EDTA Content of Liquid Hand Soap as per ASTM D1767

Table of Contents

Introduction
Sample
Sample Preparation
Configuration
Solutions
Analysis
Parameters
Results

Introduction

In detergents and soaps, complexing agents such as EDTA are used for reducing the hardness of water by removal of undesired metal ions. Utilizing cupric sulfate as the titrant and Cu-ISE as the indicator in a potentiometric titration, the content of EDTA in soaps and detergents can be determined.

Sample

Liquid hand soap.

Sample Preparation

Sample preparation is not required.

Configuration

. .
OMNIS Titrator Professional 2.1001.0310
OMNIS Sample Robot S 2.1010.1010
OMNIS Dosing Module 2.1003.0010
Analog measuring module 6.02101.010
OMNIS 10 mL cylinder unit without accessories, 2x 6.01503.210
Cable MDL PL/SO 0.5 m 6.02102.010
Electrode cable plug-in head G / plug P, 1.5 m for Cu ISE 6.02104.010
Electrode cable plug-in head U / plug P, 1.5 m for Unitrode 6.02104.610
OMNIS Stand-Alone license 6.06003.010
OMNIS instruments license: 1 license 6.06002.010
FEP tubing / M6 / 150 cm, 2x 6.1805.030
FET tubing / M6 / 40 cm, 2x 6.1805.100
Cu ISE 6.0502.140
Unitrode with Pt1000 (Head U) 6.0258.600

Solutions

. .
Titrant c(CuSO4) = 0.01 mol/L 2.497 g CuSO4 • 5 H2O is weighed into a 1 L volumetric flask and dissolved in deion. H2O. The flask is then filled up to the mark with deion. H2O.
Acetate buffer 116 g ammonium acetate is weighed into a 1 L volumetric flask and dissolved in deion. H2O. 86 mL glacial acetic acid is added. The flask is then filled up to the mark with deion. H2O.

Analysis

Approximately 5 grams of liquid soap is weighted using the balance and taken in a titration vessel. Using the pumps, around 75 mL of deionized water is added to the sample. The pH of mixture is lowered to approximately 5.0 using glacial acetic acid in a SET titration. Titration is then carried out using CuSO4 with 0.01 mol/L concentration as the titrant until after the equivalence point is achieved.

Parameters

. .
Mode MET U
Stirrer speed 8
Signal drift 30 mV/min
Max. waiting time 32 seconds
Volume increment 0.05 mL
Stop volume 10 mL
EP criterion 5
EP recognition all

Results

. .
wEDTA / % (n = 3) s(rel) / %
0.081 1.67

This information has been sourced, reviewed and adapted from materials provided by Metrohm AG.

For more information on this source, please visit Metrohm AG.

Tell Us What You Think

Do you have a review, update or anything you would like to add to this article?

Leave your feedback
Submit