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Principle, Instrumentation, Components, Application and Comparison between FES and AAS


By: ameerhamza5382 (43 month(s) ago)


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flame emission spectroscopy


inTRODUCTION Flame emission spectroscopy(FES) is also named as FLAME PHOTOMETRY FES is based on the measurement of intensity of the light emitted when a metal is introduced into a flame. Wavelenght of the colour – what the element present Colour intensity - how much of the element is present


principle When a solution of metallic species in sprayed into a flame, the fine droplet s of metallic species will be obtained. Due to thermal energy of the flame, the solvent in the droplets evaporate, leaving a fine residue , which are converted to neutral atoms. These neutral atoms are converted into exited state atoms by thermal energy of the flame. As the exited state is not stable, these exited atoms returns into ground state , with the emission of radiation of specific wavelength. The wavelength of the radiation emitted of raadiation is characteristics of the element and is used to identify the element.

Schematic diagram of FES:

Schematic diagram of FES Liquid sample Formation of droplets Fine residue Formation of neutral atoms Excitation of atoms by Thermal energy Emission of radiation of specific wavelenght Wavelength and intensity of emitted radiation measured


instrumentation Components Fuel gas Automizers Burner Mirror Slits Monochromator Filter Detector


instrumentation Block diagram of a flame photometer

Fuel gas :

Fuel gas In order to supply suitable thermal energy through flame, fuel gas is burnt in the burner. Various fuel gases like coal gas, illuminating gas, cooking gas and various hydrocarbon gases are employed. FUEL TEMPERATURE TEMPERATURE IN AIR IN OXYGEN ILLUMINATING GAS 1800 2800 METHANE 2000 2700 PROPANE 1925 2800 BUTANE 1900 2900 ACETYLENE 2000 3050 HYDROGEN 2100 2780


Atomizers This is a very integral and important part of flame photometer. The purchase of Atomizers is to introduce liquid sample into flame at stable and reproducible rate . Atomizers should be such that it should remain unaffected by solutions and solvents . Atomizers should be such that it can be readily cleaned and should be sturdy in nature .

burner :

burner In flame photometry, several burners and fuel-oxidant combinations have been used to produce anatylical flame. Some of them are, Mecker burner Total consumption burner Premix of laminar flow burner Lundergarph burner Shielded burner

Mecker burner:

Mecker burner This burner used earlier and employed natural gas and oxygen. Demerits : Produce relatively low temperatures Produce low excitation energies Chemically not homogeneous Generally used for the study of alkali metals only. These days Mecker burner is not used

Total consumption burner:

Total consumption burner The name “Total consumption burner” is used because all the sample that enters the capillary tube will enter the flame Demerits: Flame produced is noisy and turbulent

Total consumption burner:

Total consumption burner Liquid sample is drawn into flame Hydrogen and oxygen are enters and burns at the top to produce flame Liquid sample drawn at base of flame, oxygen aspirates sample leaving solid residue

Premix of laminar-flow burner:

Premix of laminar-flow burner In this type of burner, aspirated sample, fuel and oxidant are thoroughly mixed before reaching the burner opening and then entering the flame. The name “Laminar flow burner” used because the gases move in non-turbulent fashion, i.e., in laminar flow.

Premix of laminar-flow burner:

Premix of laminar-flow burner Advantages Non turbulent Noiseless stable Disadvantages when the sample contains 2 solvents, aspirated to flame, the more volatile sample will evaporate in spray chamber, leaving the sample in the form of undissociated atoms , this will reduce emission intensity , giving incorrect result.


mirrors The radiation from the flame is emitted in all direction. Much of the radiation is lost and loss of signal result. In order to maximize the amount of radiation used in analysis, a mirror is located behind the burner to reflect the radiation back to the entrance slit of the monochromator. This mirror is concave and covers as wide as possible flame.


slits The entrance and exit slits are used before and after the dispersion elements. The Entrance slits cuts out most of the radiation from the surroundings and allows only the radiation from the flame and the mirrored reflection of the flame to enter the optical system. The Exit slit is placed after the monochromator and allows only a selected wavelength range to pass through to the detector.


monochromators For isolation of spectral energy, filters and narrow slit width is commonly employed. In most simple Flame photometers, Absorption and Interference filters are used. Absorption filters are not suitable for analysing samples giving lines to those which lies in close proximity to the analytical line. Interference filters are better in giving good resolution. These filters transmit the desired emitted wavelength energy and absorb the light of the flame.


detectors The radiation coming from the optical system is allowed to fall on the detector which measures the intensity of radiation falling on it. The detector should be sensitive to radiation of all wavelengths that may be examined. Most flame photometers mainly employ either Barrier layer cell or Photo-multipler as a detector.


