Thermogravimetric analysis and chemometric based methods for soil examination: Application to soil forensics

The potential of thermogravimetric analysis combined with chemometric methods is explored for the forensic investigation of soil samples. In the present research, three milestones are achieved by thermal techniques; the identification of the patterns in the thermogram with their chemical interpretation; the development of indices to explain the extent of organic matter stability in relation with its thermal stability; and application of multivariate statistical analysis in the prediction of geographical regions of the soil. The characterization of soil samples gives an idea about the presence of organic/inorganic components. The thermal degradation of soil samples is observed by ATR-FTIR spectroscopy. The standard normal variate normalization is performed on the obtained dataset; it minimizes the variation caused by a varying amount of soil samples. The discrimination of soil samples is achieved by using multivariate algorithms including hierarchical cluster analysis (HCA), and principal component analysis (PCA). A linear discrimination function model (LDA) is developed for the classification of unknown soil samples into their respective geographical groups. The presented methodology provides a reproducible and unbiased identification and thus, makes thermal methods as attractive tools for the examination of soil/cement/clay related forensic cases.