How Flame Photometers are used in Chemical Analysis

Flame Photometer is used to quantify the concentration of Sodium and Potassium in the body.

Basic Principle of Operation of a Flame Photometer

When a sample is heated, the electrons are raised from the ground state to a higher state. The excited electrons are unstable and return to the ground state emitting photons of a particular wavelength. Sodium produces a yellow flame, while Potassium produces a violet flame and lithium produces a red flame. The intensity of light is proportional to the number of photons emitted which in turn is proportional to the atoms or cations in the solution. The intensity is detected by a detector similar to one used in a Spectrophotometer. However, it measures emission and not absorption of light as in Spectrophotometer.

The aspirator draws a sample through atomizer into the flame. Gas passes over the upper end of the capillary at a high velocity while the lower end is inserted into the sample. Fuel used is Propane, Natural gas or Acetylene with Oxygen. Lithium is used for calibration as it does not naturally occur in the body. A known concentration of lithium is added and by using ratiometric techniques, the ratio of Na/Li and K/Li is obtained.