How to Read IR Spectra

Infrared light is a spectrum of electromagnetic radiation that we can’t see with our naked eyes. Humans are able to see only a small range of light frequencies, known as visible light. Infrared light falls outside of this range, but it’s not invisible to insects and other animals that use it for detecting heat or other unseen wavelengths. If you have ever wondered what infrared optics are and how they work, this article will answer all your questions. Read on to find out more about IR Spectra and how to read IR spectra.

Infra-red spectroscopy is a type of spectroscopy that uses infrared light to examine the chemical composition of a substance. It is used in the analysis of materials such as carbon, water, and rubber. Infrared spectroscopy is also used in areas such as medicine (to detect disease) and astronomy (to determine the distance between objects).

In order to identify and interpret the infrared spectrums that are used in remote sensing devices and industrial sensors, one will need to use infrared spectroscopy.

How to Read IR Spectra

How to Read IR Spectra – FTIR Spectroscopy  Guide

Spectroscopy is the practice of breaking down light into its component wavelengths in order to identify the chemical composition of materials. It is useful in many different industries, including agriculture, environmental science, and medicine. There are many different types of spectroscopes. Each has its own uses and advantages. Infrared spectroscopy is used to detect the amount of heat emitted from objects. It does this by shooting a narrow beam of light at an object and detecting the wavelengths that are reflected back.

Infrared spectroscopy takes place at wavelengths where light can be reflected back to its source by means of a lens system or prism. The components that make up an infrared spectrum are:

  • Band 1 – wavelength range from 880nm – 890nm
  • Band 2 – wavelength range from 900nm – 950nm
  • Band 3 – wavelength range from 975nm – 1000nm
  • Band 4 – wavelength range from 1100nm – 1150nm

The infra-red spectrum is made up of different bands:

* Red band –> this band has wavelengths between 700-1000 nm (nanometers) and are typically used for chemical analysis.

* Blue band –> this band has wavelengths between 600-900 nm and is typically used for biological analysis.

* Near Infrared (NIR) band –> this band has wavelengths between 1100-2000 nm and is typically used for physical analysis (such as heat or electricity).

How to Read IR Spectra – FTIR Spectroscopy

Step 1: Examine the diagnostic region first(above 1500 cm-1)
as we realize, the fingerprint location could be very complicated, it’s miles difficult to read or pick out. Consequently, we can try to discover the spectra by gazing at the diagnostic areas.

Step 2: Look at the double bond area(1600-1800 cm-1)
At this location, the signal of double bonds consisting of a carbonyl group(c=o) and a carbon-carbon double bond(c=c ), and a benzene ring is found. Top shape= sharp sword-like height. How to read ir spectra
double bond region
if a sword-like height is present within the range of 1600-1800 cm-1 then the compound ought to have both c=o group or c=c organization.

Step 3: Have a look at the triple bond area(2100-2300 cm-1)
in case you examine any peak within the variety of 2100-2300 cm-1 then the compound has triple bonds together with c≡c(2100-2200 cm-1) and c≡n (2200-2300 cm-1). Triple bond vicinity.

Step 4: Draw a line at 3000cm-1 and observe the sign above and underneath it
the borderline 3000 cm-1 carries a small height above or underneath it. If a single small top is present around 2800-3000 cm-1, we can say that the height is due to the sp3 c-h bond( in alkane)
a small sign peak is present around 3000-3100 cm-1, then we are able to say that the height is due to sp2 c-h bond( in vinylic c-h bond). If a small top around 3300 cm-1 is present then that’s the peak due to sp c-h bond( in alkyne).

Step 5: is there any tongue-like peak? Have a look at it.

If the small tongue-like peak is a gift near 3200-3400 cm-1 then it’s because of the o-h bond. If an extensive tongue-like peak is present near 2200-2600 cm-1 then it’s because of cooh organization. Word: the peak due to the cooh group is more extensive than the oh bond because of hydrogen bonding. To distinguish these, have a look at the double bond region in which a pointy height of c=o must present in a carboxylic acid but not in alcohol.

Step 6: observe any fang like peak above 3300 cm-1.

If two fang-like peak is gifted around 3500 cm-1, the compound may be number one amine or number one amide. To distinguish those, examine the double bond region wherein a pointy height of the c=o bond is present in the amide. If a single height around 3500cm-1 is a gift then the compound may be a secondary amine or secondary amide.

Step 7: Confirm the structure of the compound.

