Fourier Transform Infrared Spectrophotometer (FTIR)

A Fourier Transform Infrared Spectrophotometer (FTIR) is a molecular analysis instrument that measures the infrared absorption characteristics of solid, liquid, and gaseous samples across the full mid-infrared spectral range simultaneously, generating a complete absorption spectrum from a single measurement that identifies chemical compounds by their unique molecular bond vibration patterns. The simultaneous multi-wavelength measurement architecture distinguishes FTIR instruments from dispersive infrared spectrophotometers that scan wavelengths sequentially, delivering faster acquisition times, higher signal-to-noise ratios, and superior wavenumber accuracy at comparable or lower instrument cost.

The optical heart of the instrument is a Michelson interferometer where infrared radiation from a globar or Nernst glower source is divided by a KBr or ZnSe beam splitter into two paths — one directed to a fixed mirror and one to a continuously moving mirror driven by a precision linear actuator. Recombination of the two beams produces constructive and destructive interference at wavelength-dependent mirror positions, generating an interferogram — an oscillating intensity signal — at the detector as the mirror scans through its range. Fast Fourier transform processing converts the interferogram into a conventional infrared spectrum plotted as percent transmittance or absorbance against wavenumber from 4,000 to 400 cm⁻¹.

Wavenumber accuracy is maintained to ±0.01 cm⁻¹ through continuous HeNe laser fringe referencing of mirror position — the Connes advantage that gives FTIR instruments superior wavelength precision compared to grating-based dispersive instruments. Spectral resolution is adjustable from 128 cm⁻¹ for fast survey scans to 0.5 cm⁻¹ or better for high-resolution gas phase analysis. Signal averaging of multiple scans improves signal-to-noise ratio proportional to the square root of the number of averaged scans, extending effective detection sensitivity for trace-level analysis.

Sampling accessories expand analytical versatility: attenuated total reflectance (ATR) for direct solid and liquid contact analysis, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) for powder and surface analysis, and gas cells from 10cm fixed path to 20-meter multi-pass White cell configurations for trace gas measurement.

In Pakistan, FTIR spectrophotometers are used in pharmaceutical quality control and release testing laboratories, polymer and materials characterization departments, forensic chemistry units, food adulteration analysis facilities, petrochemical process monitoring, and academic chemistry research programs.

Tactical Supply Pakistan supplies FTIR spectrophotometers across benchtop, portable, and process analyzer configurations for laboratory, industrial, and forensic procurement across Pakistan.