NEW FORMULATION OF DFO in HFE7100

(This article is reprinted from the October 1998 issue of FINGERPRINT WHORLD Vol 24 No 94, pp 163--167.  Thanks to Kurt Kuhn, Beverly Hills P.D., for submitting this article.)

by CLAUDE DIDIERJEAN, MARIE--HELENE DEBART & FRANK CRISPINO
Fingerprint Department,
Institut de Recherche Criminelle
de la Gendarmerie Nationale,
Rosny--sous--Bois, France

ABSTRACT

We propose a new formulation of DFO without CFC--113, non--dangerous for the ozone layer, non--toxic and non--flammable. The carrier solvent used in the solution is HFE--7l00.^TM Results are very encouraging because of equal quality or even better than those obtained with our CFC--113 based formulation.

INTRODUCTION

The treatment with DFO is a method of choice for developing latent fingerprints on porous substrates. ^l--5

HFE--7l00^TM, a hydrofluoroether developed by the 3M^TM company is the solvent we advocate as an alternative to the very commonly used CFC113 in the DFO formulation.

CFC113 was for a long time the preferred solvent, but as a result of the Montreal protocol on ozone depleting substances dating from June 16th 1987, its use is now drastically controlled and it is necessary to find alternative solvents.

Confronted by the loss of CFC113 in our laboratory, we had to find an alternative to the petrol ether formulation of DFO, which was judged to be not as efficient as our Arklone's one, but quite dangerous because of its high flammability.

Instead of abandoning the DFO sequence of fingerprint development, we tried then to find a HFE--7l00^TM solution.

Trials carried out recently by the PSDB on the possibility of introducing HFE--7l00^TM as carrier solvent in the treatment of porous substrates with ninhydrin, showed that HFE--7l00^TM can be very a very good substitute for CFC113.⁶

To our knowledge, with the exception of a formulation proposed by the BKA⁷ which we did not consider satisfactory enough because of the precipitation of the reactant a few hours after its solution is made up, any satisfactory new formulation of DFO in HFE--7l00^TM has yet to be proposed.

EXPERIMENT

HFE--7l00^TM (1 --methoxynonafluorobutan) has been very recently developed and proposed by 3M^TM as replacement for CFCs. In contrast with the very environmentally harmful CFC--113, its ozone depletion potential is zero.⁸

Moreover, it ideally fulfils all the other characteristics needed for a good carrier solvent in the DFO or ninhydrin process:

Our formulation of DFO in CFC--113

The CFC--113 based formulation described below is the one commonly used in our laboratory until now. Although slightly different from the one widely adopted in many laboratories, it leads to very good results on a large range of porous substrates. Other very efficient formulations have been developed by other fingerprint laboratories and are available in the literature.^1--5

Formulation of DFO in CFC--113 used at the IRCGN

New formulation of DFO in HFE--7l00^TM

First, the CFC--113 based formulation was kept as a starting point, and HFE--7l00^TM simply replaced CFC--113 while keeping all the other parameters unchanged. Initial experiments carried out on fresh fingerprint samples in order to assess this new mixture indicate clearly that with equal DFO concentrations (0.15 g/l, 0.88 mmol/l), development with the HFE--7l00^TM based solution was less efficient.

In order to optimize the HFE--7l00^TM formulation, the DFO concentration was increased from 0.15 g/l (0.88 mmol/l) to 0.25 g/l (1.47 mmol/l), while keeping the other parameters fixed. This solution turns out to be unstable and the DFO precipitates as fine needles a few hours after dissolution. HFE--7l00^TM is less polar than CFC 113 and therefore, the amount of polar co--solvent is not sufficient to keep all the DFO dissolved.

In order to ensure a good stability of the working solution over time, the concentration was fixed to 0.25 g/l and the amount of methanol increased to 40 ml. At the same time the amount of acetic acid was decreased to 20 ml in order to prevent ink running. This solution turns out to be very stable at room temperature, several days and weeks after its preparation.

RESULTS

Samples

Items used for the assessment of this new working solution consisted of halves of latent fingerprints on paper, one being processed with HFE--7l00^TM formulation and, its counterpart, with the reference CFC--113 mixture. The HFE--7l00^TM formulation was also assessed in a few actual cases.

