What is Spectroscopy
- The study of the relations of electromagnetic radiation with matter is called Spectroscopy. It applies to measure a sample’s absorption, emission or scattering of light to get details about its composition, structure, and properties.
- It is used in various disciplines like engineering, physics, chemistry and biology. It is utilized to determine and characterize Organic compounds, study chemical reactions, determine the structure of molecules, and analyze the properties of materials.
- It can study electromagnetic radiation coming from X-rays and gamma rays to radio waves and microwaves. Different types of radiation are best suited for different kinds of samples and measurements.
- It is a rapidly evolving field, constantly developing new techniques and instruments. Recent spectroscopy advances have helped researchers to study molecules and materials at smaller scales with greater precision.
Spectroscopy
“The study of the relations of electromagnetic radiation with matter is called Spectroscopy. It concerns analyzing how materials interact with different types of electromagnetic radiation such as visible, ultraviolet or infrared radiation, and how they absorb, emits or scatter light”.
Working Principle
Its working principle is based on the relationship between electromagnetic radiation and matter. When electromagnetic radiation such as light, interacts with matter, it can be absorbed, transmitted or scattered. How electromagnetic radiation interacts with matter depends on the material’s properties such as its composition, structure and electronic state.
A sample is placed in a source of electromagnetic radiation like a beam of light. The light passes through or interacts with the sample, and the resulting spectrum is analyzed to obtain information about the sample’s properties. The spectrum represents light intensity distribution as a function of wavelength or frequency.
Spectrometer
It is an instrument that is used to measure and examine the properties of light rays with their frequencies or wavelengths. It works by separating the different frequencies or wavelengths of light and measuring the intensity of each part.
It is used to determine the following things:
- Chemical composition of a sample
- Properties of materials
- Amount of a particular substance
- Properties of light itself
Instruments of Spectrometer
The main components of a spectrometer are given below.
- Light Source
This is part of the spectrometer that produces electromagnetic radiation, such as a lamp, laser, or LED. - Entrance Slit
It is the opening through which the light enters the spectrometer. - Collimating Lens or Mirror
This lens or mirror makes the light parallel and directs it towards the diffraction grating or prism. - Diffraction Grating or Prism
This component separates the different wavelengths of light. A diffraction grating consists of parallel lines etched on a surface. At the same time, a prism is a triangular glass or plastic element that bends light according to its wavelength. - Focusing Lens or Mirror
This lens or mirror focuses the diffracted light onto the detector. - Detector
It calculates the intensity of the different wavelengths of light. The most ordinary types of sensors are photodiodes, CCDs [charge-coupled devices] and PMTs [photomultiplier tubes]. - Data Acquisition System
This part of the spectrometer collects and processes the data from the detector. It may include a computer or specialized software.
Different types of spectrometers may have more components such as monochromators, polarizers or filters, depending on their use and the properties of the light being analyzed.
Mass Spectrometer
“A mass spectrometer is a scientific instrument that measures and analyzes ions’ mass to charge ratio [m/z]. It works by ionizing a sample, separating the ions according to their mass-to-charge ratio, and detecting the resulting ions”.
It is made up of an ion source, a mass analyzer and a detector. The ion source ionizes the sample, creating ions with a positive or negative charge. The ions are then accelerated by an electric field and enter the mass analyzer, separating them according to their mass-to-charge ratio. The most common types of mass analyzers are magnetic sector, quadrupole, time-of-flight, and ion trap. When the ions are separated, they are detected by a detecter and create an electrical signal which is proportional to the number of ions detected. The signal is then analyzed to determine the mass-to-charge ratio of each ion. The data induced by a mass spectrometer can be utilized to:
- Determine the molecules present in a sample
- Determine their molecular weight
- Measure the concentration of each molecule
Spectrophotometer
“An instrument that is utilized to calculate light intensity at different wavelengths is named as a spectrophotometer”.
It operates by a beam of light via a sample and measuring the amount of light absorbed or transferred by the sample at each wavelength. The basic components of a spectrophotometer include:
- A light source
- A monochromator that separates the light into its component wavelengths
- A sample holder
- A detector
The monochromator permits the user to choose a specific wavelength of light, which then passes through the sample. The detector detects the intensity of the light which has been passed through the sample.
Types of Spectroscopy
There are many types of spectroscopy based on different physical phenomena or techniques. The most important types of spectroscopy are given below.
Atomic Absorption Spectroscopy
“It is an analytical method to specify the existence and concentration of specific chemical elements in a sample”.
Working Principle
The working principle is based on light absorption by gaseous atoms in the ground state. The sample is vaporized, and the atoms are excited to a higher energy level by radiation from a light source, usually a hollow cathode lamp, at a specific wavelength. This energy can be measured by a detector, usually a photomultiplier tube.
