Difference Between Flame Emission Spectroscopy and Atomic Absorption Spectroscopy

The key difference between flame emission spectroscopy and atomic absorption spectroscopy is that during flame emission spectroscopy, certain wavelengths are emitted from atoms, whereas during atomic absorption spectroscopy, certain wavelengths are absorbed by atoms.

An electromagnetic wave consists of electric and magnetic fields oscillating perpendicular to each other. Thus, the full range of electromagnetic radiation wavelengths is what we call the electromagnetic spectrum. In spectroscopy experiments, we use electromagnetic radiation of specific wavelengths to analyze a sample. Atomic absorption spectroscopy and emission spectroscopy are two spectrochemical procedures that are useful for the quantitative determination of chemical elements using the absorption of optical radiation or light by the free atoms that are in the gaseous state.

CONTENTS

1. Overview and Key Difference
2. What is Flame Emission Spectroscopy
3. What is Atomic Absorption Spectroscopy
4. Side by Side Comparison – Flame Emission Spectroscopy vs Atomic Absorption Spectroscopy in Tabular Form
5. Summary

What is Flame Emission Spectroscopy?

Flame emission spectroscopy is a spectro-analytical procedure useful in determining the chemical elements in a sample quantitatively. This is also named atomic emission spectroscopy because it depends on the emission of electromagnetic ration from atoms. This technique is named as such because it uses a flame as the light source.

Atoms can be excited to a higher energy level if the required amount of energy is provided externally. The lifetime of an excited state is generally short. Therefore, these excited species have to release the absorbed energy and come back to the ground state. We call this relaxation.

The release of energy may take place as electromagnetic radiation, heat or as both types. The plot of released energy versus wavelength gives an emission spectrum. Moreover, each element has a unique emission spectrum as they have a unique absorption spectrum. Therefore, we can characterize radiation from a source by emission. Line spectra occur when the radiating species are individual atomic particles that are well separated in a gas.

What is Atomic Absorption Spectroscopy?

Atomic absorption spectroscopy is a spectro-analytical procedure useful in determining the chemical elements in a sample quantitatively. This procedure depends on the absorption of light by free metallic ions.

Electrons are in certain energy levels of an atom. We call these energy levels atomic orbitals. These energy levels are quantized rather than being continuous. The electrons in the atomic orbitals can move from one energy level to another by either absorbing or releasing the energy they have. However, the energy the electron absorbs or emits should be equal to the energy difference between the two energy levels (between which the electron is going to move).

Since each and every chemical element has a unique number of electrons at its ground state, an atom will absorb or release energy in a pattern unique to its elemental identity. Therefore, they will absorb/emit photons in a correspondingly unique pattern. Then we can determine the elemental composition of a sample by measuring the changes in light wavelength and light intensity.

After light passes through an atomic sample, if we record it, we can call it an atomic spectrum. It shows the characteristic of a type of atom. Therefore, we can use it in identifying or confirming the identity of a particular species. This kind of spectrum will have a number of very narrow absorption lines.

What is the Difference Between Flame Emission Spectroscopy and Atomic Absorption Spectroscopy?

Flame emission spectroscopy and atomic absorption spectroscopy are spectro-analytical procedures useful in determining the chemical elements in a sample quantitatively. The key difference between flame emission spectroscopy and atomic absorption spectroscopy is that during flame emission spectroscopy, certain wavelengths are emitted from atoms, whereas during atomic absorption spectroscopy, certain wavelengths are absorbed by atoms.

Below is a summary of the difference between flame emission spectroscopy and atomic absorption spectroscopy in tabular form.

Summary – Flame Emission Spectroscopy vs Atomic Absorption Spectroscopy

Flame emission spectroscopy and atomic absorption spectroscopy are spectro-analytical procedures useful in determining the chemical elements in a sample quantitatively. The key difference between flame emission spectroscopy and atomic absorption spectroscopy is that during flame emission spectroscopy, certain wavelengths are emitted from atoms, whereas during atomic absorption spectroscopy, certain wavelengths are absorbed by atoms.

Reference:

1. “FLAME EMISSION SPECTROSCOPY.” SlideShare, Available here.

Image Courtesy:

1. “ICPAES PerkinElmer 2” By Superchilum – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “FlammenAAS”- original uploader was Talos at German Wikipedia. – Transferred from de.Wikipedia to Commons by Leyo using CommonsHelper (CC BY-SA 3.0) via Commons Wikimedia