Flame photometry is the measurement of the electromagnetic radiation in ultraviolet-visible (UV-VIS) range emitted when the atoms are vaporized and then electronically excited by means of the thermal energy of the flame. Flame photometer is an instrument used to analyze and measure the concentration of certain metal ions in a sample through their characteristic emission spectra.
Flame photometry is based on atomic emission spectroscopy (figure 1), where atoms in the sample are excited to higher energy level by a flame and then emit at specific wavelengths as they return to their ground state. The colour or the wavelength of the emitted radiation helps to detect the element and the intensity of the radiation helps to find out the concentration of element in the given sample. Flame photometry was renamed as flame atomic emission spectrometry (FAES) by the committee on spectroscopic nomenclature under IUPAC (International Union of Pure and Applied Chemistry).
Components of Flame Photometer
Following are the components of flame photometer (figure 2):
- Flame Source: A flame, generally fueled by a mixture of acetylene and air or natural gas and air, is used to atomize and excite the sample.
- Sample Introduction System: The sample, generally in liquid form, is introduced into the flame in a controlled manner using nebulizer or spray chambers.
- Optical System: An optical system consisting of lenses, filters and diffraction grating or a Monochromator is employed to isolate the characteristic emission wavelength of the metal ions to be studied which is further passed through detector.
- Detector: Photomultiplier tubes and photodiodes are commonly used as detector which convert emitted light into electrical signals for further amplification and quantification.
- Data analysis and display: The output signal from the detector are processed and analysed for determination of the intensity of emitted light at the specific wavelength.
Flame photometer is used to estimate sodium, potassium, calcium, lithium etc. level in sample of serum, urine, CSF and other body fluids. It is useful for the determination of alkali and alkaline earth metals in environment. Flame photometer is highly sensitive method and can measure upto ppm (parts per million) level of concentration.
Dr. Pratyusha Kar
Department of Paramedical sciences