AAS Flashcards
It is an analytical technique that measures the concentrations of
elements. It makes use of the absorption of light by these elements in order to measure their
concentration.
ATOMIC ABSORPTION SPECTROSCOPY (AAS)
It quantifies the absorption of ground state atoms in the gaseous state.
ATOMIC ABSORPTION SPECTROSCOPY (AAS)
These are usually determined from a working curve after calibrating the instrument with standards of known concentration.
Concentration measurements
They absorb ultraviolet or visible light and make transitions to higher electronic energy levels.
atoms
It is determined from the amount of absorption.
Analyte Concentration
It is a very common technique for detecting metals and metalloids in environmental samples.
Atomic absorption
4 principal components of Atomic absorption spectrometers
1- A light source ( usually a hollow cathode lamp)
2 - An atom cell (atomizer )
3 - A monochromator
4 - A detector, and read out device.
The usual light source of the element that is being measured
hollow cathode lamp
It contains a tungsten anode and a hollow cylindrical cathode made of the element to be determined. These are sealed in a glass tube filled with an inert gas (neon or argon).
Hollow cathode lamp
Elements to be analyzed needs to be in ___
atomic sate
It is the separation of particles into individual molecules and breaking molecules into atoms.
- This is done by exposing the analyte to high temperatures in a flame or graphite furnace.
Atomization
two types of atomization:
Flame and Graphite Furnace Atomization
Gas/Air
1700-1900
Gas/O2
2700-2800
H2/Air
2000-2100
H2/O2
2550-2700
C2H2/Air
2100-2400
C2H2/O2
3050/3150
C2H2/N2O
2600-2800
It uses excited atoms
Atomic Emission
It uses ground-state atoms
Atomic Absorption
The fine mist of droplets is mixed with ___ and ____ and burned.
fuel (acetylene), and oxidant (nitrous oxide)
It is important because it influences the distribution of atoms.
- It can be manipulated by oxidant and fuel ratio.
Flame temperature
any factor that affects the ground state atom population
Interference
Factors that may affect the ability of the instrument to read this parameter
Interference
Element other than the one of interest may absorb the wavelength being used.
Absorption and Source Radiation
the formation of ions rather than
atoms causes lower absorption of radiation. This problem is overcome by adding ionization suppressors.
Ionization Interference
the atoms of the same kind that are absorbing radiation will absorb more at the center of the line than at the wings and thus resulting in the change of shape of the line as well as its
intensity.
Self Absorption
This is caused by the presence of a particle from incomplete atomization .This problem is overcome by increasing the flame temperature
Background Absorption of Source Radiation
Rate of aspiration, nebulization, or transport of the sample (e g viscosity, surface tension, vapor pressure , and density)
Transport Interference
Analyzing metals in biological fluids such as blood and urine.
Clinical Analysis
Monitoring our environment -e g finding out the levels of various elements in rivers, seawater, drinking water, air, and petrol.
Environmental Analysis
In some pharmaceutical manufacturing processes, minute quantities of a catalyst used in the process (usually a metal) are sometimes present in the final product.
By using AAS the amount of catalyst present can be determined.
Pharmaceuticals
Many raw materials are examined and
AAS is widely used to check that the major elements are present and that toxic impurities are lower than specified - e q in concrete, where calcium is a major constituent, the lead level should be low because it is toxic.
Industry
It is the analyte that you want to analyze
Standard of Known Concentration
