University college of Agriculture,University of sargodha.

1. BY
SAJID SARWAR M006
NABEEL AHMAD E258
H. ALI USMAN M042
HARIS ALI E293

2. The production and discharge of something,
especially gas or radiation.
Emission is the process by which a higher energy
quantum mechanical state of a particle becomes
converted to a lower one through the emission of a
photon, resulting in the production of light.
The frequencies of light that an atom can emit are
dependent on states the electrons can be in.

3. The emission spectrum of a chemical element or
chemical compound is the spectrum of frequencies of
electromagnetic radiation emitted due to an atom or
molecule making a transition from a high energy state
to a lower energy state.
WHAT IS SPECTROSCOPY?
Spectroscopy is the study of the interaction
between matter and electromagnetic radiation.

4. Atomic emission spectroscopy or AES is a procedure
of analysing chemicals that employs the intensity of
light from a plasma, flame, arc or spark at a definite
wavelength to calculate the quantitative presence of
an element in a particular sample.
The atomic spectral line wavelength identifies the
element
The intensity of light is proportional to the atom count
of the element.
Atomic emission spectroscopy (AES or OES) uses
quantitative measurement of the optical emission from
excited atoms to determine analyte concentration

5. Emission lines from hot gases were
first discovered by Angstrom, and
the technique was further
developed by David Alter, Gustav
Kirchhoff and Robert Bunsen.

6. Atomic emission spectroscopy is based on the
principle that when a molecule is applied energy in the
form of light or heat, the molecules get excited and
move from lower energy level to higher energy level.
At this state the molecules are unstable. Therefore, the
excited molecule jumps from higher energy level to
lower energy level, emitting radiation. The radiations
are emitted in the form of photons. The wavelengths of
photons emitted are recorded. These radiations are
recorded in the emission spectrometer.

7. Instrumentation for atomic emission
spectroscopy is similar in design to that
used for atomic absorption. Many atomic
emission spectrometers, however, are
dedicated instruments designed to take
advantage of features unique to atomic
emission, including the use of plasmas,
arcs, sparks, and lasers, as atomization and
excitation sources and have an enhanced
capability for multielemental analysis

8. Atomic emission requires a means for converting
an analyte in solid, liquid, or solution form to a free
gaseous atom. The most common methods are
1. Flames Sources
2. Plasmas Sources
Both of which are useful for liquid or solution
samples. Solid samples may be analysed by
dissolving in solution and using a flame or plasma
atomizer.

9. A flame provides a high-
temperature source for
desolvating and vaporizing
a sample to obtain free
atoms for spectroscopic
analysis.
Atomization and excitation
in flame atomic emission is
accomplished using
nebulization and spray
chamber.
The burner head consists
of single or multiple slots

10. A plasma consists of a hot, partially ionized gas,
containing an abundant concentration of cations and
electrons that make the plasma a conductor
Plasmas operate at much higher temperatures than
flames
They provide better atomization and more highly
populated excited states
Besides neutral atoms, the higher temperatures of a
plasma also produce ions of the analyte

11. A direct-current plasma
(DCP) is created by an
electrical discharge
between two electrodes.
Samples can be deposited
on one of the electrodes,
or if conducting can make
up one electrode.
Insulating solid samples
are placed near the
discharge so that ionized
gas atoms sputter the
sample into the gas phase
where the analyte atoms
are excited. This sputtering
process is often referred to
as glow-discharge
excitation.

12. An inductively coupled
plasma (ICP) is a very high
temperature (7000-8000K)
excitation source that
efficiently desolvates,
vaporizes, excites, and
ionizes atoms.
Molecular interferences are
greatly reduced with this
excitation source but are
not eliminated completely

13. When a high-energy laser
pulse is focused into a gas
or liquid, or onto a solid
surface, it can cause
dielectric breakdown and
create a hot plasma. For
solids the laser pulse also
ablates material into the
gas phase. The energy of
the laser-created plasma
can atomize, excite, and
ionize analyte species,
which can then be
detected and quantified
by atomic-emission
spectroscopy

