This PPT tell about Flame emission spectroscopy and its instrumentation

1. FLAME PHOTOMETRY
BASIC CONCEPTS, INSTRUMENTATION, AND
APPLICATION
Mrs. Poonam Sunil Aher (M.Pharm, PhD)
Assistant Professor
Sanjivani College of Pharmaceutical Education
and Research (Autonomous),
Kopargaon, Ahmednagar-423603 (M.S.), INDIA
Mobile: +91-9689942854

2. INTRODUCTION:
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 intensity of the light
emitted when a metal is introduced into flame.
The wavelength of colour tells what the element is (qualitative)
The colour's intensity tells us how much of the element present
(quantitative)

3. Flame photometer working principle:
When a solution of metallic salt is sprayed as fine droplets into a
flame. Due to the heat of the flame, the droplets dry leaving a fine
residue of salt. This fine residue converts into neutral atoms.
Due to the thermal energy of the flame, the atoms get excited and
after that return to ground state. In this process of return to
ground state, excited atoms emit radiation of specific wavelength.
This wavelength of radiation emitted is specific for every element.
This specificity of the wavelength of light emitted makes it a
qualitative aspect. While the intensity of radiation depends on the
concentration of element. This makes it a quantitative aspect.
The process seems to be simple and applicable to all elements. But
in practice, only a few elements of Group IA and group IIA (like Li,
Na, k & Ca, Mg) are only analyzed.
The radiation emitted in the process is of a specific wavelength.
Like for Sodium (Na) 589nm yellow radiation, Potassium 767nm
range radiation.

4. 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  subjected to hot flame  specific quantum of
thermal energy absorbed by orbital electrons  become unstable at
high energy level  release energy as photons of particular
wavelength  change back to ground state.
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. Events occurring in the flame:
Flame photometry employs a variety of fuels mainly air, oxygen or
nitrous oxide (N2O) as oxidant. The temperature of the flame depends
on fuel-oxidant ratio.
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.
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.

7. BASICCONCEPT:
Liquid sample contaning metal salt
solution is introduced into a flame,
Solvent is first vaporized, leaving particles
of solid salt which is then vaporised into
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.

8. Theintensityofthelightemittedcouldbedescribedby
theScheibe-Lomakinequation:
I=K .C
I is Intensity of emitted light
K is proportionality constant
C is the concentration of sample

9. Under constant and controlled conditions, the light intensity of the
characteristic wavelength produced by each of the atoms is directly
proportional to the number of atoms that are emitting energy, which in
turn is directly proportional to the concentration of the substance of
interest in the sample.
Various metals emit a characteristic colour of light when heated.

10. Structure of Flame:
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

11. 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.
interconal zone – 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.

12. INSTRUMENTATION:
THE FLAME PHOTOMETER

13. Major Components:
1. Sample Delivery
System
2. Fuel and oxidant
3. Source
4. Monochromator
5. Detector
6. Read out device13
Schematic Representation of the Flame Photometer

15. 1.Sample Delivery System:
There are three components for introducing liquid sample:
Nebulizer – it breaks up the liquid into small droplets.
Nebulization the is conversion of a sample to a mist of finely divided
droplets using a jet of compressed gas.
The flow carries the sample into the atomization region.
Pneumatic Nebulizers: (most common)
Aerosol modifier – it removes large droplets from the stream and allow
only smaller droplets than a certain size to pass
Flame or Atomizer – it converts the analyte into free atoms

16. 2.Source:
A Burner used to spray the sample solution into fine droplets.
The flame should possess the ability to evaporate the liquid droplets
from sample solution resulting in the formation of solid residue.
The flame should decompose the compounds in the solid residues and
resulting in the formation of atoms
The flame must have ability to excite the atoms formed and cause
them to emit radiant energy

17. 1. Macker Burner
This burner was used earlier and employed natural gas and
oxygen
This burner produced relatively low temp and low excitation
energies therefore it was generally used for study of alkali metals
only.
Disadvantage:
Flame produced by this burner is not homogenous chemically.
Atomic excitation in the flame is differ in different region
This burner is not used.

18. 2. Premix or laminar- flow burner.
In this energy type of burner, aspirated sample, fuel and oxidant
are thoroughly mixed before reaching the burner opening and
then entering the flame.
In this burner the gases move in non- turbulent fashion ie., in
laminar flow.
An important feature of laminar-flow is that only 5 % of the
sample in the form of small droplets reaches the flame and is
easily decomposed.
By easy in means that an efficient atomization of the sample in
the flame will takes place.
larger droplets from the aspirator impinge on the side of the
spray chamber and are drained off.
Thus in this burner 95% of the sample may be wasted, thereby,
resulting in a loss of sensitivity.
The flame produced by premix burner is non turbulent ,
noiseless and stable.

