Principle Interferences Instrumentation and Applications The principle of flame photometer is based on the measurement of the emitted light intensity when a metal is introduced into the flame. The wavelength of the colour gives information about the element and the colour of the flame gives information about the amount of the element present in the sample. Flame photometry is one of the branches of atomic absorption spectroscopy. It is also known as flame emission spectroscopy. Currently, it has become a necessary tool in the field of analytical chemistry. Used to Determine the concentration of certain metal ions like potassium,lithium, calcium, cesium etc. In flame photometer spectra the metal ions are used in the form of atoms. (IUPAC) Committee on Spectroscopic Nomenclature has named this technique as flame atomic emission spectrometry (FAES). Principle of Flame photometer The compounds of the alkali and alkaline earth metals (Group II) dissociate into atoms when introduced into the flame. Some of these atoms further get excited to even higher levels. But these atoms are not stable at higher levels. Hence, these atoms emit radiations when returning back to the ground state. These radiations generally lie in the visible region of the spectrum. Each of the alkali and alkaline earth metals has a specific wavelength. Instrumentation-Source of flame, Nebuliser, Monochromator(Prism monochromator, Grating monochromators)DETECTOR ( The radiation emitted by the elements is mostly in the visible region and measured by photo detector. Hence conventional detectors like photo voltaic cell or photo tubes or photomultiplier tube is used), READ OUT DEVICE [The signal from the detector is shown as a response in the digital read out device. The readings are displayed in an arbitrary scale (% Flame Intensity).], working of flame photometer, Advantages and disadvantage of flame photometer, Errors /interference in Flame Photometry-Flame Temperature, chemical interference, Radiation interference Application of flame photometry

1. Mrs Vandana Sharma
Assistant Professor

2.  Principle
 Interferences
 Instrumentation and
 Applications

3.  Principle of flame photometry-2
 Give principle, interferences and applications of flame
photometry.-5
 Different type of burners used in flame photometry.- 8
 Write a short note on instrumentation of flame photometry. 8
 Explain the instrumentation of flame photometer and describe
the methods of analysis of a sample.-8
 What is the principle of flame photometry? Discuss
instrumentation of flame photometer.-8
 Write a short note on instrumentation of flame photometry. 8

4.  During 1980s Bowling Barnes, David Richardson, John Berry and
Robert Hood developed an instrument to measure the low
concentrations of sodium and potassium in a solution. They
named this instrument as Flame photometer.
 The principle of flame photometer
 is based on the measurement of the emitted light intensity when
a metal is introduced into the flame.
 The wavelength of the colour gives information about the
element and
 the colour of the flame gives information about the amount of
the element present in the sample.
 Flame photometry is one of the branches of atomic absorption
spectroscopy.
 It is also known as flame emission spectroscopy.
 Currently, it has become a necessary tool in the field of
analytical chemistry.

5.  Used to
 Determine the concentration of certain metal ions like
 potassium,
 lithium,
 calcium
 cesium etc.
 In flame photometer spectra the metal ions are used in the
form of atoms.
 (IUPAC) Committee on Spectroscopic Nomenclature has
named this technique as flame atomic emission spectrometry
(FAES).
 Note- IUPAC
The International Union of Pure and Applied Chemistry
sodium,

6.  Principle of Flame photometer
 The compounds of the alkali and alkaline earth metals (Group II)
dissociate into atoms when introduced into the flame.
 Some of these atoms further get excited to even higher levels.
But these atoms are not stable at higher levels.
 Hence, these atoms emit radiations when returning back to the
ground state.
 These radiations generally lie in the visible region of the
spectrum.
 Each of the alkali and alkaline earth metals has a specific
wavelength.
Element Emitted wavelength Flame color
Sodium 589 nm Yellow
Potassium 766 nm Violet
Barium 554 nm Lime green
Calcium 622 nm Orange
Lithium 670 nm Red

7.  For certain concentration ranges,
The intensity of the emission or the light emitted ά the number
of atoms returning to the ground state or the concentration of the
sample.
Liquid sample
Formation of droplets
Fine residue
Formation of neutral atoms
Excitation of atoms by thermal energy
Emission of radiation of specific wavelength
λ& Intensity of emitted radiation measured

8. NOTE-
 The wavelength of the radiation emitted is characteristic of the
elements and is used to identify the elements (Qualitative
Analysis).
 The intensity of the radiation emitted depends upon the
concentration of the element analysed (Quantiative Analysis).

