Atomic absorption spectroscopy

Atomic absorption spectroscopy ppt

1. PRESENTED BY:KULKARNI TUKAI N. M.PHARM 1 ST YEAR NANDED PHARMACY COLLEGE . 1 ATOMIC ABSORPTION SPECTROSCOPY GUIDED BY:DR.M.H.GHANTE DEPARTMENT OF CHEMISTRY NANDED PHARMACY COLLEGE.

2. CONTENTS 2 INTRODUCTION PRINCIPLE INSTRUMENTATION APPLICATIONS CONCLUSION REFERANCES.

3. INTRODUCTION 3 Atomic absorption spectroscopy is an absorption spectroscopic method where radiation from a source is absorbed by non-excited atoms in the vapour state. Atomic absorption spectroscopy deals with the absorption of specific wavelength of radiation by neutral atoms in the ground state. Atomic absorption spectroscopy technique was introduced for analytical purpose by Walsh, Alkemede and Milatz in 1956.

4. PRINCIPLE 4 The basic principle of atomic absorption spectroscopy is to analyze the concentration of metals in solution. When a solution of metallic species is introduced into a flame, it results in formation of droplets. Due to thermal energy of the flame, the solvents in the droplets evaporate, leaving a fine residue that is converted to neutral atoms. These neutral atoms absorbs radiation of specific wavelength emitted by Hallow cathode lamp and intensity is measured by using photometric detector.

5. INTRUMENTATION 5 Atomic absorption spectrophotometer is an instrument that detects the concentration of metals in liquid samples. It consists of following components: Radiation source Chopper Atomizer Monochromators Detectors Read-out device.

6. 6 FIG 1:ATOMIC ABSORPTION SPECTROMETER

7. 7 FIG 2: Line diagram of AAS

8. LIGHT SOURCE 8 Hollow Cathode Lamp are the most common radiation source in AAS. It contains a tungsten anode and a hollow cylindrical cathode. These are sealed in a glass tube filled with an inert gas (neon or argon ) . When a potential is applied about 300V between the two electrodes, causes ionization of the inert gas and generation of a current of 5 to 10 mA . The lamp window is made up of either q uartz, silica or glass. FIG 3: HALLOW CATHODE LAMP

9. The another radiation source commonly used is Electrode-less discharge lamp. 9 It consists of evacuated tube in which metal of interest is placed. The tube is filled argon gas at low pressure and tube is sealed. The sealed tube is placed in a microwave discharge cavity that causes excitation of metals inside the sealed tube. FIG 4: ELECTRODE-LESS DISCHARGE LAMP

10. ATOMIZERS 10 Atomization is separation of particles into individual molecules and breaking molecules into atoms . This is done by exposing the analyte to high temperatures in a flame. In order to achieve absorption of atoms, it is necessary to reduce the sample into a atomic state. This is done by- Flame atomizers Non-flame atomizers .

11. FLAME ATOMIZERS 11 A flame atomizer contains a pneumatic nebulizer, which converts the sample solution into a mist, or aerosols. In most atomizers, the high pressure gas is the oxidant, and the aerosol containing oxidant is subsequently mixed with fuel. The burners commonly used in atomic absorption spectroscopy are laminar and total consumption burners.

12. CONT… 12 In Total consumption burner, the sample solution, the fuel, and oxidizing gases are passed through separate passages to meet at the opening of the base of flame. Sample in liquid form then the flame breaks into the droplets which are evaporated and burns. Leaving the residue which is reduced to atoms. Total consumption burners do use oxygen with hydrogen or acetylene, gives very hot flames. The only disadvantage of this burner is that it is noisy and hard to use.   FIG 5: Total Consumption Burner

13. MONOCHROMATORS 13 The main purpose of the Monochromator is to isolate a single atomic resonance line (wavelength) from the lines emitted by the hollow cathode lamp. It is an adjustable filter that selects a specific, narrow region of the spectrum for transmission to the detector. A monochromator consists of an entrance slit, a dispersion device and an exit slit.

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15. DETECTORS 15 The light selected by the monochromator is directed or passed to a detector whose main function is to convert light signal into an electric signal. For atomic absorption spectroscopy, photomultiplier tube is the most common detector used. In photomultiplier tube, there is an evacuated envelope which consists of a photocathode, dynodes and an anode. Photocathode is fixed to the terminal of power supply and when voltage is applied to electrodes, the photon hit the cathode and generates electrons which eventually flow towards cathode and resultant current is produced. The resultant current further goes into an recorder where the signals are recorded.

16. 16 FIG 6: Photomultiplier tube

17. RECORDER 17 In most atomic absorption measurements, a chart recorder is used as a read-out device. A chart recorder is a potentiometer using servometer to move the recording pen. Digital read-out devices are also used in some atomic absorption measurements . FIG 7: Recording devices

18. APPLICATIONS 18 Determination of even small amounts of metals (lead, mercury, calcium, magnesium, etc.) Environmental studies: drinking water, ocean water, soil. Food industry. Pharmaceutical industry. Sodium, potassium and calcium in ringer solutions are estimated by this method. In cement industry, estimation of sodium, potassium, calcium and magnesium is carried out to determine the quality of cement.

19. REFERANCES 19 Dr. A. V. Kasture , Dr. G. Wadodkar , A Textbook of Pharmaceutical Analysis, Nirali Prakashan , 2 nd edition, pp 23.1-23.12 Douglas A. Skoog , Principles of Instrumental analysis, 6 th edition, Cengage Learning Publisher, pp 670-689. Gurdeep . R. Chatwal , Instrumental methods of chemical analysis, Himalaya Publishing House, 6 th edition, pp 2.340-2.366.

20. 20 Thank you..!