- Since every material has a unique response to light, the analysis of the light interacting with a certain material can reveal a lot of information about its composition. The analysis of light to determine the properties of materials is what spectroscopy is all about.
- Light interacting with materials is essentially a spectrum of electromagnetic waves with different wavelengths. Fundamentals of bands absorbed by materials are found in Mid-InfraRed (MIR) region of light (wavelengths >3,500 nm). The Near InfraRed (NIR) region of light is absorbed by the energy bands related to the overtones and combinations of the fundamentals bands.
How is spectral information analyzed?
- The unique information from the vibrational absorption bands of a molecule is reflected in the NIR spectrum, but some spectral numerical processing and statistical analysis are required to “unlock” this information. The application of statistical methods to the analysis of experimental data is known as chemometrics.
Typical flow for the development of an analysis model
Why not just use conventional analysis methods?
- It may appear that NIR spectroscopy is an indirect way for material analysis and that the development of an analysis model is a complex process. In practice however, the advantages of using NIR for material analysis justify the efforts required to build the analysis models.
The results of spectral analysis are instantaneous. Unlike wet chemical and other conventional analysis methods, there is no need to wait for certain transformations to happen in the sample.
Different physical and chemical parameters of the sample can be analyzed with a single scan.
Minimum to no sample preparation
Analysis can be done without preparing the sample.
Analysis can be done while keeping the sample intact.
What are the typical usage models of NIR spectroscopy?
- NIR spectroscopy tends to be used for well-targeted applications, and results are based on the well- proven analyses and/or property measurements. In practice, there are three traditional ways to use the spectral data obtained
Quantification: The measurement of multi-component systems for material concentration or for modeled physical/chemical properties
Detection: The confirmation of a material make-up (quality control/quality assurance) by correlation methods
Identification: Material identification using positive or negative correlation methods.