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The Horizon™ multiple reflection ATR accessory is a powerful tool for examining liquids, pastes, powders, and soft surface solids by infrared spectroscopy.
The unobstructed, horizontal sampling surface of the Horizon™ makes analysis easy. Samples of various sizes may be simply placed on top of the ATR crystal. For high quality spectra without atmospheric interference, this HATR accessory features PermaPurge™. This permits sample and crystal exchange while maintaining the purge through the FT-IR spectrometer and the accessory. This is ideal for quality control and other applications, which require rapid sample exchange.
Figure 1. The Horizon™ Solid Sampler.
Figure 2. Schematic of the Infrared Beam Profile of the Horizon as the Beam Passes through the ATR crystal.
The Horizon™ is shown in Figure 1. Mirrors M1 and M2 direct the incident infrared beam to mirror M3. This spherical mirror focuses the beam and, due to its off-axis orientation, elongates the beam to match the rectangular entrance aperture of the ATR crystal. The beam is internally reflected along the length of the crystal, where it interacts with the sample, and then exits the ATR crystal. The beam, which has interacted with the sample, is then reflected from spherical mirror M4 to mirror M5. Mirror M5 reflects the beam to mirror M6 and onto the detector of the FT-IR spectrometer.
The ATR crystal is positioned relative to the focal points of the two spherical mirrors so that the beam shape is elongated to match the aperture of the crystal at both its entrance and exit (see Figure 2).
Upon entering the crystal, the light continues converging in the direction parallel to the width of the crystal. When it reaches the center of the crystal, it starts diverging. Thus within the crystal, the radiation is kept away from the edges of the crystal. This eliminates spectral interference from the adhesive used to seal the crystal onto the mounting plate. This optical design results in a highly efficient multiple reflection ATR accessory.
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Representative infrared spectra obtained using the Horizon are shown in Figures 3 through 6.
Figure 3. ATR Spectrum of Sweetened Coffee (without Milk) Relative to Water.
Figure 4. ATR Spectrum of an Adhesive on Paper.
Figure 5. ATR Spectrum of Anhydrous Maleic Acid
in Molten Polypropylene Recorded at 185°C.
Figure 6. ATR Spectrum of Black Foam Packing Material.
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