Hello Myriam,

I'm not familiar with your problem, but I was very suprised to see that you decalcify your samples for three month. It doesnt take me that long. Perhaps I use a much stronger EDTA-solution (25%) than you. Maybe you can try mine.
- 500 gram EDTA
- 400 ml distilled water.
- Heat till booiling
- Add 1600 ml distilled water
- Add 40 gram NaOH.
- Solution becomes clear after a while.
- Let it cool down to roomtemperature
- Bring the pH to 7,4 with a NaOH

Decalcify at roomtemperature while stirring.

Good luck!
leon