TM149-TM 149 Chelation Value of Aminopolycarboxylic Acids

Description

Untitled

TEST METHODS ARE DELIVERED AS A LINK IN YOUR EMAILED RECEIPT.

AATCC TM149-2023, Chelation Value of Aminopolycarboxylic Acids and Their Salts: Calcium Oxalate

Developed in 1976 by AATCC Committee RR90; editorially revised and reaffirmed 1977, 1985 (with title change), 1977; reaffirmed 1980, 2002, 2007, 2012; editorially revised 1984, 1986, 1988 (with title change), 2010, 2019; revised 1992, 2018 (with title change), 2023.

Foreword

The titration in this method yields a value that includes partially-substituted EDTA, HEDTA, DTPA, nitrilotriacetic acid (NTA), iminodiacetic acid (IDA), glycolate and other weak chelating agents found in some commercial products. An alternative procedure, excluding the effect of partially-substituted products, is provided in AATCC TM168, Test Method for Chelation Value of Polyaminopolycarboxylic Acids and Their Salts: Copper PAN.

1. Purpose and Scope

1.1 The active content of ethylenediaminetetraacetic acid (EDTA), N-hydroxyethylenediaminetriacetic acid (HEDTA) and diethylenetriaminepentaacetic acid (DTPA) and their salts is usually expressed by the calcium chelation value (CaCV). This value indicates the amount of calcium (as calcium carbonate) which will be chelated by a known weight of chelating agent.

2. Principle

2.1 The chelation value is determined experimentally by titrating a weighed sample of chelating agent with a calcium ion solution of known concentration. A precipitating anion (oxalate) is present during the titration. As the calcium solution is added, the ions are chelated by the chelating agent and no permanent precipitate is formed as long as there is free chelating agent present. Beyond this point, any excess calcium ion that is added reacts with oxalate anion to form a cloudy precipitate which is the endpoint. Ê

2.2 The (CaCV) indicates the amount of calcium (as calcium carbonate) which will be sequestered by a known weight of chelating and is expressed as milligrams of calcium carbonate (CaCO3) per gram of chelating agent (mg calcium carbonate/g chelating agent).

Copyright American Association of Textile Chemists and Colorists, RTP, NC, USA. All rights reserved.

The above information is only a summary of the AATCC test method.