Energy dispersive spectroscopy (EDS) is an interesting analytical spectroscopic technique. It is mainly used to characterize and find the relative abundance of different chemical elements present in a sample. EDS is particularly valued for its stability and reliability.
In this article, we have discussed the working principle, instrumentation, equipment, and importance of energy dispersive spectroscopy (EDS).
Furthermore, this article also covers the fundamental introduction of energy-dispersive X-ray spectroscopy and its limitations. So, let’s begin reading.
What is energy dispersive spectroscopy (EDS)?
As the technique’s name is self-explanatory, energy dispersive spectroscopy is used to quantitatively analyze an element by studying its energy spectrum.
In energy dispersive spectroscopy, the characteristic composition of a sample is determined by bombarding it with a beam of high-energy particles, mostly electrons or protons. The energy spectrum (such as X-rays) emitted by different elemental atoms present in the sample as a result of this electronic bombardment is, in turn, recorded. Finally, this energy spectrum is analyzed to characterize individual elements of a specimen via energy dispersive detectors.
What is the basic working principle of energy dispersive spectroscopy?
The primary working principle of energy dispersion spectroscopy (EDS) includes the following:
- The bombardment of a beam of high-energy particles (mostly electrons) on the specimen to be analyzed.
- These high-energy particles, upon reaching the elements of the specimen, have the ability to reach the “core” of the atom and kick-out electrons from the inner shells. This creates a “hole” in there.
- That “hole” is immediately filled with a higher energy outer shell electron, where it relaxes and releases unique energy in the form of x-rays to get stable.
- This unique x-ray energy is distinctive to each element present in the Periodic Table which can then be analyzed.
In this way, via energy dispersive spectroscopy (EDS), bombarding a sample with high-energy particles help in composition characterization as well as the quantification of elements present in a specimen.
Energy dispersive spectroscopy- Instrumentation and equipment
The major components of an energy dispersion spectroscopy (EDS) instrument are briefly mentioned below. So, let’s look at their contribution to the whole process.
1. The exciting beam (high energy particle) probe
An exciting beam probe of high-energy particles such as electrons or protons is used in electron dispersion spectroscopy (EDS). This exciting beam is bombarded on the specimen.
2. Specimen holder
The sample present in the specimen holder absorbs the high-energy particle beam. As a result of that, absorbed energy reaches the “core” of the atoms to eject electrons from the inner shells (not from outer shells) of the atoms by creating a “hole.”
Outer shell high energy electrons then immediately proceed to fill that “hole” and, by reaching there, release their extra energy to get stable. This energy is released in the form of X-rays.
An x-ray is a high-energy electromagnetic radiation of wavelength 10-0.01 nm. It is distinctive in character to the atoms present in the specimen to be analyzed.
3. Energy-dispersive detector
Energy-dispersive detector is present in the instrument for the detection of characterized X-rays coming from the elements present in the specimen in the form of an electric signal.
An energy-dispersive detector is further divided into five components that ensure its efficient working.
- A Collimator that collects x-rays produced by the excitation of the sample.
- An Electron trap that allows entry to only particular x-rays.
- A window composed of polymers that keeps the detector and the microscope chamber isolated. It gives entry to even low-energy (< 0.1 KeV) x-rays.
- A semiconductor crystal detector
- Electric detector for detecting and recording a charge and its conversion into a voltage pulse before it finally reaches the pulse analyzer.
4. Signal amplifier
The signal amplifier present in the energy dispersion spectroscope increases the x-ray signal intensity to keep the strength of the signal transmission consistent. It also avoids any possibility of a loss of weak signals.
5. Pulse analyzer
The pulse analyzer in EDS measures the produced and amplified electric signals to determine distinctive and unique x-rays. It helps reveal the identity of different elements present in the sample.
6. Data Analyzer
The data analyzer in EDS analyzes the measured qualitative and quantitative signals of x-rays and their intensity distribution. The data analyzer displays the obtained spectroscopic data in readable and understandable data formats.
