Sample Handling Techniques in Infrared (IR) Spectroscopy

Sample Handling Techniques in Infrared (IR) Spectroscopy cover methods for preparing solids, liquids, and gases.

Proper sample preparation is essential for obtaining accurate IR spectra.
Techniques vary based on the sample’s physical state: solid, liquid, gas, or solution.

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Solid Sampling:
1. KBr Pellet Technique:
  - Solid is ground with potassium bromide (transparent to IR) and pressed into a pellet.
2. Mull Technique:
  - Solid is mixed with mineral oil to form a mull, then spread between NaCl salt plates.
3. Diffuse Reflectance (DRIFT):
  - Used for solids unsuitable for other methods. The sample is mixed with a reflective medium, and the reflected IR radiation is analyzed.
Liquid Sampling:
1. Thin Film:
  - A thin liquid film is placed between NaCl plates for analysis, suitable for non-corrosive liquids.
2. Solution Technique:
  - Sample dissolved in an IR-transparent solvent and analyzed in a liquid cell or between salt plates.
Gas Sampling:
1. Gas Cells:
  - Special cells with salt windows and variable path lengths are used. The gas is sealed in the cell for analysis.
Solution Sampling:
1. Salt Plates:
  - A drop of solution is placed between plates. After solvent evaporation, the remaining solute is analyzed.
2. Liquid Cells:
  - Two salt plates, separated by a thin spacer, form a liquid cell. The solution is added for spectrum measurement.