Flame photometry, also known as flame atomic emission spectrometry, is an instrumental method of analysis used primarily for the determination of alkali and alkaline earth metals in samples.
Principle:
When a metal is introduced into a flame, it gets vaporized and the metal atoms are excited to higher energy levels.
As these atoms return to their ground state, they emit energy in the form of visible light.
The wavelength and intensity of the emitted light are characteristic of each element.
Procedure:
1. Sample Preparation:
The sample is typically dissolved in water or another suitable solvent to produce a solution.
2. Introduction into Flame:
A small volume of the sample solution is introduced into a flame.
The solvent evaporates, leaving the solute to be vaporized and atomized.
3. Emission:
As the metal atoms become excited in the flame, they emit radiation (light) at specific wavelengths characteristic of the element in question.
4. Detection:
The emitted light passes through a monochromator, which selects the specific wavelength of interest.
A photodetector then measures the intensity of the emitted light.
5. Calibration and Quantification:
To determine the concentration of the metal in the sample, the intensity of the emitted light is compared to a calibration curve.
This curve is constructed using standard solutions of known concentrations.
Advantages:
Simple and relatively inexpensive.
High sensitivity for alkali and alkaline earth metals.
Limitations:
Limited to elements that can be atomized in flames and emit visible or UV radiation.
Interference from other species in the flame can affect results.