19. Advantage:
1. easy decomposition of the sample takes place which
results in an efficient atomization of the sample in the
flame.
2. Premix burners can handle solutions up to several %
without clogging.
Disadvantages:
i. Lower rate of sample introduction Possibility of
selective evaporation of mixed solvents in the mixing
chamber, create analytical uncertainties.
ii. Mixing chamber contains a potentially explosive
mixture that can flash back if the flow rates are too low.

21. 3.Total Consumption Burner( turbulent flow
burner):
In this fuel and oxidant are hydrogen and
oxygen gases
From the tubing hydrogen and oxygen
gases are entering and both are burning at
the top of the burner to produce flame
As soon as liquid sample is dawn into the
base of the flame, the oxygen aspirates the
sample solution and leaving a solid residue.
Atomization and excitation of sample then
follow.
Entire sample is consumed. Hence its name
is total consumption burner.

23. Advantage:
introduce relatively large & representative sample into
the flame.
Disadvantage:
1. When the sample contains two solvents then is aspirated
into the flame, the more volatile sample will evaporate in
spray chamber and leaving the sample in the form of
undissociated atoms in less volatile component. Thus
smaller no of atoms would reach the flame.
2. Low intensity
3.A relatively short path length through flame Problems with
clogging of the tip
4.Burners noisy from electronic and auditory stand point

24. 4. Lundergarph burner:
For this burner sample mast be liquid form
It is aspirated into spray chamber
Large droplets condense on the side and drain away
Small droplets and vaporised sample are swept into the
base of the flame in the form of cloud.

26. 3.Fuel and oxidants: Fuel and oxidant are required to
produce the flame such that the sample converts to
neutral atoms and get excited by heat energy.
The temperature of flame should be stable and also
ideal. If the temperature is high, the elements in sample
convert into ions instead of neutral atoms. If it is too low,
atoms may not go to excited state. So a combination of
fuel and oxidants is used such that there is desired
temperature.

28. 4.Monochromator:
Prism: Quartz material is used for making prism, as quartz is
transparent over entire region
Grating: it employs a grating which is essentially a series of parallel
straight lines cut into a plane surface
5.Detectors:
Photomultiplier tubes
Photo emissive cell
Photo voltaic cell
Photovoltaic cell:
It has a thin metallic layer coated with silver or gold which act as
electrode, also has metal base plate which act as another electrode
Two layers are separated by semiconductor layer of selenium, when
light radiation falls on selenium layer.
This creates potential diff. between the two electrode and cause flow
of current.

29. Read-out Device:
It is capable of displaying the absorption spectrum as well absorbance
at specific wavelength
Nowadays the instruments have microprocessor controlled electronics
that provides outputs compatible with the printers and computers
Thereby minimizing the possibility of operator error in transferring
data.
Element wavelength Detection
limit
Element wavelength Detection
limit
Al 396 0.5 Pb 406 14
Ba 455 3 Li 461 0.067
Ca 423 0.07 Mg 285 1
Cu 325 0.6 Ni 355 1.6
Fe 372 2.5 Hg 254 2.5
Elements, their characteristic emission wavelengths and detection limits

30. APPLICATIONS:
To estimate sodium, potassium, calcium, lithium etc. level in sample
of serum, urine, CSF and other body fluids.
Flame photometry is useful for the determination of alkali and
alkaline earth metals.
Used in determination of lead in petrol.
Used in the study of equilibrium constants involving in ion exchange
resins.
Used in determination of calcium and magnesium in cement.

31. •Flame photometer has both quantitative and qualitative
applications.
•to detect the presence of a particular metal in the
sample. This help to determine the availability of alkali
and alkaline earth metals which are critical for soil
cultivation.
•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

32. 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.

33. Disadvantages:
•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.

34. •Limited number of elements that can be analyzed.
•The sample requires to be introduced as a solution
into fine droplets. Many metallic salts, soil, plant and
other compounds are insoluble in common solvent.
Hence, they can’t be analyzed by this method.
•Since the sample is volatilized, if a small amount of
sample is present, it is tough to analyze by this method.
As some of it gets wasted by vaporization.
•Further, during solubilization with solvents, other
impurities might mix up with the sample and may lead
to errors in the spectra observed.

35. THANK YOU