Kuwait University

Fourier Transform Infrared Spectroscopy (FTIR)

Varian 640-IR

  • Every different type of chemical bond that absorbs infrared light naturally vibrates at a specific frequency.
  • Small variations result in peak position and height allow for differentiation.
  • IR spectrum can serve as a compound’s fingerprint.

FT-IR spectroscopy for analytical measurements:

  • FT-IR analysis is simple to perform.
  • FT-IR provides incredibly accurate results.
  • Results are available within seconds to minutes.
  • The method is versatile (can accommodate various sample sizes and types).
  • Powerful tool for analysis of any gas, liquid or solid.
  • Provides both quantitative and qualitative results.
  • FT-IR analysis can be non-destructive.
  • FT-IR spectroscopy is an affordable method.
  • FT-IR can require very little amount.

FT-IR spectrometers are ideal for routine QA/QC analyses. Their use ranges from very simple analyses, to very complex and informative nanosecond time resolved experiments.

FT-IR is application based helps to have a basic understanding of the scope of applications in order to feel comfortable discussing how it can solve analytical problems.

Application for FT-IR spectroscopy:

Biosciences, Pharmaceuticals, Polymers, Forensics, Food & Agriculture, Chemical Analysis, Environmental Analysis, Fuels and Energy and Material Sciences.

It offers affordable performance in all of the above listed areas, sample identification, verification, and education. This tool provides performance, flexibility, and upgradeability for demanding QA/QC tasks, as well as product development, troubleshooting, and applied research & development.

Sample Preparation for IR:

  • Cast Films - For solid powders and polymers and non-volatile solvents.
  • Mulls - For powders which could not be dissolved, or would not melt and flow.
  • Pressed Pellets - For solids and powders.
  • Gas Analysis - Gases much weaker infrared absorbers, use longer pathlength to increase absorbance signal intensity.
  • Liquid Cells - Two infrared transparent windows, separated by a metal or polymer (typ. PTFE) spacer, 0.05 to 1 mm path length.


The Varian 640-IR spectrometer design is based on a 38 mm dynamically aligned, 60° mechanical bearing Michelson interferometer and comes standard with 0.18 cm-1 resolution. It includes a revolutionary air-cooled source for delivering optimum power to the sample.

Basic concepts of FT-IR spectroscopy:
Infrared spectroscopy (IR) is a powerful tool for the analysis of a wide array of samples. IR spectroscopy is the study of the interactions between infrared electromagnetic energy and matter, and allows for qualitative and quantitative measurements of samples.

Infrared light is a portion of the electromagnetic spectrum, and is just beyond the visible portion of the spectrum

For convenience of applications and instrumentation, the infrared spectrum is divided into near-, mid-, and far-infrared radiation. The most commonly used region is the mid-infrared.                                                          

If infrared light energy is absorbed by a sample, it will cause an excitation of the sample’s molecular vibrations. This excitation causes the amplitude of chemical bonds to change. It is this change that is measured in infrared spectroscopy.

IR spectroscopy can be used to analyse samples from all three states of matter – it can be used to analyze gasses, liquids, and solids. Infrared spectroscopy has been a cornerstone of analytical measurements for over 50 years. Almost all compounds (whether they be organic or inorganic) absorb various portions of infrared light. Specifically, only chemical bonds that have a dipole moment that changes as a function of vibrations are capable of absorbing infrared light.

Basic principle of infrared spectroscopy:

  • IR-active bonds produce peaks - Group frequency theory.