An investigation of isatin as a potential reagent for latent fingermark detection on porous surfaces

This study investigated isatin as a potential fingermark enhancement reagent for use on porous surfaces. A number of parameters were investigated, including concentration, solvent system, pH of the solution, and optimization of the development conditions. It was determined that isatin at a concentration of 0.05% (w/v) provided the optimum balance between the luminescence of the fingermark ridges and background. A carrier solvent of dioxane mixed with acetone [12.5% (v/v)] produced the most intense luminescence. It was determined that the optimum pH for the development of fingermarks was 5.0 and that this could be reached by the addition of 4% (v/v) sodium carbonate buffer. The use of a dry heat press at 180°C for 10 s provided optimal development conditions. The possible enhancement of isatin-treated fingermark impressions using metal salts was investigated and it was determined that secondary treatment with an ethanolic zinc chloride solution provided enhanced luminescence emission. However, little color change to the developed fingermarks was observed. A comparison of isatin with 1,2-indanedione-zinc (IND-Zn) and DFO demonstrated that the latter two reagents provided greater sensitivity and luminescence than isatin despite the fact that isatin generated strong room-temperature luminescence.