Infrared (IR) spectroscopy and Fourier-transform infrared spectroscopy (FTIR) are related techniques used to analyze the interaction of infrared radiation with matter. FTIR is a specific implementation of infrared spectroscopy, and the main difference between the two lies in the method of data collection.
- Infrared Spectroscopy:
- Principle: Infrared spectroscopy measures the absorption, emission, or reflection of infrared light by a sample. The infrared spectrum is a plot of the intensity of the absorbed or emitted light as a function of the wavelength or frequency of the light.
- Instrumentation: Traditional infrared spectrometers use a dispersive element, such as a grating or prism, to separate different wavelengths of light. The resulting spectrum is obtained by scanning through the range of interest.
- FTIR (Fourier-Transform Infrared) Spectroscopy:
- Principle: FTIR is a more advanced and faster technique that uses interferometry to collect data. It measures the interference pattern of a sample’s response to infrared radiation over a broad range of frequencies. The resulting data is then mathematically transformed into a spectrum.
- Instrumentation: Instead of scanning through individual wavelengths, FTIR uses a Michelson interferometer to collect interferograms, which represent the signal as a function of time. A mathematical technique called Fourier transformation is then applied to convert the interferogram into a spectrum.
Key Differences:
- Speed: FTIR is generally faster than traditional infrared spectroscopy because it collects data simultaneously across a wide range of frequencies.
- Sensitivity: FTIR is often more sensitive than traditional infrared spectroscopy due to the ability to collect more data in a shorter amount of time.
- Resolution: FTIR typically provides higher resolution because it can collect data at narrower intervals across the entire spectrum.
- Signal-to-Noise Ratio: FTIR often has a better signal-to-noise ratio, resulting in more accurate and reliable data.
- Instrument Complexity: Traditional infrared spectrometers can be simpler in design compared to FTIR instruments, which involve more complex optics and interferometers.
In summary, while infrared spectroscopy is a general term encompassing various methods of measuring infrared light absorption, emission, or reflection, FTIR specifically refers to a technique that uses interferometry and Fourier transformation for data collection and analysis. FTIR has become widely popular in many applications due to its speed, sensitivity, and improved signal-to-noise characteristics.
