Definition of FTIR spectrometer

Photonics Dictionary

FTIR spectrometer: FTIR (Fourier transform infrared) spectrometer is a powerful analytical instrument used to obtain an infrared spectrum of absorption or emission of a solid, liquid, or gas sample. It operates based on the principle of interferometry, specifically Fourier transform infrared spectroscopy.

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Here are the key components and functions of an FTIR spectrometer:

Source: The FTIR spectrometer typically uses a broadband infrared light source, such as a ceramic heater, globar, or a quartz halogen lamp. This source emits radiation across a wide range of infrared wavelengths.

Sample compartment: The sample compartment holds the sample being analyzed. The sample can be in various forms, including liquids, solids, or gases. For transmission measurements, the sample is usually placed between two windows made of materials transparent to infrared radiation (e.g., potassium bromide, sodium chloride).

Interferometer: The heart of the FTIR spectrometer is the interferometer. It consists of a beamsplitter, which divides the infrared beam into two paths, and two mirrors. One mirror is fixed, while the other mirror moves, causing one beam to travel a longer path than the other. This creates an interference pattern when the beams are recombined.

Detector: The detector is placed at the output of the interferometer and measures the intensity of the interference pattern generated by the recombined beams. Common detectors used in FTIR spectrometers include thermal detectors (such as mercury cadmium telluride) and photoconductive detectors (such as lead sulfide or indium antimonide). Modern FTIR spectrometers often use detectors like deuterated triglycine sulfate (DTGS) or pyroelectric detectors, which offer improved sensitivity and signal-to-noise ratio.

Data acquisition system: The detector output is sent to a data acquisition system, where it is digitized and processed. The interferogram generated by the interferometer is Fourier transformed to obtain the infrared spectrum of the sample. This spectrum provides information about the absorption or emission of infrared radiation by the sample as a function of wavelength.

Software and data analysis: The FTIR spectrometer is controlled by software that allows users to set experimental parameters, acquire data, and perform data analysis. The software typically provides tools for baseline correction, spectral manipulation, peak identification, and quantitative analysis.

Accessories: FTIR spectrometers may be equipped with various accessories to enhance their capabilities and accommodate different types of samples. These accessories include sample holders, attenuated total reflectance (ATR) units for analyzing solid samples without the need for sample preparation, and gas cells for analyzing gases.

FTIR spectrometers are widely used in research, quality control, and process monitoring across various fields, including chemistry, biology, pharmaceuticals, materials science, environmental science, and forensics. They provide valuable information about the molecular structure, chemical composition, and functional groups present in the sample, making them indispensable tools for analytical laboratories.