| The profusion of ATR accessories on the market today attests to the utility of the technique and its popularity in FT-IR spectroscopy. Each accessory is designed to achieve optimum performance with a particular sample type. Diamond ATR devices, such as Smart Orbit, are highly suitable for hard or corrosive samples, whereas a germanium accessory is preferred for highly absorbing samples. The development of these accessories has greatly simplified sampling for FT-IR.
However, ATR does present challenges. An infrared spectrum of a sample obtained using an ATR accessory is not identical to the spectrum obtained by transmission. The ATR technique introduces relative shifts in band intensity and absolute shifts in frequency. The relative intensity shift is well known and is readily corrected. The shift in frequency, which can result in a displacement of the peak maximum by several wavenumbers, is at once more serious and less often accounted for.
As most commercially available spectral libraries and published peak tables contain and refer to transmission spectra, differences between ATR and transmission spectra can lead to poor spectral search results and ambiguous interpretation.
The Advanced ATR Correction Algorithm article explains the reasons for these differences and demonstrates a technique for their correction.
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