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Atomic absorption spectroscopy
- 1. Analysis Of EvidencesThrough Atomic Absorption Spectroscopy Presented By Mansi Gupta M.Sc. Forensic Science First Semester Submitted to :- Dr. A.P.J. Abdul Kalam Institute of Forensic Science and Criminology Bundelkhand University , Jhansi A A S
- 2. CONTENT Introduction tospectroscopy. Introduction to Atomic Absorption Spectroscopy. Historical Overview. Concept behind AAS. General construction of AAS. Instrumentation. Interference and control measures. Analysis of metals in contaminated soil. Applicability of AAS in investigation. AASAASAAS A A S
- 3. SPECTROSCOPY Spectroscopy isthe branch of science dealing with thestudy of interaction of electromagnetic radiation with matter. G.R. Krichoff & R.Bunsen are known as father of modern spectroscopy. A A S INTERACTION WITH MATTER
- 4. Spectroscopy Absorption Emission Ground stateto Excited state Excited state to Ground state Matter Excited state Ground state Ground state Excited state EMR EMR A A S
- 5. ATOMIC ABSORPTION SPECTROSCOPY AASis most useful technique for the determination of an element’s concentration in a sample. AAS is widely used because of its: 1. Simplicity 2. Effectiveness 3. Relatively low cost It can analyse over 62 elements. A A S Elements highlighted in pink are determined by AAS
- 6. HISTORICAL OVERVIEW In1955, first Atomic Absorption Spectromerter was built by CSIRO A.Walsh, C.T.J Alkamade and J.M.W Milatz. Shown in the picture Alan walsh (left) with a spectrometer. In 1959, the first commercial use of atomic absorption spectrometer was introduced. Source: archieve.mass.museum A A S
- 7. CONPECT BEHIND AAS AAS quantifies the absorption of ground state atoms in the gaseous state. Atoms absorb UV or Visible light and make transitions to higher electronic energy levels. Atoms absorb the radiation and the decrease in the intensity of the radiation is directly proportional to the atoms present in the ground state. The absorption of radiation follows Beer-Lambert law. Intensity = 1/ conc. Of absorbing medium Intensity= 1/ length of absorbing medium A A S
- 8. BLOCK DIAGRAM OFAAS MONO CHROMATOR A A S
- 9. INTRUMENTATION Source: wheal janelaboratory.co.uk/aas atomic absorption spectrometry MONOCHROM ATOR A A S
- 10. Source- Hollow CathodeLamp Anode : Tungsten Cathode: Element of interest Glass window: Borosilicate Gas filled: Neon and Argon Pressure applied: 1-5 Torr Voltage:300-500 V A A S
- 11. ATOMISER ATOMISER REDUCESTHE SAMPLE TO THE ATOMIC STATES WITH CONTINUOUS ATOMISER, SAMPLE ARE INTRODUCED IN A CONTINUOUS MANNER. WITH DISCRETE ATOMISER, SAMPLE IS INTRODUCED IN A DISCRETE MANNER. ATOMISER CONTINOUS FLAME ATOMISER (TOTAL CONSUMPTION , PREMIXED) DISCRETE ELECTROTHERMAL ATOMISER (CARBON ATOMISER, GRAPHITE ATOMISER) A A S
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- 13. TPYES & PROPERTIESOF FLAME USED IN AAS FUEL OXIDANT TEMPERATURE MAX. BURNING VELOCITY (cm/s) Natural Gas Natural Gas Hydrogen Hydrogen Acetylene Acetylene Acetylene Air Oxygen Air Oxygen Air Oxygen Nitrous oxide 1700-1500 2700-2800 2000-2100 2550-2700 2100-2400 3050-3150 2600-2800 39-43 370-390 300-1400 900-1400 158-266 1100-2480 285 A A S
- 14. Flame Structure Mostsuitable zone for absorption- Interzonal Zone Interzonal zone Rich in free atoms Absorb the wavelength emitted by the source. source - lab-training.com A A S
- 15. ELECTROTHERMALATOMISER DRYING ASHING ATOMISATION GRAPHITEFURNACE ATOMISER L’VOV PLATFORM SOURCE- BLOGS.MARYVILLE.EDU A A S
- 16. COMPARISON BETWEEN FAAS& GFFA FAAS • Easy to use and analysis is fast. • Sample size is large. • Lowest capital cost. • Less sensitive. GFAAS • Slower analysis. • Sample size is small. • Moderate cost. • More sensitive. A A S
- 17. MONOCHROMATOR Separate outall of the thousands of lines. Select the specific wavelength of light which is absorbed by the sample and exclude other wavelength. Most common monochromator are: 1-Prism. 2- Grating. A A S
- 18. DETECTOR PHOTOMULTIPILER DETECTOR •Consist of photocathode,a series of electrodes called dynodes and an anode. •Measure the decrease intensity of light absorb by analyte. •Convert the decrease intensity into electrical intensity. PHOTOMULTIPIER DETECTOR source: hamamatsu.com A A S
- 19. READOUT DEVICES &CURVE Servometer Potentiometer Digital readout devices Curve recorded between absorption and concentration ABSORPTION CONCENTRATION A A S
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- 21. INTERFERENCE & CONTROL MEASURES INTERFEREN CE& CONTROL MEASURES NON SPECTRAL Chemical Add a excess of another element or compound. Using a hotter flame. Ionization Adding an excess of an element which is very easily ionized. SPECTRAL Background Absorption Continuum source background correction. Zeeman background correction. A A S
- 22. ANALYSIS OF LEADIN CONTAMINATED SOIL A A S SAMPLE COLLECTION Sample collected Should collected at15cm depth Sample homogenized and seived Sample air dried, placed in electric oven Results in fine powder for digestion DIGESTION OF SOIL SAMPLE 1g of dried sample placed in 250ml beaker 15ml of nitric acid is added Digest the mixture at high temp. till it become transparent Solu. Filtered through whatsman filter paper Sample solu. was analyze for conc. of metals ANALYSIS OF SOIL SAMPLE Compressor turned on Beam from cathode adjusted to hit target zone Preparation of blank solu. And a series of calibration were made Blank and standard were atomised in turn Response measured
- 23. APPLICABILITY OF AAS IN INVESTIGATIONAAS Trace Material (soil, cement) Analysis of metals Checking the adulterati -on Metallic poison in human body GSR (Pb, Ba,Sb) A A S
- 24. REFERENCE 1. Chatwal ,Gurdeep R and Anand , Sham k ; Instrumental Methods of Chemical Analysis, Himalaya Pub. House(2004) 2. Willard, Hobert H. & Merett Lynne L., Dean Frank, Jhon A. ; Instrumental Methods of Analysis 7th ed. CBS Pub. & Distributors (1986) 3. Srivastava, Meena & Yadav ,Rajesh Singh; Principles of Laboratory Techniques and Methods, Idbc Pub. (2009) 4. Skoog, Douglas A.& Holler, James ,Crouch, Stanley R.; Principles of Instrumental Analysi, 6th ed. Cengage Learning (2007) 5. Maurya, ashutosh & kesharwani ,lav (2013) ‘Analysis of Heavy Metals in Soil through Atomic Absorption Spectroscopy For Forensic Consideration’ International Journal for Research in Applied & Engineering Technology. A A S
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