The transmission technique does not require a separate accessory. The user simply places a sample directly into the infrared (IR) beam. As the IR beam passes through the sample, the transmitted energy is measured and a spectrum is generated. However, the analyst must often prepare the sample into a pellet, mull, film, etc. before the transmission measurement can be made. This requires expertise and can be time consuming.
Excellent quality spectra can be obtained for many types of samples using transmission. The transmission technique can be used alone or in conjunction with accessories such as microscopes and liquid or gas cells to analyze:
- Organic powders in pellet or mull form
- Thermoplastic powders
- Soluble polymers
- Thin polymer films
- Regular-shaped polymers (with preparation)
- Irregular-shaped polymers (with preparation)
- Dark polymer films (not carbon-filled)
- Liquids (free-flowing or viscous)
- Gases (high concentrations to trace amounts)
- Economical – cells and mounts are generally inexpensive
- Well established – most traditional form of sample measurement
- Excellent spectral information – ideal for qualitative measurements
- Great for quantitative work – many standard operating procedures are based on transmission
Dr. Michael Bradley received his BS degree in chemistry from the University of South Carolina and his PhD in physical chemistry from the University of Illinois, and also completed his MBA in management. He taught graduate and undergraduate chemistry for 15 years, prior to becoming a field applications scientist with Thermo Nicolet, subsequently Thermo Fisher Scientific, in 2002. He is the Global Training Manager for FTIR products.
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