12.  The wavelength of the radiation emitted is given by the
following equation :-
λ = hc/ E2-E1
Where,
h = Planks constant
c= Velocity of light
E2 = energy levels of exited and
E1 =ground state respectively
 BOLTZMAN LAW
 The fraction of free atom that are thermally exited is governed
by a Boltzman Distribution
N* / N = Ae–∆E/kT
N* =is the number of exited atom
N = is the number of atom remainin in the ground state
ΔE = is the difference in energies levels
k = The Boltzman constant
T = the tempeature

14.  Additional information
 Each element will emit radiation at wavelength specific for that
element.
 The whole process can be categorised as below
 1. Desolvation-The particles in the flame are dehydrated by the
flame and process of desolvation takes place. Water and other
solvent is vaporized leaving minute particles of dry salt
 CaCl2 (solution) ----- CaCl2 (solid)
 2. Vaporization- Evaporation of the solvent occurs as the second
step at the high temp of the flame
 CaCl2 (Solid) ------- CaCl2 (Gas)
 Atomization- Flame heat converts a part of all the gaseous
molecules/ metal particles to give neutral ions
 Ionization and Excitation- The vapours of neutral atoms or
molecules containing the metal atoms are excited by the thermal
energy of flame resulting into ionization and excitation of neutral
atoms.
 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 shifted to the excited energy state.

15.  Emission process-
 The excited energy state is unstable and atom return to the
initial stable lower energy state with the emission of energy in
the form of radiation of characteristic wavelength, which is
measured by the photo detector.
 To obtain emission spectra, suitable flames are required.
 Example-
 CaCl2 (solution) CaCl2 (solid) CaCl2 (gas)
 CaCl2 (g) Cl2 (g) + Ca (g)
Δ
Aspiration vaporization
Dissociation by
Δ
Flame

16.  All the species example
Ionized atom and neutral atom of Ca, molecule of CaO and CaOH
Are excited by thermal energy of flame
these Ionized atom and neutral atom of Ca, molecule of CaO and
CaOH fall to the ground state
Emission spectra are produced
Type 1 spectra- those containing lines originated from excited atoms or
ions
Type 2 spectra- the band of spectra resulting from molecules
From this excited state when

17. Flow Representation

18. Gases eg. Acetylene, Hydrogen,
Propane, butane
Oxidant-
oxygen or
(Condensing)
Slit
Prism
Photomultiplier
Total consumption burner
Premixed burner-
Filter

20.  A simple flame photometer consists of the following basic
components:
Source of flame: A Burner in the flame photometer is the source of
flame.
 It can be maintained in at a constant temperature.
 The temperature of the flame is one of the critical factors in
flame photometry.

Fuel-Oxidant mixture Temperature (°C)
Natural gas-Air 1700
Propane-Air 1800
Hydrogen-Air 2000
Hydrogen-Oxygen 2650
Acetylene-Air 2300
Acetylene-Oxyen 3200
Acetylene-Nitrous oxide 2700
Cyanogen-Oxygen 4800

21. Nebuliser: Nebuliser is used to send homogeneous solution into
the flame at a balanced rate.
Monochromator:
 Filters are generally made from materials which are transparent in
a small selective wavelength region.
 The filter chosen -has a wavelength range in which it is
transparent to emission from the element of interest.
 A condenser lens system is employed to collect the emitted light
and sends the rays through the filter as an approximately
collimated (parallel) beam to reach the detector.
 Filters have been designed for use in the determination of
lithium, sodium, potassium, calcium and other elements.
 The radiation source-- emits the polychromatic light which--
contains the wide range of frequencies.
 Monochromators are used for converting the polychromatic light
into monochromatic light.
 Eg. of monochromators are prism and grating monochromators.
 Prism monochromators: When polychromatic light passes
through the prism, it is refracted.

