Atomic Absorption Spectroscopy is an instrumental analysis technique for rapid trace metal analysis.It is based on element specific wavelength light absorption by ground state atoms in the flame or electrothermal graphite furnace. It finds immense applications in the analysis for trace metals in soils, lakes, rivers, oceans, and drinking water, pharmaceuticals, foods and beverages, geological and mineralogical samples, petroleum products, biological fluids and specimens and forensic analysis. It is common to get results in ppm levels and a higher sensitivity of ppb levels when we using graphite furnace atomisation.
Why not start with a short video?
An illustrated video will depict the changes that take place when a sample containing a trace metal is aspirated into a flame. Such physical changes are accompanied by changes in absorption of light by ground state atoms and measurement of absorption signal for quantitative estimations is illustrated in the video.
Glossary of AAS terms
The glossary will help you to understand the terminology in case you aren’t already familiar with the technique.
|Atomic Absorption Spectroscopy||Study of element specific light absorption by ground state atoms for estimation of concentration of the element in the sample solution.|
|Atomisation||Process of reduction of sample to ground state atoms by application of heat by means of a flame or a graphite furnace.|
|Atom||The smallest particle of an element or compound. It comprises of a central nucleus containing neutral particles called neutrons and positively charged protons. The electrons revolve the central nucleus in shells of different energy levels. The number of electrons equals the number of protons in the neutral atom.|
|Atomic Emission Spectroscopy||Qualitative identification and quantification of element by emission of characteristic wavelength of light on excitation of an element by means of a flame or plasma|
|Atomic Fluorescence Spectroscopy||Measurement of light emitted on decay of elements from excited states.Measurement is made at an angle to the optical beam path so that the detector sees only the fluorescence in the flame and not incidental light from the lamp.|
|Absorbance||The amount or fraction of incident light absorbed by the ground state atoms. It is directly proportional to the number of ground state atoms in the beam path and also on the optical path length of the flame in accordance to Beer Lambert law of light absorption|
|Absorbance unit||a ratio of intensity of transmitted flight to the intensity of incident light. It is a unit less quantity but is commonly expressed in absorbance units (EU)|
|Aspiration||losses of reduction of liquid sample stream into fine droplets for introduction into the flame|
|Acetylene||Commonly used gas as fuel to support combustion of the flame.Provides temperatures in the range 2150-23000C|
|Argon||Gas used commonly as a filling gas in hollow cathode lamps and as sample carrier in graphite furnace analysis|
|Air||Used as oxidant in combination with acetylene as fuel gas to support the flame|
|Air compressor||Device for delivery of air to the atomic absorption spectrometer. Oil less air compressor is preferred as contamination from oil is thereby avoided|
|Burner||A component of AAS system made of solid metal body having slit on the flat top surface to provide the flame required for atomisation of the sample|
|Blaze angle||It is the angle of cut of a mechanically ruled grating at which the angle of incidence is equal to the angle of reflection so that light intensity is greatest with minimal loss due to diffraction. For greater efficiency dual blazed ratings are used which provide greater light throughput over the wavelength range of the spectrometer|
|Background||any extraneous light other than the transmitted light that reaches the detector and affects the signal absorption|
|Background correction||Means applied to reduce the effects of background on the signal|
|Concentration||The amount of element present in a unit volume of solution.Usually expressed as ppm (mg/lit) or ppb (μg/lit)|
|Characteristic concentration||Concentration of an element expressed in mg/lit required to produce a 1% absorbance or 0.004 absorbance signal. Knowledge of characteristic concentration helps predict the concentration range required to produce optimum absorbance levels for analysis|
|Collimation||Condensation of beam of light as per size requirement|
|Cathode||An electrode inside the lamp made from the pure metal whose analysis is required in the sample solution|
|Chopper||A half transparent half opaque disc that rotates in the beam path to split the beam so as to alternately allow its passing through the sample or around it to give effective double beam performance|
|Cold vapour mercury analyser||Analyser fo mercury without using a heated sample cell as mercury is only element which exists as a liquid at room temperature|
|Deuterium sources||A broadband light source for providing background correction in flame analysis
|Detector||A component of the system that records the intensity of the transmitted light. Photomultiplier tube is the commonly used detector in AAS|
|Double beam system||Optical arrangement which alternately permits the light beam to pass through the sample and round it as a reference beam.|
|Desolvation||Refrom sample droplets by heat inside the flame|
|Exhaust ventilation system||An assembly for removal of hot corrosive combustion gases and vapours arising from the flame|
|Electrode/discharge lamp||a lamp used for analysis of volatile elements.It is a high energy light source which has a longer life than corresponding hollow cathode lamps.|
|Excitation||Excitation of a ground state atom to higher energy states by means of electromagnetic radiation|
|End Cap||Removable cover of spray chamber that serves to introduce sample into spray chamber and also hold the nebuliser|
|Flow spoiler||A device inside spray chamber used for removal of large droplets of sample|
|Flame||Atomisation system which uses a flame. Commonly air – acetylene gas mixture or nitrous oxide – acetylene for higher temperature combustion|
|Flashback||Reverse movement of flame inside burner towards spray chamber due to greater proportion of oxidant or even pure oxygen in flame. It often results to a loud explosion and damage to spray chamber|
