3. Radiation source
1 .Hollow cathode lamp
Consist of evacuated glass tube with a tungsten anode and
cylindrical cathode .
It is made up of alloy enclosed by glass to avoid the diffusion
of atom produced .
Glass tube filled inert gas.potential – 100 to 200 volts across
the electrodes cause the ionization of inert gas The charged
gas then migrates at high velocity towards cathode and
collides metal atom .
Metal atom excited higher energy level transmit lower energy
level emit radiation .
Spectral line produced are narrower than absorption of the
source
Example:
copper cathode emits a copper spectrum.
4. 2. Electrodless discharge lamps
■ It is used to determine the volatile element.
■ Each lamb is consist of sealed quartz tube filled with
inert gas .the test metal is placed .
■ Lamp is placed in microwave radiation field the
sample element vapourise higher energy level to lower
level ,the metal element is emitted.
■ The emitted intensity of radiation 10 times more tha
obtained using cathode lamps.
5. Chopper
■ Rotating wheel called chopper placed between radiation source and flame.
■ Function:
■ To breaks the steady beam of light from the source into pulsating light which in
turns induces a pulsating current in the detector.
■ Steady current produced by flame ,but pulsating current is amplified and recorded.
6. 3. Atomizers
■ It is used for converting liquid sample into gaseous
form
■ Flame atomiser like
■ Total consumption burner / pneumatic Nebulizer
■ Premix burner
(A) pneumatic Nebulizer :
■ Hydrogen + oxygen = flame
■ Liquid sample reach base of the flame it converts
fine droplets and then gets evaporated.The residue
left further reduced into atom which are then
excited .
7. (b) Premix burner
■ Also called laminar air flow burner.liquid sample aspirated with air thoroughly mixed
with fuel and oxidant.
■ Mixture the reaches opening of burner and enters into flame. 5% sample forms of fine
droplets reaches the flame .large droplets 95% of sample drains out from the side of
spray chamber (burner).
■ Small portion of sample easily decomposed in the flame helps in effective atomization
of sample
8. Monochromators
■ Commonly used monochromators are
■ Prism monochromators
■ Grating monochromators.
■ It is used to select the specific wavelength of light
9. Detector
■ Devices which convert light energy into
electrical signals ,that are displayed on the
readout devices .
■ After passing through sample cell,part of
radiation absorbed by sample and remaining
transmitted .
■ Transmitted radiation fall on the detector
which determines the intensity of radiation
absorbed by sample
■ Photo multiplier tube
10. Readout devices
Read out devices includes
Meters,
Chart recorders.
Digital readout devices