22.  Grating monochromators: Grating is nothing but the lines made
on the glass which is previously coated with aluminium.
 Rotation of these gratings converts the polychromatic light to
monochromatic light more efficiently when compared to prism
monochromators.
DETECTOR :-
 The radiation emitted by the elements is mostly in the visible
region and measured by photo detector.
 Hence conventional detectors like photo voltaic cell or photo
tubes or photomultiplier tube is used as detector In a flame
spectrophotometer Here the emitted radiation is converted to an
electrical signal with the help of photo detector.
 These electrical signals are directly proportional to the intensity
of light emitted.
READ OUT DEVICE :-
 The signal from the detector is shown as a response in the digital read
out device. The readings are displayed in an arbitrary scale (% Flame
Intensity).

24.  Working procedure
 Both the standard stock solution and sample solution are
prepared in fresh distilled water.
 The flame of the photometer is calibrated by adjusting the air
and gas. Then the flame is allowed to stabilize for about 5 min.
 Now the instrument is switched on and the lids of the filter
chamber are opened to insert appropriate colour filters.
 The readings of the galvanometer are adjusted to zero --by
spraying distilled water into the flame.
 The sensitivity is adjusted --by spraying the most concentrated
standard working solution into the flame. Now the full scale
deflection of the galvanometer is recorded.
 Again distilled water is sprayed into the flame -- to attain
constant readings of galvanometer. Then the galvanometer is
readjusted to zero.
 Now each of the standard working solutions is sprayed into the
flame for three times and the readings of galvanometer are
recorded. After each spray, the apparatus must be thoroughly
washed.

25.  Finally sample solution is sprayed into the flame for three times
and the readings of galvanometer are recorded. After each
spray, the apparatus must be thoroughly washed.
 Calculate the mean of the galvanometer reading.
 Plot the graph of
 concentration against the galvanometer reading
 to find out the concentration of the element in the sample.

26.  Flame photometer as measures the emitted radiation, the optical
and electronic system is used in spectrophotometer is similar.
Any model of flame photometer consists of the following parts:
1. Fuel gas, Pressure regulator or flow meter
2. The atomizer
3. The optical system
4. Photosensitive detectors
5. Recording or reading meter
Note-
1. Fuel gas- Propane, Butane, Hydrogen, Acetylene
2. The atomizer- Flame Atomiser: I) Flames II) Burners
Non flame Atomizers- 1) Graphite Furnace 2) Electrical
discharges 3) Plasmas
3. Optical System- Filters (Na, K, Ca, Li etc )and monochromator
(diffraction grating or prism)
4. Photosensitivity detector- Photomultiplier
5. Recording - Galvanometer

28. 1. Fuel gas, Pressure regulator or flow meter
 fuel gas is burnt in the burner - In order to supply suitable
thermal energy through flame
 Region A -The unburnt fuel gas emerging from this region. Eg of
fuel gas- Propane, Hydrogen, Acetylene
 Pre-heating region B - Fuel gas mixes with oxidant (air/oxygen)
at outlet of burner comes into this region.
 Gases emerging from this mainly consist of CO, H2, CO2, and
hydrocarbons.
 On burning, a steady temperature is provided throughout the
outer mantle of flame.

