The Flame Photometer: An Overview of Its Operating Principles C

  • Bowling Barnes, David Richardson, John Berry, and Robert Hood developed a device in the 1980s that could measure the low concentrations of sodium and potassium found in solutions. They decided to give this device the name Flame photometer. When a metal is added to a flame, the flame photometer works by measuring the change in the amount of light that is released as a result of the addition of the metal. The color of the flame provides information about the concentration of the element in the sample, while the wavelength of the color provides information about the element itself.

    One of the subfields that falls under the umbrella of atomic absorption spectroscopy is called flame photometry. Flame emission spectroscopy is another name for this technique. The field of analytical chemistry now considers flame photometer an essential piece of equipment to have at their disposal. The concentration of various metal ions, such as sodium, potassium, lithium, calcium, and cesium, among others, can be ascertained with the assistance of a flame photometer. Spectra obtained from flame photometers use metal ions represented as atoms rather than their usual form. This methodology is referred to as flame atomic emission spectrometry (FAES), and it was given that name by the Committee on Spectroscopic Nomenclature of the International Union of Pure and Applied Chemistry (IUPAC).

    The Flame Photometer's Working Principle

    When introduced into the flame, the compounds of the alkali and alkaline earth metals that make up Group II dissociate into their constituent atoms. Some of these atoms experience additional excitation, which takes them to even higher levels. However, at higher levels, these atoms do not maintain their stability. As a consequence of this, these atoms give off radiation when they transition back to their ground state. In most cases, the visible part of the spectrum is where these radiations can be found. There is a distinct frequency associated with each of the alkali and alkaline earth metals.

    The intensity of the emission is directly proportional to the number of atoms that are transitioning back to their ground state for certain concentration ranges.

    The amount of light that is released is, in turn, proportional to the sample's level of concentration.

    Components that make up a flame photometer

    The following elements make up the fundamental components of a straightforward flame photometer:

    The origin of the flame:The flame in the flame photometer comes from a Burner inside the device. It is possible to keep the temperature stable in there. In flame photometry, one of the most important factors to take into consideration is the temperature of the flame.

    Nebuliser: A nebuliser is a device that is used to send a homogenous solution into the flame at an even rate.

    Convex mirrors and convex lenses make up the optical system, which is made up of all convex components. The light that is emitted from the atoms can be seen because of the convex mirror. Additionally assisting in directing the emissions to the lens is the convex mirror. The light is helped to concentrate on a single point or slit by the lens.

    Simple color filters: The reflections from the mirror are allowed to travel through the slit, where they are then absorbed by the filters. The wavelength that needs to be measured can be separated from other wavelengths' emissions by using filters.

    Photodetector: This device measures how intensely the flame is radiating by taking pictures of it. With the assistance of a photo detector, the radiated energy is then changed into an electrical signal. These electrical signals have a relationship that is directly proportional to the amount of light that is present.

    Typical steps in operation

    In order to prepare the standard stock solution and the sample solution, fresh distilled water is used throughout the process.

    Calibration of the photometer's flame requires making adjustments to both the air and the gas. The fire is then left alone for about five minutes so that it can reach its steady state.

    Following this step, the instrument is powered on, and the lids of the filter chamber are removed so that the correct color filters can be inserted.

    The readings on the galvanometer are reset to zero by spraying distilled water into the flame while the instrument is in operation.

    Adjusting the sensitivity involves spraying the flame with the most concentrated version of the standard working solution. At this point, the galvanometer's full scale deflection reading is being taken.

    In order to maintain constant readings on the galvanometer, distilled water is sprayed into the flame once more. After that, the zero point is reset on the galvanometer.

    The readings of the galvanometer are then recorded after each of the standard working solutions have been sprayed into the flame three times. After each application of spray, the apparatus needs to go through a thorough cleaning.

    The final step consists of spraying the sample solution into the flame three times while simultaneously recording the galvanometer's readings. After each application of spray, the apparatus needs to go through a thorough cleaning.

    Find out what the average reading on the galvanometer is.

    Find out the concentration of the element in the sample by plotting the graph of concentration against the reading from the galvanometer.