Modern pharmaceutical analytical techique

1. Submitted By:
ROHIT
M.Pharmacy 1st Year
R.K.S.D COLLEGE OF PHARMACY, KAITHAL (HRY)

2. Introduction:
o Based on measurement of intensity of light emitted,
when a metal is introduced into the flame.
o The wavelength of the colour tells us what the
element is, and the colour's intensity tells how much
the element is present.
o Also known as Flame Photometry, because of the use
of flame to provide energy for excitation of atom.

3. Theory:
oThe liquid sample of metallic salt is
introduced into the flame and following
steps takes place:
1. Solvent is vaporised, leaving the particles
of solid salt.
2. Salt is vaporised or converted into gaseous
state.
3. Gaseous molecule get dissociated to form
neutral atom or radical.

4. These neutral atoms are excited by thermal energy of
flame which are unstable & emit photon & return to
lower energy level & finally wavelength of emitted
light is measured by-
E2 - E1 = hν
ν = c/λ
E2 – E1 = hc/λ
λ = hc/(E2 – E1)
The fraction of free atoms which are thermally
excited is given by Boltzmann distribution eqn
N*/No = Δe
-ΔE/Kt

5. Limitation of Flame Emission
Photometry:
 The number of excited atoms in flame is very
small. It is the alkali and alkaline earth metals
that can be practically determined.
 It needs perfect control of flame temperature.
 Interference by other elements is not easy to be
eliminated.
 Heavy and transition metals , the number of
absorption and emission lines is enormous and
the spectra are complex.

6. Instrumentation:
 Burner
 Mirror
 Slit
 Monochromator
 Filters
 Detector.

8. Burner:-
It Requires fuel (H2) or oxidant.
Various types of burner are used in the
spectroscopy:
a. Mecker Burner
b. Total Consumption Burner
c. Lundergarph Burner

9. Mecker Burner:
 Used natural gas or Oxygen.
 Produce Relatively low temperature and low
excitation energy
 Generally used for the study of Alkali metals only.
These days, Mecker Burner is not used.

10. Total Consumption Burner:
 In this burner fuel and oxidant
are H2 and O2 gases respectively.
 Liquid sample is drawn into the
flame from the side tubings, H2
and O2 are entering & both are
burning at the top & produce
flame.
The flame is noisy and turbulent produced by it.
 From the liquid sample, solvent is evaporated &
leaving the solid residue.
 It is used because all the samples that enters the
capillary tube will enter the flame in form of droplets.

11. Lundergarph burner:
 In this, the sample must be in liquid form.
 Large droplets condense on the side and drain away;
small droplets and vaporised sample are swept in the
flame in the form of cloud.
 An important feature of this burner is that only 5% of
the sample reaches the flame. The rest of the droplets
condense and are drained away.
Other type of burner used are:
• Premix or Laminar Flow Burner
• Shielded Burner
• Nitrous oxide Acetylene Burner

12. Mirror:
 The radiation from the flame is emitted in all the
direction and in order to maximize the amount of
radiation, a mirror is located behind the burner to
reflect the radiation back to the entrance slit.
SLIT:
• With the best equipment, entrance and exit slits
are used before and after dispersion element.

13. Entrance slit:
The entrance slit cuts out most of the radiation from
the surrounding and allow only radiation from the
flame.
Exit slit:
The exit slit is placed after the monochromator and
allow only selected wavelength range to pass through
the detector.

14. Monochromator:
 Monochromator is the Prism. But in expensive
models, the Grating monochromator is used.
FILTERS:
• An optical filter may be used in place of slit and
monochromator system.
• When filter is kept between flame and detector,
the radiation of desired wavelength from the
flame will be entering the detector and measured.
• The remaining undesired wavelength will be
absorbed by filter and not measured.

15. Detector:
 The radiation coming from the optical system is
fell on the detector which measure the intensity of
radiation falling on it.
Photomultiplier Detector are used in
a good Flame Photometer.

16. INTERFERENCE IN FLAME PHOTOMETRY:
Spectral interference
Ionisation interference
Cation – Anion interference
Cation – Cation interference
Oxide formation interference

17. Application:
Qualitative Analysis:
This is only used to detect the element present in
group I and group II in periodic table. i.e. Na, K,
Lithium, Mg, Ca, Strontium & Barium.
Quantitative Analysis:
This is used for rapid quantitative determination of
the elements in group I and group II of the periodic
table.