29.  To supply sufficient temperature between 1000-3000o
C fuel
gases are used. Eg of fuel gases-
1. Coal gases (Hydrogen 50% Methane 35% Carbon monoxide 10%)
2. Illuminating gas ( Propane, Acetylene)
3. Cooking gas (Propane and butane)
 Mixture of fuel gas with (oxidant) air/oxygen = to obtain
sufficient high temperature
Fuel-Oxidant mixture Temperature (°C)
Natural gas-Air 1700
Propane-Air 1800
Hydrogen-Air 2000
Hydrogen-Oxygen 2650
Acetylene-Air 2300
Acetylene-Oxyen 3200
Acetylene-Nitrous oxide 2700
Cyanogen-Oxygen 4800

30.  Fuel gas generally obtained from – Cylinders (Store under
pressure)
 To obtain steady flame for giving emission (release)= gas
pressure and gas flow (by operating capillary flow rate meter or
rotameter) is maintained constant.
 Fuel gas generally obtained from – Cylinders (Store under
pressure)
 To obtain steady flame for giving emission (release)= gas
pressure and gas flow (by operating capillary flow rate meter or
rotameter) is maintained constant.
Rotameter
Cylinder

31. 2. Atomizer-
 Atomization and Excitation:
 Atomization --is the process of converting a solid, liquid, or
solution to be analyzed into a free gaseous atom– usually by a
thermal energy using various sources.
 Excitation is the process - the outer most electrons of atoms
absorb energy and shifted to higher energy state. (means the
same source of thermal energy serves as the excitation source)
 Atomization and excitation is the process involved in all atomic
spectroscopic techniques.
 The common sources used for atomization are
1. Flames
2. Burners
 Purpose of atomizer- is to introduced liquid sample into flame at
stable and reproducible rate
 Qualities of atomizer –
 Should remain unaffected by solutions and solvents
 Can be readily cleaned and shold be sturdy in nature
Flame Atomiser

32.  Atomizer can be classified in to 2 types
 Flame Atomiser: I) Flames II) Burners
 Non flame Atomizers- 1) Graphite Furnace 2) Electrical
discharges 3) Plasmas
 Flame Atomizer:
 I) Flames-Most of molecules are dissociated into free atoms and
excited by heating energy produced by flames
Premixed flame- Premixed flames occur
in any homogeneous mixture where the
fuel and the oxidant are mixed before to
the reaction or combustion.
Ex. the Bunsen burner flame
Diffusion flame -When the
oxygen feeding the
combustion gets to the flame
from the air, the flame is
called diffusion flame.
Eg. a candle flame

33.  Fuel and oxidants-
 Fuel and oxidant required-- to produced flame
 Combination of fuel and oxidants is important--- It should be
suitable for conversation of samples-- to neutral atoms --
followed by the excitation of atoms
Temperature of flame plays a major role-
High temprature of flame - the elements in sample may get
convert into ions instead of neutral atoms.
Similarly with low temperature of flame there may not be
excitation of atoms occurs
 NOTE- so a combination of fuel and oxidants is used in such that
there is desired temperature to facilitate atomization and
excitation.
 Structure of flame-
 the flame may be divided into the following regions or zones:
1. Preheating zones.
2. Primary reaction zone or inner zone.
3. Internal zone.
4. Secondary reaction zone.

34.  Primary combustion Zone/Primary reaction zone- Don't take part
in the flame emission process– Usually blue in color
 Interconal regions-
 take part in emission process- Most important region.
 It is rich in free atoms and involve in the excitation process.
 The outer zone- covert the products to stable oxide
Or inner
zone

35.  1.Burner :-
 Main requirement of burner is that when fuel gas
is supplied along with air/oxygen at a constant
pressure, it should produce a steady flame.
 For low temperature flame Meeker burner is used.
It carries a metal grid across the burner open tube
which prevent flame from striking back down.
 There are two common types of atomizer burner
employed in flame photometers. These are-
 Total consumption burner
 Premixed burner- The sample is nebulized and
mixed with the fuel and oxidant prior to
introduction into the flame, with the used of a
series of buffles
 Sample is drawn from the sample container via
vacuum created by rushing the fuel and oxidant
(Aspiration)
 Advantage of is the uniformity of flame produced.
Open tube
metal grid
Across
the burner
Meeker Burner

