Nephelometry & Turbidimetry: Instrumentation, Principal
Nephelometry
:-
It is deals with
analysis of colloidal system. It is based on the scattering of light by
particle suspended in a liquid.
Principal
:-
- Nephelometry is concerned with
measure of the intensity of scattered light as
a function of concentration of the suspended particle in a suspension.
- Intensity of scattered light is
directly proportional to the concentration of the suspended particle.
- Hence greater concentration of
particle more the intensity of light.
- The intensity of the scattered
light is usually measure at 90° to the incident light.
Turbidimetry
:-
It deal with analysis
of colloidal system and the technique is based on transmission of light by
particle suspended in a liquid.
Principal
:-
- Turbidimetry is concerned with
the measure of the intensity of the transmitted light as a function of
concentration of the suspended particle in a suspension.
- The intensity of transmitted
light is measured in a line i.e 180° to the incident light.
- Intensity of transmitted
light is inversely proportional to the concentration of the suspended
particle
- Hence concentration is more
transmission is less.
Instrumentation
of Nephelometry & Turbidimetry :-
1. Radiation source :-
The common radiation source is used as tungsten filament.
2. Monochromator :-
usually prisms or grating monochromator are used.
3. Detector :- mostly
Photomultiplier tube are use.
4. Filter :- There are
two types of filter are used
A. Absorption filter
B. Interference filter
Comparison Between Nephelometry &Turbidimetry
1. Principal :-
Nephelometry:- it is work on light scattered. It is
similar to fluorimetry.
Turbidimetry
:- It is work on light
transmission. It is similar to colorimetery.
2. Sensitivity :-
Nephelometry:- it is more sensitive because it is used
for low concentration suspension.( <100 mg/ litre).
Turbidimetry
:- it is less
sensitive.
3. Effect of
concentration on intensity :-
Nephelometry:- linear realtion ship between
concentration and intensity of the light.
Turbidimetry
:- Relationship
between concentration and intensity of the light are depends on the below
equation :-
log Io/I =kbc
Where,
Io = Intensity of
incident light
I = intensity of
transmitted light
K = Turbidity co
efficient
C = concentration of
particle
b = pathlength
4. Effect of
wavelength on intensity :-
Nephelometry:- wavelength is not much important white light is
used.
Turbidimetry
:- wavelength play
important role relations between wavelength and turbidity is given by following
equation :-
T= S/λt
Where,
T = turbidity
S= constant for a
given system
λ = wavelength
t = it’s value depends
on particle size.
5. Filter :-
Nephelometry:- visible filter are used as secondary filter.
Turbidimetry
:- Blue filter is
used or adjusted at 530 nm.
Application
of Nephelometry & Turbidimetry :-
- Analysis of inorganic compound.
- Analysis of organic compound.
- Analysis of the water purity.
- Analysis of the air and water
pollutants.
- Determination of impurity and
particularly matter in pharmaceutical aersol, injection, suspension and
other liquid preparation.