14. A high-power CO2 laser
that is focused into a
support gas, such as Ar,
can maintain a hot plasma.
The energy of the plasma
can atomize, excite, and
ionize analyte species
present in the support gas,
which can then be
detected and quantified
by atomic-emission
spectroscopy

15. A microwave-induced plasma consists of a quartz
tube surrounded by a microwave cavity.
Microwaves produced from a magnetron (a
microwave generator) fill the cavity and cause the
electrons in the plasma support gas to oscillate.
The oscillating electrons collide with other atoms in
the flowing gas to create and maintain a high-
temperature plasma. Atomic emission is measured
from excited analyte atoms as they exit the
microwave waveguide or cavity.

16. Atomic emission spectroscopy is ideally
suited for multi- elemental analysis because
all analytes in a sample are excited
simultaneously. A scanning monochromator
can be programmed to move rapidly to an
analyte’s desired wavelength, pausing to
record its emission intensity before moving
to the next analyte’s wavelength. Proceeding
in this fashion, it is possible to analyse three
or four analytes per minute.

17. Spark and arc excitation sources use a
current pulse (spark) or a continuous
electrical discharge (arc) between two
electrodes to vaporize and excite analyte
atoms.
The electrodes are either metal or graphite.
If the sample to be analyzed is a metal, it
can be used as one electrode. Non-
conducting samples are ground with
graphite powder and placed into a cup-

19. The development of a quantitative atomic emission
method requires several considerations, including
 CHOICE OF ATOMIZATION AND EXCITATION
SOURCE
Except for the alkali metals, detection limits when
using an ICP are significantly better than those
obtained with flame emission. Plasmas also are
subject to fewer spectral and chemical
interferences. For these reasons a plasma
emission source is usually the better choice.

20. The choice of wavelength is dictated by the
need for sensitivity and freedom from
interference due to unresolved emission
lines from other constituents in the sample.
The easiest approach to selecting a
wavelength is to obtain an emission
spectrum for the sample and then to look for
an emission line for the analyte that provides
an intense signal and is resolved from other
emission lines

21. Flame and plasma sources are
best suited for the analysis of
samples in solution and liquid form.
Although solids can be analysed by
direct insertion into the flame or
plasma, they usually are first
brought into solution by digestion or
extraction.

22. The most important spectral interference is a
continuous source of background emission
from the flame or plasma and emission
bands from molecular species. Background
corrections for flame emission are made by
scanning over the emission line and drawing
a baseline. Because the temperature of a
plasma is much higher, background
interferences due to molecular emission are
less problematic.

23. Flame emission is subject to the same types
of chemical interferences as atomic
absorption. These interferences are
minimized by
1. Adjusting the flame composition
2. Protecting agents
3. Releasing agents
4. Ionization suppressors.
An additional chemical interference results
from self-absorption.

24. When possible, quantitative analyses
are best conducted using external
standards. Emission intensity, however,
is affected significantly by many
parameters, including
1. The temperature of the excitation
source and
2. The efficiency of atomization.

25. Scale of Operation
The scale of operations for atomic emission is ideal for
the direct analysis of trace and ultra trace analytes in
macro and meso samples. With appropriate dilutions,
atomic emission also can be applied to major and
minor analytes.

26. When spectral and chemical interferences
are insignificant, atomic emission is capable
of producing quantitative results with
accuracies of 1–5%.
Accuracy in flame emission frequently is
limited by chemical interferences.
Accuracy when using plasma emission often
is limited by stray radiation from overlap-
ping emission lines.

27. The most important factor affecting precision
is the stability of the flame’s or plasma’s
temperature. For example, in a 2500 K
flame a temperature fluctuation of ±2.5 K
gives a relative standard deviation of 1% in
emission intensity. Significant improvements
in precision may be realized when using
internal standards.

28. Sensitivity in flame atomic emission is
strongly influenced by
 The temperature of the excitation
source
 The composition of the sample
matrix.
With plasma emission, sensitivity is
less influenced by the sample matrix.

29. The selectivity of atomic emission is similar
to that of atomic absorption. Atomic
emission has the further advantage of rapid
sequential or simultaneous analysis