Advances in Fingerprint Technology.pdf

een prepared and evaluated as fingerprint reagents by Della, Kobus, and coworkers.
116,117 Other analogues that have been prepared and tested as fingerprint
reagents are amino- and hydroxy-ninhydrins and a pyridine analogue
(Almog et al. 118,119 ), arylated ninhydrins (Joullié et al. 111,120-122 and Della
et al. 116,117 ), a thiophene analogue (Joullié, Cantu, and co-workers 123 ), two
“ninhydrin dimers” (Joullié et al. 124 ), a pyrazine analogue (Frank et al. 125 ),
and a phenyldiazo-ninhydrin (Della and Taylor 116 ). Alkyl ninhydrins were
synthesized to obtain better solubility in nonpolar solvents (Hark and
Joullié 122 and Pounds 126) . The effect of various alkoxy groups on the solubility
and fluorogenicity of the analogues was recently reported by a joint team of
the National Research Institute of Police Science and the Pharmaceutical
Institute of Tohoku University in Japan. 127
A list of ninhydrin analogues that have been prepared and evaluated can
be found in Petrovskaia’s Ph.D. thesis. 112 A comprehensive list of analogues,
containing more than 80 compounds that have been published over the years,
not only for fingerprint research, was recently composed by Hark. 128
A joint team of the British PSDB and the Israel Police recently reported
that the high hopes of benzo[f]ninhydrin had not been fulfilled. Despite the
better contrast and fluorescence produced by this compound, the total number
of latent prints that could be visualized by it was less than with ninhydrin.
129 Also, the longer homologue of ninhydrin, naphtho[f]ninhydrin (XXI,
Figure 5.10), reported by Hallman and Bartsch gave disappointing results. It
did not produce any visible reaction with amino acids. 130,131 Elber et al. have
recently used computational methods to study Ruhemann’s purple and analogous
compounds. They suggest a theoretical explanation for the limited
success in improving the color of the developed prints. Based on theoretical
considerations, they have also designed new analogues that might afford
more intense colors with latent fingerprints. Their best “candidates” are
modified ninhydrin molecules, in which one or two of the side carbonyl
oxygens are replaced by either divalent sulfur or by methylene groups. 132
These compounds have not yet been prepared.
Ninhydrin derivatives that are not exactly “analogues” but that are also
used in fingerprint visualization are ninhydrin-hemiketals. Compounds of
this type have been prepared by Takatsu et al. in Japan to substitute ninhydrin
for fingerprint development on thermal paper which is contaminated by the
conventional ninhydrin formulations. The rationale behind their study is
that, like ninhydrin, its hemiketals might react with latent fingerprints, but
they are much more soluble than ninhydrin in nonpolar solvents. Indeed,
the hemiketal derived from ninhydrin and 3,5,5-trimethyl-1-hexanol
(Figure 5.12) in hexane solution developed good prints on thermal paper
without any contamination. 133 It is currently used by forensic science laboratories
in Japan. 91