Interference In Atomic Absorption Spectroscopy.

Raghavendra Institute of Pharmaceutical Education and Research - Autonomous
K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721
Interference In Atomic Absorption
Spectroscopy
A Seminar as a part of curricular requirement
for Master of Pharmacy, I Year - I semester
Presented by
SHAIK GOUSE ULAZAM
(20L81S0708)
Pharmaceutical analysis
Under the guidance of
Dr. P. Ramalingam M.Pharm, Ph.D.
Professor & Director of R& D cell

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Contents
 Introduction
 Principle
 Instrumentation
 Applications
 Interference
 References

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INTRODUCTION
 Atomic Absorption Spectroscopy is a very common technique for detecting metals
and metalloids in samples.
 It is very reliable and simple to use.
 It also measures the concentration of metals in the sample.
 Atomic Absorption Spectroscopy is an analytical technique that measures the
concentration of an element by measuring the amount of light that is absorbed at a
characteristic wavelength when it passes through cloud of atoms.
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Principle of Atomic Absorption Spectroscopy
 The technique uses basically the principle that free atoms generated in an
atomizer can absorb radiation at specific frequency.
 Atomic Absorption Spectroscopy quantifies the absorption of ground state
atoms in the gaseous state.
 The atoms absorb UV or Visible light & make transition to higher electronic
energy level. The analyte concentration is determined from the amount of
absorption.

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Schematic diagram of Atomic Absorption Spectrophotometer
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Instrumentation

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Applications of Atomic Absorption Spectroscopy
 Determination of small amount of metals (lead, mercury, calcium,
magnesium)
 AAS is widely used in metallurgy, alloys and in inorganic analysis.
 Biochemical Analysis : A number of elements present in biological
samples can be analysed by AAS. These include estimated of sodium,
calcium, potassium, zinc, iron, lead, mercury, etc.

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Interferences In Atomic Absorption Spectroscopy
 Interference is a phenomenon that leads to change in intensity of analyte signal
in spectroscopy.
 Interferences in AAS fall into two basic categories :
1. Non-Spectral Interference : Which affect the formation of analyte Atoms
- Matrix interference
- Chemical interference
- Ionization interference
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2. Spectral Interferences :high light absorption due to presence of absorbing
species
- Background absorption
- Continuum source Background Correction
- Others spectral interferences

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Non-spectral Interferences
Matrix interferences :
 When a sample is more viscous or has different surface tension than the
standard it result in difference in sample uptake rate due to changes in
nebulization efficiency.
 Such interferences are minimized by matching the matrix composition of
standard and sample.
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Figure : Matrix interference from viscosity effects
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 If a sample contains a species which forms a thermally stable compound with
analyte that is not completely decomposed by the flame energy then chemical
interferences exist.
 Such interferences are minimized by using higher flame temp.
 To provide higher dissociation energy.
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Chemical Interferences:

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Figure : Interference of phosphate on calcium.

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Ionization Interference
 It is more common in hot flames.
 The dissociation process doesn’t stop at formation of ground state atoms.
 Excess energy of the flame lead to excitation of ground state atoms to ionic
state by loss of electrons thereby resulting in depletion of ground state atoms.
 Ionization interference is eliminated by an excess of an element which is easily
ionized thereby creating a large number of electrons in the flame &
suppressing the ionization of the analyte.
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Figure : Effect of added potassium on ionization.

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Spectral Interferences
 Atomic Spectral interferences are caused by presence of another absorption
line or a molecular absorbance band close to the spectral line of element of
interest.
 Most of these interferences are due to molecular emission from oxides of
other element is a sample.
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Background Absorption:
 Background Absorption Extends over a broad wavelength band.
 It is referred to as molecular absorption or non specific absorption.
 Background absorption is caused by light absorption due to un vapourised
solvents droplets in flame.
 The absorption and scattering of radiation due to matrix interference give
rise to sample background which becomes a problem at wavelength below
350nm.
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Continuum Source Background Correction
 Continuum source background correction is a technique for automatically
measuring and compensating for any background component which might be
present in an atomic absorption measurement. This method incorporates a
continuum light source in a modified optical system.
 The broad band continuum (‘‘white’’ light) source differs from the primary
(atomic line) source in that it emits light over a broad spectrum of
wavelengths.
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Other Spectral Interferences
 If the atomic absorption profile for an element overlaps the emission line of an
other, a spectral interference is said to exist. As has already been mentioned,
this is an infrequent occurrence, because of the very wavelength-specific
nature of atomic absorption.
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References :
 Dr.A.V. Kasture, Dr. S.G. Wadodkar, Nirali prakashan , Pharmaceutical
analysis Instrumental methods Volume II, page no. 23.9 - 23.12.
 G.R. Chatwal, S.K. Anand, Instrumental methods of Chemical analysis
,Himalaya publishing house, fifth edition page no. 2.340 - 2.360.
 Richard D. Beaty and Jack D.Kerber, , Instrumentation and Techniques
in Atomic Absorption Spectroscopy.
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Thank you
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Interference In Atomic Absorption Spectroscopy.

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