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 |
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This information has been sourced, reviewed and adapted from materials provided by Metrohm AG.
For more information on this source, please visit Metrohm AG.