Interference In Atomic Absorption Spectroscopy.

In this slide contains Interference In Atomic Absorption Spectroscopy and applications.
Presented by: Shaik Gouse ul azam. ( department of pharmaceutical analysis.)
RIPER, anantpur.

1. 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 UL AZAM (20L81S0708) Pharmaceutical analysis Under the guidance of Dr. P. Ramalingam M.Pharm, Ph.D. Professor & Director of R& D cell

2. 2 Contents Introduction Principle Instrumentation Applications Interference References

3. 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. 3

4. 4 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.

5. Schematic diagram of Atomic Absorption Spectrophotometer 5 Instrumentation

6. 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.

7. 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 : Non-Spectral Interference : Which affect the formation of analyte Atoms Matrix interference Chemical interference Ionization interference 7

8. 8 2. Spectral Interferences :high light absorption due to presence of absorbing species Background absorption Continuum source Background Correction Others spectral interferences

9. 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. 9

10. Figure : Matrix interference from viscosity effects 10

11. 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. 11 Chemical Interferences:

12. 12 Figure : Interference of phosphate on calcium.

13. 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. 13

14. 14 Figure : Effect of added potassium on ionization.

15. 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. 15

16. 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. 16

17. 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 . 17

18. 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. 18

19. 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. 19

20. Thank you 20