Question

Explain in detain the different types of interferences associated with GF-AAS and the steps that can be taken to minimise their effects.

Answer 1

An interference is a phenomenon that affects the analysis of ground state atoms.
There are many types of interferences associated with atomic absorptiob spectroscopy. They are:

1. Spectral Interferences: They are caused by the radiation overlap for the absorption line due to emissions from another element or compound.

To minimize the effect:

Use alternate wavelength;Use smaller slit width;Use blank

a) Scattering:It is a spectral interference arise when particulate matter scatter the incident radiation from the source.

The absorption and scattering of radiation can be corrected by using a blank.

b) Background Absorption: It is caused by light absorption due to unvaporised solvent droplets in the flame.

To correct it, use sources with already fitted atomic absoprption; No standard addiction method available

2. Chemical interferences: Chemical interference occurs when an analyte is less decomposed in flame

a) Compound Formation: Some anions form stable compounds with metals and hence decrease the absorption of analyte.

To minimize it: By using protective agents to form volatile but stable compounds

b)Ionization Interferences : It occurs in hot flames. On excitation, loss of electrons take place.

To minimize it: By using Ionization Buffer, which ionizes to give a mass of electrons that shift the equilibrium of analyte to form atoms. This increases the concentration of electrons in the flame for absorbtion at the right wavelength.

c) Dissociation