Fingerprint Reagents with Dual Action: Color and Fluorescence

Abstract

We define "dual fingerprint reagents" as chemical formulations that produce with latent fingerprints in one stage impressions that are both colored and fluorescent. Solutions containing ninhydrin and group IIb metal salts appear to be true dual reagents. Application of these formulations to latent fingerprints on paper is as efficient as the two-step process beginning with ninhydrin and followed by treatment with metal salt. In the color mode, fingerprint detectability with the two ninhydrin-metal salt reagents (one with zinc chloride and the other with cadmium chloride) is comparable with that of ninhydrin itself, in spite of the difference in color. The sensitivity is significantly higher in the fluorescence mode. To view the latent impressions the exhibits are treated with ninhydrin-metal salt reagents and observed under white light illumination and under fluorescence conditions. Cooling to liquid nitrogen temperature enhances the fluorescence considerably. In the shorter wavelength domain, ninhydrin-metal salt reagents exhibit higher sensitivity than the recently reported dual reagent, genipin. The latter is advantageous, however, in the longer wavelength domain, on paper items with strong self-fluorescence, such as brown wrapping paper or paper printed with fluorescent ink. Upon reduction of the ninhydrin concentration 10-fold, ninhydrin-metal salt formulations become purely fluorogenic reagents; no color is noticed but the fluorescence is as intense as with concentrated solutions. Working at lower concentrations is an advantage from ecological and economical viewpoints.

Dual Fingerprint Reagents with Enhanced Sensitivity: 5‐Methoxy‐ and 5‐Methylthioninhydrin

“…Lowering the temperature to −200°C was not necessary–it only marginally increased the fluorescence. Like in the previous study with unsubstituted ninhydrin (1), it seems that the metal ions, which are pre‐mixed with the ninhydrin analogues, do not interfere with the reaction with amino acids and they react only with the initially formed Ruhemann’s purple. The metal ions could potentially prevent the formation of Ruhemann’s purple by reacting with the many intermediates that are formed in the ninhydrin reaction with amino acids, but this is not the case.…”

“…The results were compared with those obtained with DFO under the same conditions, in the color and fluorescence modes. Results were also compared with those obtained with the ninhydrin–zinc chloride dual reagent, on which we reported earlier (1). For a more accurate, semi‐quantitative comparison, similar experiments were also carried out on amino acid stains of known concentrations.…”

Chemical Sensing and Detection in Forensic Science

“…It was found that ninhydrindeveloped marks, when posttreated with a metal salt and cooled with liquid nitrogen, exhibited photoluminescence, which could be used to significantly enhance detection sensitivity and contrast [75]. Since these early studies, the main focus of amino acid-reagent research has been on developing reagents that exhibit good color and superior photoluminescence without the need for additional treatments (such as metal salt treatment or cooling) [112]. Photoluminescence is observed by illuminating the developed fingermark with a filtered light source (or laser) and viewing through appropriate filters (Fig.…”

2-(2-Hydroxy-5-nitrobenzylidene)-1,3-indanedione versus Fluorescein Isothiocyanate in Interaction with Anti-hFABP Immunoglobulin G1: Fluorescence Quenching, Secondary Structure Alteration and Binding Sites Localization

“…During the last few years, a series of indanedione compounds were synthesized [7] and reported in the literature for their fluorescent properties [8,9]. Although substituted indane-1,3-dione derivatives have been used in the fields of medicine [10] and biology [11], literature data on their chemical and physical interactions with proteins is scarce [12,13], and no chemical and physical studies of their interaction with immunoglobulins, and their applicability as fluorescent labels were found.…”