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Análise não destrutiva de tintas de instrumentos de escrita manual : uma contribuição para a investigação forense de documentos
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| 3.84 MB | Adobe PDF |
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Abstract(s)
Enquadramento: A exigência da preservação de prova em tribunal continua a constituir um desafio à investigação laboratorial, em particular na análise forense de documentos, onde a resposta à discriminação dos utensílios de escrita e datação de documentos é recorrente nos quesitos solicitados. Objetivo: Pretendeu-se desenvolver uma ferramenta pericial, com base em técnicas não destrutivas, que permita a caracterização e discriminação de tintas de canetas comerciais, bem como a identificação de parâmetros de envelhecimento e eventual datação destas tintas.
Materiais e Métodos: Foi efetuada uma pesquisa bibliográfica sistematizada para identificar técnicas não destrutivas que permitam a discriminação e datação de tintas e adquiridos corantes e instrumentos de escrita manual comerciais. Procedeu-se ao depósito dos corantes e das tintas em papel corrente e de filtro. Foram igualmente realizadas soluções em metanol e 2-fenoxietanol. As amostras obtidas foram caracterizadas por VSC, colorimetria e espectroscopias UV-Vis, Raman e FORS. Os dados foram tratados com recurso a excel, softwares spectragryph e KNIME Analytics Platform.
Resultados e Discussão: Das 51 canetas exploradas por VSC, foram selecionadas 26 de diferentes tipos e modelos, que permitiram a construção de um modelo preditivo com base nos dados da colorimetria apresentando um poder discriminatório entre os 94,545% e 95,385%. Deste subconjunto, apenas 11 (5 azuis e 6 verdes) apresentaram sinal Raman e foram sujeitas a análise por UV-Vis e FORS. As espectroscopias UV-Vis e Raman sugerem a presença do corante solvente azul 38 em 9 das canetas das 11 canetas estudadas, a presença de ftalocianina de cobre (II) em duas delas e residualmente de outros corantes. Com base nos espectros obtidos por FORS e Raman foi igualmente construído um modelo preditivo com um poder discriminatório de 81,818% para FORS e de 72,727% para Raman. Foi ainda possível reconhecer parâmetros de envelhecimento para a tinta de 2 canetas azuis.
Conclusão: Este estudo permitiu a construção de uma potencial ferramenta de discriminação de tintas de canetas com recurso a técnicas não destrutivas e a identificação de parâmetros de envelhecimento que poderão no futuro permitir a datação de tintas.
Background: The requirement of preservation of evidence in court continues to be a challenge for laboratory research, particularly in the forensic analysis of documents, where the answer to the discrimination of writing utensils and dating of documents is recurrent in the requested questions. Objective: This study aimed to develop an expert tool, based on non-destructive techniques, which allows the characterization and discrimination of commercial pen inks, as well as the identification of aging parameters and possible dating of these inks. Materials and Methods: A systematic bibliographic research was carried out to identify non-destructive techniques that allow the discrimination and dating of inks and acquired dyes and commercial handwriting instruments. The dyes and inks were deposited on current and filter paper. Solutions in methanol and 2-phenoxyethanol were also made. The obtained samples were characterized by VSC, colorimetry and UV-Vis, Raman and FORS spectroscopies. The data were processed using excel, software spectragryph and KNIME Analytics Platform. Results and Discussion: From 51 pens explored by VSC, 26 of different types and models were selected, which allowed the construction of a predictive model based on colorimetry data presenting a discriminatory power between 94.545% and 95.385%. From this subset, only 11 (5 blue and 6 green) showed Raman signal and were subjected to UV-Vis and FORS analysis. The UV-Vis and Raman spectroscopies suggest the presence of the solvent dye blue 38 in 9 of the 11 pens studied, the presence of copper (II) phthalocyanine in two of them and residually of other dyes. Based on the spectra obtained by FORS and Raman a predictive model was also built with a discriminatory power of 81.818% for FORS and 72.727% for Raman. It was also possible to recognize aging parameters for the ink of 2 blue pens. Conclusion: This study allowed the construction of a potential tool for discriminating pen inks using non-destructive techniques and the identification of aging parameters that may in the future allow the dating of inks.
Background: The requirement of preservation of evidence in court continues to be a challenge for laboratory research, particularly in the forensic analysis of documents, where the answer to the discrimination of writing utensils and dating of documents is recurrent in the requested questions. Objective: This study aimed to develop an expert tool, based on non-destructive techniques, which allows the characterization and discrimination of commercial pen inks, as well as the identification of aging parameters and possible dating of these inks. Materials and Methods: A systematic bibliographic research was carried out to identify non-destructive techniques that allow the discrimination and dating of inks and acquired dyes and commercial handwriting instruments. The dyes and inks were deposited on current and filter paper. Solutions in methanol and 2-phenoxyethanol were also made. The obtained samples were characterized by VSC, colorimetry and UV-Vis, Raman and FORS spectroscopies. The data were processed using excel, software spectragryph and KNIME Analytics Platform. Results and Discussion: From 51 pens explored by VSC, 26 of different types and models were selected, which allowed the construction of a predictive model based on colorimetry data presenting a discriminatory power between 94.545% and 95.385%. From this subset, only 11 (5 blue and 6 green) showed Raman signal and were subjected to UV-Vis and FORS analysis. The UV-Vis and Raman spectroscopies suggest the presence of the solvent dye blue 38 in 9 of the 11 pens studied, the presence of copper (II) phthalocyanine in two of them and residually of other dyes. Based on the spectra obtained by FORS and Raman a predictive model was also built with a discriminatory power of 81.818% for FORS and 72.727% for Raman. It was also possible to recognize aging parameters for the ink of 2 blue pens. Conclusion: This study allowed the construction of a potential tool for discriminating pen inks using non-destructive techniques and the identification of aging parameters that may in the future allow the dating of inks.
Description
Dissertação para obtenção do grau de Mestre no Instituto Universitário Egas Moniz
Keywords
Datação Identificação Instrumentos de escrita manual Raman