The thin film method of IR refers to a technique used in Infrared (IR) spectroscopy to analyze samples by preparing them as a thin layer on a suitable IR-transparent plate or window.
This method is particularly useful for obtaining clear IR spectra from various sample types. As highlighted in IR sampling techniques, the choice of specific thin-film method depends on the physical state of the substance being studied.
Types of Thin Film IR Sampling
According to standard practice described in texts like "Thin-film IR Sampling Techniques", there are two primary ways to prepare samples using this method, based on whether the compound is a liquid or a solid:
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Thin-Liquid Film IR Sampling Technique:
- This technique is used if the compound to be studied is a liquid.
- A small amount of the liquid sample is applied directly onto an IR plate (often made of materials like NaCl, KBr, or other IR-transparent salts).
- The plate is typically covered with another plate, creating a thin layer of the liquid between them for analysis.
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Thin-Solid Film IR Sampling Technique:
- This technique is used if it is a solid.
- Solid samples are often prepared by dissolving them in a volatile solvent, depositing the solution onto an IR plate, and allowing the solvent to evaporate, leaving a thin film of the solid sample behind. Alternatively, some solids can be melted and cast as a thin film if they are low-melting.
Choosing the appropriate thin film method ensures that the sample is in a state suitable for interaction with the infrared beam, yielding an informative spectrum for identification and analysis.