Recorder The photo-current produced by the detectors is often amplified and recorder in a strip chart recorder.


limitation This techniques is not the method of choice because of the relatively low energy available from a flame and therefore the relatively low intensity of the radiation from the metal atoms It tells little or nothing about the molecular form of the metal in the original sample. It has not been used for the direct detec tion and determination of the metals, halides or inert gases. All of these elements require more energy than the flame provides in order to become excited.


applications Flame photometry has been widely used in various industries like chemicals and pharmaceuticals, soils and agriculture, ceramics and glass, plant materials and water, oceanography and in biological and microbiological laboratories. Determination of sodium, potasium, calcium and magnesium in biological fluids like serum, plasma, urine etc.


Cont…, Analysis of industrial water, natural water for determining elements responsible for hard water like calcium, magnesium, barium,etc is standard procedure for many laboratories Soil samples are routinely analysed mainly for sodium, potassium , calcium and magnesium In glass industry , flame photometry is used in determining of sodium, potassium, boron, lithium, etc. In cement industry , this method is used to estimation of sodium(Na 2 O), potassium(K 2 O), calcium(CaO), magnesium(MgO), Maganese(MnO 2 ) and lithium(Li 2 O)


Cont…, Flame photometry is extensively used in estimation of alkaline-alkaline earth metals and others metals present in metallurgical products, catalysts, alloys etc. Flame photometry has been used in determination of certain metals like lead, maganese, in petroleum products like gasoline, lubricating oils and organic solvents.

Commercial products of fes:

Commercial products of fes Digital Clinical Flame Photometer - Edutek Instrumentation Multiparameter Photometer - Linear Instruments (HI 83200 2008 Series) Bti-185 Flame Photometer - Bluefic Industrial & Scientific Technologies Flame Photometer - Simtronics Analytical & Lab Instruments Digital Flame Photometer – Microteknik Flame Photometer - Accumax India Shamboo Scientific Glass Works Popular Science Apparatus Workshops Pvt. Ltd. http://www.aimil.com/Products.aspx?Product_Id=195



PowerPoint Presentation:

Developed by Alan Walsh (below) of the CSIRO in early 1950s


introduction Atomic absorption spectroscopy is an analytical technique involves the study of the absorption of radiation by neutral atoms in gaseous state. The principle is to analyze the concentration of metals in solution and almost independent of the molecular form of the metal in the sample.


principle When a solution of metallic species in introduced into a flame, the droplet s of metallic species will be obtained. Due to thermal energy of the flame, the solvent in the droplets evaporate, leaving a fine residue , which are converted to neutral atoms. These neutral atoms absorbs radiation of specific wavelength, emitted by hollow cathode lamp(HCL) is filled with the vapour of elements, which gives specific wavelength of radiation.

Schematic diagram of AAS:

Schematic diagram of AAS Liquid sample Formation of droplets Fine residue Formation of neutral atoms Neutral Absorb Specific Wavelength of radiation from Cathode Lamp Measurement of intensity of radiation absorbed by using Photometric detector


instrumentation Components Radiation source Chopper Atomisers Monochromators Detectors Amplifiers Read – out devices

Arrangement of AAS:

Arrangement of AAS

Radiation source:

Radiation source The radiation source is important part in AAS, these are required to emit spectra of the elements to be determined and the spectra should have sharp lines, negligible background and highly stable. Hollow Cathode Lamp Electrode Discharge Lamp

Hollow cathode lamp:

Hollow cathode lamp Cathode – hollow cup Anode – tungsten wire The 2 electrodes are housed in a tube containing an inert gas(pure helium or argon ). The lamp window is constructed of either quartz, silica or glass . Metal atoms absorb energy by colliding with fast-moving filler gas ions, are elevated to excited electronic states, and return to ground state. Lines are separated by a monochromator

Hollow cathode lamp:

Hollow cathode lamp

Hollow cathode lamp:

Hollow cathode lamp Merits The spectral line produced by the hollow cathode lamp are so narrow that they completely absorbed by atoms. By this method, one can easily detect and measure the atomic absorbtion. Demerits Each HCL emits the spectrum of that metal which is used in the cathode. Eg., copper cathode emits the copper spectrum, zinc cathode emits the zinc spectrum. For this reason, a different hollow cathode lamp has to be used for each element to be analyzed by AAS and is not very convenient.

Electrodeless discharge lamp:

Electrodeless discharge lamp It consits of an evacuated tube in which the metal of interest is place. The tube is filled with argon at low pressure and sealed off. The sealed tube is placed in a microwave discharge cavity. This causes excitation of the metal sealed inside the tube.


atomisers In order to achieve absorption of atoms, it becomes necessary to reduce the sample to the atomic state. This is done by Flame atomisers Non- atomisers Flame atomisers Total consumption burner Premixed burner Non- atomisers Carbon atomisers

PowerPoint Presentation:

Properties of flames


monochromators The function of the monochromators is to select a given line in the emission spectrum of the light source and isolate it from all other lines. In AAS, the most common monochromators are Prisms and Gratings .


