inorganic chemistry

1. RADIOPHARMACEUTICALS
PREPARED BY:AKSHITA
B.PHARMACY-1
1503

3. RADIOACTIVITY
 It refers to the radiations or particles which are emitted from
nuclei as a result of nuclear instability.
 These radiations are generally emitted from heavy metals like:
uranium , thorium , radium , etc.
 The substances that emits such radiations are called
RADIOACTIVE SUBSTANCE.
 The phenomenol of spontaneous and continuous emition of
such radiations is called RADIOACTIVITY.

4. PROPERTIES OF
RADIOACTIVITY
 These radiations can penetrate through solid material , can ionize
the gases , produce a glow on zinc sulphide[ZnSO4] paint or affect
the photographic plates.
 These radiations are emitted without any external agencies.
 These are independent of temperature , pressure ,
concentration , or catalyst.

5. TYPES OF RADIATIONS
 The radiations emitted by the radioactive isotopes is in the
form of charged particles i.e. ALPHA RAYS AND BETA
RAYS[alpha is positively charged and beta is negatively
charged]
 There are some uncharged particles also that are called
GAMMA RAYS .

6. MEASUREMENT OF
RADIOACTIVITY
 To measure the radiations of alpha beta and gamma rays
many techniques involving DETECTION and COUNTING
OF INDIVIDUAL PARTICLES , PHOTONS have been
available.
 The method selected for the measurement of radioactivity
depends upon the “extent of energy dissipation and
penetrability of radiation.”

7. MEASUREMENT OF
RADIOACTIVITY
 For measurement of radioactivity many devices are used. Some are
listed below:
 IONIZATION CHAMBER
 PROPORTIONAL CHAMBER
 SCINTILLATION COUNTER
 GEIGER-MULLER COUNTER
 SEMICONDUCTOR DETECTORS
 PHOTOGRAPHIC PLATE METHOD

8. IONIZATION CHAMBER

9. IONIZATION CHAMBER
 These are of various shapes and sizes.
 A chamber is filled with GAS and is fitted with TWO
ELECTRODES kept a different potentials .
 It is connected to a measuring device to indicate the FLOW OF
ELECTRIC CURRENT.
 The filled gas can be He , Ar , etc.
 They have poor resolution due to large number of chrge carriers.

10. PRINCIPLE:
 The radiation causes ionization of gas molecules or produce
ions which result in the emission of electrons.
 This shows change in electric current which is measured
with measuring device.
 The current produced is of 10-15 ampere.

11. PROPORTIONAL
COUNTER

12. PROPORTIONAL
COUNTER
 The proportional counter is a type of gaseous ionization detector
device used to measure particles of ionizing radiation.
 The key feature is its ability to measure the energy of incident
radiation, by producing a detector output that is proportional to the
radiation energy; hence the detector's name.

13. SCINTILLATION
COUNTER

14. SCINTILLATION
COUNTER
 A scintillation counter is an instrument for detecting and
measuring ionizing radiation by using the excitation effect of
incident radiation on a scintillator material, and detecting the
resultant light pulses.
 The counter consists of a scintillation crystal coupled with
PHOTOMULTIPLIER TUBE , an AMPLIFIER and a SCALER.

15. PRINCIPLE
 When ionizing radiation strikes certain substances like
phosphorous [or a flurogenic materials] a flash of light is given
out .
 The flash is collected by a photomultiplier tube which
produces electric impulse.
 This impulse , on further amplification , is recorded by
means of a scaler.

16. TWO MAIN TYPES:
 INORGANIC SCINTILLATOR[ SODIUM IODIDE]:
This is for gamma rays.
 ORGANIC SCINTILLATOR
This is for alpha and beta rays.

17. GEIGER COUNTERS
 The Geiger counter is an instrument used for
measuring ionizing radiation used widely in applications such
as radiation dosimetry , radiological protection, experimental
physics and the nuclear industry.
 This is commomly known as GEIGER MULLER[GM] and is
the best of all radiation detectors.
 They can detect all the three types of radiations [ alpha , beta
and gamma]

18. CONSTRUCTION
 A Geiger counter consists of a
Geiger-Müller tube, the sensing
element which detects the radiation
and the processing electronics
which displays the result.

19. PRINCIPLE
 The Geiger-Müller tube is filled with an inert gas such as helium, neon,
or argon at low pressure, to which a high voltage is applied. The tube briefly
conducts electrical charge when a particle or photon of incident radiation makes
the gas conductive by ionization. The ionization is considerably amplified within
the tube by the Townsend discharge effect to produce an easily measured
detection pulse, which is fed to the processing and display electronics. This large
pulse from the tube makes the G-M counter relatively cheap to manufacture, as
the subsequent electronics is greatly simplified.[2] The electronics also generates
the high voltage, typically 400–600 volts, that has to be applied to the Geiger-
Müller tube to enable its operation.

20. SEMICONDUCTOR
DETECTOR
 They are useful in measuring X-rays and Gamma rays.
 In this, charge carriers produced by ionizing radiation are
electron-hole pairs.
 These travel towards the positive electrodes with high
velocities.

21. PHOTOGRAPHIC PLATE
METHOD
 An ionizing particle causes an activation and darkening of a
photographic plate.
 The degree of darkening gives the measure of the total
activity.
 This method is used to locate the exact distribution of
radioactive material in a thin section.
 This method is mainly detect the GAMMA Rays.