36. Sample or
1 2
3 4

38. Total consumption burner
 It consist of inlets for fuel and
oxidants at the base of the apparatus
 Sample is also kept at the base to be
aspirated.
 Acetylene -commonly used as fuel
and air -used oxidant are forced,
under pressure, into the flame
 The sample is drawn into the flame
by aspiration by vacuum created
because of movement of fuel and
oxidant.
 The aspirated sample reaches-- the
burner head with a nebulizing effect.
 This sample is mixed with fuels and
oxidant at the base of the flame.
 Advantage over other is the entire
consumption of sample,
 Limitation
 The resulting flame is turbulent and
not homogeneous
Acetylene
air

39. 3.Optical system-
 Function-
 1. Is to collect the light from steady flame, render it
Monochromatic by means of lens, prism, --and focus on to the
phototube.
 2. Concave mirror- placed behind flame to collect scattered
radiation and focus back into flame- By this mechanism intensity
of emitted light is nearly doubled
 Filters and monochromator -are needed to isolate the light of
specific wavelength from the remaining light of the flame
 Simple filter is sufficient in case of few elements Ca, Na, K and Li.
 So a filter wheel with filter is for filter is taken with instrument
 Type of filter- 1) absorption glass filter 2) interference filter
 Interference filter is better
 Glass absorption filters are used to pass a specific band of
wavelengths.
 Interference Filters - These filters differ from absorption filters in
the fact that they reflect and destructively interfere with
unwanted wavelengths as opposed to absorbing them.

41.  Dispersion medium- Prism or Diffraction grating is employed in
flame spectrophotometer
4. Photo- Detector-
 Phototube
 Photo- multiplier
 Barrier layer cell
Or diffraction grating

43. Photo- multiplier

45.  The method of analysis is very simple and
economical.
 It is quick, convenient, selective and sensitive
analysis.
 It is both and qualitative and quantitative in
nature.
 Even very low concentrations (parts per
million/ppm to parts per billion/ppb range) of
metals in the sample can be determined.
 This method compensates for any unexpected
interfering material present in the sample
solution.
 This method can be used to estimate elements
which are rarely analyzed.

46.  In spite of many advantages, this analysis technique has quite a
few disadvantages:
 The accurate concentration of the metal ion in the solution
cannot be measured.
 It cannot directly detect and determine the presence of inert
gases.
 Though this technique measures the total metal content present
in the sample, it does not provide the information about the
molecular structure of the metal present in the sample.
 Only liquid samples may be used. Also sample preparation
becomes lengthy in some cases.
 Flame photometry cannot be used for the direct determination of
each and every metal atom. A number of metal atoms cannot be
analysed by this method.
 The elements such as carbon, hydrogen and halides cannot be
detected due to their non-radiating nature.

47. 1. Flame Temperature-
 It is very essential to have proper temperature of flame to bring
about excitation and release of energy
 If flame temperature is very low – It would be insufficient to cause
vaporization, dissociation and excitation of atom.
 No line or weak lines would be obtained
 The temperature should not be too high to have deteriorating
effect
 2. Chemical interference-
 When another component is present in the sample as impurity,
error occurs.
 The magnitude of error depends upon -
 the ratio of concentration of contaminant with the element under
examination

48.  In determination of certain metal ions (cations), anions present
in the solution have depressant effect on the intensities of
number of cation liones, eg. More than 5% oxalate, sulphate,
phosphate ions bring decrease in emission intensities of alkaline
earth cations
 Thus the contaminants are present, they need to be eliminated
by precipitations/complexations or by other methods.
 3. Radiation interference-
 Sometimes, presence of certain element, causes radiation
interference-- by emitting light of wavelength, identical to that
of element under examination.
 The detector is thus unable to distinguish the line and their
intensities.
 This difficulty is generally eliminating by removing the
interfering element or by adding an identical amount of the
solution for constructing calibration curves

