Ninhydrin (CAS No 485-47-2) is a chemical compound widely used in the biochemical and forensic sciences Originating as a synthetic reagent it primarily functions by reacting with free amino groups in proteins and peptides resulting in a deep blue or purple color known as Ruhemann s purple This makes it particularly useful for detecting amino acids and analyzing protein structure In vitro ninhydrin demonstrates high sensitivity for amino acid detection in the nanomolar to low micromolar range It is frequently used in applications including the visualization of fingerprints protein and amino acid quantification and various drug screening protocols In laboratory settings ninhydrin often serves in cell models and animal studies to detect and quantify biomolecules significantly aiding in the complex analysis of biochemical pathways Experimental concentrations typically depend on the specific research design