Volatile-compound fingerprinting and discrimination of positional isomers in stamp-pad ink tracing using HS-GC-IMS combined with multivariate statistical analysis

Yinghua Qi; Xinhua Lv; Junchao Ma; Mingyuan Lei; Chao Feng; Wenhui Lu; Zhongyuan Ji; Yichen Wang; Yuchen Wang; Xuebo Li

doi:10.1007/s00216-023-05121-8

Volatile-compound fingerprinting and discrimination of positional isomers in stamp-pad ink tracing using HS-GC-IMS combined with multivariate statistical analysis

Anal Bioanal Chem. 2024 Feb;416(5):1293-1305. doi: 10.1007/s00216-023-05121-8. Epub 2024 Jan 8.

Authors

Yinghua Qi^{1

2}, Xinhua Lv², Junchao Ma^{3

4}, Mingyuan Lei², Chao Feng², Wenhui Lu^{1

2}, Zhongyuan Ji², Yichen Wang², Yuchen Wang², Xuebo Li^{5

6}

Affiliations

¹ Key Laboratory of Forensic Science, Ministry of Justice (Academy of Forensic Science), Shanghai, China.
² Characteristic Laboratory of Forensic Science in Universities of Shandong Province, Shandong University of Political Science and Law, Jinan, 250014, Shandong Province, China.
³ Key Laboratory of Forensic Science, Ministry of Justice (Academy of Forensic Science), Shanghai, China. majunchao@sdupsl.edu.cn.
⁴ Characteristic Laboratory of Forensic Science in Universities of Shandong Province, Shandong University of Political Science and Law, Jinan, 250014, Shandong Province, China. majunchao@sdupsl.edu.cn.
⁵ Key Laboratory of Forensic Science, Ministry of Justice (Academy of Forensic Science), Shanghai, China. lixuebo@sdupsl.edu.cn.
⁶ Characteristic Laboratory of Forensic Science in Universities of Shandong Province, Shandong University of Political Science and Law, Jinan, 250014, Shandong Province, China. lixuebo@sdupsl.edu.cn.

PMID: 38189918
DOI: 10.1007/s00216-023-05121-8

Abstract

The rising crime rate associated with document forgery has a significant impact on public safety and social stability. In document fraud cases, determining the origin of a particular stamp-pad ink is the most important objective. In this study, a comprehensive analysis of the volatile compounds in quick-drying stamp-pad inks from six commonly used brands were performed for the first time, utilizing a combination of headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) and multivariate statistical analysis methods. Visual and comparative analysis of the differential volatile components among different stamp-pad ink samples was conducted using fingerprints and volcano plots. A total of 127 volatile compounds were accurately identified, with ketones, esters, alcohols, and aldehydes being the most abundant compounds in the stamp-pad inks. Hierarchical clustering analysis (HCA), including dendrograms and clustering heatmaps, was utilized to explore the correlations between these compounds and the samples. Additionally, the precise identification of positional isomers and functional group isomers of aliphatic compounds was achieved. To achieve accurate discrimination of various stamp-pad ink samples, a multivariate statistical analysis method was utilized to establish a classification model for them. Based on the results obtained from HS-GC-IMS, effective discrimination among different brands of stamp-pad ink samples was achieved through principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA). The model exhibited excellent performance, with the fit index of dependent variables (R²Y) and the predictive index of the model (Q²) values of 0.99 and 0.984, respectively. These results provided significant theoretical evidence for the application of HS-GC-IMS as an efficient technique in the analysis of volatile compounds, identification of positional isomers and functional group isomers, as well as tracing the origin of stamp-pad ink and analyzing the formation time of documents.

Keywords: Headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS); Multivariate statistical analysis; Positional isomers; Stamp-pad inks; Volatile compounds.

Abstract

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