Flame photometry

for pharma students

1. FLAMEPHOTOMETER Y
PRESENTED BY-
SNEHIL SINGH
ASSISTANT PROFESSOR
IEC GROUP OF INSTITUTIONS GREATER NOIDA

2. INTRODUCTION
Atomic spectroscopy is thought to be the oldest instrumental method for the determination of elements.
These techniques are introduced in the mid of 19
th Century during which Bunsen and Kirchhoff showed that the
radiation emitted from the flames depends on the characteristic element present in the flame.
Flame photometry (more accurately called Flame Atomic Emission Spectrometry)is a branch of spectroscopy in which
the species examined in the spectrometer are in the form of atoms.
A photoelectric flame photometer is an instrument used in inorganic chemical analysis to determine the concentration
of certain metal ions among them sodium, potassium, calcium and lithium.
Flame Photometry is based on measurement of intensityof the light emitted when a metal is introduced into flame.
The wavelength of colourtells what the element is (qualitative)
The colour'sintensity tells us how much of the element present (quantitative)

3. BASICCONCEPT
Liquid sample contaningmetal salt solution is
introduced into a flame,
Solvent is first vaporized, leaving particles of
solid salt which is then vaporisedinto gaseous
state
Gaseous molecule dissociate to give
neutral atoms which can be excited (made
unstable) by thermal energy of flame
The unstable excited
atoms emit photons
while returning to
lower energy state.
The measurement
of emitted photons
forms the basis of
flame photometry.

4. PRINCIPAL
The basic principle upon which Atomic Spectroscopy works is
based on the fact that "Matter absorbs light at the same
wavelength at which it emits light".
Atoms of elements is subjected to hot flame specific
thermal energy absorbed by orbital electrons become
unstable at high energy level release energy as photons of
particular wavelength change back to ground state.

5. PRINCIPAL
•When a metal salt solution is burned, the metal provides
a colored flame and each metal ion gives a different
colored flame.
•Flame tests, therefore, can be used to test for the absence
or presence of a metal ion.

6. Various metals emit a characteristic colourof light when heated.

7. STRUCTURE OFFLAME
As seen in the figure, the
flame may be divided into the
following regions or zones.
•Preheating zones
•Primary reaction zone or inner zone
•Internal zone
•Secondary reaction zone

8. preheating zone-In this,
combustion mixture is heated
to the ignition temperature by
thermal conduction from the
primary reaction zone.
primary reaction zone-This
zone is about 0.1 mm thick at
atmospheric pressure
There is no thermodynamic
equilibrium in this zone and
the concentration of ions and
free radicals is very high.
This region is not used for
flame photometry.
interconalzone –It can extend
up to considerable height. The
maximum temperature is
achieved just above the tip of
the inner zone.
This zone is used for flame
photometry.
secondary reaction zone -In
this zone, the products of the
combustion processes are
burnt to stable molecular
species by the surrounding air.
Structure ofFlame

9. INTERFERENCES:
In determining the
amount of a particular
element present, other
elements can also affect
the result.
Such interference may be
of 3 kinds:

10. Chemical interferences: The chemical interferences
arise out of the reaction between different
interferentsand the analyte. Includes:
Cation-anaioninterference:
The presence of certain anions, such as oxalate,
phosphate, sulfate, in a solution may affect the
intensity of radiation emitted by an element. E.g.,
calcium + phosphate ion forms a stable substance, as
Ca3(PO4)2 which does not decompose easily,
resulting in the production of lesser atoms.
Cation-cationinterference:
These interferences are neither spectral nor ionic in
nature
Eg. aluminum interferes with calcium and magnesium.

11. INSTRUMENTATION

12. INSTRUMENTATION

13. INSTRUMENTATION
1. Source of flame
A burner that provides
flame and can be
maintained in a
constant form and at a
constant temperature.
2. Nebuliser and mixing
chamber
Helps to transport the
homogeneous solution
of the substance into
the flame at a steady
rate.

14. The optical
system
comprises
three
Convex mirror
Lensfilter
3. Optical system (optical filter)

15. 4. Photo detector
Detect the emitted
light and measure the
intensity of radiation
emitted by the flame.
That is, the emitted
radiation is converted
to an electrical signal
with the help of photo
detector.
The produced
electrical signals are
directly proportional to
the intensity of light.

16. A schematic representation of flame photometer

17. Mechanism of working
Nebulisation
The solution of the substance
to be analyzed is first placed
into the burner, which is then
dispersed into the flame as
fine spray particles.

18. Mechanism
1.Thesolventis firstevaporated
leaving fine divided solid particles.
2. This solid particles move towards the
flame, where the gaseous atoms and
ions are produced.
3. The ions absorb the energy from the
flame and excited to high energy levels.
4. When the atoms return to the ground
state radiationof theelement is
emitted.
5.The intensity of emitted light is related
to the concentration of the element

19. Events occurring in the flame
Flame photometry employs a variety of
fuels mainly air, oxygen or nitrous oxide
(N
2O) as oxidant. The temperatureof the
flame depends on fuel-oxidant ratio.

20. Events occurring in the flame
The various processes in
the flame are discussed
below:
Desolvation: The metal
particles in the flame are
dehydrated by the flame
and hence the solvent is
evaporated.
Vapourisation: The metal
particles in the sample
are dehydrated. This also
led to the evaporation of
the solvent.
Atomization: Reduction of
metal ions in the solvent
to metal atoms by the
flame heat.

21. Events occurring in the flame
Excitation: The
electrostatic force of
attraction between the
electrons and nucleus of
the atom helps them to
absorb a particular
amount of energy. The
atoms then jump to the
exited energy state.
Emission process: Since
the higher energy state is
unstable the atoms jump
back to the stable low
energy state with the
emission of energy in the
form of radiation of
characteristic wavelength,
which is measured by the
photo detector.

22. APPLICATIONS OF FLAME PHOTOMETRY…
Flame photometer has both quantitative and qualitative applications.
Flame photometer with monochromators emits radiations of characteristic wavelengths which help to
detect the presence of a particular metal in the sample.
In agriculture, the fertilizer requirement of the soil is analyzed by flame test analysis of the soil.
In clinical field, Na+ and K+ ions in body fluids, muscles and heart can be determined by diluting the blood
serum and aspiration into the flame.
Analysis of soft drinks, fruit juices and alcoholic beverages can also be analyzed by using flame photometry.

23. ADVANTAGES
Simple quantitative analytical test based on the flame analysis.
Inexpensive.
The determination of elements such as alkali and alkaline earth metals is
performed easily with most reliable and convenient methods.
Quite quick, convenient, and selective and sensitive to even parts per million
(ppm) to parts per billion (ppb) range.

24. The concentration of the metal ion in the solution
cannot be measured accurately..
A standard solution with known molarities is
required for determining the
concentration of the ions which will corresponds to
the emission spectra.
It is difficult to obtain the accurate results of ions with
higher concentration.
The information about the molecular structure of the
compound present in the sample solution cannot be
determined.
The elements such as carbon, hydrogen and halides
cannot be detected due to its non radiating nature.
Disadvantages:

25. THANKYOU