Flame Atomic Absorption Spectroscopy analysis
A flow spoiler or an impact bead is positioned at the exit of the nebulizer stream in the spray chamber and it serves to remove the large droplets in the aerosol stream to the burner head and eventually into the flame.
In Flame Atomic Absorption Spectroscopy the sample solution is never introduced as a stream direct into the flame as it can destabilize the fame or even extinguish it. The sample is first reduced to an aerosol with the help of a nebulizer. The liquid drops vary in size depending on the efficiency of the nebulizers under the given set of operating conditions. Larger size droplets condense on the walls of the spray chamber and the impact device and get drained out into the waste reservoir. Only small droplets are permitted to enter the flame.
Flow Spoiler
Atomic Absorption Spectroscopy flow spoiler is a multi- vane fan shaped device made of chemically inert material and is more efficient at removing large droplets then the impact bead. This results in reduction in sensitivity as lesser amount of sample enters the flame. However, its benefit is that the interference from sample matrix also get reduced proportionately due to reduction in sample amount.
Impact Bead
An Atomic Absorption Spectroscopy impact bead is made of glass or ceramic and has lower efficiency for removal of large droplets. It thereby contributes to sensitivity improvement making it possible to analyze samples at lower detection levels. However, glass or ceramic beads can introduce memory effects of previous analysis and lead to more interferences.
Several physical variables control the droplet size such as velocity of the nebulizer stream, sample liquid density and its viscosity. In essence the choice of the intercepting device – flow spoiler or impact is based on the Atomic Absorption Spectroscopy analysis requirements. When you require to determine low concentrations use an impact bead and when interference is an issue then flow spoiler is preferable.
Please share your experiences on the choice of the impacting device and do forward your comments.
What is the purpose of a flow spoiler or impact bead in Flame AAS?
A flow spoiler or impact bead is positioned at the exit of the nebulizer stream in the spray chamber and serves to remove large droplets from the aerosol stream before it reaches the burner head and flame.
Why is the sample not introduced directly as a stream into the flame?
The sample solution is never introduced as a direct stream because it can destabilize or even extinguish the flame, so it is first reduced to an aerosol by a nebulizer.
What is the difference between a flow spoiler and an impact bead?
A flow spoiler is a multi-vane, fan-shaped device made of chemically inert material that removes large droplets more efficiently than an impact bead, while an impact bead, made of glass or ceramic, is less efficient at removing large droplets.
When should an impact bead be chosen over a flow spoiler?
An impact bead should be used when analyzing low concentrations since its lower droplet-removal efficiency allows more sample into the flame and improves sensitivity, while a flow spoiler is preferable when matrix interference is the main concern.
What are the drawbacks of using a glass or ceramic impact bead?
Glass or ceramic impact beads can introduce memory effects from previous analyses and lead to more interferences, even though they improve sensitivity for low-level detection.
What factors influence the droplet size produced by the nebulizer?
Droplet size is controlled by several physical variables, including the velocity of the nebulizer stream and the sample liquid density and viscosity.