NIR
The Science Behind NIR Spectroscopy
At its core, NIR spectroscopy involves the interaction of light with a material, utilizing electromagnetic radiation, which behaves in waves. The distance between these waves’ peaks, known as the wavelength, is measured in nanometers (nm).
The light spectrum visible to the human eye stretches from about 400 nm to 800 nm. Beyond this range lies the infrared spectrum, extending from approximately 2500 nm to 25000 nm. NIR spectroscopy covers the unique middle ground between these two regions, spanning from 750 nm to 2600 nm.
How Does NIR Spectroscopy Work?
Molecules, composed of bonded atoms, have unique vibration frequencies. These chemical bonds absorb energy at specific wavelengths when exposed to NIR light, leading to the absorption spectrum that characterizes the sample. Each type of bond within a molecule has its distinct absorption pattern, making NIR a powerful ‘fingerprint’ tool for identifying different substances.
When NIR energy, produced by a light source such as a lamp, passes through a sample, the interaction causes changes in the light’s energy as it reaches a detector. Each bond type absorbs specific wavelengths while others are reflected. The difference in energy between what enters the sample and what exits is essential for analysis.
The relationship between the energy exiting and entering a sample can be expressed as a ratio, known as transmittance. Multiplied by 100, it forms the Transmittance Spectrum (T%), indicating how much light passes through the sample. The inverse of this measurement provides the Absorbance Spectrum (A%), revealing the intensity of the light absorbed. This absorbance information is critical for both qualitative and quantitative analysis.
NIR spectroscopy extends its capabilities with Hyperspectral Imaging (HSI), which digitizes the spectra into pixels. Image acquisition can be conducted sequentially (pixel by pixel) or simultaneously, resulting in an image cube that represents a three-dimensional dataset. Each element of this dataset provides detailed NIR intensity at specific spatial coordinates (X, Y), enabling comprehensive spatial and chemical analysis of the sample.
Why NIR Spectroscopy Matters
NIR spectroscopy’s ability to identify molecular structures and predict sample composition non-destructively is invaluable. Its applications in quality control, product development, and research make it a cornerstone technology for industries aiming for precision and efficiency. Whether it’s analyzing the nutritional content in food or assessing the quality of pharmaceuticals, the potential of NIR spectroscopy is profound.
By understanding the principles of NIR spectroscopy, businesses and researchers can harness its power for accurate, efficient, and non-invasive analysis. It is not just a method; it is a pathway to greater insights and better decision-making.