|Furnace||A graphite tube about a cm long with a hole on top for atomisation of sample using electrical heating of the tube|
|FIAS||Flow injection analysis system for automated analysis using hydride generation|
|Graphite furnace||same as furnace|
|Grating||A light dispersing device used in the monochromator|
|Hollow cathode lamp||A light source used for AAS analysis which is specific for metal to be analysed in the sample. For some elements multielement hollow cathode camps are also used|
|Hydride generation technique||Used for analysis of volatile hydride forming elements such as As, Bi, Ge, Pb, Sb, Se, Sn, Te.|
|Impact bead||A device inside spray chamber for removal of large sized droplets from sample stream|
|Interference||Effects resulting in variation of results due to spectral or non-spectral interferences|
|L’vov platform||small platform made from solid pyrolytically coated graphite which is placed at bottom inside graphite tube. Sample is put into a depression in the platform. Permits uniform heating and delays atomisation till stable temperature conditions are preached inside the furnace|
|Monochromator||A device used for dispersion of incident light using prism or grating, reflecting mirrors and a combination of entrance and exit slits for isolation of required wavelength and collimation of the light beam|
|Mirror's||Light reflecting component of monochromator with a aluminium or gold coated surface to reduce corrosion damage and provide high reflectivity|
|MHS||Mercury hydride system for analysis of volatile elements by hydride formation|
|Matrix interference||Interference arising due to differences in parameters such as viscosity, surface tension between sample and standards solutions|
|Microwave Reaction System||Automated digestion of samples in closed tubes using sonic waves. It offers advantages of speed of f digestion, cost and freedom from toxic vapours|
|Matrix modifier||Substance used for reduction of chemical interferences|
|Nebuliser||A device for producing an aerosol of sample inside spray chamber|
|Orifice||Small bore tube opening|
|Polychromatic||A light dispersion device using an array of detectors for simultaneous detection of elements in a sample|
|Photomultiplier tube detector||A detection device used in AAS which amplifies the current produced by impact of photons on a light sensitive surface|
|Prism||A light dispersing element|
|Quartz||A UV transparent material used for making hollow cathode lamp and graphite tube end windows|
|Slit width||Width of monochromator entry and exit slits expressed in millimeters|
|STPF||Stabilised temperature platform furnace is a combination of instrumental and analysis factors for providing high accuracy of results|
|Transverse heating||Heating of graphite furnace perpendicular to its axis to provide uniform heating of graphite tube along its length|
|UV range||Wavelength range 180 - 350 nm. Most elements have specific absorption bands in this region|
|Zeeman background correction||Advanced background correction used in graphite furnace analysis involving application of a magnetic field perpendicular to the graphite furnace. Effective for background correction of complex matrices.|
Refresh your concepts by registering for the free course which will provide you an introduction to the technique and even prepare you for an interview if you are applying for a job in the laboratory equipped with AAS systems.
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Want to read all the AAS free course modules right now? Here are all links to all the modules for you!
- Introduction to Atomic Absorption Spectroscopy course
- Module 1 : Scope of Spectroscopic Analysis
- Module 2 : Evolution of Atomic Absorption Spectroscopy
- Module 3 : Introduction to AAS component parts
- Module 4 : Types of Light Sources in AAS
- Module 5 : Flame Atomic Absorption Spectroscopy
- Module 6 : Graphite Furnace Atomic Absorption Spectroscopy
- Module 7 : Dispersion and Resolution of Light in Atomic Absorption Spectroscopy
- Module 8 : Interferences in Atomic Absorption Spectroscopy
- Module 9 : Background correction in Atomic Absorption Spectroscopy
- Module 10 : 10 Interview questions in Atomic Absorption Spectroscopy
Want to learn more about Atomic Absorption Spectroscopy? Continue with our library of articles on AAS below –
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- What is the Benefit of using Blazed Gratings in AAS Spectrometers?
- Which Technique Should I use for Trace Metal Analysis?
- Dispersion of Light in Spectroscopy
- What Processes take place in the Flame during Atomic Absorption Analysis?
- Know the Performance Parameters of AAS Monochromator
- Comparison between Electrode-less Discharge Lamps and Hollow Cathode Lamps as light sources in AAS
- Multi Element Hollow Cathode Lamps – How they compare with Single Element Hollow Cathode Lamps?
- Flow Spoiler or Impact Bead – which is the optimum choice in Flame AAS analysis?
- Influence of Burner Head Geometry on Flame characteristics in AAS analysis
- Air or Nitrous oxide – which is the right oxidant gas for Flame Atomic Absorption Spectroscopy analysis?
- Fusion and Ashing of samples for Atomic Absorption Spectroscopic analysis
- How to Minimize Cross Contamination Errors in Atomic Absorption Spectroscopic Analysis?
- Container Material Considerations for Collection and Storage of Atomic Absorption Spectroscopy Samples
- Benefits of Microwave Digestion over Open Acid Digestions
- Safety Guidelines for Operation of Atomic Absorption Spectrometer
- Factors deciding choice between Flame and Graphite Furnace Atomization in Atomic Absorption Spectroscopic Analysis
- AAS Free e course : Introduction to Atomic Absorption Spectroscopy course
- Comparison between Single Beam and Double Beam Atomic Absorption Spectrometer Systems
- Evolution of Atomic Absorption Spectroscopy
- Graphite Furnace Atomic Absorption Spectroscopy
- Dispersion and Resolution of Light in Atomic Absorption Spectroscopy
- Interferences in Atomic Absorption Spectroscopy
- 10 Interview questions in Atomic Absorption Spectroscopy
- Background correction in Atomic Absorption Spectroscopy
- Introduction to AAS component parts
- Types of Light Sources in AAS
- Flame Atomic Absorption Spectroscopy
- Atomic Absorption Spectroscopy