Rapid Molecular Imaging Using Attenuated Total Internal Reflection Planar Array Infrared Spectroscopy for the Analysis of Counterfeit Pharmaceutical Tablets

Abstract

A planar array infrared (PA-IR) spectrograph containing an attenuated total internal reflection (ATR) accessory has been constructed in order to permit rapid analysis of poorly transmitting materials. The technique has been optimized to allow molecular spectroscopic information to be collected in roughly 2 seconds with a corresponding peak-to-peak noise value as low as 2.14 × 10−4 absorbance units. Additionally, up to 150 spectra could be extracted from sample sizes as large as 6 mm where each spatial element measured 40 × 200 μm at the sample position. An application study for this technique entailed developing an embedding method that allows cross-sectioned pharmaceutical tablets to be brought into intimate contact with the internal reflection element (IRE) of the accessory. A supplemental investigation involved calculating the yield strength of multiple IRE materials in order to determine the maximum amount of pressure that can be applied to a sample without damaging the IRE. Finally, feasibility was demonstrated for using the instrument/accessory as a means to rapidly authenticate suspected counterfeit pharmaceutical tablets.