Comparative study of ATR and DRIFT infrared spectroscopy techniques in the analysis of soil samples

The primary goal of this investigation is to determine the feasibility of using vibrational spectroscopy techniques for the analysis of soil samples in order to characterize a specific area and hence create a soil map for use in forensic investigation. We compare spectra of "artifacts" which are exclusive to a single location or area rather than focus on the general intrinsic components of soil. Comparison of these artifacts may allow the creation of a map of different regions and thus allow matching of soil evidence to these regions (spectra). For this purpose, we compare the feasibility of two mid-infrared sampling techniques to discriminate among collected soil samples. The techniques used are Attenuated Total Reflectance (ATR) and Diffuse Reflectance Infrared spectroscopy (DRIFT). The data is analyzed and classified using multivariate statistical Linear and partial least squares discriminant analysis as well as principal component analysis. Although both ATR and DRIFT techniques show promising results in soil discrimination, the data shows that DRIFT is more sensitive in the application of soil discrimination. It is suggested that, to obtain better results both techniques should be coupled with multivariate statistical analysis of the collected data.