1. Atomic Absorption Spectroscopy

2. Developed by Commonwealth Scientific and Industrial Research Organisation (CSIRO), Dr. Alan Walsh in the 1950s.
a spectroanalytical procedure for the quantitative determination of chemical elements using the absorption of optical radiation (light) by free atoms in the gaseous state.
Used to measure the concentration of metals in different sample.
Atomic absorption methods measure the amount of energy absorbed by the sample.

3. TYPES OF MEASURING DEVICE

4. TYPES OF MEASURING DEVICE
Water Sampling
Rainwater
Particulate
Seawater
Groundwater
Sludges
Sediments
Riverwater
Waste water

5. TYPES OF MEASURING DEVICE
There are 3 steps involved in turning a liquid sample into an atomic gas:
Evaporation of the liquid to leave a dry sample
Vaporising the solid sample to a gas
Atomisation to break down the compounds present into free atoms.

6. Metals that can be detected by Atomic Absorption Spectroscopy
TYPES OF MEASURING DEVICE
Metals that can be detected by Atomic Absorption Spectroscopy
Aluminium (Al)
Cadmium (Cd)
Lead (Pb)
Niobium (Nb)
Antimony (Sb)
Cobalt (Co)
Lithium (Li)
Ruthenium (Ru)
Arsenic (As)
Copper (Cu)
Magnesium (Mg)
Tin (Sn)
Beryllium (Be)
Gallium (Ga)
Manganese (Mn)
Tungsten (W)
Barium (Ba)
Hafnium (Hf)
Mercury (Hg)
Vanadium (V)
Calcium (Ca)
Indium (In)
Molybdenum (Mo)
Zinc (Zn)
Chromium (Cr)
Iron (Fe)
Nickel (Ni)
Zirconium (Zr)

7. TYPES OF MEASURING DEVICE
Atomic absorption spectrometry has many uses in different areas of chemistry
Analysing metals in biological fluids such as blood and urine
Clinical Analysis
Monitoring our environment
Finding out the levels of various elements
Environmental analysis
Amount of catalyst present can be determined
Pharmaceuticals
Check that the major elements are present and toxic impurities are lower than specified
Industry
Amount of metals such as gold in rocks can be determined
Mining

8. OPERATING PRINCIPLE

9. Principle of Atomic Absorption Spectrophotometer
Principle of the Atomic Absorption Method
Atomized elements each absorb energy of a wavelength that is peculiar to that element. The atomic absorption method uses as its light source a hollow cathode lamp which emits light of a wavelength that is peculiar to each element. Elements within a solution are heated in a flame or electrically (2000K to 3000K) and subsequently determined using the fact that the degree of absorption will vary with its concentration.
Light absorption process of atoms
Lambert-beer’s Law
I = I0 e-k .l .C
Density C l I0 I
Abs = -logI/I0 = k .l. C
k : proportional constant
l : path length
C : density (concentration)

10. Flame Method
Flame Atomization Method

11. Flameless Method (Graphite Furnace)
シール
Graphite cap
Graphite holder
Cooling block
Aperture plate socket
Sample
inlet
Seal
Graphite tube
Eject arm
Spring
Fixing knob
Graphite tube

12. Hydride Vapor Generation Technique
As, Se, Sb, Sn, Te, Bi, Hg and other metals produce a metal hydride by this method
Elements
Concentration (ppb) As
5~20 Sb Te Bi Se
10~40 Hg
20~80 Sn
30~90
6BH4- +As3++ 3H+ 3B2H6+3H2 +AsH3 (gas)
Absorption Cell
Burner Head
of AAS
Peristaltic Pump
Manifold
Gas Liquid Separator
Reaction Coil
Drain
Sample
HCl
NaBH4
Carrier Gas Ar
Structural Diagram of Hydride Vapor Generator

13. ADVANTAGES AND DISADVANTAGES

14. Flame Atomic Absorption Spectroscopy (F-AAS)
Advantages
Disadvantages
Low maintenance cost is required.
It can only analyse solutions.
Relatively short measurement time.
Sensitivity limitations.
Simple.
Higher initial sample volumes required.
Convenient.
The efficiency of atomization is poor.
Short residence time of analyte in optical path.

