ATR accessories

The experimental apparatus consists of a gas flow system with a four-port valve, a multi-reflection Attenuated Total Reflection (ATR) accessory (Pike Technologies), and a custom reactor manifold mounted to the ATR top plate, shown in Fig. 45.1. The ATR reactor manifold consists of (i) a Cap2 window for UV irradiation, (ii) an inlet and outlet port, and (iii) an injection port for the liquid phase reactant. 

The infrared technique has been described in numerous publications and recent reviews were published by Davies and Giangiacomo (2000), Ismail et al. (1997) and Wetzel (1998). Very few applications have been described for analysis of additives in food products. One interesting application is for controlling vitamin concentrations in vitamin premixes used for fortification of food products by attenuated total reflectance (ATR) accessory with Fourier transform infrared (FTIR) (Wojciechowski et al., 1998). Four vitamins were analysed - Bi (thiamin), B2 (riboflavin), B6 (vitamin B6 compounds) and Niacin (nicotinic acid) - in about 10 minutes. The partial least squares technique was used for calibration of the equipment. The precision of measurements was in the range 4-8%, similar to those obtained for the four vitamins by the reference HPLC method. 

IR spectra of starch can be obtained with an IR spectrometer such as a Digilab FTS 7000 spectrometer, Digilab USA, Randolph, MA, equipped with a thermoelectrically cooled deuterated tri-glycine sulfate (DTGS) detector using an attenuated total reflectance (ATR) accessory at a resolution of 4 cm by 128 scans. Spectra are baseline-corrected, and then deconvoluted between wavenumbers 1200 to 800 cm . A half-band width of 15 cm and a resolution enhancement factor of 1.5 with Bessel apodization are employed. Intensity measurements are performed on the deconvoluted spectra by recording the height of the absorbance bands from the baseline. 

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. 

Figure 7. IR spectra (at 2.90 fim, 4.65 fim and 6.15fi m) of films collected on germanium plate from aqueous phase at 25° C, pH 5.6. Upper panel 0.075M CaCU at different pH values without DPL films. Lower panel DPL films spread on either 0.I5M NaCI or 0.0I0M CaCU. The solution, with or without the lipid film, was left to stand at room temperature for a given time. The germanium plate then was dipped through the interface four times, dried under a stream of N gas, and examined in the ATR accessory (for details, see...

The use of an ATR accessory normally requires a Mercury-Cadmium-Telluride (MCT) detector to achieve enough sensitivity. The detector requires liquid nitrogen cooling, which limits the on-site usage of this method. 

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...

FTIR Spectra of Paper Documents. Good quality IR spectra can be obtained with the FTIR spectrometer and the ATR accessory without... 

CXE2C1, C1E3C1, and CXE4C1 were commercially supplied, while CxEsCx and CxEgCx were prepared by the Williamson ether synthesis. The infrared spectra of aqueous solutions of these compounds were measured for various concentrations at room temperature by using a horizontal ATR accessory with a ZnSe prism. Tibe lowest concentration studied was a mole fraction of approximately 0.005. The spectra were recorded on a JASCO FT/IR-7300 spectrometer. Each of the spectra was obtained by the coaddition of 200 scans at a resolution of 4... 

Figure 9.8 Schematic optical diagram of the ATR accessory FastIR, demonstrating the different angles of incidence on the interface of the sample and the ATR reflection element. Adapted from http //www.harricksci. com/accessories/H fastir.cfm. The variably...

The applicability of ATR-FT-IR imaging ranges from micro ATR imaging using a microscope objective to the use of ATR accessories with focused or expanded optics, without need to use the microscope. The ATR crystal in a prism shape... 

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... 

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