FTIR Spectrum Analysis--Meaning and Application of Each Peak

FTIR Spectrum Overview

Fourier Transform Infrared Spectroscopy (FTIR) is a critical tool for identifying and analyzing the chemical structure of substances. By measuring how materials absorb infrared light, FTIR reveals detailed information about the chemical bonds and functional groups present within a material. Each peak on an FTIR spectrum represents different chemical components within the material.

Figure 1 Load-Displacement (P-h) Curve

Peak Interpretation

2.1 Calculation of Hardness H

Peak interpretation in FTIR analysis involves understanding and explaining the various peaks on the spectrum. These peaks represent the sample's absorption of infrared light, with each peak corresponding to a specific chemical bond or functional group absorbing infrared light at a particular wavelength. Understanding these peaks is essential for analyzing the chemical composition of materials. Here's a detailed explanation of how to interpret the peaks in an FTIR spectrum:

1.Peak Position (Wavenumber): The position of each peak (measured in wavenumbers, cm-1) indicates which type of chemical bond or functional group is absorbing the light. Wavenumbers reflect the energy state of chemical bonds, with different types of bonds absorbing infrared light at different wavenumber regions.

2.Peak Shape and Width:

3.Sharp Peaks: Typically indicate a high purity compound, as specific chemical bonds in a pure compound usually absorb light sharply and distinctly.

4.Broad Peaks: May indicate a complex mixture or a compound with multiple overlapping absorptions, causing the peak to widen.

5.Peak Intensity:

6.Strong Peaks: Suggest a high concentration of the corresponding chemical bond or functional group.

7.Weak Peaks: Indicate a lower concentration of the chemical bond or functional group.

8.Peak Quantity: The number of peaks reflects the sample's complexity. Multiple peaks often suggest the presence of various chemical bonds or functional groups.

By interpreting these peaks, scientists and researchers can analyze the specific chemical structure of materials, understanding their properties and potential uses. FTIR analysis is widely used in pharmaceutical analysis, plastic manufacturing, chemical research, and environmental science.

Significance of Common Peaks

In FTIR analysis, common peaks represent the characteristics of specific chemical bonds or functional groups within the sample. The position, shape, and intensity of these peaks provide crucial information about the chemical structure of the sample. Below are details of some common chemical bonds and functional groups, along with their representative peaks and significance:

1.C=O Bond (Carbonyl):

Position: Around 1700 cm-1
Characteristics: A very typical strong absorption peak.
Found in: Ketones, aldehydes, carboxylic acids, esters, and amino acids.
Significance: The presence of carbonyl groups is key to many biochemical and organic reactions.

2.O-H Bond (Hydroxyl):

Position: Around 3200-3550 cm-1
Characteristics: Usually appears as a very broad strong peak, especially in alcohols and acids.
Found in: Alcohols, acids, phenols, and some hydrates.
Significance: Hydroxyl groups are involved in hydrogen bonding, significantly affecting solubility and reactivity.

3.N-H Bond:

Position: Around 3300 cm-1 (stretching vibration of primary amines NH2) and 1550-1650 cm-1 (bending vibration of secondary amines)
Characteristics: The N-H stretching vibration of primary amines is typically sharp and strong.
Found in: Amines and some proteins.
Significance: Amino groups are fundamental components of proteins and other biomolecules.

4.C-H Bond:

Position: 2850-3000 cm-1 (stretching vibration of saturated hydrocarbons) and above 3000 cm-1 (stretching vibration of unsaturated hydrocarbons)
Characteristics: Depending on the type of hydrocarbon (saturated or unsaturated), these peaks can be sharp or broad.
Found in: All carbon-containing compounds.
Significance: C-H bonds are the most common bonds in organic chemistry, forming the basic structure of organic compounds.

By identifying these common peaks and their characteristics, scientists can analyze which types of chemical bonds or functional groups are present in a sample, further inferring the sample's possible structure and properties. This analysis is crucial in material science, drug research, environmental monitoring, and other fields.

Applications of FTIR in Various Industries

Fourier Transform Infrared Spectroscopy (FTIR) is a powerful analytical technique that provides information about the chemical structure of materials. It is widely used across various industries, from drug discovery and manufacturing to food safety, environmental monitoring, chemical industry, and material science. Below are the specific applications of FTIR in these industries:

Pharmaceutical Industry

1.Drug Component Analysis: FTIR is used to confirm the chemical structure of active pharmaceutical ingredients (APIs), ensuring the purity and quality of chemicals used in production.

2.Quality Control: Monitoring the quality of drugs during production, ensuring the final product meets predefined chemical and physical standards.

3.Formulation Development: Analyzing interactions between components in drug formulations to optimize the formulation.

Environmental Science

1.Pollutant Detection: Monitoring and analyzing pollutants in air, water, and soil samples, such as detecting industrial emissions and harmful chemicals.

2.Environmental Monitoring: Long-term monitoring of environmental changes, assessing the effectiveness of environmental protection measures.

Food Industry

1.Component Verification: Determining the components in food, such as fats, proteins, and other nutrients.

2.Adulteration Detection: Detecting illegal additives or low-cost substitutes in food products.

Chemical Industry

1.Chemical Analysis: Confirming the structure and purity of chemical reactions' products and raw materials.

2.Process Control: Monitoring intermediates and products in chemical processes, optimizing production efficiency and product quality.

Polymer and Plastics Industry

1.Material Performance Evaluation: Analyzing the chemical structure of plastics and polymers, predicting and testing their physical properties.

2.New Material Development: Developing new plastic formulations and composites to meet specific industrial needs.

Cultural Heritage Conservation and Archaeology

Artifact Material Analysis: Determining the material composition of ancient objects such as paintings, sculptures, and other artworks, guiding conservation and restoration efforts.

Petroleum and Petrochemical Industry

Crude Oil and Fuel Analysis: Analyzing the chemical composition of crude oil and petrochemical products, optimizing the processing process.

These applications demonstrate the importance of FTIR as a versatile and efficient analytical tool that provides rapid and accurate chemical information, helping various industries improve product quality, optimize production processes, and ensure environmental safety.