Why is EDS important in chemical analysis- Applications
In the characteristic chemical analysis, energy dispersion spectroscopy (EDS) has a huge level of importance as:
- EDS is used to identify and evaluate components present in an unknown sample.
- It is used to detect contaminants while checking the purity of the specimens.
- It is used for analyzing the elemental diffusion profile in diffusion studies.
- Energy dispersion spectroscopy is used in failure analysis by identifying unknown substances in a complex sample.
- EDS is used in the chemical industry for material verification and for quality control screening.
Also, check out our special article on the applications of analytical spectroscopic techniques.
What are the advantages of EDS?
- EDS is a non-destructive chemical analytical technique.
- It is usually coupled with a scanning electron microscope (SEM) or transmission electron microscope (TEM). Hence, it can provide morphological details of the sample.
- EDS is less time consuming and is relatively faster than other analytical techniques.
- EDS can simultaneously perform qualitative as well as quantitative analysis.
- The scientists can obtain information about a specimen at different depths by adjusting the excitation voltages.
- EDS is used in forensics for the chemical investigation of explosives.
- EDS can be used to detect nanoparticles in drug delivery studies quantitatively.
- Energy dispersive spectroscopy helps investigate the heavy metals accumulation in tissues in biomedical research.
What is energy-dispersive X-ray spectroscopy?
Energy dispersive x-ray spectroscopy (EDX) is a synonymous and interchangeable term used for energy dispersive spectroscopy (EDS). Some technologists refer to EDS as an energy dispersive spectrometer, the main instrument, contrarily EDX as the method, technique, or analysis protocol.
How is energy-dispersive X-ray spectroscopy different from wavelength-dispersive X-ray spectroscopy?
| Features | Energy dispersive X-ray spectroscopy (EDS or EDX) | Wavelength dispersive x-ray spectroscopy (WDX) |
| Definition | Energy dispersive X-ray spectroscopy (EDX or EDS) is an analytical technique used for the chemical characterization of a specimen. | Wavelength dispersive x-ray spectroscopy (WDX) is used to count the number of x-rays of known elements and is usually used in conjunction with EDS. |
| Uses | – It is mostly used in the chemical identification and evaluation of materials. – EDS is used in quality control screening, such as in material verification and contaminant hunt. |
– WDX is applied in the identification of spectrally overlapped elements to avoid any chances of analytical errors. – It is used to analyze low atomic number elements and detect low- concentration species (10-100 ppm). |
| Spectral resolution | High (up to 160 eV ) | Low (2-10 eV) |
| Detection limit | 1000-5000 ppm | <100-500 ppm |
| Specifications | It is a quick, inexpensive, versatile and widely available analytical technique. | It analyzes the low concentration of elements with high sensitivity and allows superior peak resolution. |
What are the limitations of energy-dispersive X-ray analysis?
- A very small fraction of the specimen is used in EDS. Therefore, it is important to carefully prepare a smooth surfaced sample, as minute roughness can affect the results.
- While moving from the heavier to lighter elements, the x-ray intensity usually decreases, which may affect the accuracy of the EDS.
- EDS results are compared with the fixed standard peaks, which somehow limits the analysis of unknown and new materials.
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References
- Kalyane, D., Maheshwari, R., Raval, N., Chauhan, A.S. and Tekade, R.K., 2019. Transportation and bio interaction properties in nanomaterials across biological systems. In Basic Fundamentals of Drug Delivery (pp. 343-368). Academic Press.
- Ngo, P.D., 1999. Energy dispersive spectroscopy. Failure analysis of integrated circuits: Tools and techniques, pp.205-215.
- Shindo, D., Oikawa, T., Shindo, D. and Oikawa, T., 2002. Energy dispersive x-ray spectroscopy. Analytical electron microscopy for materials science, pp.81-102.
- Hodoroaba, V.D., 2020. Energy-dispersive X-ray spectroscopy (EDS). In Characterization of Nanoparticles (pp. 397-417). Elsevier.