The structure of the unknown compound is then confirmed by using comparing the spectra of the standard compound. Take into account 5 important regions/peaks in the spectra
tongue like height(3200-3400 cm-1)
sword-like top (1600-1850 cm-1)
borderline round 3000 cm-1
triple bond area (2100-2300 cm-1)
the fang-like structure around 3500 cm-1

These are the steps that will guide you about how to read ir spectra,

Infra-Red Spectroscopy Spectrum

Let’s take a quick look at the infrared spectrum that is produced by the combustion of methane (CH4). The graph below will help you identify the wavelengths of this spectrum. When the methane burns, a graph like the one below will be created using a spectrometer. Depending on how much heat the graph produces, you can determine how much methane is present in the atmosphere. This is helpful in many industries, as methane is a harmful gas that can be used as a fuel source. Now that you know a bit more about infrared light and infrared spectrums, try your hand at identifying some spectrums. You can understand infrared spectrums using the steps [How to read IR Spectra] above!

FTIR Spectrum of Aspirin

Aspirin is an organic compound that is mostly used as an anti-inflammatory and analgesic drug. It is mostly made from salicylic acid and acetylsalicylic acid. The infrared spectrum of aspirin has a major absorption peak at around 1750 cm-1. As we can see in the spectrum, there is a major absorption peak at around 1750 cm-1. This frequency of infrared light is absorbed by the hydrogen atom present in salicylic acid groups.

How to Read IR Spectra of aspirin



IR Spectrum of salicylic acid

Salicylic acid is an organic compound that is widely used as an anti-inflammatory, anti-fungal, and anti-coagulant drug. It is found in many plants such as Willow, Wintergreen, and Blackcurrant. Salicylic acid is a major part of the aspirin drug. The infrared spectrum of salicylic acid consists of two major absorption peaks at around 1730 cm-1 and 1220 cm-1. The 1730 cm-1 absorption peak is due to the H-C-H bending vibration of the methyl group. The 1220 cm-1 absorption peak is due to the stretching vibration of the OH group. Since salicylic acid is a part of the aspirin drug, we can say that the absorption peaks are the same for both compounds.

How to Read IR Spectra


What is Infrared Light?

Infrared light is electromagnetic radiation (EM) that falls outside of the visible spectrum. It carries less energy than visible light and has longer wavelengths, while ultraviolet light has higher energy and shorter wavelengths. Infrared spectrums are measured in microns, with wavelengths ranging between 0.7 microns and 3000 microns. Infrared light is commonly used in heat lamps, industrial sensors, and remote sensing devices. You may have also heard of thermal imaging, which is a method of detecting infrared radiation emitted by objects and converting it into an image. Thermal imaging cameras can be used to detect people through barriers and can be helpful in a wide variety of industries, from law enforcement to healthcare.

Uses of infrared light

Thermography Thermography is the process of using infrared cameras to create temperature maps of objects. Infrared cameras can detect temperature variations, which indicate potential problems in industrial facilities or medical facilities. – Wildlife Research and Surveys Wildlife researchers use infrared cameras to track and study animals and birds without disturbing their habitats. Infrared cameras are used to observe nocturnal predators, nest locations, and mating rituals. They can also be used to track endangered species. – Remote Sensing Remote sensing technology is used to analyze the earth’s surface without the need to physically visit the location. Various satellites and unmanned aerial vehicles (UAVs) use infrared spectrums to observe and measure the earth’s surface. –

Astronomy Astronomers use infrared spectrums to study celestial bodies and galaxies. – Human Body Scan A human body scan uses infrared light to create images of the human body. The images created by infrared light can reveal abnormalities in the body that would not be visible in visible light images. Human body scans are used for many different purposes, including medical diagnoses, research, and artistic expression. – Other Industrial Applications There are many other uses for infrared light, including cooking, thermal storage of energy, and many more!


When it comes to infrared light, less energy = longer wavelengths. Humans are able to see only a small portion of the electromagnetic spectrum, known as visible light, which also happens to be the area in which most of our energy is found. Infrared light is electromagnetic radiation that falls outside of the visible light spectrum. It carries less energy than visible light and has longer wavelengths. In order to understand how infrared light works, we need to familiarize ourselves with some basic concepts of light.

Now that we know what infrared light is and how it works, and how to read ir spectra let’s take a look at some common infrared spectrums used by humans. If you ever need to identify an infrared spectrum, understanding these concepts will be helpful. It’s important to note that not all infrared spectrums are created equally. Each infrared spectrum will have a slightly different wavelength and energy level.

By Mirza

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