Treatment

The processing of items is typical:

It should be noted however that the working solution turns cloudy before precipitating after several dippings. The solution should thus be regularly discarded to avoid this effect and the eventual contamination of substrates by undissolved DFO particles.

Observation

Fingerprints developed with DFO show maximum fluorescence under excitation at 495 nm and are visible through an orange filter.

Luminescent fingerprints resulting from processing with the HFE--7l00^TM based solution of DFO (or CFC113 for comparison) are presented as photographic illustrations.

DlSCUSSlON
Side by side comparisons of split--depleted fingerprints were observed:

Ridges of the fingerprints obtained with the reference CFC113 formulation are yellow and very luminescent. In the HFE--7l00^TM solution they seem to be darker orange, slightly less luminescent.

Fingerprints developed with the HFE--7l00^TM based formulation show a better definition of ridges (better resolution).

Ridges of fingerprints developed with the HFE--7l00^TM formulation are more regular. The little aggregates of DFO observed all along the ridges are less luminescent and therefore ridges look less dotted. Minutiae, therefore, look clearer with better definition.

Taken as a whole, results obtained with the new formulation of DFO in HFE--7l00^TM seem to be of equal quality and sometimes superior to those obtained with our usual CFC113 based formulation.

CONCLUSION

HFE--7l00^TM seems to be a very good replacement solvent for the CFC--113 in the DFO mixture.  It can be handled without any health hazard, it is not harmful to the ozone layer and compatible with all kind of substrates to be processed.

As a consequence, waiting for a more optimum DFO formulation, we adopted the proposed HFE--7l00^TM one. This new formulation of DFO is now implemented in the Fingerprint Department of IRCG as follows:

Results obtained in our trials and particularly in a few actual cases are very satisfactory. At this stage an assessment over a longer time period and over a larger number of actual cases is necessary in order to confirm this preliminary study.

For further information, contact:
Cne Frank CRISPINO
Departement Empreintes Digitales
Institut de Recherche Criminelle de la Gendarmerie Nationale
1 , boulevard Theophile SUEUR
93111 Rosny sous Bois cedex
France
00 33+ 1 49 35 50 54
00 33+ 1 35 50 27 (Fax)
e--mail:  Frank.Crispino<GERE@Mail.codix.fr>

Bibliographic References

¹ Pounds, C.A., Grigg R.: The use of l,8--diazafluoren--9--one (DFO) for the fluorescent detection of latent fingerprints on paper. A preliminary evaluation, J. Forensic Sci. (35):  169--147 1989

² Stoilovic, M.: Improved method for DFO development of latent fingerprints, Forensic Science International (60): 141--153, 1993

³ McComiskey, P.: DFO. A simple and quick method for the development of latent fingerprints, Fingerprint Whorld, 16(62), 1990

⁴ Masters, N.E., Morgan, R., Shipp, E.: DFO, its usage and results, J. Forensic Ident. 41(1): 3--10, 1991

⁵ Hardwick, S., Kent T., Sears, V., Winfield, P.: Improvements to the formulation of DFO and the effects of heat, Fingerprint Whorld, 19(73), 1993

⁶ Hewlett, D., Sears, V., Suzuki, S.: Replacements for CFC--113 in the Ninhydrin process: part 2, J. Forensic Ident. 47(3): 300--306, 1997

⁷ Bundes Kriminal Amt, Oral Communication, First European Meeting of Forensic Science, 1997

⁸ Product information distributed by the 3M^TM Society

(Editor--—Kurt Kuhn, who submitted this article, also submitted purchase information for the HFE7100.  Thanks again Kurt).

HFE7100^TM
$19.75/lb
1 gallon = 12 lbs.

Gallade Chemical Inc.
1230 East Saint Gertrude Place
Santa Ana, CA 92707
(714) 546--9901

This article was printed in “THE PRINT”
Volume 15(1) January / February 1999, pp 6 - 8
and has been obtained from the online library provided by the
Southern California Association of Fingerprint Officers
www.scafo.org