Sensitive FT-IR External and Internal Reflection Techniques for the Identification of Mineral Samples-potential Applications in Forensic Science - Abstract
The use of a nondestructive reflection technique to identify small mineral particles in the mid-infrared is reported. The results of this technique for six minerals are compared with those obtained via conventional diamond ATR spectroscopy on powdered samples from the same minerals. Although peak height variability is large, sufficient peak position wavelength reproducibility is demonstrated to indicate potential for forensic applications. In the second section of this study, the results using two different ATR configurations in the same FTIR accessory are compared. The first configuration used a triangular prism ATR element with a sampling area of approximately 1.5 mm diameter. The second configuration used a hemispherical ATR element with a sampling area of 0.5 mm diameter. Powdered samples were prepared from three mineral specimens: gypsum, malachite, and sodalite. Modifications were made to the accessory to reduce the amount of powder sample required. Although mineral samples were used in this study, the conclusions should be applicable to other powdered samples, both inorganic and organic. In the third section, an instrumental change is made to increase sample pressure in an attempt to improve performance with softer samples. Also, sample preparation enhancements are made to study their effect on reproducibility.