Near-Infrared Spectroscopy (NIR)
Definition
Spectroscopic technique using wavelengths from approximately 700 nm to 2500 nm. NIR probes overtones of molecular bond vibrations (C-H, N-H, O-H) and is used for both molecular identification and quantification in complex matrices.
- Wavelength range
- About 700 to 2500 nm
- Detects
- Overtones of C-H, N-H, O-H bond vibrations
- Use
- Molecular identification and quantification
- Sample type
- Complex matrices, minimal preparation
Common questions
Why is NIR used for bloodstain age estimation rather than a more specific technique?+
NIR can be applied non-destructively and quickly to a stain without extraction or reagent application, and changes in the bond vibration overtones as blood degrades over time correlate with stain age, making it suited to rapid, on-scene or preliminary screening ahead of confirmatory laboratory methods.
How does NIR spectroscopy differ from mid-infrared (FTIR) spectroscopy for the same sample?+
NIR probes weaker overtone and combination bands and generally needs less sample preparation but gives broader, more overlapping peaks, while mid-infrared probes the fundamental vibrations directly and produces sharper, more specific peaks, at the cost of usually requiring more sample handling.
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