Fatty Acid Structure and Degradation Analysis in Fingerprint Residues

Abstract

Abstract. GC-MS investigations were carried out to elucidate the aging behavior of unsaturated fatty acids in fingerprint residues and to identify their degradation products in aged samples. For this purpose, a new sample preparation technique for fingerprint residues was developed that allows producing N-methyl-N-trimethylsilyltrifluoroacetamide (MSTFA) derivatives of the analyzed unsaturated fatty acids and their degradation products. MSTFA derivatization catalyzed by iodotrimethylsilane enables the reliable identification of aldehydes and oxoacids as characteristic MSTFA derivatives in GCMS. The obtained results elucidate the degradation pathway of unsaturated fatty acids. Our study of aged fingerprint residues reveals that decanal is the main degradation product of the observed unsaturated fatty acids. Furthermore, oxoacids with different chain lengths are detected as specific degradation products of the unsaturated fatty acids. The detection of the degradation products and their chain length is a simple and effective method to determine the double bond position in unsaturated compounds. We can show that the hexadecenoic and octadecenoic acids found in fingerprint residues are not the pervasive fatty acids Δ9-hexadecenoic (palmitoleic acid) and Δ9-octadecenoic (oleic acid) acid but Δ6-hexadecenoic acid (sapienic acid) and Δ8-octadecenoic acid. The present study focuses on the structure identification of human sebum-specific unsaturated fatty acids in fingerprint residues based on the identification of their degradation products. These results are discussed for further investigations and method developments for age determination of fingerprints, which is still a tremendous challenge because of several factors affecting the aging behavior of individual compounds in fingerprints.

Changes in Fingerprints Depending on Physiological Factors

“…In our experiment, the subjects with the highest BMI, that is, overweight individuals, and those with the lowest BMI, that is, underweight persons, had fingerprints with significantly wider ridges than subjects with normal BMI (Table ). In the case of people who are overweight, the results can be explained by the larger skin area as well as the greater amount of sweat and sebum produced and susceptibility to sweating . In the case of underweight people, the significantly wider friction ridge impression is probably due to the fact that this group was dominated by women, who as mentioned above had used emollients in the morning.…”

“…The difference in the width of the ridges between the prints from women and men was 11% (p < 0.001). These results are surprising, as research by Pleik (6) shows that men secrete more sweat and sebum than women, which contributes to the durability of their prints (15). This is due in part to the number and distribution of sweat ducts, with men having more of them, as well as to hormone metabolism (16).…”

“…The formation of fingerprints depends largely on the physiological state of the body (6,14). Factors such as gender or BMI are very important in their formation, which was confirmed in our study (Table 1).…”

Analysis of amino acid enantiomers from aged fingerprints

“…4 Pleik et al focused on the identication of degradation products of common fatty acids in ngerprints as potential tool for age determination. 5 Van Dam et al used uorescence spectroscopy to determine the relative amount of uorescent oxidation products to estimate the age of ngerprints from male donors up to three weeks old, within several days' accuracy. 6 Alternatively, Oonk et al, using a proteomics approach, suggested several potential protein markers to estimate ngerprint age.…”

The Analysis of the Fatty Acid Content of Fingerprint Residues Using Gas ChromatographyMass Spectrometry

“…fingerprint residues using GC/MS. They found that Δ6-Hexadecenoic acid and Δ8octadecenoic acid, as well as associated degradation products, could be useful in determining the age of a fingerprint left on a surface [23]. This information could ultimately be useful in a forensic investigation to exclude a fingerprint that was not deposited contemporaneous with the predicted time that the crime of interest occurred.…”