The above uploaded slide is prepared as per the syllabus copy of PCI. The chapter is the part of Instrumental Methods of Analysis.

1. Mr. Nimish Shirish Khandekar
Roll no. 45; Final year B. Pharm
ADCBP, Ashta
Under the guidance of:
Ms. Nisha Jagtap Ma’am
Assistant Professor
ADCBP, Ashta

2. 2
Nepheloturbidometry

3. Introduction
 Transmission and diffraction of electromagnetic
radiation.
 Amount of light scattered is directly proportional
to the concentration or the density of the
insoluble particles → k/as Tyndall Effect
 Scattering is defined as:
The phenomenon where, beams of light when
impinges with particulate matter change its
direction of propagation from one to multiple
planes without changing net radiating power of
energy.
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Nepheloturbidometry

4. Introduction CONT..
Scattering
Elastic
Transmittance of radiation
without the change of energy
Inelastic
Transmittance of radiation
with the change of energy
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5. Introduction CONT..
 Scattering depends on:
1. Number of particulate matter present
2. Dimension of particle
3. Wavelength of light
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Nepheloturbidometry

6. Introduction CONT..
 Nephelo-turbidimetric analysis → measures the
extent of elastic scattered of light when it comes
in contact with particulate matter.
 Nephelo-turbidimetric analysis and Turbidimetry
→ measurement of intensity of scattered or
unscattered light .
 Turbidimetry → high concentration suspension
Nephelo-turbidimetry → low concentration
suspension
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7. Turbidity
 Turbidity is expressed as:
T = 1/λ. λn. Io/It
Where,
λ = Length of dispersion through which light
passes
Io = Intensity of incident light
It = Intensity of transmitted light
n = Refractive index of the dispersion medium
 Turbidity is directly proportional to the
concentration of the suspension.
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Nepheloturbidometry

8. nephelometry
 Nephelometry is expressed as:
Is = Ks x Io x C
Where,
Is = Intensity of scattered radiation
Io = Intensity of incident radiation
Ks = Constant, depends on the nature of
suspended particles
C = Concentration of the solution
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9. Factors affecting scattering
 Order and rate of mixing of substance within a
solution.
 Agitation of solution containing particulate matter.
 Temperature of the solution. (Affect on solubility)
 Viscosity of Medium
 Presence or absence of electrolyte or protective
colloid.
 Concentration of solution.
 Number of particulate matter suspended
 Wavelength of the radiating beam
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Nepheloturbidometry

10. Introduction CONT..
 Turbidimetric analysis → high concentration of
particulate matter.
 Smaller diameter of particles gives symmetric
scattering; bigger particle size gives asymmetrical
scattering
 Nephelometry → smaller dimension of particles
→ scattered light right angle to the incident beam
→ measurment of intensity of scattering done at
90o
 Turbidimetry → larger dimension of particles →
measurment of intensity of scattering done at
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Nepheloturbidometry

11. Introduction CONT..
 Scattering of shorter wavelength > Scattering
of longer wavelength
 Transmittance of longer wavelength >
Scattering of shorter wavelength
 Reflection of shorter wavelength > Reflection
of longer wavelength
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Nepheloturbidometry

12. Differenctiate betn
Nephelometry Turbidimetry
Suspended particles < 100 mg/L Suspended particles > 100 mg/L
Intensity of scattered light is measured Intensity of unscattered light is
measured
Low concentration suspension is used High concentration suspension is used
Scattering is uniform Scattering is not uniform
Intensity of scattered light →
proportional to the concentration
Intensity of transmitted light →
inversely proportional to the
concentration
Measured at 90o Measured at 180o
Detector: Sensitive Photomultiplier Detector: Photocell
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Nepheloturbidometry

13. principle
 Nepheloturbidimetry → instrumental technique
of analysis → based on the phenomenon of
scattering of light by particulate matters
present in the solution.
 Transperent medium → intensity of incident
light = intensity of transmitted light
 Opaque or translucent medium → intensity of
incident light > intensity of transmitted light.
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Nepheloturbidometry

14. principle
 Nepheloturbidimetry → detector at 90o
 Turbidimetry → detector at 180o
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Nepheloturbidometry

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Nepheloturbidometry

16. principle
 Turbidimetry → determines difference between
two large signals.
 Nephelometry → determines the difference
between two small signals
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Nepheloturbidometry

17. instrumentation
1. Radiation Source
2. Filters and monochromators
3. Sample cell
4. Detectors
5. Read out devices
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Nepheloturbidometry

18. Radiation source
Mercury Arc Lamp Tungsten
Lamp
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19. Filters and monochromators
 Monochromatic light.
 As per the feasibility → colorimeter with a blue
filter (530nm) is turbidimeter; fluorimeter with a
visible secondary filter is a nephelometer.
 Absorption filters and Interference filters → used
in Nepheloturbidimetry.
 Absorption filters → made up of glass or coated
with pigment that absorbs unwanted light.
 Interference filters → dielectric spacer films →
made up of CaF2, MgF2 between two silver films.
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Nepheloturbidometry

20. Sample cell
 Cuvette or sample cells → made up of
transperent glasses.
 Shape → Cylindrical / Rectangular or Special
cells with path length 1cm.
 Special Cell → Measure light scattering → at
45o, 90o and 135o → employed in
nepheloturbidimetric analysis.
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21. Detectors
 For turbidimetric analysis → detector placed at
180o
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22.  For Nepheloturbidimetry analysis → detector
placed at 900
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23. Applications
 Determination of particle size.
 Determination of average molecular weight.
 Measuring of atmospheric pollutants.
 Determination of concentration of solution.
 Growth of bacterial cell in liquid nutrient
medium.
 Determination of end point of precipitation
titration., etc
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Nepheloturbidometry

24. THANK YOU!