ORIGIN OF SPECTRA FLAME PHOTOMETRY THEORY OF FLAME PHOTOMETRY SCHEIBE LOMAKIN EQUATION BOLTZMAN EQUATION BOHR’S EQUATION

1. Presented by :
Miss Harshita singhai
B. Pharm sem. 7
Roll no. Y17150116
DEPARTMENT OF PHARMACEUTICAL SCIENCES
DR. HARISINGH GOUR VISHWAVIDYALAYA SAGAR (M.P.)
( A CENTRAL UNIVERSITY )
THEORY TO flame photometry - origin of spectra
Session 2020
1

2. CONTENTS
• ORIGIN OF SPECTRA
• FLAME PHOTOMETRY
• THEORY OF FLAME PHOTOMETRY
• SCHEIBE LOMAKIN EQUATION
• BOLTZMAN EQUATION
• BOHR’S EQUATION
• REFERENCES

3. Origin of spectra
Spectra are of two kinds, band spectra and line spectra. Band
spectra are very complex and originate in molecules. Line
spectra are of varying degrees of complexity and have their
origin in atoms.
All compounds which can be excited to luminosity without
decomposition give rise to band spectra, but the application of
sufficient energy results in the appearance of the spectra of the
component elements. Similarly, an element which gives a band
spectrum in its molecular form will yield a line spectrum when
the energy which excites it to luminosity is capable of
dissociating the molecules into their constituent atoms.

4. For example, the hand spectrum of oxygen or nitrogen may be
produced by the passage through the gas of uncondensed dis-
charges from an induction coil and the line spectrum by the
passage of the more intense condensed discharges.
Some of the earlier workers in spectroscopy were urged on by
the idea that a spectrum must provide a clue to the structure of
the atoms or molecules which produce it, and probably also to
the mechanism of radiation. The majority of spectra, how ever,
are exceedingly complex, and it was evident that the first step
towards the elucidation of these problems was discover the
laws governing the distribution of the lines or bands.

5. From the flame test to the atomic absorption spectrometer
(AAS)
• Atomic spectroscopy is thought to be
the oldest instrumental method for the
determination of elements. Kirchhoff
and Bunsen were able to show that a
specific spectral line belongs to each
chemical element. What was new was
that the specific spectral lines were
completely independent of the
chemical compound. This was the
decisive basis for the development of
AAS as an elementary analytical
process.
• After decades of expanding theoretical
foundations, Max Planck discovered
the quantum absorption and emission
of radiation and realized that every
atom can only absorb and emit
radiation of a specific wavelength.
#Gustav Kirchhoff (left) and
Robert Bunsen (right).

7. In the mid-nineteenth century, Walsh and Alkemade independently
published the analytical methods of atomic absorption spectrometry.
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.
Atomic spectroscopy is an unavoidable tool in the field of analytical
chemistry. It is divided into three types which are absorption, emission,
and luminescence spectroscopy.
The different branches of atomic absorption spectroscopy are
1: Flame photometry or flame atomic emission spectrometry in which the
species is examined in the form of atoms
2: Atomic absorption spectrophotometry, (AAS),
3: Inductively coupled plasma-atomic emission
spectrometry (ICP-AES).

8. *TYPES OF SPECTRUM

9. THEORY OF FLAME PHOTOMETERY
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.
The intensity of the emission is directly proportional to the number
of atoms returning to the ground state. And the light emitted is in
turn proportional to the concentration of the sample.

10. Examples are as follow-
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

11. Complete sequence of the process occurs in this spectroscopy is as
follow -
At first the sample containing suitable amount of metal is sprayed in to
the flame, where it converted in to the liquid droplets & vapors;
These vapors or droplets get evaporated and solid residues left behind;
The reaming solid residues converted to gaseous state & dissociates into
its constituent atoms;
These dissociated atoms get excited by thermal excitation reaches to their
respective higher energy levels will lead ultimately to a condition
whereby they radiate energy and gets back to their ground state. The
phenomenon of radiate energy is also called flame emission. This
emitted energy is measured by Flame Emission Spectroscopy (FES)
The five processes occurring in the flame can be summarised as follows:
1:MX (soln.) MX (solid)
2:MX (solid) MX (vap.)
3:MX (vap.) M + X
4:M (ground state) M* (excited state)
5:M* M + h−

12. *Flame photometry

13. The wavelength of the radiation emitted is given by the following
equation :-
λ = hc/ E2-E1
Where, E1,E2= energy levels of exited and ground state respectively
h = Planks constant
c= Velocity of light
The following processes
occur in the flame:
• Desolvation.
• Vapourisation.
• Atomisation.
• Excitation
• Emission of radiation

14. SCHEIBE-LOMAKIN EQUATION
• Scheibe-Lomakin equation describes intensity of light emitted with
the help of following formula:
I = k × cn
Where:
I = Intensity of emitted light
c = Concentration of the element
k = Proportionality constant
• At the linear part of the calibration curve n~1,
• Then I = k × c. In other words, the intensity of emitted light is directly
related to the concentration of the sample.

15. 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 remaining in the ground state
• AE = is the difference in energies levels
• k = The Boltzman constant
• T = the tempeature

16. BOHR’S EQUATION BOHR’S
E2-E1 = h ν ……. (1)
Where, E2 = Higher energy state
E1 = Lower energy state
h = Planck’s constant
ν = Frequency of emitted light
The frequency may be defined as;
ν = c/λ ……. (2)
Where, c = Velocity of the light
λ = Wavelength of absorbed radiation
Combining eq. (1) & (2);
E2-E1 = hc/λ ……. (3)
λ = hc/ E2-E1 ……. (4)
Using equation (4) we can calculate;
Wavelength of the emitted radiation;
Type of element (each element has its own specific wavelength);
Amount of element (by intensity of radiation)

17. REFERENCES
• CHATWAL G.R. AND ANAND S.K., “INSTRUMENTAL
METHOD OF CHEMICAL ANALYSIS”,ED-5,BY
HIMALYA PUBLISHING HOUSE,PG.NO. 2.367-2.385.
• SIDDIQUI A.A.,SIDDIQUE S., “PHARMACEUTICAL
ANALYSIS”,ED-3,VOLUME-2,BY CBS PUBLISHERS
AND DISTRIBUTORS,PG.NO.90-95.
• SHANKAR S.R., “A TEXTBOOK OF PHARMACEUTICAL
ANALYSIS ”,ED-4,BY RX PUBLICATIONS,PG.NO. 6-67
TO 6-72.
• http://adsabs.harvard.edu/full/1924JRASC “ORIGIN OF
SPECTRA”