Quantitative ATR-FT-IR Imaging

As with ordinary ATR spectroscopy, ATR-FT-IR imaging results can be analyzed quantitatively, some recent examples including the study of tablet dissolution in water. In this case, the concentration profiles of hydroxylpropylmethylcellulose (HPMC) and niacinamide, at different stages of the dissolution process, were utilized to provide an understanding of the drug release mechanism [54]. Using this technique, it could be shown that the concentration profiles of different components could be obtained with the partial least squares (PLS) method. Here, with 

It is important to note that the measurement should operate at least a few degrees above the critical angle in order to avoid a strong dispersion of the refractive index effect to the spectrum. 

To demonstrate that the gradient effect can be removed in an aligned system, similar experiments were performed by measuring a homogeneous sample of mineral oil (refractive index c 1.48), using both the ZnSe ATR accessory and the diamond ATR accessory (Supercritical Fluid Analyzer, Specac, UK). Both results 

---