The effect of zinc chloride, humidity and the substrate on the reaction of 1,2-indanedione-zinc with amino acids in latent fingermark secretions |
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Authors: | Spindler Xanthe Shimmon Ronald Roux Claude Lennard Chris |
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Institution: | Centre for Forensic Science, University of Technology, Sydney, Ultimo, NSW, Australia. Xanthe.Spindler@uts.edu.au |
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Abstract: | Anecdotal evidence from forensic practitioners and studies conducted under controlled conditions have indicated that the reaction between 1,2-indanedione and the amino acids present in latent fingermark deposits is highly susceptible to ambient humidity. The addition of catalytic amounts of zinc chloride to the 1,2-indanedione working solution--usually in the order of 1:25 to 1:4 molar ratio (indanedione:zinc)--significantly improves the colour and luminescence of fingermarks treated under dry conditions but appears to have a negligible effect on fingermarks treated in humid environments. The results presented in this paper confirmed that zinc(II) ions added to the 1,2-indanedione working solution act as a Lewis acid catalyst, stabilising a key intermediate during a rate-limiting hydrolysis step. Furthermore, studying the reaction using a chromatography-grade cellulose substrate method previously reported confirmed that cellulose substrates play a major role in facilitating the indanedione-amino acid reaction by acting as a surface catalyst in the early stages of the reaction and by directing the formation of the desired luminescent product (Joullié's Pink). |
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