-0.51 g specimen of the solu-

tion to an accuracy of 0.01 g.

10. Preparation of Reagents

10.1 Cupric Nitrate Solution: Dissolve

23.30 g of cupric nitrate 2.5 hydrate and

dilute to 1.000 L with distilled water in a

volumetric flask. Calculate the molarity

of the cupric nitrate solution (see 10.4).

10.2 PAN Indicator: Dissolve 0.025 g

of 1-(2-pyridylazo)-2-naphthol in 50 mL

of methanol. Store in a refrigerator in a

stoppered bottled. Prepare fresh weekly.

10.3 Acetate Buffer Solution: (pH =

4.65). Dissolve 34.0 g of sodium acetate

trihydrate in 500 mL of distilled water

and add 15 mL of glacial acetic acid. Mix

well and store in a closed container.

10.4 Standardization of Copper-Nitrate

Solution: Weigh to the nearest 0.0001 g

approximately 0.5 g of pure reagent

grade EDTA acid powder into each of the

three 250-mL Erlenmeyer flasks. Add

150 mL of distilled water and 6.5 mL of

1.0N sodium hydroxide (or five drops of

50% sodium hydroxide) and stir the mix-

ture until the EDTA is dissolved. Add 25

mL of sodium acetate buffer. Adjust to

pH 4.5-5.5 with 1.0N acetic acid or 1.0N

sodium hydroxide, if necessary. Add 1

mL PAN indicator and titrate immedi-

ately with copper nitrate to a permanent

purple end point. Calculate the molarity

of copper using Equation 1:

(Eq. 1)

where:

M= Molarity of copper nitrate, ex-

pressed in moles/L

W= Weight of EDTA acid in grams

P= Percent purity of EDTA acid

V= Volume of copper nitrate titrant

in mL

K= 0.042994

11. Procedure

11.1 Transfer the specimen to a 500-

mL Erlenmeyer flask and add 150 mL of

distilled water (see 9.2, 9.3 and 9.4).

Wash any residual chelating agent from

the weighing paper or dish into the flask,

and swirl to mix (dissolve).

11.2 Add 25 mL of pH 4.65 acetate

MW()P()K()

---------------------------=

1000()mL/L

100()232.59 g/mole()

------------------------------------------------------

0.042994 mole mL–

gL–

---------------------------

AATCC TM168-2023

Test Method for Chelation Value of Polyaminopolycarboxylic

Acids and Their Salts: Copper PAN

Provided by Accuris under license with AATCC

No reproduction or networking permitted without license from Accuris Not for Resale, 2025-04-14 18:24:10 UTC

Sold to: Nawal Analytical Labs India Private limited

Order Number: 00015024

318 AATCC TM168-2023 AATCC Manual of International Test Methods and Procedures/2025

buffer solution to the flask and swirl to

mix. Check the pH and adjust to 4.5-5.5

with 1.0N acetic acid or 1.0N sodium hy-

droxide, if necessary.

11.3 Add 1 mL of PAN indicator to the

flask and swirl to mix.

11.4 Titrate with 0.1000 M cupric ni-

trate solution to a purple end point that

persists for at least 1 min.

12. Calculation

12.1 Calculate the CaCV for each

specimen to 3 significant digits for each

titration using the Equation 2:

(Eq. 2)

where:

CaCV = Calcium chelation value, ex-

pressed as mg CaCO3/g

chelating agent

V= Volume of cupric nitrate ti-

trant in mL

CaCV 100.1()V()M()

-------------------------------------=

M= Molarity of cupric nitrate so-

lution, expressed in mmoles/

100.1 = Molecular weight of calcium

carbonate, expressed in mg/

mmole

12.2 Average the CaCV values for the

3 specimens tested.

13. Report

13.1 Report for each sample tested:

13.1.1 A description or identification

of the sample.

13.1.2 Evaluation was performed using

AATCC TM168-2022.

13.1.3 Average CaCV, to 3 significant

digits.

13.1.4 Any modifications of the test

method.

14. Precision and Bias

14.1 Precision. The interlaboratory,

single operator, single apparatus, same

day precision of the test method is ± 2

(1.60) standard deviations. The interlabo-

ratory precision of the test method (over

five participating laboratories) is ± 1

(0.54) standard deviations.

14.2 Bias. Chelation value can be de-

fined only in terms of a test method.

There is no independent method for de-

termining the true value. As a means of

estimating this property, the method has

no known bias.

15. History

15.1 Revised in 2023 to clarify and align

with prescribed AATCC style guidelines.

15.2 Editorially revised 2019; revised 2018;

reaffirmed 2012; editorially revised 2010; edi-

torially revised and reaffirmed 2007; re-

affirmed 2002; editorially revised and

reaffirmed 1997; revised 1992; editorially re-

vised and reaffirmed 1989; reaffirmed 1988.

15.3 Developed in 1987 by AATCC Com-

mittee RR90. Maintained by RA99.

Provided by Accuris under license with AATCC

No reproduction or networking permitted without license from Accuris Not for Resale, 2025-04-14 18:24:10 UTC

Sold to: Nawal Analytical Labs India Private limited

Order Number: 00015024

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摘要：

本文档详细介绍了AATCC TM168-2023标准，即采用PAN（1-(2-吡啶基偶氮)-2-萘酚）铜法测定聚氨基多羧酸及其盐类螯合值的专业测试方法。该标准旨在为纺织、水处理、清洁剂及工业化学品领域提供一种准确、可重复的定量分析手段，用于评估聚氨基多羧酸类螯合剂的螯合能力。通过PAN铜络合物的显色或滴定反应，该方法能够精确测定样品对金属离子的螯合性能，帮助企业与质检机构控制产品质量、研发新型高效螯合剂，并确保其在金属离子控制、污垢分散及染色工艺中的实际效果。遵循本规范，用户可系统完成样品准备、

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