Instrumentation
A typical AAS instrument consists of four major components:
- A light source
- A sample atomizer
- A monochromator
- A detector.
The light source produces a beam of radiation at a specific wavelength, which the sample absorbs. The atomizer converts the sample into gaseous atoms, which are excited by the radiation from the light source. The monochromator selects a specific wavelength of light for measurement, and the detector measures the energy absorbed by the atoms at that wavelength.
Sample Preparation
Sample preparation is an important step in AAS analysis. The sample must be in a form that can be vaporized and atomized in the instrument. Solid samples are usually digested in acid to dissolve the elements of interest, while liquid samples are directly aspirated into the atomizer. Sometimes, samples must be treated with a reducing agent to convert certain aspects to their atomic form.
Advantages and Disadvantages
- It is a highly selective method for specifying the concentration of trace components in a sample.
- It is also a relatively simple and fast technique compared to other ways, such as Inductively Coupled Plasma (ICP) Spectroscopy.
- It has some disadvantages like the requirement for a separate measurement for each element which can be time consuming and costly.
NMR Spectroscopy
“It is a powerful analytical technique utilized to study the structure, dynamics and chemical properties of molecules”.
Working Principle
Nuclear magnetic resonance [the capacity of certain atomic nuclei to absorb and emit electromagnetic radiation] is the working principle of NMR Spectroscopy.
Instrumentation
A typical NMR instrument consists of three main components:
- a magnet
- a radiofrequency transmitter and receiver
- a computer system.
The magnet generates a strong, uniform magnetic field that aligns the nuclear spins of the sample. The radiofrequency transmitter creates the electromagnetic radiation utilized to excite the nuclei while the receiver detects the signals radiated by the nuclei as they replace their original state. The computer system processes and analyzes the data to generate a spectrum.
Sample Preparation
The sample is typically dissolved in a deuterated solvent to minimize interference from the solvent. In addition, the sample must be free from paramagnetic impurities, which can quench the NMR signal.
Advantages and Disadvantages
- It is non destructive and non invasive, allowing for the study of living systems and dynamic processes.
- It provides molecular structure and dynamics.
- Its relatively low sensitivity and the need for specialized equipment and expertise.
Mass Spectroscopy
“It is a powerful analytical technique to identify and characterize molecules based on their mass to charge ratio [m/z]”.
Working Principle
It is based on the separation of ions based on their mass to charge ratio. A sample is ionized, usually by electron impact or electrospray ionization, and the resulting ions are separated in a mass analyzer based on their m/z values. The separated ions are then detected by a detector, which generates a mass spectrum, a graph of ion abundance versus m/z.
Instrumentation
A mass spectrometer consists of 3 main components:
- An Ion source
- A mass analyzer
- A detector
The ion source ionizes the sample, generating a mixture of ions with different m/z values. The mass analyzer separates the ions based on their m/z values, and the detector detects the dissolved ions and generates a mass spectrum.
Sample Preparation
The sample is typically melted in a suitable solvent and subjected to purification methods such as chromatography to remove impurities.
Advantages and Disadvantages
- It provides information about a sample’s molecular structure and composition.
- It can detect trace amounts of molecules in complex mixtures.
- It has a requirement for a pure sample and specialized equipment and expertise.
IR Spectroscopy
“Infrared [IR] spectroscopy is utilized to determine and characterize molecules based on their absorption of infrared radiation”.
Working Principle
It is based on the absorption of infrared radiation by a molecule which causes its chemical bonds to vibrate. Details about the structure and composition of molecules can be received by calculating the absorption of infrared radiation at different frequencies.
Instrumentation
It consists of the following:
- A sample holder
- A monochromator
- A detector
- A computer system
The source generates infrared radiation, which is directed through the sample holder. The monochromator selects a specific frequency of infrared radiation, and the detector measures the intensity of the radiation that has passed through the sample. The computer system processes and analyzes the data to generate a spectrum.
Sample Preparation
The sample is typically prepared as a thin film or a liquid solution, and any impurities or contaminants must be removed to avoid interference with the IR spectrum.
Advantages and Disadvantages
- It is non destructive and non invasive which allows the study of living systems and dynamic processes.
- It can provide detailed information about molecular structure and composition.
- It has relatively low sensitivity and the need for specialized equipment and expertise.
FTIR Spectroscopy
Fourier Transform Infrared [FTIR] spectroscopy is used to study the vibrational modes of molecules by measuring the absorption or transmission of infrared radiation. A sample is exposed to infrared radiation in this technique and the resulting spectrum supplies information about the functional groups and chemical bonds present in the sample.
UV Vis Spectroscopy
“UV Vis [Ultraviolet Visible] spectroscopy is used to measure light absorption in the ultraviolet and visible regions of the electromagnetic spectrum”.
