Atomic Absorption & Emission Spectroscopy
UV-Visible Spectroscopy
There are two regions;
- UV region 200nm to 400nm
- Visible region 400nm to 850nm
When a beam of sun light is passed through a prism it splits into seven colors i.e. red, orange, yellow, green, blue, indigo, and violet. This set of colors obtained by splitting the white light is called spectrum. Different colors are associated with different energy and wavelength. For example red light has smallest energy and longest wavelength.
Energy goes on increasing and wavelength goes on decreasing as we move from red to violet color. Therefore, the violet color has the maximum energy and minimum wavelength.
Electromagnetic spectrum:
In addition to white light with its seven different colors or radiations, there are many more different types of radiations. Some of them are more energetic and some are less energetic than the visible white light. The electromagnetic spectrum consist of the following radiations;
(i) Cosmic rays: these rays come from sun and are known to be the radiations of highest energy. They have wavelength less than 10-3 nm.
(ii) γ rays and X rays: they are less energetic than cosmic rays their wavelength range is between 10-3 nm to 10-1 nm.
(iii) UV light: these are the rays which are less energetic but more energetic than visible light. The range of wavelength of UV region is 200nm to 400nm.
(iv) Visible light: it is ordinary light and it is composed of several different radiations (from red to violet) and the wavelength range is 400nm to 850nm.
Principle:
When a beam of electromagnetic radiation is passed through a compound certain radiations are observed. There is some energy associated with energy radiation and is given by the following equation;
𝑬 = 𝒉𝝂
Atomic Absorption spectroscopy
The technique was introduced in 1955 by Walsh in Australia. The first commercial atomic absorption spectrometer was introduced in 1959.
Definition: When we study the absorption of energy by the atoms in the flame, we call this technique as Atomic Absorption Spectroscopy AAS.
Atomic Absorption Spectroscopy (AAS) is an analytical technique that measures the concentrations of metals and metalloids in samples. It makes use of the absorption of light by these elements, in order to measure their concentration.
Principle:
Atomic-absorption spectroscopy quantifies or measures the absorption of energy radiation by ground state atoms in the gaseous state.
The absorption of the ultraviolet or visible light energy that has the right wavelength causes the electrons of the sample to be promoted from a lower energy level to a higher energy level. The analyte concentration is determined from the amount of absorption.
Atomic emission spectroscopy
Definition: When we study the emission of energy by the atoms in the flame, we call this technique as Atomic Emission Spectroscopy AES.
Atomic Emission Spectroscopy (AES) is an analytical technique that measures the concentrations of elements in samples. It makes use of the emission of light by these elements, in order to measure their concentration.
Principle:
In atomic emission the sample is atomized and the analyte atoms are excited to higher energy levels. The analyte concentration is determined from the amount of emission.
The analyte atoms are promoted to a higher energy level by the sufficient energy that is provided by the high temperature of the atomization sources. The excited atoms decay back to lower levels by emitting light. Emissions are passed through monochromators or filters prior to detection by photomultiplier tubes.
Fluorescence spectroscopy
Fluorescence spectroscopy FS is an analytical technique that measures the concentration of fluorescent substance present in the sample. It makes the use of the fluorescence in order to measure their concentration.
While, fluorescence is the emission of the light by a substance which absorbs light or Electromagnetic radiation.
Principle:
Molecular fluorescence spectrometry is based on the emission of light by molecules that have become electronically excited subsequent to the absorption of electromagnetic radiation.
It uses the UV visible spectra along with some part of IR region of electromagnetic radiation. It is a sensitive technique by which we can detect the sample raging from ppm – ppt.
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