Near InfraRed Analysis NIR yields different information when compared to Mid InfraRed MIR spectra. The peaks or bands observed in MIR give information about the bonds between atoms in a molecule, NIR analysis gives information about organic functional groups such as hydroxyl, ethyl or amide in a molecule for plastics, raw materials and pharmaceuticals as well as evaluation of water contents. In addition the supplied software is capable of providing derivative spectra capable of providing further information.
NIR analysis may be used to analyse small samples but can be used to analyse much larger samples. It is suitable for identification and quantification of bulk materials, especially where the other components of the sample are known..
LPD Lab Services have a Near InfraRed accessory that enables the Perkin Elmer Frontier FTIR instrument to be used for NIR analysis. The NIRA accessory can be used for non-destructive analysis of samples from around 100mg to 100g or more. It is particularly suitable for the analysis of bulk powders and liquids and has a wavenumber range from 4000 to 10000cm-1 (2500 to 1000nm wavelength) which provides a convenient overlap with the MIR range of this instrument which is from 450 to 6000cm-1.
With solid samples this accessory uses Diffuse Reflectance which is different from both the direct transmission and attenuated reflectance modes of infrared analysis encountered elsewhere but the result is a spectrum.
For liquid samples the laboratory have a Tranflectance accessory with a fixed pathlength giving the opportunity for qualitative and quantitative measurements. The results from this accessory are similar to those obtained from the attenuated reflectance mode of other accessories.
Our experts on NIR are Harry Knappett and Kim Nickson.