Working Principle
The principle of UV-Vis spectroscopy is based on the absorption of light by a sample. A sample is exposed to a beam of UV or visible light and the amount of light absorbed is measured. The amount of light absorbed is proportional to the concentration of the sample and its extinction coefficient. The extinction coefficient is a constant that depends on the molecular structure and composition of the sample.
Instrumentation
It consists of the following:
- A light source
- A monochromator
- A sample holder
- A detector
- A computer system
The light source generates a beam of UV or visible light, which is directed through the monochromator that selects a specific wavelength of light. The sample holder maintains the sample and the detector calculates the intensity of the light that has passed through the sample. The computer system processes and analyzes the data to generate a spectrum.
Sample Preparation
Sample preparation is critical in UV-Vis spectroscopy. The sample must be in a suitable form that allows for the measurement of light absorption. The sample is typically dissolved in a suitable solvent, and any impurities or contaminants must be removed to avoid interference with the spectrum.
Advantages and Disadvantages
- It is non destructive & non invasive and requires minimal sample preparation.
- It is also a rapid and straightforward technique that provides quantitative data.
- It has limited sensitivity and the requirement for a pure sample.
Raman Spectroscopy
“Raman spectroscopy is a powerful analytical technique used to study the vibrational modes of molecules. It is based on the Raman effect, which is an inelastic scattering of light in molecules”.
Working Principle
The principle of Raman spectroscopy is based on the interaction of light with the chemical bonds in a sample. When a sample is illuminated with a laser, a small fraction of the scattered light undergoes a frequency shift due to the excitation of vibrational modes in the molecule. This frequency shift is called the Raman shift, which is proportional to the energy of the vibrational mode.
Instrumentation
It consists of the following:
- A laser source
- A sample holder
- A monochromator
- A detector
- A computer system
The laser source generates a beam of monochromatic light directed onto the sample. The scattered light is collected and passed through a monochromator that selects a specific frequency of the Raman shift. The detector measures the intensity of the Raman scattered light, and the computer system processes and analyzes the data to generate a spectrum.
Sample Preparation
Sample preparation is critical in Raman spectroscopy. The sample must be in a suitable form that allows for the measurement of Raman scattering. The sample is typically in a solid, liquid, or gas phase, and any impurities or contaminants must be removed to avoid interference with the Raman spectrum.
Advantages and Disadvantages
- It is non destructive & non invasive, which requires minimal sample preparation.
- It is also highly specific and can provide detailed information about a sample’s molecular structure and composition.
- It has relatively low sensitivity and powerful laser source requirements.
Fluorescence Spectroscopy
“Fluorescence spectroscopy is utilized to study the interaction of light with a sample”.
Working Principle
It is based on the absorption of light by a molecule which enables an electron to a higher energy state. The excited molecule then relaxes to a lower energy state by emitting light at a longer wavelength than the absorbed light. The emitted light is called fluorescence and is detected and analyzed to provide information about the sample.
Instrumentation
It consists of the following:
- A light source
- A monochromator
- A sample holder
- A detector
- A computer system
The light source generates a beam of light of a specific wavelength that excites the sample. The monochromator selects a particular wavelength of the emitted fluorescence light. The detector measures the intensity of the fluorescence light, and the computer system processes and analyzes the data to generate a spectrum.
Sample Preparation
Sample preparation is critical in fluorescence spectroscopy. The sample must be in a suitable form that allows for fluorescence measurement. The sample is typically dissolved in a suitable solvent, and any impurities or contaminants must be removed to avoid interference with the fluorescence spectrum.
Advantages and Disadvantages
- It is highly sensitive and can detect low concentrations of a sample.
- It is also highly specific and can provide detailed information about a sample’s molecular structure and composition.
- Its susceptibility to interference from other fluorescent molecules and its dependence on the environment of the sample.
Photoelectron Spectroscopy
“Photoelectron spectroscopy [PES] is utilized to study the electronic structure of atoms, molecules and solids”.
Working Principle
It is based on the absorption of light by a sample, which promotes an electron to a higher energy state. The electron then escapes from the sample and is detected and analyzed to provide information about the sample’s electronic structure.
Instrumentation
It consists of the following:
- A light source
- A monochromator
- A sample holder
- An electron analyzer
- A detector
The light source emits a beam of light with a specific wavelength that enlightens the sample. The monochromator selects a particular wavelength of light. The electron analyzer detects and measures the kinetic energy and angular distribution of the emitted photoelectrons, and the detector measures the intensity of the emitted photoelectron.
Sample Preparation
Sample preparation is critical in photoelectron spectroscopy. The sample must be in a suitable form that allows for photoemission measurement. The sample is typically in a solid or gas phase, and any impurities or contaminants must be removed to avoid interference with the photoemission spectrum.
