ATR Advantages and Disadvantages

For all its advantages ATR has important disadvantages. The crystal must be kept clean and scratch-free. Scratches are a problem because they interfere with sample/hot spot contact. Be careful of paper towels—some of them contain wood fibers that can scratch softer ATR crystals such as ZnSe. These crystals can also be scratched by some samples, which is generally not a problem with diamond crystals. Since the evanescent wave passes above the crystal, any dirt or crud on the surface of the crystal will contaminate the spectrum of the sample. Lastly, don t drop an ATR crystal on the floor—it may break, and they are not cheap to replace. 

Lastly, ATR is probably the most expensive FTIR sampling technique available. Very basic accessories cost several thousand dollars, and diamond ATRs cost even more. That being said, the time saved in sample preparation often pays for the ATR accessory. Table 4.13 lists the advantages and disadvantages of the ATR sample preparation technique. 

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