Flame Atomizer

This atomizer is the type of continuous atomizer in which the analyte is introduce in a steady manner.

In a flame atomizer, a solution of the sample is nebulized by a flow of gaseous oxidant. It mixed with a gaseous fuel and carried into a flame where atomization occurs.

At low temperature in flame atomizer, acetylene is used as fuel and oxygen is used as oxidant. We use fuel in greater proportion then oxidant so that oxidation does not occur in sample particles. In this way we can get more accuracy.

At high temperature in flame atomizer, acetylene is used as fuel and Nitrous oxide is used as oxidant. Nitrous oxide is used as an oxidant gas when hotter flames are required. It has no explosive hazard and temperatures in the range of even 3000°C. At such temperatures the sample atoms can easily be atomized.

Following two types of burner in used in flame atomizer:

Pre-mixing Burner

Components of premixing burner are divided into two chambers:

Aspirating chamber or Nebulizer:

Nebulizer convert the sample into a fine mist of finely divided droplets using a jet of compressed gas and mix this mist with the aspirating air. It flows towards the pre-mixing chamber.

Pre-mixing Chamber:

The nebulized mist is desolvated (the solvent is evaporated) leaving a finely divided solid molecular aerosol. It occur when the aerosol is mixing the fuel with oxidant. The solid is then volatized which produces an atomic gas. This chamber has a series of baffles in it that creates an obstructed pathway up to the burner head. The purpose of the baffles is to allow only the finest aerosol particles to reach the flame. Larger particles strike the baffles, collect and empty out by the drain tube. Only a small percentage of samples are atomized and 98% of the sample becomes waste that can be draining out by an outlet.

Total Consumption Burner

In total-consumption burner, the fuel and oxidant are mixed and combust at the tip of the burner. The fuel, oxidant and sample all meet at the base of flame. The sample is drawn up into the flame by the ‘Venturi Effect’, by the support gas. The gas creates a partial vacuum above the capillary barrel, causing the sample to be forced up the capillary. It is broken into a fine spray at the tip where the gases are turbulently mixed and burned. This is the usual process of ‘nebulization’.

The burner is called total consumption because the entire aspirated sample enters the flame or in other words the sample solution is directly aspirated into the flame. All desolvation, atomization, and excitation occur in the flame. The length of flame is approximately 5cm and radiation pass through 2.5 cm of the flame. Most of the atomization occurs in interconal region.

Zones of Flame:

Flame is divided into four zones which are differentiated on the basis of color and temperature.

• Ø Preheating zone
• Ø Interconal zone
• Ø Primary reaction zone
• Ø Secondary reaction zone