DFO (9H-1,8-Diazafluoren-9-one)

Preparation method( Collection of samples)

As porous surface for the fingerprints deposition, it was selected white office paper in sheets of A4 size with a paper weight of 75 g/m2. Two female and three male subjects were chosen to deposit the fingerprints. Each subject deposited by rotation the fingerprints of all fingers on four different sheets of paper, two for each hand, divided into 30 quadrants (5 columns 6 rows). On the first sheet, natural fingermarks were collected; on the second sheet charged fingerprints were deposited after running the fingers on the areas of maximum secretion of the face, such as the forehead, nose or chin. This procedure was repeated six times, waiting half an hour between two subsequent depositions, to ensure the regeneration of natural secretions on the hands of the donor. The columns of the sheet corresponded to the days in which the analyses were made and the rows corresponded to the different solutions with which the fingerprints were treated. Once the deposition was completed, the sheets were cut to separate the quadrants with only one fingerprint deposited. Each quadrant was then immerged in a different solution (S1, S2, S3 or SD （ DFO (9H-1,8-Diazafluoren-9-one) solution）) within a plastic tray until it was completely soaked, then air-dried for a few seconds and finally placed in an oven for 3 min at 170 ℃.

DFO solution preparation

the solution of DFO (9H-1,8-Diazafluoren-9-one) was prepared: DFO solution (SD): 0.0625 g of DFO, 7.5 mL of methanol, 5 mL of glacial acetic acid, 70 mL of HFE-71DE, 180 mL of HFE-7100.

Sample handling

Tried to simulate the initial condition under which a natural fingermark is deposited on the paper. As done during the qualitative analysis, the quadrants of paper were immersed in the IND-Zn and DFO (9H-1,8-Diazafluoren-9-one) solutions, air-dried for a few seconds and placed in an oven at 170 ℃ for 3 min. Once pulled out of the oven, all the paper samples had assumed a pink color, indicating that the reaction had occurred. Subsequently, the quadrants were further cut into squares all having the same size and each of them was placed in an Eppendorf tube containing the carrier solvent of the solution in which they were previously immersed. So, for the samples treated with S1 it was used as extraction solvent the petroleum ether, for those treated with S2, S3, and SD, it was used the HFE-7100. Then, the tubes were centrifuged for 2 min at 10,000 rpm to complete the extraction process and make the sample ready to be transferred in the fluorometer and analyzed.

Applications

DFO (9H-1,8-Diazafluoren-9-one) shows orange fluorescent fingerprints. DFO, which is up to date the enhancing reagent most used in the forensic laboratories of the RIS, confirmed its excellent qualities from the point of view both of the fluorescence intensity and of the definition of the fingerprints enhanced, showing performances sufficiently effective even after the 3 months of shelf-life expected.

References:

[1].Marriott C, Lee R, et,al. Evaluation of fingermark detection sequences on paper substrates. Forensic Sci Int. 2014 Mar;236:30-7. doi: 10.1016/j.forsciint.2013.12.028. Epub 2014 Jan 6. PMID: 24529772.