Ir spectroscopy

ir spectroscopy application and instrumentation

1. WELCOME Abdul Favas E - 1 st M.VOC -

2. Topic:- Infrared Spectroscopy Application and Instrumentation

3. INTRODUCTION Infrared spectroscopy (IR spectroscopy) is the spectroscopy that deals with the infrared region of the electromagnetic spectrum, that is light with a longer wave length and lower frequency than visible light. As with all spectroscopic techniques, it can be used to identify and study chemicals

4. The infrared portion of the electromagnetic spectrum is usually divided into three regions; the near-; mid-; and far- infrared ; REGION WAVELENGTH RANGE WAVELENGTH NO; NEAR 0.78-2.5 12800-4000 MIDDLE 2.5-50 4000-200 FAR 50-1000 200-10

5. Basic principle IR radiation does not have enough energy to induce electronic transitions as seen with UV. Absorption of IR is restricted to compounds with small energy differences in the possible vibrational and rotational states. For a molecule to absorb IR, the vibrations or rotations within a molecule must cause a net charge in the dipole moment of the molecule.

6. The alternating electrical field of the radiation interacts with fluctuations in the dipole moment of the molecule. If the frequency of the radiation matches the vibrational frequency of the molecule then radiation will be absorbed , causing a change in the amplitude of molecular vibration.

7. Instrumentation The main parts of IR spectrometer are as follows; Radiation source Sample cells and sampling of substances Monochromators Detectors Recorder

8. IR spectroscopy

9. IR radiation sources IR instruments require a source of radiant energy which emit IR radiation which must be steady, intense enough for detection and extend over the desired wavelength. Various sources of IR radiations are as follows; Nernst glower Incandescent lamp Mercury arc Tungsten lamp Glober source Nichrome wire

10. Sample cells and sampling of substances It is used for the characterization of solid, liquid, or gas sample. Solid :-Various techniques are used for preparing solid samples such as pessed pellet technique, Solid run in solution, Solid film..etc Liquid :- Aqueous solvent cannot be used as they will dissolve alkali halides. Only organic solvents like chloroform can be used Gas :- It is similar to the sampling of liquids

11. Monochromators Various type of monochromators are prism, grating and filters. Prisms are made of Potassium bromide, Sodium chloride or Caesium iodide. Filter are made up of Lithium Fluoride and Diffraction gratings are made up of alkali halides.

12. Detectors Detectors are used to measure the intensity of unabsorbed infrared radiation. Type of detectors are; Bolometers Golay cell Pyro - electric detector Thermocouple and thermopile

13. Recorders Recorders are used to record the IR spectrum

14. Application Widely used in organic chemistry. Used for the analysis of complex bio-molecules such as proteins, lipids and nucleic acid. It can be used to determine molecular structure. Bond length, bond angles in a molecule can be calculated. Functional groups present in the given compound can be known by correlating. Quantitative analysis of the given compound is possible.

15. Detection of impurities. Used for analysis of petroleum, oil and gas Examination of old paintings and artifacts.

16. Thank you