Diamond ATR

Significantly, for the enantioselective hydrogenation of a,p-unsaturated ketones catalyzed by Pd/C (occurring in a three-phase system), it was concluded that the measurement of dissolved species was unaffected by the presence and fouling of Pd/C catalyst particles or other solids in the suspension on the diamond ATR... 

In recent years, more efficient ATR accessories that are suitable for quantitative analyses were developed. In particular, small diamond ATR crystals that have a capacity of — I pi have been successfully tested and are recommended for trans fat analysis. 

Automation 12 [A 12] Golden Gate Single Reflection Diamond ATR Unit... 

Golden Gate - single reflection diamond ATR unit, http //www.lot-oriel.de,... 

Parchment et al. (67) used a diamond ATR probe to monitor decontamination of mustard gas, sarin, soman, and VX. They conclude that because of relatively low sensitivity of the method, it can only be used for analysis of CWA in realistic concentrations in real time and in situ. 

Our group was the first to report imaging with a diamond ATR accessory that provided a field of view of ca. 1 mm2 and the spatial resolution of ca. 15 pm without the use of an infrared microscope [18], The demonstration of the applicability of a diamond ATR accessory for FTIR imaging opened up a range of new opportunities in polymer research, from compaction of tablets [21-23] to studying phase separation in polymer blends subjected to supercritical fluids [24], This imaging approach was successfully utilised for the study of dissolution of tablets in aqueous solutions [25], We have also demonstrated macro... 

Fig. 9 FT-IR image of a finger surface acquired using the diamond ATR accessory. An extracted spectrum from the area indicated by the arrow is shown on the right...

The IR spectra of polyester oligomers are almost identical to those of polyester fibres. The oligomers can be prepared as KBr pellets, as a molten film between NaCl or KBr platelets or else they can be investigated directly by the diffuse reflection or the diamond ATR method. 

Large ZnSe Variable angle ATR accessory Medium ZnSe Diamond ATR Micro ATR with lOx Ce objective... 

Figure 10.2 ATR-FT-IR images of a copper grid with a thick film of PDMS pressed behind and measured using (a) the ordinary and (b) the new imaging diamond ATR accessory (c) the white light image of the copper grid measured with a 5x objective.

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... 

Figure 10.6 ATR-FT-IR image of mineral oil measured on a diamond ATR accessory showing the integrated absorbance at 1480-1420cm. The histogram showing the number of detector pixels for different values of the integrated absorbance at the same range for the ATR-FT-IR measurement.

The in situ compaction study is only possible by using hard ATR crystals, due to the high compressive force used for tablet compaction. Consequently, diamond is the material of choice here, and use of the diamond ATR accessory to obtain ATR-FT-IR images of compacted tablets has been demonstrated previously [35]. ATR-FT-IR images of a model pharmaceutical formulation containing... 

Figure 10.10 Schematic diagram showing the idea of in situ imaging of tablet compaction using a diamond ATR accessory.

One important aspect of this type of dissolution approach is that a good contact between the crystal surface and the sample is essential, not only for the imaging of the tablet or pharmaceutical formulation but also to ensure that water penetrates into the sample only from the side of the tablet. This is especially important when mathematical modeling of the dissolution process is compared with experimental data. When using the diamond ATR approach, the tablet is pressed onto the diamond, and hence the leakage of water between the diamond surface and the tablet is not expected [66]. 

Photopolymerization of acrylic monomers and related systems is a challenging area for the application of real-time MIR spectroscopy since the reactions are often completed within seconds, so there needs to be an excellent SNR in the spectra if reliable kinetic data are to be generated. The temporal resolution of an FT-IR spectrometer at a resolution of 16 cm is 11 ms, so 100 spectra can be gathered in the time frame of the fastest reaction, but without multiplexing to improve the SNR. Using a diamond ATR element of area 4 mm that could also be heated to 200 C, uniform irradiation was possible and the cure reactions of films of thicknesses ranging from 1 to 20 pm could be followed (Scherzer and Decker, 1999). 

Figure 10.10 Fourier transform infrared spectrophotometer. The optical bench of the 380 FTIR, equipped with a diamond ATR accessory (reproduced courtesy of Nicolet).

Fig. 9.11 Typical reaction data using a diamond ATR probe. 

Fourier Transfer Infrared (FTIR) spectra of lignin were acquired on a Thermo Nicolet Nexus 470 FTIR spectrometer with a Golden Gate Heatable Diamond ATR (attenuated total reflectance) accessory at room temperature. The number of scans for each sample was 32. The assignments of absorbance peaks were based on published FTIR database for lignin (77). 

Utihzing spectroscopic probes is generally straightforward for hquid and gas/hquid systems. This is also the case for ATR probes, which form part of the widely apphed ReactlR system supplied by Mettler Toledo [13, 14, 24, 25]. However, this system is expensive and therefore not always the tool of choice. Standalone diamond ATR probes can also be readily used in conjunction with standard FTIR spectrometers via respective coupled optics [11, 38, 39]. 

The ATR fibre system was built up by a FT-IR spectrometer Bruker Matrix F in connection with an ATR fibre probe (A.R.T. Photonics, Berlin 0 12 mm) and a MCT (mercury cadmium telluride) detector (Belov Technology, Co., Inc.). The probe was directly inserted through the ground neck of the reaction vessel and comprised two 1 m silver halide fibres (0 1 mm) connected to a conical two bounce diamond ATR element housed in a rod of hastelloy. Using this set-up it was possible to follow the reactions to be studied in real-time covering a spectral range from 600 to 2000 wavenumbers. 

---