Examination of 5-Alkoxyninhydrins as Latent Fingerprint Visualization Reagents

• NCJ Number: 189957
• Journal: Canadian Society of Forensic Science Journal Volume: 34 Issue: 2 Dated: June 2001 Pages: 73-79
• Author(s): H. Ohta; K. Ogasawara; Y. Suzuki; R. Sugita; S. Suzuki
• Date Published: June 2001
• Length: 7 pages
• Publication Format: Article
• Publication Type: Report (Study/Research)
• Language: French; English
• Country: United States of America

Annotation

This article reports on the synthesization and examination of four side-chain-elongated analogues of 5-methoxyninhydrin as reagents for latent fingerprint visualization for the purpose of improving the solubility of ninhydrin.

Abstract

Ninhydrin is a useful amino-acid-detecting reagent and is widely used for amino acid analysis in the biological use of visualization of latent fingerprints on porous surfaces in forensic investigations. A large number of ninhydrin analogues have been synthesized and examined in an attempt to improve the efficient detection of latent fingerprints; however, it is difficult to create reagents that can replace ninhydrin, but there are still possibilities to improve the detectability of latent fingerprints by using fluorescence through the introduction of an alkoxy group to ninhydrin. The current study attempted to increase the solubility of ninhydrin in nonpolar solvents and reduce the precipitation of ninhydrin through the introduction of an aliphatic chain, so as to improve the ability to detect latent fingerprints by fluorescence. All the synthesized 5-alkoxyninhydrins were thick oils or amorphous and soluble in n-hexane if 1-3 percent (v/v) ethanol and 1 percent (v/v) acetic acid were added. The solubilities of the entire group of synthesized compounds in n-hexane were higher than ninhydrin and increased by side-chain elongation as expected. n-Hexane solution of 5-ethoxyninhydrin showed stronger fluorescence at room temperature and higher solubility than ninhydrin, and it was stable in working solutions for 2 months; however, fingerprint visualization by using these compounds showed that the emax of RP, color depth of the fingerprints, fluorescence of the fingerprints were all reduced unexpectedly by side-chain elongation. The reason for the decrease is under consideration, but the possible reason might be the decrease of the conjugation between the alkoxy group and the aromatic ring or the decrease of the coplanarity of the RP because of steric hindrance of hydrocarbon chains. 6 figures and 12 references