Advances in Fingerprint Technology.pdf

less volatile 1,1,2-trichloroethane, was recommended by J.R. Morris for
spraying. 45 A standard working solution of NFN contains about 0.5% ninhydrin
(w/v), 0.9% acetic acid (v/v), and 1.8% ethyl alcohol, in Fluorisol.
Ethyl alcohol is required to dissolve the solid ninhydrin, and acetic acid
provides the acidity required to balance the alkalinity of some papers. 46
The authors also mentioned some disadvantages of the new formulation
in their original paper. It forms background coloration on papers with a
particular surface coating, such as banknotes, some checks and postal money
orders, and rag-based writing papers, and on surfaces that have been exposed
to high humidity. NFN reagent is not suitable for application to nonabsorbent
surfaces such as plastics or ceramics. 42 An attempt to further improve the
formulation was reported in 1984 by Tighe. The solution suggested, “Freon
plus two,” is also based on Fluorisol, but instead of ethyl alcohol it contains
methyl alcohol and ethyl acetate. 47 Margot, Lennard, and co-workers reported
that the addition of acetic acid improves upon the results obtained by the
“Freon plus two” formulation. In 1986, they reported that the main advantage
of this formulation is the ease of its preparation; however, in all other respects
it resembles the original NFN reagent. 48
NFN formulation was the recommended composition in the Fingerprint
Development Techniques Guide, published in 1986 by the Scientific Research and
Development Branch (SRDB), of the British Home Office. The editor, T. Kent,
recommended the use of this reagent for paper, cardboard, raw wood, and
plasterboard. In his chapter on ninhydrin, Kent surveyed all the operational
aspects of this technique, including the preparation of solutions, necessary laboratory
equipment, the mode of application, and safety requirements. 49
The NFN formulation has become a general-purpose reagent, applicable
to a wide range of paper and other surfaces, with minimal background effects.
The production of Fluorisol was banned within the European community,
the U.S., and many other countries since the end of 1994 under the 1992
Brussels Amendment to the “Montreal Protocol on Substances that Deplete
the Ozone Layer.” In 1993, Watling and Smith suggested the use of heptane
as an alternative carrier to Freon 113. 50 W.O. Jungbluth, of the U.S. Army
Laboratory, reported in the same year that Genesolv 2000, a hydrochlorofluorocarbon,
was an acceptable replacement for Freon 113, “provided the
evidence does not possess … handwriting for possible examination.” 51 Good
results with heptane, comparable to those obtained with Freon 113, were
reported also by Hewlett and Sears, but they did not recommend its use for
fingerprint development due to the high flammability of the solvent. 52 Supercritical
carbon dioxide was reported as a potential substitute for Freon 113
by Hewlett et al. in 1996. 53
A recent formulation that appears to satisfy all the requirements for
fingerprint work is based on the work of Hewlett, Sears, and Suzuki from