presentation on quenching

1. QUENCHING AND FACTORS
AFFECTING QUENCHING
PRESENTED BY GUIDED BY
PRIYANKA GOSWAMI ARUP CHAKROBORTY
M.PHARM ASSISTANT PROFESSOR
DEPARTMENT OF PHARMACY DEPARTMENT OF PHARMACY
ASSAM DOWN TOWN UNIVERSITY ASSAM DOWN TOWN UNIVERSITY

2. QUENCHING
It is a process that decrease the fluorescence
intensity of given substance. It may occur due to
various factors like pH, temperature, viscosity,
complex formation.
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3. TYPES OF QUENCHING
 Concentration quenching: At low concentration linearity
is observed. But as the concentration of the same
substance increased the flourescence intensity is
decreased.
Fig:1 Fig:2
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4. TYPES OF QUENCHING
 Chemical quenching: it may be of various factor like
 pH: aniline at pH 5-13 gives blue flouresence when exited at
290 nm. But at pH <5 and pH >13 it does not exhibit
flouresence
 Oxygen: presence of oxygen leads to quenching because of
its parmegnatic property.
 Halides and electron withdrawing group: Halides like
chloride bromide , iodide and electron withdrawing group like
nitro and carboxylic group decreases the flouresence intensity.
 Heavy metals: Presence of heavy metals also leads to
quenching because of collision and triplet ground state.
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5. TYPES OF QUENCHING
 Static quenching: In these process the
quenching agent forms a non-fluorescent
complex with the quenching agent.
 Collisional quenching: Quenching take place
when number of collision are increased due to
several factor like presence of halides, heave
metals increased temperature and decrease in
viscosity.
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6. FACTORS AFFECTING QUENCHING
 pH
 Oxygen
 Temperature
 Halides
 Heavy metals
 Electron withdrawing group
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