Chemical Composition of Latent Fingerprints by Gas Chromatography–Mass Spectrometry. An Experiment for an Instrumental Analysis Course

Abstract

Attention from the media and general public has recently soared with regard to forensic chemistry. This rising awareness can be attributed to television shows such as CSI and Forensic Files that have made chemical analysis exciting. By utilizing a forensic-based experiment in an instrumental methods course, student interest in the laboratory can be stimulated. In addition, students will gain valuable experience with an analytical technique(s) that is used in real situations by forensic laboratories.The oldest method of personal identification for forensic purposes is latent fingerprint analysis. The ability to identify suspects from fingerprints left at a crime scene is a result of the arrangement of ridges on the finger pads being unique and permanent to each person (1). Recently, with advances in modern technology, scientists have begun to examine whether information in addition to ridge patterns can be gained from fingerprints. For example, researchers have discovered that they can obtain a suspect's DNA profile by applying the polymerase chain reaction to skin debris present in fingerprints left on forensic evidence (2, 3). In parallel to this advancement, progress has been made in determining the chemical composition of a latent fingerprint using infrared (IR) microspectroscopy and gas chromatography-mass spectrometry (GC-MS) (4-8).Fingerprints primarily consist of material secreted by the eccrine glands located in the palms and fingertips and the sebaceous glands that are located most abundantly on the scalp and face (6). These chemical components include inorganic salts such as iron and sodium, amino acids, and lipids such as fatty acids, wax esters, squalene, and cholesterol (9). IR (7,8) and GC-MS (4-6) studies have examined whether differences in the chemical composition of fingerprints can be used to establish age, gender, and so forth. This information could allow a suspect pool to be reduced even if the fingerprints obtained from a crime scene were smudged or patterns were not matched after being processed in the Integrated Automated Fingerprint Identification System (10).We have adapted a procedure described by Asano et al. (5) and Archer et al. (4) for fingerprint extraction and analysis by GC-MS for use in an undergraduate instrumental analysis course. In the experiment, students collect fingerprint residue samples on glass beads or glass slides, extract the chemical constituents from the residue using chloroform, convert the fatty acids and other components into trimethylsilyl derivatives, and finally, analyze the products using GC-MS. By converting the constituents into less polar, thermally stable materials through silylation, students gain experience in a technique that is frequently required to make samples amenable to GC analysis (11). Furthermore, students can perform a MS library search to identify the components present in their fingerprint residue and then compare their results to demonstrate that more information than just ridge pattern might be obtained from fingerprints found at crime...

Fingerprint composition and aging: A literature review

“…Composition can be affected by gender, although there have been differing conclusions as to the significance of the variations observed [16,19,69,70]. Recent findings in small scale experiments indicate fatty acids tend to be present in higher concentrations in male donors, such as saturated C15, C16 and C17 acids [16,19,70], although wide variations in composition were observed due to the sampling protocol [16].…”

Separation of fingerprint constituents using magnetic silica nanoparticles and direct on-particle SALDI-TOF-mass spectrometry

“…The averaged intensity value of lysine also improved after separation. Although glycine and serine were reported as 2 of the major amino acids found in fingerprints [48], neither was significantly detected after separation. Referring to Table 1, glycine and serine were 2 of the 5 amino acids completely suppressed by the addition of squalene.…”

“…Squalene was chosen in this experiment to represent one of the most abundant hydrophobic compounds found in fresh latent fingerprints [47,48]. The amount of squalene added (1 g) corresponded to the minimum amount of squalene that is commonly found in latent fingerprints [49].…”

“…Prior to and after the separation process, the fingerprints were analysed by MS for the commonly reported fatty acids and amino acids found in fingerprints [48]. Signal to noise values for most fatty acids did not differ considerably before and after separation.…”

Chemical Sensing and Detection in Forensic Science

“…Fundamental studies of the latent fingermark residue in situ, including aging studies, would aid this area of research. While there have been a number of reports in the literature regarding chemical analysis of the fingermark residue [119][120][121][122], most have tended to involve removal of the residue from the surface, thus losing any potential spatial information on the distribution of chemical species. There is also no doubt that the local environment, identity, and condition of the substrate, as well as the nature of the latent figure mark deposit itself, will have a large effect on the efficacy of any detection technique.…”