Fourier Transform Infrared (FTIR) analysis is a widely used laboratory technique for identifying chemical compounds, functional groups, and material characteristics. It is used across pharmaceutical research, chemistry, food analysis, materials science, environmental testing, and many other fields.
Unlike some analytical techniques that require complex separation procedures, FTIR can often provide useful information about a sample relatively quickly by examining how it interacts with infrared radiation.
For researchers, manufacturers, students, and quality-control laboratories, understanding how FTIR works can help when choosing the right analytical method for a particular sample.
What Is FTIR Analysis?
FTIR stands for Fourier Transform Infrared Spectroscopy. It is an analytical technique that measures how a sample absorbs infrared light at different wavelengths or frequencies.
Molecules contain chemical bonds that can vibrate in different ways, including stretching, bending, and other molecular motions. When infrared radiation interacts with a sample, certain frequencies are absorbed by specific chemical bonds.
The resulting spectrum creates a characteristic pattern that can provide information about the chemical structure of the material.
This makes FTIR particularly useful for identifying functional groups and comparing unknown samples with known reference materials.
How Does FTIR Spectroscopy Work?
An FTIR instrument passes infrared radiation toward a sample and measures the infrared light that is absorbed or transmitted.
The process generally involves several stages:
- Infrared radiation is generated by the instrument.
- The radiation interacts with the sample.
- Certain frequencies are absorbed by chemical bonds within the sample.
- The instrument detects the resulting signal.
- A mathematical Fourier transform converts the measured signal into an infrared spectrum.
- The spectrum is interpreted to identify chemical features or compare the sample with reference data.
The final spectrum is usually displayed as a graph showing infrared intensity against wavenumber, commonly expressed in cm⁻¹.
What Can FTIR Analysis Identify?
FTIR analysis is particularly useful for identifying chemical bonds and functional groups.
Depending on the sample, FTIR may provide information about groups such as:
- Hydroxyl groups (O–H)
- Carbonyl groups (C=O)
- Amines (N–H)
- Alkanes (C–H)
- Alkenes (C=C)
- Ethers (C–O–C)
- Carboxylic acids
- Esters
- Aromatic compounds
The presence, absence, position, and shape of characteristic absorption bands can help researchers understand the chemical composition of a material.
However, FTIR does not always provide a complete identification of every compound on its own. Complex samples may require additional analytical techniques for confirmation.
Understanding an FTIR Spectrum
An FTIR spectrum contains peaks or bands associated with molecular vibrations.
The functional group region, commonly found at higher wavenumbers, can help identify important chemical bonds. The lower-wavenumber region is often referred to as the fingerprint region because it can contain a complex pattern that is characteristic of a particular compound or material.
Researchers can compare this pattern against:
- Reference spectra
- Spectral libraries
- Known standards
- Previously characterised samples
A strong match can provide useful evidence about the identity or composition of a sample.
What Types of Samples Can Be Analysed?
One of the advantages of FTIR is its broad range of applications. Depending on the instrument and sampling method, laboratories can analyse many different types of materials.
These may include:
- Powders
- Solids
- Films
- Polymers
- Oils
- Liquids
- Pharmaceutical materials
- Plant extracts
- Herbal products
- Chemicals
- Food products
- Environmental samples
Sample preparation depends heavily on the physical and chemical characteristics of the material.
For example, some solid samples can be analysed directly using an ATR accessory, while other samples may require a different preparation method.
FTIR Analysis Using ATR
Attenuated Total Reflectance (ATR) is one of the most common approaches used with modern FTIR instruments.
ATR allows many samples to be analysed with relatively little preparation. A sample is placed directly against a specialised crystal, and the infrared radiation interacts with the material near the surface.
ATR-FTIR is particularly useful for materials such as:
- Plastics and polymers
- Powders
- Pharmaceutical products
- Oils
- Rubber
- Coatings
- Fibres
- Biological materials
The reduced sample preparation can make ATR-FTIR convenient for routine identification and material comparison.
Applications of FTIR Analysis
FTIR has applications across many scientific and industrial areas.
Pharmaceutical Research
FTIR can be used to characterise pharmaceutical ingredients, excipients, raw materials, and finished products. Researchers may also use it to investigate chemical changes and compare materials.
For pharmaceutical analysis, FTIR can be combined with techniques such as HPLC, GC-MS, or other instrumental methods when more detailed identification or quantification is required.