detectors For AAS, the Photomultiplier tube is most suitable which convert radiant energy signal into an electrical one. There is an evacuated envelope which contains a photocathode, a series of electrodes called Dynodes and an anode . Photocathode is fixed to the terminal of the power supply. Photon strikes and accelerate between cathode and anode, the resultant electron current which is goes into amplifier and read out system


amplifier The electric current from the photomultiplier detector is fed to the amplifier which amplifies the electrical current many times. Generally, Lock-in amplifiers are preferred which provide a very narrow frequency band pass and help to achieve an excellent signal-to-noise ratio. Read out devices In most of the AAS, Chart recorders are used as read out devices. In some AAS, digital read-out devices are used

applications of AAS:

applications of AAS AAS is very widely used in metallurgy, alloys and in inorganic analysis . Biochemical analysis : A number of elements present in biological samples can be analysed includes estimation of sodium, potassium, lead, zinc, mercury, cadmium, calcium, magnesium and iron . Pharmaceutical analysis : Estimation of zinc in insulin preparations, oils, creams, and in calamine, calcium in number of calcium salts, lead in calcium carbonate and also impurities in chemical salts .

PowerPoint Presentation:

Sodium, potassium and calcium in Saline and Ringer solutions are estimated by this method. In Petroleum industry , metallic impurities in petrol, lubricating oils have been determined. In cement industry , estimation of sodium, potassium, magnesium, calcium is carried out to determine the quality of cement. Determination of Metallic elements in Food industry like copper, zinc and nickel. E.g., determination of nickel in vegetable oils and copper in beer

Analysis of Pharmaceuticals:

Analysis of Pharmaceuticals

Commercial products of aas:

Commercial products of aas Atomic Absorption Spectrophotometer - Scientific International, New Delhi Atomic Absorption Spectrophotometer - (SLE-7000 SERIES AAS) - Spectro Analytical Labs Limited Beam Atomic Absorption Spectrophotometer - Elico Limited Atomic Absorption Spectrophotometer (AA 7000) - Labindia Instruments Private Limited Atomic Absorption Spectrophotometer (Aasm-01) - Spectro Analytical India AAS 8000 Series (Atomic Absorption Spectrometer) -  MSP Lab Instruments.

PowerPoint Presentation:

FES is based on the measurement of the intensity of the light emitted when a metal is introduced into a flame. The excitation of neutral atoms is brought only by the thermal energy of the flame. Temperature of the flame is important because of intensity is greatly influenced by temperature AAB is based on the analysis of absorption of specific wavelength of radiation by neutral atoms in the ground state. The excitation of neutral atoms is brought only by radiation from hollow cathode lamp. Temperature of flame is not critical FLAME EMISSION SPECTROSCOPY (FES) ATOMIC ABSORPTION SPECTROSCOPY(AAB)

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Does not obeys Beer’s law Analytical signal in flame emission is the sum of all energies emitted as excited atoms drops to the ground state. The signal comes entirely from the emitting atoms The relation between the absorbance and concentration is nearly liner i.e., obeys Beer’s law. The signal is obtained from the difference between the intensity of the source in the absence and presence of metallic elements in the liquids present in the optical path FLAME EMISSION SPECTROSCOPY (FES) ATOMIC ABSORPTION SPECTROSCOPY(AAB)

Safety hazards:

Safety hazards Safety tips when carrying out atomic absorption analysis include: 1. Wear safety glasses for mechanical protection. 2. Check the integrity of the gas system. Make sure the cylinders are secured to immovable objects and that tubing and connectors do not have gas leaks. 3. Check the integrity of the burner. 4. Check the integrity of the drain. 5. Avoid viewing the flame or furnace during atomization unless wearing protective eyewear.


Cont…, 6.The exhaust vent should be placed over the flame to take care of toxic combustion products. 7. Never leave the flame unattended. 8. Make sure a fire extinguisher is located nearby. 9. Allow the burner head to cool to room temperature before handling. 10. Hollow cathode lamps are under negative pressure and should be handled with care and disposed of properly to minimize implosion risks. Also, make sure the lamps are turned off and cool before handling.


BOOK REFERENCE Instrumental Methods of Chemical Analysis -B.K.SHARMA Spectroscopy -KAUR Instrumental Methods of Chemical Analysis -GURDEEP R.CHATWAL,SHAM K. ANAND Text book of Pharmaceutical Analysis -Dr.S.RAVISANKAR Instrumental Method of Analysis - WILLARD, MERRIT, DEAN, SETTLE A Textbook of Pharmaceutical analysis (Instrumental Methods) -Dr.A.V.KASTURE, DR.K.R.MAHADIK, DR.S.G.WADODKAR, DR.H.N.MORE


NET REFERENCES http://www.labmanager.com/?articles.view/articleNo/1152/article/Flame-Atomic-Absorption--FLAA--Safety-Precautions Analysis of Pharmaceuticals using AAS http://www.shimadzu.com.br/analitica/aplicacoes/espectrofotometros/aa/c122-e008.pdf http://catalogs.indiamart.com/cgi/catprdsearch.mp?ss=atomic+absorption+spectrophotometers www.wikipedia.com

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