Why does Ninhydrin Solution Turn Purple after 60minutes?

25 September 2023 0 6K Report

We recently started to try a Ninhydrin method to test for amino acid concentration. We are having some issues with the Ninhydrin solution itself. From the method we are trying to accomplish they created a 8% Ninhydrin solution in Acetone. When we make this solution after ~60minutes the Ninhydrin Solution will start to turn purple color. We have tried in multiple different containers/vials and have eliminated possible causes of contamination. What would be causing the solution to be turning purple after ~60minutes?

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