应用环境离子化质谱法对南美驼毛纤维进行法医鉴定：羊驼、骆马和原驼。

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

机构信息

National Fish and Wildlife Forensic Laboratory, 1490 E. Main St., Ashland, OR 97520, USA.

Universidad Mayor, Chile.

出版信息

Rapid Commun Mass Spectrom. 2020 Dec 15;34(23):e8916. doi: 10.1002/rcm.8916.

DOI:10.1002/rcm.8916

PMID:32770752

Abstract

RATIONALE

The keratin fleece of the endangered vicuña (Vicugna vicugna) commands a high value in international markets, and this trade has caused illegal poaching and a substantial decrease in vicuña 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 vicuña (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 vicuña 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 vicuña, 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.

摘要

原理

濒危的小羊驼（Vicugna vicugna）的羊毛在国际市场上价值很高，这种贸易导致了非法偷猎和小羊驼数量的大量减少。毛发的形态分析没有分辨率来确定骆驼科天然纤维的起源物种。此外，骆驼科羊毛的商业交易还包括羊驼（Vicugna pacos）和原驼（Lama guanicoe）羊毛的合法贸易。

方法

使用 X 射线荧光（XRF）光谱法、水平衰减全反射傅里叶变换红外（HATR-FTIR）光谱法和实时直接分析飞行时间质谱（DART-TOFMS）收集了 19 只小羊驼、20 只原驼和 20 只羊驼的角蛋白纤维光谱。每种技术的分析都评估了数据，以确定这三个分类群是否可以使用描述性或多元统计数据进行分离。

结果

XRF 分析表明，三种物种检测到的元素及其相对浓度相似，而 HATR-FTIR 分析可以识别羊驼的羊毛，但无法区分小羊驼和原驼。使用 DART-TOFMS 进行环境电离检测到的离子，无论是正离子模式还是负离子模式，都能得到最好的结果，并表明每个分类群都是独特的。对质谱的多元分析创建了强大的模型，可以分辨出每个物种（LOOCV=99.9%）。对 8 个验证样本的分析正确地分配到了适当的物种，证明了 DART-TOFMS 推断分类来源的可靠性。