Advantages and Disadvantages
- It provides information about the electronic structure of a sample including the energy levels and the distribution of electrons.
- It is also highly specific and can provide detailed information about a sample’s chemical composition and bonding.
- Its relatively low sensitivity and the requirement for a high vacuum environment.
Applications of Spectroscopy
- Analytical Chemistry
It is used to determine the quantity of chemical composition of a sample. IR spectroscopy, ultraviolet visible spectroscopy & NMR spectroscopy are used to analyze and identify compounds. - Materials Science
Spectroscopy is used to study the properties & structure of materials. Photoelectron & Raman spectroscopy are used in this field. - Environmental Science
It is used to study the physical & chemical properties of the environment. Techniques like mass spectrometry, FTIR spectroscopy and laser induced breakdown spectroscopy is used to analyze air, water and soil samples. - Astronomy
It is used to study the properties and composition of celestial objects in Astronomy. X-ray and Optical spectroscopy analyze the light emitted by stars, galaxies and other celestial objects. - Forensics
Spectroscopy is used in forensic science to identify and analyze evidence. IR spectroscopy and mass spectrometry examine drugs, explosives, and other forensic evidence.
FAQ’s
What can a person do to limit exposure to x-rays?
A person can avoid unnecessary medical X-rays and record their X-ray history. They can also ask healthcare providers to use protective shields during X-rays and consider alternatives to X-rays such as ultrasound or MRI scans. Avoiding exposure to X-ray-emitting devices like airport scanners can help minimize radiation exposure.
What are gamma rays?
It is high energy electromagnetic radiation created by the decay of atomic nuclei. They have no mass or electric charge and travel at the speed of light. This is the most energetic form of electromagnetic radiation. They can penetrate deep into the matter to make them useful for medical imaging and radiation therapy but also potentially harmful to living organisms in high doses.
How fast do radio waves travel?
They travel at the speed of light approximately 299,792,458 meters per second in a vacuum. It means they can travel about 7.5 times in one second around the circumference of the Earth. The speed of radio waves is constant in a vacuum but it can be decreased when passing through materials like air or water which causes refraction and other effects.
How do Microwaves work
Microwaves produce electromagnetic waves that cause water molecules in the food to vibrate rapidly, generating heat. This heat is then transferred to other parts of the food [cooking it from the inside out]. Microwaves are absorbed by glass, plastic and metal, so microwave-safe containers are necessary.
When were microwaves invented
Microwaves were invented in 1945 by Percy Spencer, an engineer at Raytheon Corporation. Spencer was working on radar technology when he noticed a candy bar in his pocket had melted after exposure to microwaves. It led to the development of the first microwave oven called the Radarange. The Radarange was large, expensive, and only used in commercial kitchens until the 1960s, when smaller, more affordable models became available for home use.
How long do microwaves last
The lifespan of a microwave oven varies depending on usage and maintenance. Typically, a microwave oven lasts between 5 and 10 years. If the microwave is well maintained and used correctly, it can last longer. Regular cleaning and avoiding overheating the microwave can help extend its lifespan. It’s also important to replace the microwave if it shows signs of damage or malfunctioning.
How to become a forensic psychologist
A bachelor degree in psychology or a closely related subject is required. It would be best to pursue forensic psychology-focused master’s and doctoral degrees in psychology. You’ll also need to complete supervised clinical hours and obtain a license to practice as a psychologist. Additionally, some states may require additional certifications or exams for forensic psychology.
How is mitochondrial DNA (mtdna) typing used in forensic science?
Mitochondrial DNA (mtDNA) typing is used in forensic science to identify individuals or determine familial relationships. Mitochondria of DNA is often used in cases where the available DNA sample is limited or degraded, such as in old or badly decomposed remains. It is passed down maternally and does not change as frequently as nuclear DNA. It can also be used to trace ancestry or migration patterns.
What are Kirchhoff’s 3 laws of spectroscopy?
Kirchhoff’s three laws of spectroscopy are:
1- A hot solid or gas under high pressure produces a continuous radiation spectrum.
2- A hot gas under low pressure produces a spectrum of bright or emission lines at specific wavelengths.
3– A cool gas in front of a continuous spectrum source produces a spectrum of dark lines or absorption lines at specific wavelengths.
Who is the father of spectroscope?
Gustav Kirchhoff is considered the father of the spectroscope. He developed the first spectroscope in 1859 with Robert Bunsen, allowing scientists to study the unique spectral patterns of various elements. Kirchhoff’s assistance in spectroscopy made him multiple awards and honors.
What is the formula of spectroscopy?
This technique has no formula but rather a combination of equations to analyze light’s interaction with matter. Ordinary equations used in spectroscopy include Beer-Lambert law, Planck’s law, Schrodinger equation, and Boltzmann distribution.
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