Grazing angle reflection-absorption spectroscopy

Other recent applications of FT-IR in pharmaceutical analysis include reaction monitoring by fiberoptic FT-IR/ATR spectroscopy140 and stability studies of pharmaceutical emulsions using FT-IR microscopy.141 A novel equipment cleaning verification procedure using grazing angle fiberoptic FT-IR reflection-absorption spectroscopy was described by Perston et al.142... 

B.B. Perston, M.L. Hamilton, B.E. Williamson, PW. Harland, M.A. Thomson and P.J. Melling, Grazing-angle fiber-optic Fourier transform infrared reflection-absorption spectroscopy for in situ detection and quantification of two active pharmaceutical ingredients on glass. Anal. Chem., 79, 1231-1236 (2007). 

A modification of the simple grazing-angle experiment is the multiple reflection -absorption spectroscopy, which was first described by Gaines (Figure 6) (24). It has a unique value for the detection of order-disorder transformations in the structure of a... 

Reflection-Absorption IR spectroscopy (RAIRS) where the linearly polarized IR beam is specularly reflected from the front face of a highly reflective sample, such as a metal single crystal surface (Figure 3.1(a)). This is also sometimes referred to as IRAS (IR reflection absorption). The IR beam comes in at grazing angle (i.e. almost parallel to the surface), and although absorption bands in RAIRS have intensities that are some two orders of magnitude weaker than in transmission studies on... 

Reflection-absorption (RA) or grazing-angle spectroscopy, is a very useful technique that gives information about the direction of transition dipoles in a sample. Figure 3 present an optical setup for a grazing-angle experiment (22). 

Reflection-Absorption Infrared Spectroscopy (RAIS) operating at the grazing-angle which is one of the most powerful resonance absorption phenomenon and is the most sensitive optical absorption technique available for measuring low concentrations of chemical componnds adhered to surfaces and even allows for the non-destractive mono layer chemical analysis on the surface. Figure 6 shows the FOC-GAP-FTIR spectra 5 and 10 ug/cm 2-CEES deposited as a trace residue on stainless steel surface. It is clear from the spectra shown that low limits of detection (LOD) achievable could be as low as nanograms/cm (milligrams/m ). 

Characterization of the Unmodified and PLL-g-PEG-Modified Surfaces. 3.2.1. RAIRS Measurements of the PLL(20)-g[3.5]-PEG(2) Monolayer. Reflection-absorption infrared spectroscopy (RAIRS) is well suited to study adsorbates on metallic surfaces, which are highly reflective. It relies on reflecting an infrared beam at near-grazing incidence from the metallic surface on which the thin film of interest has been deposited. Only the component of the vibrational transition dipole moments perpendicular to the surface plane contributes to the absorption spectra. The intensity of an absorption band is proportional to the squared cosine of the angle between the transition dipole moment and the surface normal. Therefore, RAIRS provides information not only on fimctional groups but also on orientation and conformation of adsorbed molecules or molecular entities. Metal oxides... 

Infrared external reflection spectroscopy (IR-ERS) is generally based on single external reflection of IR radiation at the surface of a metal or metal film. This method is also called reflection-absorption infrared spectroscopy (RAIRS) or grazing angle... 

---