Advances in Fingerprint Technology.pdf

Figure 5.6 The 1,3-dipole form of the intermediate imine in the ninhydrin
reaction.
Figure 5.7 Protonated (XII) and deprotonated (XIII) forms of Ruhemann’s purple.
(From Grigg, R., Malone, J.F., Mongkolaussavaratana, T., and Thianpatanagul, S.,
J. Chem. Soc., Chem. Commun., 421, 1986.
Ninhydrin is a valuable reagent for the detection of the non-biuret dialyzable
amino acids. Various tissues, milk, urine, saliva, blood, plasma, serum,
lymph, cyst contents, fresh eggs, albumin, fresh and boiled meat, and sweat
contain substances which dialyze and react with ninhydrin. The fact that
sweat gives an intense reaction is of importance in carrying out the test.
Caution must be taken that nothing is touched which later comes in contact
with the reagent.
In the following years, ninhydrin became a common reagent in various
biochemical and medical test methods. Following the introduction of chromatographic
techniques in the early 1940s, ninhydrin was routinely used to
locate amino acids on chromatograms. Thus, it is somewhat surprising that
despite its usage over the years and the oft-repeated admonition against
touching chromatograms or other test material to be exposed to ninhydrin,
only in 1954 was ninhydrin recognized as a latent fingerprint reagent. Two
Swedish scientists, Oden and von Hofsten, were the first to suggest the use
of ninhydrin as a means to develop latent fingerprints. 36 A year later, Oden
patented the process. 37,38
As mentioned previously, one of the outstanding features of ninhydrin
compared with other chemical processes for paper is the fact that amino