Photonics Dictionary

near-infrared spectroscopy

Near-infrared spectroscopy (NIRS) is a non-invasive analytical technique that uses the near-infrared region of the electromagnetic spectrum to study the absorption of light by molecules in a sample. This technique is commonly applied in fields such as chemistry, biology, medicine, and agriculture for qualitative and quantitative analysis of various substances.

Key features and principles of near-infrared spectroscopy include:

Near-infrared region: NIRS typically covers the spectral range from about 700 to 2500 nanometers in the electromagnetic spectrum. This region is known as the "near-infrared" because it is adjacent to the visible light spectrum.

Molecular absorption: Near-infrared light is absorbed by the vibrational transitions of certain molecular bonds, such as C-H, N-H, and O-H bonds. The absorption of light at specific wavelengths corresponds to the presence and concentration of particular chemical groups in the sample.

Non-destructive and non-invasive: NIRS is a non-destructive and non-invasive technique, making it suitable for analyzing samples without altering their composition. This is particularly advantageous in applications such as medical diagnostics.

Quantitative analysis: Near-infrared spectroscopy is widely used for quantitative analysis, allowing the determination of the concentration of various components in a sample. Calibration models are often developed using known reference values to correlate the spectral data with the sample composition.

Multicomponent analysis: NIRS is well-suited for the analysis of complex samples containing multiple components. It can be used to simultaneously determine the concentrations of different constituents in a mixture.

Applications: Near-infrared spectroscopy has diverse applications, including pharmaceutical analysis, food and beverage quality control, agricultural monitoring, environmental analysis, and medical diagnostics. In the medical field, it is used for monitoring oxygen levels in tissues, assessing brain function, and analyzing blood components.

Instrumentation: NIRS instruments typically consist of a light source, a sample holder, and a detector. The transmitted or reflected light is analyzed to generate a spectrum that provides information about the sample's composition.

NIRS has become a valuable tool in various industries due to its speed, versatility, and non-invasive nature. Its ability to provide rapid and on-site analysis makes it particularly useful in situations where quick decisions or monitoring of dynamic processes is required.
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