Herbal and Plant Products
FTIR can help researchers characterise herbal medicines, plant extracts, and natural products by identifying important chemical functional groups.
It can also be used as part of a broader approach to compare samples and investigate differences in chemical composition.
Polymer and Plastic Analysis
FTIR is widely useful for identifying polymers and investigating changes caused by factors such as heat, oxidation, chemical exposure, or environmental conditions.
A researcher can compare the spectrum of an unknown plastic sample against reference materials to help determine its polymer type.
Food Analysis
FTIR can be applied to food and agricultural research for characterising materials and investigating chemical composition.
It may be used as part of studies involving oils, fats, proteins, carbohydrates, additives, and other components.
Environmental Testing
Environmental researchers can use FTIR to investigate materials and contaminants, particularly when identifying organic compounds or characterising substances collected from environmental samples.
The exact suitability of FTIR depends on the contaminant and sample matrix, so other analytical techniques may sometimes be more appropriate.
Materials Research
FTIR is also useful in materials science for studying coatings, composites, polymers, ceramics, adhesives, and other materials.
Researchers can use it to investigate chemical changes before and after processing, treatment, or exposure to environmental conditions.
FTIR vs Other Analytical Techniques
FTIR is powerful, but it is not designed to answer every analytical question.
For example:
FTIR: Useful for identifying functional groups and characterising chemical structures.
HPLC: Useful for separating, identifying, and quantifying components in mixtures.
GC-MS: Useful for separating and identifying many volatile and semi-volatile compounds.
XRD: Primarily used to investigate crystalline phases and crystal structures.
XRF: Used to determine elemental composition.
SEM-EDS: Provides information about surface morphology and elemental composition.
Because these techniques provide different types of information, researchers may combine several methods when a sample requires comprehensive characterisation.
Factors That Can Affect FTIR Results
The quality and usefulness of FTIR analysis can depend on several factors, including:
- Sample preparation
- Sample thickness
- Moisture content
- Instrument condition
- Sampling technique
- Background correction
- Resolution
- Spectral range
- Contamination
- Quality of reference spectra
Poor sample preparation or contamination can introduce unexpected peaks and make interpretation more difficult.
This is why proper laboratory procedures and appropriate sample handling are important.
Is FTIR Suitable for Quantitative Analysis?
FTIR can be used for quantitative analysis under suitable conditions, particularly when an appropriate calibration method has been developed.
However, its suitability for quantitative measurement depends on the sample, analyte, concentration range, matrix, instrument configuration, and analytical method.
For some applications, techniques such as HPLC, GC-MS, or other quantitative analytical methods may provide more appropriate measurements.
The right technique should therefore be selected based on the specific research question rather than simply the availability of an instrument.
Why FTIR Analysis Is Important
FTIR provides researchers with a relatively rapid way to investigate chemical characteristics and identify materials.
Its main advantages include:
- Broad application across different materials
- Useful functional-group identification
- Relatively rapid analysis
- Small sample requirements in many applications
- Minimal preparation for some samples
- Ability to compare unknown samples with reference spectra
- Useful support for research and quality-control investigations
When combined with other analytical techniques, FTIR can provide valuable information for understanding the chemical and physical characteristics of a sample.
How to Prepare a Sample for FTIR Testing
Sample preparation depends on the material and the FTIR sampling method being used.
Before submitting a sample, researchers should provide relevant information such as:
- Sample name or identification
- Physical form
- Expected composition, if known
- Research objective
- Any known hazards
- Required analytical information
Avoid unnecessary contamination of the sample with substances such as oils, dirt, moisture, or other materials that could interfere with the spectrum.
If you are unsure how your sample should be prepared, it is better to discuss the material and testing objective with the laboratory before submission.
Final Thoughts
FTIR analysis is an important analytical technique for identifying chemical bonds, functional groups, and material characteristics. From pharmaceutical research and herbal products to polymers, food, environmental samples, and materials science, FTIR can provide useful chemical information relatively quickly.
However, an FTIR spectrum should be interpreted within the context of the sample and research objective. When detailed identification, separation, elemental analysis, or accurate quantification is required, FTIR may need to be combined with techniques such as HPLC, GC-MS, XRD, XRF, or SEM-EDS.
If you need laboratory analysis for a research, pharmaceutical, environmental, materials, or chemical sample, you can explore AnalysisAfrica's analytical testing services to find a suitable testing option.
You can also read more laboratory analysis guides on the AnalysisAfrica blog for practical information about analytical techniques and laboratory testing.
