Soil and Plant Analysis

Factors that Influence the Intensity of Emitted Radiation in a Flame Photometer

A number of factors will influence the intensity of light emission from a given solution. Some of these are as follows:

Viscosity

• The addition of a substance which increases the viscosity of the solution (e.g., sucrose) decreases the intensity of light emission. This decrease results in due to a reduction in the efficiency of atomization.

Presence of Acids

• When an acid is present in the sample solution, this decrease the light intensity. This decrease arises due to the disturbance of the initial dissociation equilibrium.

Presence of Other Metals

• If other metals are present, these also alter the intensity of emitted radiation. In order to remove this defect, special filters are used which will absorb radiation due to the element, which is to be estimated in the sample solution.

Advantages:
1. Their atoms reach the excited state at a temperature lower than that at which most other elements are excited.
2. Their characteristic wavelengths are easily isolated from those of most other elements due to wide spectral separation.
3. The analysis of Na, K, Li, Ba and Ca are typically determined at low temperatures, i.e. 1500- 2000°C, therefore suitable fuel mixtures are propane/air, butane/air and natural gas/air.

Disadvantages
Low temperature makes this method susceptible to, particularly, interference and the stability (or lack thereof) of the flame and aspiration conditions.

Many different experimental variables affect the intensity of light emitted from the flame.
Fuel and oxidant flow rates and purity, aspiration rates, solution viscosity, concomitants in the samples, etc. affect these.

Therefore, careful and frequent calibration is necessary for good results and it is very important to measure the emission from the standard and unknown solutions under conditions that are as nearly identical as possible.