15. Graphite Furnace Atomic Absorption Spectroscopy (GF-AAS)
Advantages
Disadvantages
Small sample size.
The sample may not completely atomized.
Direct analysis of solid samples.
Limited analytical range.
Sensitivity is enhanced.
It requires experienced operators.
Very little or no sample preparation is needed.
It is an expensive technique.
The atomization process is more efficient.
Low sample throughput.
Analysis of liquid samples even when organic matrix is present.
The precision is poor than flame method.
Analysis of liquid samples with permanent inorganic matrix.
High matrix interference.
Low spectral interference.
Slow measurement time.

16. Hydride Vapour Generation Atomic Absorption Spectroscopy (HVG-AAS)
Advantages
Disadvantages
Low detection limits.
The specific chemical form of the analyte is required.
Quite fast measurement.
High chemical interference.
Most of interferences disappear when the analyte is transferred to a gaseous state.
A large excess of the hydride-forming element makes determination of traces of the other one impossible.

17. EXAMPLE OF SAMPLE TESTING

18. Example of Sample Testing
1. Determination of Vanadium in Lubricating Oil
Theory :
High temperature corrosion and fouling can be attributed to vanadium in the fuel.
During combustion, the element oxidize and form semi-liquid and low melting salts (vanadium pentoxide), which adhere to exhaust valves and turbochargers.
The oil is dissolved in white spirit and the absorption of this solution is compared with the absorption of standard.

19. Procedure :
Weight out 5g of the oil sample, dissolve in small volume of white spirit and transfer to 50ml flask.
Using same solvent, make up the solution to the mark.
Set up a vanadium hollow cathode lamp selecting a resonance line of wavelength 318.5nm.
Adjust gas controls to give a fuel rich acetylene-nitrous oxide flame
Aspirate into the flame the solvent blank, standard solutions and finally the test solution.
Recording the absorbance reading. Plot the calibration curve and ascertain the vanadium content of the oil.

20. 2. Determination of Trace Elements (Lead) in Contaminated Soil Theory : -sample of approximate 50g should be taken from specified sampling points on the site. -The sampling point should include surface soil and two further samples taken at depth, at 0.5 and 1.0m. -The exact location of these points should be noted, for it may be necessary to take further samples.

21. Procedures :
Weight out about 1g of sieved soil and transfer to a 100ml beaker. Add 20ml of 1:1 nitric acid.
Boil gently on a hot plate until the volume of nitric acid is reduced to 5ml.
Add 20ml of deionised water and boil gently again until the volume is 10ml.
Cool the suspension and filter through a whatman filter paper, washing the beaker and filter paper with deionised water until a volume of about 25ml is obtained.
Transfer the filtrate to a 50ml flask and make up to the mark with deionised water.
Setup acetylene-air flame with resonance line 217.0nm.
Standard lead solutions containing 1-10mg ml-1 are suitable for measurement.

22. QUESTION AND ANSWER

23. What are the steps of turning a liquid sample into an atomic gas?
Evaporation of the liquid to leave a dry sample
Vaporising the solid sample to a gas
Atomisation to break down the compounds present into free atoms.

24. List down 5 advantages and disadvantages for Graphite Furnace Atomic Absorption Spectroscopy (GF-AAS)
Advantage
Disadvantage
- small sample size
- sample may not completely atomized
- low spectral interference
- slow measurement time
- sensitivity is enhanced
- high matrix interference
- the atomization process is more efficient
- low sample throughout
- very little or no sample preparation is needed
- requires experienced operators

25. Atomic Absorption Spectroscopy (AAS) have many uses in different areas in chemistry. Elaborate.
Clinical Analysis
- analysing metals in biological fluids such as blood and urine
Environmental analysis
- monitoring our environment
Pharmaceuticals
- determine the amount of catalyst present
Industry
- examine the raw materials
- check the toxic impurities
Mining
- determine the amount of metals

26. THANK YOU