Forensic identification of the keratin fibers of South American camelids by ambient ionization mass spectrometry: Vicuña, alpaca and guanaco

Abstract

Rationale The keratin fleece of the endangered vicuna (Vicugna vicugna) commands a high value in international markets, and this trade has caused illegal poaching and a substantial decrease in vicuna populations. Morphological analysis of hairs does not have the resolution to determine the species of origin of camelid natural fibers. In addition, commerce in camelid fleece also includes the legal trade of alpaca (Vicugna pacos) and guanaco (Lama guanicoe) wool. Methods The keratin fiber spectra of vicuna (n = 19), guanaco (n = 20) and alpaca (n = 20) were collected using X-ray fluorescence (XRF) spectrometry, Horizontal attenuated total reflectance Fourier transform infrared (HATR-FTIR) spectroscopy and direct analysis in real time time-of-flight mass spectrometry (DART-TOFMS). Analysis with each technique evaluated the data to determine if the three taxa could be separated using either descriptive or multivariate statistics. Results XRF analysis showed that the elements detected and their relative concentrations were similar in all three species, whereas HATR-FTIR analysis could identify alpaca fleece but could not differentiate vicuna from guanaco. Ions detected by ambient ionization using DART-TOFMS, in either positive- or negative-ion mode, gave the best results and showed that each taxonomic group is distinctive. Multivariate analysis of the mass spectra created robust models which resolved each species (LOOCV = 99.9%). The analyses of eight validation samples were correctly assigned to the appropriate species and demonstrated the reliability of DART-TOFMS to infer taxonomic source. Conclusions The DART-TOFMS spectra of unmodified keratin fibers infer that the chemotype of each species is heavily influenced by fatty acids, cholesterol and its analogs, and that these ions are useful in separating the fleece of vicuna, alpaca and guanaco. We posit that the etiological source of these chemotype differences is consistent with genetic modulations and is less influenced by diet. Accurate taxonomic identification of fleece is important to identify violations and assists in the protection of rare species.

Rationale The keratin fleece of the endangered vicuna (Vicugna vicugna) commands a high value in international markets, and this trade has caused illegal poaching and a substantial decrease in vicuna populations. Morphological analysis of hairs does not have the resolution to determine the species of origin of camelid natural fibers. In addition, commerce in camelid fleece also includes the legal trade of alpaca (Vicugna pacos) and guanaco (Lama guanicoe) wool. Methods The keratin fiber spectra of vicuna (n = 19), guanaco (n = 20) and alpaca (n = 20) were collected using X-ray fluorescence (XRF) spectrometry, Horizontal attenuated total reflectance Fourier transform infrared (HATR-FTIR) spectroscopy and direct analysis in real time time-of-flight mass spectrometry (DART-TOFMS). Analysis with each technique evaluated the data to determine if the three taxa could be separated using either descriptive or multivariate statistics. Results XRF analysis showed that the elements detected and their relative concentrations were similar in all three species, whereas HATR-FTIR analysis could identify alpaca fleece but could not differentiate vicuna from guanaco. Ions detected by ambient ionization using DART-TOFMS, in either positive- or negative-ion mode, gave the best results and showed that each taxonomic group is distinctive. Multivariate analysis of the mass spectra created robust models which resolved each species (LOOCV = 99.9%). The analyses of eight validation samples were correctly assigned to the appropriate species and demonstrated the reliability of DART-TOFMS to infer taxonomic source. Conclusions The DART-TOFMS spectra of unmodified keratin fibers infer that the chemotype of each species is heavily influenced by fatty acids, cholesterol and its analogs, and that these ions are useful in separating the fleece of vicuna, alpaca and guanaco. We posit that the etiological source of these chemotype differences is consistent with genetic modulations and is less influenced by diet. Accurate taxonomic identification of fleece is important to identify violations and assists in the protection of rare species.