50.  Flame photometry is widely used in various chemicals and
pharmaceuticals, soils and agriculture, ceramics and glass, plant
materials and water, oceanography, and in biological and
microbiological laboratories
1. Determination of Na, K, Ca, and Mg in biological fluids like
serum, plasma, urine etc is routinely carried out by flame
photometer
2. Analysis of industrial water, natural water for determining
elements responsible for hard water (like Ca, Mg, Ba etc) is
standard procedure in many laboratories
3. Soil samples are routinely analyzed mainly for Na and K and also
for Ca and Mg (after removing other interfering elements) by
flame photometer
4. Some important elements which are commonly determined by
this method are Al, Ba, Ca, cesninum, chromium, Cu, Fe, lead,
Mg, Manganese, K, Na, strontium and zinc

51. 5. In glass industry- flame photometry is used in determination of
Na, K, boron, lithium etc
6. In cement industry, this method is used in estimation of Sodium
(Na2O), Potassium (K2O), Calcium (CaO), magnesium (MgO),
manganese (MnO2) and Lithium (Li2O).
7. Flame photometry used in estimation of alkali-alkaline earth
metals besides other metals present in metallurgical products,
catalysts, alloys etc.
8. Flame photometry has also been used in determination of certain
metals like lead, manganese, in petroleum products like gasoline,
lubricating oils and organic solvents.
9. Analysis of ash by flame photometer is routinely carried out in
various industries for estimating alkali and alkaline earth metals
as their oxides

52. 1. Which of the following is the principle of Flame emission
photometers?
a) Radiation is absorbed by non-excited atoms in vapour state and are
excited to higher states
b) Medium absorbs radiation and transmitted radiation is measured
c) Colour and wavelength of the flame is measured
d) Only wavelength of the flame is measured
2. Which of the following is not an advantage of Laminar flow burner
used in Flame photometry?
a) Noiseless
b) Stable flame for analysis
c) Efficient atomization of sample
d) Sample containing two or more solvents can be burned
efficiently
3.Which of the following is not a detector used in Flame emission
photometers?
a) Photronic cell
b) Photovoltaic cell
c) Photoemissive tube
d) Chromatogram

53. 4. If Propane and air are used in burner how many °C temp. is
produced ?
a)1900°C
b)2200°C
c)2300°C
d)2100°C
5. If Hydrogen and air are used in burner how many °C temp. is
produced ?
a)1900°C
b)2200°C
c)2300°C
d)2100°C
6. Which is not application of flame photometry ?
a)To estimate sodium, magnesium, calcium
b) Assay of metformin.
c)Used to determine magnesium and calcium in cement.
d) To detected metalic ions in sample.

54. 7. BOLTZMANN Equations is
a)N* / N =R Ae–∆E/kT
b)N* / N = e–∆E/kT
c)N* / N = Ae–∆E/kT
d)N* / N = Ae–∆E/kc
8. Choose correct sequence of flame photometry ?
a) Sample residue → excited state atoms → Return in ground
state → Emission of radiation
b)Sample residue → ground state → excited state → Emission of
radiation
c) Emission of radiation → excited state →ground state → Sample
residue
d) Sample residue → ground state → excited state → Emission of
radiation
9. Which equations are used to determine wavelength of radiation ?
a)λ = hc/ E2-E1
b)N* / N = e–∆E/kT
c) λ = h/E2-E1
d)N* / N = Ae–∆E/kT

55. 10. Which is application of flame photometry ?
a) To determine functional group
b) To study of chemical structure
c) To assay of drug
d) To estimate metalic ions like sodium, potassium, etc.