Why in news?
A report on post‑blast forensic investigations highlighted how experts use Fourier Transform Infrared (FTIR) spectroscopy to analyse chemical residues from explosion scenes. The technique helps identify explosive materials and trace evidence quickly and non‑destructively.
Background
FTIR spectroscopy is an analytical method that measures how a sample absorbs infrared light. Every molecule vibrates at characteristic frequencies; when infrared radiation passes through a substance, specific wavelengths are absorbed, leaving a spectral “fingerprint.” By recording this absorption pattern and applying a mathematical Fourier transform, scientists can identify the molecular structure of unknown substances.
How it works
- Infrared source: A broad spectrum of infrared radiation is directed at the sample.
- Interferometer: The light is split and recombined in an interferometer, creating an interference pattern that encodes information from all wavelengths simultaneously.
- Detector and Fourier transform: The combined light reaches a detector. A computer uses a Fourier transform algorithm to convert the raw interference data into a conventional absorption spectrum, plotting intensity against wavenumber.
- Interpretation: Analysts compare the resulting spectrum with reference libraries to identify functional groups and chemical compounds present in the sample.
Applications
- Forensics: FTIR helps investigators identify residues from explosives, gunshot particles, paints, plastics and drugs at crime scenes without destroying evidence.
- Environmental monitoring: Regulators use FTIR to monitor air pollutants, test water quality and analyse soil for contaminants.
- Industrial and research uses: The technique is widely employed in quality control of polymers, pharmaceuticals and food products, as well as in chemical research to elucidate molecular structures.
Benefits
- Non‑destructive: Samples remain intact for further analysis.
- Rapid and reliable: FTIR provides results within minutes and can detect compounds at low concentrations.
- Versatile: It can analyse solids, liquids and gases and requires minimal sample preparation.
Sources: Gossman Forensics, Agilent Technologies