Evaluating new blends of HFE-7100 iodine α-naphthoflavone sprays for fingermark development

Abstract

A global phase-out of the hydrochlorofluorocarbon solvent AK-225 (HCFC-225), a carrier solvent used in certain all-in-one iodine solutions, has mandated a reassessment of HFE-7100 as an alternate carrier solvent. Direct substitution of AK-225 for HFE-7100 failed owing to incompatible solubility, prompting evaluation of blends containing both heptane and dichloromethane. This evaluation of heterogenous formulations of HFE-7100 has yielded a new iodine solution, a modified α-naphthoflavone fixing solution, and an all-in-one iodine developer solution with stability of ~4 hours. The all-in-one blended HFE-7100 spray reagent delivers approximately equivalent fingermark development to the AK-225 all-in-one developer on gyprock, tile, and plastic surfaces in preliminary trials. Sequentially applying HFE-7100 iodine solution, followed by α-naphthoflavone solution, allowed for clear development of fingermarks on paper surfaces. This work outlines alternate HFE-based developers as a stopgap measure in light of the current phase-down of HFC solvents in Australia, and elsewhere, and also provides an updated assignment of the chromophore produced by the iodine-naphthoflavone reaction that is supported by mass spectrometry evidence.