Banca de QUALIFICAÇÃO: HELLYDA KATHARINE TOMAZ DE ANDRADE SILVA

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : HELLYDA KATHARINE TOMAZ DE ANDRADE SILVA
DATE: 31/01/2023
TIME: 08:00
LOCAL: videoconferência
TITLE:

Development of analytical methodologies based on spectroanalytical techniques (NIRS and ATR-FTIR) and chemometrics applied to forensics.

KEY WORDS:

Taxonomic categories. NIR spectroscopy. ATR-FTIR spectroscopy. Sarcophagidae. Entomotoxicology. Terbufos. Multivariate analysis.

PAGES: 146
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUBÁREA: Química Analítica
SPECIALTY: Métodos Óticos de Análise
SUMMARY:

This thesis presents the development of alternative spectroanalytical methodologies based on near infrared (NIRS) and medium infrared (ATR-FTIR) spectroscopy combined with unsupervised chemometric techniques (PCA and HCA); variable selection and multivariate classification (PCA-QDA, SPA-QDA and GA QDA) applied to forensic entomology and entomotoxicology. In the first study, NIR spectroscopy was used for spectral acquisition of nine species of flies with forensic potential (Diptera: Calliphoridae and Sarcophagidae) of two regions (dorsal and ventral) of the insect with the subsequent construction of PCA and HCA models aiming to evaluate the potential of the methodology in segregating/grouping specimens into taxonomic categories. The best model was reached from the average dorsal and ventral spectra, observing the segregation of the species Chrysomya albiceps, Lucilia eximia and Ravinia belforti, the resulting loadings punctuated absorptions associated with O-H, C-O, C-H and N-H stretches, the latter possibly being associated with chitin (poly-N-acetyl-glucosamine) carbohydrate constituent of the procuticle of insects, as well as stretches of olefinic C–H and fundamental C-H for an unsaturated carbon associated with lipid compounds. In the dendrogram, a clear separation between the specimens by family (Calliphoridae and Sarcophagidae) and genera (Chrysomya, Lucilia, Oxysarcodexia, Peckia and Ravinia) was observed, the species Oxysarcodexia and Peckia did not present such established groups, but with considerable overlap. In the second study, ATR-FTIR spectroscopy was applied together with variable selection and multivariate classification techniques (PCA-QDA, SPA-QDA and GA-QDA) to discriminate larvae from scavenger flies (Diptera: Sarcophagidae) into groups: control and intoxicated after eating rat carcasses exposed to the organophosphate pesticide terbufos. The results showed that the proposed methodology has the potential to classify samples with sensitivity and specificity values greater than 90%. Among the three models, GA-QDA was the best model to detect alterations in the cellular biochemical composition of larvae exposed to terbufos, successfully classifying intoxication based on five variables and reaching values of 98.9% of sensitivity and specificity. Therefore, the reported results suggest the potential of NIRS and ATR-FTIR spectroscopies combined with multivariate analysis as alternative tools to identify taxonomic properties of flies, such as family and genera, providing rapid evidence for species identity and in the detection of terbufos poisoning in scavenger fly larvae from carcasses of intoxicated rats, respectively.

COMMITTEE MEMBERS:
Externo à Instituição - CAMILO DE LELIS MEDEIROS DE MORAIS - UECE
Presidente - 1714946 - KASSIO MICHELL GOMES DE LIMA
Externo à Instituição - LEOMIR AIRES SILVA DE LIMA - Estácio
Externo à Instituição - TACIANO DE MOURA BARBOSA - UFPE