Problems in EDTA Assay
Posted: Mon Nov 20, 2017 8:30 am
We are analysing EDTA in a pharmaceutical product and we have a peak that appears and grows with time.
The mobile phase is a mixture of 10 mM tetrabutylammonium hydroxide at pH 7.5 and Methanol in a proportion 75 : 25 v/v. The diluent is a solution of copper (II) nitrate 1.6 mM.
The fresh sample shows a peak of EDTA but after 40 minutes appear a new peak.
Is it possible that this peak correspond to a different protonation specie of EDTA? Is it recommended to control the pH of the sample diluent?
The mobile phase is a mixture of 10 mM tetrabutylammonium hydroxide at pH 7.5 and Methanol in a proportion 75 : 25 v/v. The diluent is a solution of copper (II) nitrate 1.6 mM.
The fresh sample shows a peak of EDTA but after 40 minutes appear a new peak.
Is it possible that this peak correspond to a different protonation specie of EDTA? Is it recommended to control the pH of the sample diluent?