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Interference of Ninhydrin Pretreatment on Leuco Crystal Violet Visualization of Bloodstains

NCJ Number
Canadian Society of Forensic Science Journal Volume: 34 Issue: 3 Dated: September 2001 Pages: 109-116
G. M. Miskelly; M. R. Kelderman
Date Published
September 2001
8 pages
This article describes the interference caused by prior ninhydrin treatment on the acidic Leuco Crystal Violet (LCV)- hydrogen peroxide test and explains its cause.
A standard ninhydrin solution was sprayed onto a pattern of bloodstains on an impervious floor and dark purple stains were obtained as a result. Subsequent treatment of the floor with an acidic LCV – hydrogen peroxide solution led to rapid decolorization of both the ninhydrin-induced color and the bloodstains themselves, with no appearance of color due to Crystal Violet. Results indicate that the observed decolorization on ninhydrin-treated bloodstains when treated with acidic LCV-hydrogen peroxide solution is due to two main factors. The first is the preferential oxidation of Ruhemann’s Purple (the purple product of the ninhydrin reaction) or its hydrolysis products rather than LCV. The second is the decomposition of the heme in acidic hydrogen peroxide solutions. Under these conditions the Ruhemann’s Purple can be decolorized and the heme destroyed prior to any color development due to the oxidation of LCV to Crystal Violet. Given the fact that LCV treatment has failed to develop color when used after ninhydrin at an actual crime scene, and given the possible variation in blood and reagent composition in the field, it is advisable that ninhydrin treatment not be followed by treatment with LCV-hydrogen peroxide–sulfosalicylic acid solution. It has been reported that an alternative formulation of LCV in which the pH has been increased slightly by the addition of sodium acetate can be used following ninhydrin treatment. 2 figures, 2 footnotes, 22 references