DFO (1,8-DIAZAFLUOREN-9-ONE)
Introduction
1,8-DIAZAFLUOREN-9-ONE
(DFO) is a Ninhydrin analogue which reacts to the amino
acids present in the body protein. Research has shown
using DFO on paper evidence develops 2.5 times more latent
prints than when Ninhydrin is the sole process used.
Safety
As with all chemicals,
always read the MSDS (material safety data sheet) to learn
about the health hazards of each chemical. Due to the
flammable nature of some of these carriers, caution should
be exercised in the use and storage of these solutions.
They should be mixed and used in a fume hood. If no fume
hood is available, the technician mixing and using these
chemicals should be protected with a full-face breathing
apparatus, gloves and other protective clothing. No one
else should be near this operation unless similarly protected.
DFO is classified as "Harmful if Swallowed."
Mixing Instructions
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Do not mix the working solution until
you are ready to use it. The DFO powder and the DFO stock
solution have longer shelf lives than the working solution has.
It is recommended to mix only enough working solution that will
be used within two to three weeks. It may last longer than three
weeks, but the effectiveness may be less.
STOCK SOLUTION: Measure
and mix these solvents in a fume hood. While a magnetic stirrer
is not necessary, it does make the mixing process go faster.
Dissolve 0.5 gram of DFO powder in 100 ml of methanol. When
the powder is dissolved, add 100 ml of ethyl acetate. When it
is thoroughly mixed, add 20 ml of acetic acid. Store this solution
in a dark brown glass or polypropylene bottle and label it.
WORKING SOLUTION: Measure
and mix these solvents in a fume hood. Do not mix this solution
until you are ready to use it. The manufacturer recommends for
best results, do not use any working solution that is older
than two to three weeks. If a liter (1000 ml) of working solution
is needed, take the entire 220 ml of stock solution and add
780 ml of petroleum ether, mixing thoroughly. If less working
solution is desired, halve or quarter the solutions accordingly.
Processing Instructions
The paper specimen should
be dipped into the solution for ten seconds and allowed to dry.
This step should be repeated, as two dippings and dryings seem
to be better than one application. (Although it is possible
to spray this solution, it is not recommended due to the health
hazards involved and its inability to soak the specimen adequately.)
Heat is then applied. While expensive chemical ovens can be
used, a regular household toaster oven will work. The specimen
should be heated for ten minutes at 100° C (212° F).
View the paper item under a Forensic Light Source or laser.
As an alternative, a hair
dryer or dry iron will work. If using one of these alternative
heat sources, place a thick towel or other protective material
on the counter first. Then, place a few paper towels on it,
the paper evidence goes next and a few more paper towels on
top of that. Apply dry heat to the surface for several minutes.
A dry iron can be placed directly on top of the paper towels.
It is possible to stop ironing to check the progress with a
forensic light and, if the latent prints are not very bright,
continue to iron for a few minutes longer. Sometimes this added
application of heat will improve the results. The latent prints
may or may not be visible to the naked eye, but should be viewed
under a Forensic Light Source or laser.
Fluorescence Examination
DFO excels in the development
of latent prints on white papers, most pastel colored papers
and glassine envelopes/packets (commonly submitted in drug cases).
Suggested viewing wavelengths with the orange goggles are 450,
485, 525, and 530 nanometers for most papers. Good results can
be expected on manila envelopes, brown paper bags, cardboard,
Kraft paper, and most yellow legal pad paper when viewed at
570 to 590 nanometers through a red filter. Experimentation
is suggested with any piece of evidence to obtain the best amount
of fluorescence with different colored goggles and different
excitation wavelengths.
Sequential Processing
When DFO, Ninhydrin and
Physical Developer are each going to be used in the processing
of a specimen, DFO must be used as the first process if there
is to be any fluorescence. DFO will not fluoresce on a specimen
if the Ninhydrin compound has been applied first. However, for
those agencies without a Forensic Light Source, applying DFO
after Ninhydrin has been shown to enhance some latent prints.
On some specimens Ninhydrin will develop prints that DFO fails
to develop; therefore, in most instances, Ninhydrin should also
be used. Physical Developer can then be used after Ninhydrin.
Photography
Latent prints developed
with each process must be photographed before going on to the
next chemical process, as each subsequent process may obliterate
the latent prints developed from the previous one. It is necessary
to use a filter over the camera lens when photographing a latent
print illuminated with forensic light sources. Include a fluorescent
scale in the photograph. Match the camera lens filter color
to the color of the goggles being used to view the latent prints.
A Nikon 056 equates to the orange goggles and a Wratten 29 equates
to the red goggles. Any type of panchromatic black and white
film will work, as will color print film and color slide film.
For more information on fluorescence photography, see our fluorescent
photography technical note
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