Since the concentration of the analyte element is considered to be proportional to the ground state atom population in the flame, any factor that affects the ground state population of the analyte element can be classified as an interference.
Factors that may affect the ability of the instrument to read this parameter can also be classified as an interference. The following are the most common interferences:
A) Spectral interferences are due to radiation overlapping that of the light source. The interference radiation may be an emission line of another element or compound, or general background radiation from the flame, solvent, or analytical sample. This usually occurs when using organic solvents, but can also happen when determining sodium with magnesium present, iron with copper or iron with nickel.
B) Formation of compounds that do not dissociate in the flame. The most common example is the formation of calcium and strontium phosphates.
C) Ionization of the analyte reduces the signal. This is commonly happens to barium, calcium, strontium, sodium and potassium.
D) Matrix interferences due to differences between surface tension and viscosity of test solutions and standards.
E) Broadening of a spectral line, which can occur due to a number of factors. The most common linewidth broadening effects are:
1. Doppler effectThis effect arises because atoms will have different components of velocity along the line of observation.
2. Lorentz effectThis effect occurs as a result of the concentration of foreign atoms present in the environment of the emitting or absorbing atoms. The magnitude of the broadening varies with the pressure of the foreign gases and their physical properties.
3. Quenching effectIn a low-pressure spectral source, quenching collision can occur in flames as the result of the presence of foreign gas molecules with vibrational levels very close to the excited state of the resonance line.
4. Self absorption or self-reversal effectThe atoms of the same kind as that emitting radiation will absorb maximum radiation at the centre of the line than at the wings, resulting in the change of shape of the line as well as its intensity. This effect becomes serious if the vapour which is absorbing radiation is considerably cooler than that which is emitting radiation.
A) Spectral interferences are due to radiation overlapping that of the light source. The interference radiation may be an emission line of another element or compound, or general background radiation from the flame, solvent, or analytical sample. This usually occurs when using organic solvents, but can also happen when determining sodium with magnesium present, iron with copper or iron with nickel.
B) Formation of compounds that do not dissociate in the flame. The most common example is the formation of calcium and strontium phosphates.
C) Ionization of the analyte reduces the signal. This is commonly happens to barium, calcium, strontium, sodium and potassium.
D) Matrix interferences due to differences between surface tension and viscosity of test solutions and standards.
E) Broadening of a spectral line, which can occur due to a number of factors. The most common linewidth broadening effects are:
1. Doppler effectThis effect arises because atoms will have different components of velocity along the line of observation.
2. Lorentz effectThis effect occurs as a result of the concentration of foreign atoms present in the environment of the emitting or absorbing atoms. The magnitude of the broadening varies with the pressure of the foreign gases and their physical properties.
3. Quenching effectIn a low-pressure spectral source, quenching collision can occur in flames as the result of the presence of foreign gas molecules with vibrational levels very close to the excited state of the resonance line.
4. Self absorption or self-reversal effectThe atoms of the same kind as that emitting radiation will absorb maximum radiation at the centre of the line than at the wings, resulting in the change of shape of the line as well as its intensity. This effect becomes serious if the vapour which is absorbing radiation is considerably cooler than that which is emitting radiation.
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Interference Analysis