Flame photometry (Flam Emission Spectroscopy and Atomic absorption Spectroscopy) and ATOMIC ABSORPTION SPECTROSCOPY

1. Flame photometry (Flam Emission
Spectroscopy and Atomic
absorption Spectroscopy)
Amit Kumar Singh
Asst. Professor (Clinical Biochemistry)
USMAS Rayat Bahra University Mohali Punjab
23/05/2021

2. Flame photometry (Flam Emission
Spectroscopy)

3. • Flame photometry is a device used in
inorganic chemical analysis to determine to
conc. Of certain metal ions. Such as Sodium,
potassium, lithium and calcium.
• In flame photometry neutral atoms are
obtained by introduction of sample into flame.
Hence the name flame photometry since
radiation is emitted it is also called as flame
emission spectroscopy.

4. Principle
 When a solution of metallic salt is sprayed as fine droplet
into a flame due to 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 there after 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 specific of wavelength of light emitted makes it a
quantitative aspect. While the intensity of radiation
depends on conc. Of the element.

6. Components
1. Burner: - This is the part which produce excited atoms. Here the
sample solution is sprayed into fuel and oxidant combination. A
homogenous flame of stable intensity is produced.
2. Monochromator:-Filter and monochromator are needed to
isolate the light of specific wavelength from remaining light flame.
For this sample filter are sufficient as we are study only few
element like Ca, Na, K and Li. So a filter wheel with for each
element is taken. When a particular element is analyzed the
particular filter is used so that is filters all other wavelength.
3. Detector:- Flame photometric detector is similar to that used in
spectrophotometer. The emitted radiation is in the visible region
(400nm-700nm) further the radiation is specific for each element
so simple detectors are sufficient for purpose like photo voltaic
cells, photo tubes etc.
4. Record and Display:- These are the device to read out the
recording from detectors.

7. Flame photometry uses/Application
1. For qualitative analysis of samples by
comparison of spectrum emission
wavelength with that standards.
2. For quantitative analysis to determine the
conc. Of group IA and IIA elements.
Example- Na, K, Cl, etc.

8. Limitations
1. Limited number of elements that can be analyzed.
2. The sample requires to be introduced as solution into
droplets, many metallic salts, soil plants and other
compounds are insoluble in common solvents Hence
they cannot be analyzed by this method.
3. Since sample is volatilized if small amount of sample
present it is tough to analyze by this method. As some
it gets wasted by vaporization.
4. Further during solubilisation with solvents other
impurities might mix up with sample and may lead to
errors in the spectra observed.

9. ATOMIC ABSORPTION
SPECTROSCOPY

10. • Atomic Absorption Spectroscopy was invented
by Alan Walsh in 1950’s for the qualitative
determination of trace metals in liquids. The
superiority of the technique over other is
based on the fact that by this technique 50-60
elements can be determined without any
interference from trace to big quantities.

11. Principle
When a solution having a mixture of metallic
species is introduced into the flame, the
solvent evaporates and vapour of metallic
species is obtained. Some of metal atoms can
be raised to an energy level sufficiently high to
emit characteristics radiation of metal-a
phenomenon that is used in flame
photometry. Here a large amount of metal
atoms remain in non-emitting ground state.

12. These ground state atoms of a particular
element are receptive of light radiation of
their own specific resonance wavelength. In
this way, when a light of this wavelength
passes through a flame, a part of light will be
absorbed and this absorption will be
proportional to the intensity of atoms in the
flame.
Note:- So in atomic absorption spectroscopy
the amount of light absorbed is determined
because the absorption is proportional to the
concentration of the element,

14. Component of atom absorption
spectroscopy
The apparatus consist of:
a) Radiant Source.
b) Atomizer
c) Monochromator
d) Lenses and Slits and
e) Detectors.

15. a) Radiant Sources: Generally a hydrogen lamp is
used as continuous source of radiation.
b) Atomizer: Generally burners are used to break
the liquid sample into droplets which are then
allowed to enter into flame. The droplets are
then evaporated and sample element is left in
residue. The residue is then decomposed by
flame. Thus in this process the sample is
reduced to atoms.
c) Hollow Cathode Lamp: For atomic absorption
spectroscopy the radiation source is a hollow
cathode lamp (shown in figure).

16. It consists of the following parts:
Cathode: is made of the element to be determined or
coated with it.
Anode Anode is made of tungsten, zinconium or nickel.
Window is made of Pyrex glass depending on wavelength
of emitted radiation.
The lamp is filled with neon or argon gas.

17. d)Monochromator: Generally the
monocchromators are gratings and prisms.
e)Filters or slits: Filters or slits are used for isolation
of required spectral line if element has a simple
line spectrum. Filter photometers are used for
determination of potassium, sodium calcium,
magnesium etc. in samples.
f)Detectors: Generally photomultipliers are used as
detectors. In some instruments two filters and
two detectors are used to compensate the
fluctuation in the sources.

18. Applications
There are many applications for atomic absorption:
Clinical analysis (blood sample: whole blood,
plasma, serum; Ca, Mg, Li, Na, K, Fe)
Environmental analysis: Monitoring our
environmental – eg finding out the levels of
various elements in rivers, seawater, drinking
water, air, and petrol
Mining: By using AAS the amount of metals such
as gold in rock can be determined to see whether
it is worth mining the rocks to extract the gold.

19. Comparison between Atomic Absorption
and Emission Spectroscopy
Absorption Emission
Measure trace metal concentration in
complex matrices.
Measure trace metal concentration in
complex matrices.
Atomicabsorption depends upon the
number of ground state atoms.
Atomic emission depends upon the
number of excited atoms.
Itmeasures the radiation absorbed by
the ground state atoms.
It measures the radiation emitted by
the excited atoms.
Presence of a light source. Absence of the light source.
The temperature in the atomizer is
adjusted to atomize the analyte atoms
in the ground state only.
The temperature in the atomizer is big
enough to atomize the analyte atoms
and excite them to a higher energy
level.