uv visible spectropy for instrumentation engineering students

UV0vis

1. UV- Visible Spectroscopy Instrumentation

2. Spectroscopy – the branch of Science that deals with the study of interaction of electromagnetic radiation with matter Instrument used to measure the absorbance in UV (200 – 400 nm) or Visible (400- 800 nm) region is called UV – Visible Spectrophotometer

3. COMPONENTS OF SPECTROPHOTOMETER Source Wavelength Selectors or Dispersing Devices Sample Compartment / Cuvette Holder Detector Recorder

4. Should be Stable , continuous radiation, have sufficient intensity for the transmitted energy to be detected at the end of the optical path LIGHT SOURCE HYDROGEN DISCHARGE LAMPS > a pair of electrodes is enclosed in a glass tube filled with hydrogen gas under relatively high pressure > Range of 160 -375 nm > Stable robust and widely used

5. 2. DEUTERIUM LAMPS Deuterium is filled in place of hydrogen Range of 185 – 400 nm More expensive than hydrogen lamps Intensity of radiation emitted is 3-5 times of a hydrogen lamp

6. 3. TUNGSTEN LAMP Range – 320 – 2500 nm Similar functioning to an electric bulb Continuous Source of Light

7. 4. XENON DISCHARGE LAMP Xenon gas is stored at 10-30 atm pressure It contain 2 tungsten electrode that are separated by a distance of about 8 mm Range of 320 to 2400 nm

8. 4. Mercury Arc Lamp Mercury vapour is stored under high pressure and the excitation of mercury atoms is done by electric discharge

9. WEVELENGTH SELECTORS Converts polychromatic light to monochromatic light Filters monochromators are used for this purposes FILTERS It is frequently necessary to filter or remove wide bands of radiation from a signal

10. 1. Absorption Filters These filters have a bandwidth that ranges from 30 -250 μ m. The absorption filters consists of coloured glass or dye suspended in gelatin and sandwitched between the two glass plates