Sample Handling in the Infrared

If not working with an ATR FT-IR, the standard techniques of sample preparation employed to obtain infrared spectra of microscale laboratory products are the use of capillary films with liquids on NaCl (or AgCl) plates and the use of KBr disks and melts in solids. This, of course, assumes that for a spectrum to be obtained in the infrared region, the sample must be mounted in a cell that is transparent to the radiation. V 4th an ATR FT-IR spectrometer, liquids and solids are placed in direct contact with the ATR crystal. Since glass and quartz absorb in this spectral region, cells constructed of these materials cannot be 

Back plate fits Into holder on spectrophotonneter 

Liquid Samples. For materials boiling above 100 °C, the procedure is very simple. Using a syringe or Pasteur pipet, place 3-5 jxL of sample on a polished plate of sodium chloride or silver chloride or directly on the ATR crystal. If working with a NaQ or AgCl plate, cover it with a second plate of the same material and clamp it in a holder that can be mounted vertically in the instrument. Be sure that the plates are clean when you start and when you are through Obviously, the sodium chloride plates cannot be cleaned with water. Silver chloride is very soft and scratches easily it also must be kept in the dark when not in use because it darkens quickly in direct light. Spectra obtained in this fashion are referred to as capillary film spectra (Fig. 8.4). 

Solution Spectra and the Spectra of Materials Boiling Below 100 C. 

Solid Samples using non-ATR Spectrometers. SoM powders could be mounted on horizontal sodium chloride plates, and the beam diverted 

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