FLAME PHOTOMETRY AND FLUORIMETRY

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FLAME PHOTOMETRY AND FLUORIMETRY Sridhar M.Pharm 1 st year, Dept. Pharmaceutical Analysis and Quality Assurance, FLAME PHOTOMETRY AND FLUORIMETRY

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Flame photometry is a measure of intensity of emission radiation when the sample molecule are subjected to flame. It is mainly used for the atoms of 1 st & 2 nd group elements of periodic table i.e Na,K,Ca,Li etc. It is not applicable to the metals of periodic table other then the 1 st & 2 nd group elements. The elements like gold, silver & inert atoms and other atoms are not analysed by flame photometry because they need higher energy to bring about excitation state then the 1 st & 2 nd group elements

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THEORY (OR) PRINCIPLE: flame photometry is a type of emission spectroscopy and the main principle involved is the measurement of emission radiation. The sample molecules(atoms) are brings to excitation state by using thermal energy rather then the EMR. when a sample solution is exposed to a flame the following events are going to happen. The 1 st solvent evaporate and leaves the residue of solute, The residue is converted into gases state, The gases state is converted into atomic state(individual atoms)/ionic state. THEORY (OR) PRINCIPLE:

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The atoms which released from a gases state undergoes excitation by using thermal energy and comes back to the ground state by the emission of a radiant energy(hv). In the excitation process the electron present in the molecular orbitals moves to higher molecular orbital. When the electrons moves from one orbital to another takes away the energy and comes back to original by the liberation of particular radiation for each atoms.

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INSTRUMENTATION: The basic components for flame photometer are as follows: INSTRUMENTATION: INSTRUMENTATION: Burner(source) Mirrors Monochromators Filter Detector

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SCHEMATIC REPRESENTATION OF FLAME PHOTOMETRY SCHEMATIC REPRESENTATION OF FLAME PHOTOMETRY

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1)BURNERS 1)BURNERS BURNERS used in the flame photometry should have following properties : The flame should have ability to evaporate the solvent to give a residue. The flame should convert this residue into gases state atoms and finally to individual atoms. The effect of flame is depends upon the temperature of flame and this temperature can be monitored by following methods : Fuel to air ratio Type of solvent for preparing sample solution. Amount of solvent which is entering into the flame. Type of burner used in flame photometer.

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1)MECKER BURNER 1)MECKER BURNER This burner was used earlier and employed natural gas and oxygen. Produces relatively low temp. and low excitation energies. This are best used for ALKALI metals only. Now-a-days it is not used.

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TOTAL CONSUMPTION BURNER 2)TOTAL CONSUMPTION BURNER 2)TOTAL CONSUMPTION BURNER In this the air & fuel are mixed in a chamber which is delivered through nozzle, where the sample is aspirated. The main advantage of this burner is the total usage of sample solution.

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3)PREMIX OF LAMINAR FLOW BURNER : 3)PREMIX OF LAMINAR FLOW BURNER : In this type of the burner, aspirated sample, fuel and oxidant are thoroughly mixed before reaching the burner opening and then entering the flame. There is high loss of sample(95%) as large droplets which are drained out.

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4)LUNDERGARTH BURNER : 4)LUNDERGARTH BURNER : In this sample & air mixed in chamber,this mixed composition send to fuel nozzle where it burn.

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2)MIRRORS : The radiation from the flame is emitted in all the directions in space. Much of the radiation is lost and loss of signal results. A mirror is located behind the burner to reflect the radiation back to the entrance slit of the monochromator . The reflecting surface of the mirror is front-faced. These mirrors are very easily scratched when subjected to chemical attack e.g. acid vapors. Great care should be taken to protect them from corrosive atmosphere. 2)MIRRORS :

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3)MONOCHROMATORS: 3)MONOCHROMATORS: The emitted light from flame produces a straw radiation. This straw radiation is filtered by entrance slit and required radiation is passes through a prism followed by exit slit. The radiation from the exit slit enters respective filters.

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4)FILTERS 4)FILTERS: They are different filters are available based on the ions to be detected like Na,K,Ca,Li,Mg filters etc. These filters allow the specified radiations to the detectors. The function of a detector is to measure the intensity of radiation falling on it. Photo emissive cells or photomultiplier tubes are commonly employed 5)Detector: 5)Detector:

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APPLICATIONS OF FLAME PHOTOMETRY: APPLICATIONS OF FLAME PHOTOMETRY: QUALITATIVE APPLICATIONS: Some of these elements can be detected visually by the color in the flame, e.g. sodium produces yellow flame. The best method is to use flame photometer and when a radiation of the characteristic wavelength is detected, it will indicate the presence of the metal in the sample. This is done by peak matching technique.

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Flame photometry is used to determine the concentration of various soil components. For agricultural purposes, an analysis of a proper mixture of surface soil and subsoil is carried out to determine the fertilizer requirement of the soil. In clinical chemistry, it is very important to determine the concentration of sodium and potassium ions in body fluids since their ratio controls the action of muscles including the heart. This is achieved by diluting the blood serum and aspiration into the flame. Food and drinks are analyzed for alkali metals. QUANTITATIVE APPLICATIONS:

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Fruit juices and alcoholic beverages can be analyzed. Flame photometry is used in quantitative estimation of alkali and alkaline earth metals in Mineral Extraction and Pharmaceuticals. It is also used in cement, petroleum industries.

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FLUORIMETRY When the electro magnetic radiation passed through a sample, the molecule absorb radiation energy and moves from ground state to excited state. When the excited molecules come back to ground state by they emit a radiation of longer wavelength (λ) then the incident radiation. This entire process is called “ LUMINESCENCE ”. This is a divided into two types: Fluorescence: In this excited molecules comes back to the ground state by emission radiation from 10 -8 to 10 -2 sec. after the incident radiation is cut off. Phosphorescence: In this excited molecules comes back to the ground state by emission of radiation from 10 -2 to 100sec. even after cut off incident radiation.

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THEORY (OR) PRINCIPLE: THEORY (OR) PRINCIPLE: All the molecules before irradiation are in the ground state, when an EMR passed through this the molecules move from ground state to excited state. When molecules absorb energy the spin quantum state of electron are going to change in excited state. in ground state the paired electrons always contain opposite spin/antiparallel direction. When these electrons gain energy there are two possible spin changes occur. excited singlet state excited triplet state ground state 1) Singlet and Triplet State:

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2) Electron transition state: when a molecule in ground singlet state absorb energy it moves from different vibrational level of ground singlet state to excited singlet state.

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In each electronic excited state there are no. of vibrational levels. This means in excited singlet state the electrons are at different vibrational levels. When the electrons move from excited state to ground state following possible changes occur. The electrons in excited state comes back ground state by without emission of radiation by release of heat. The electrons in the excited singlet state posses different vibrational level and reach the ground state. The electrons in the higher vibrational level should come back to the lower vibrational level and this processes takes 10 -8 to 10 -2 sec.Once it reaches lower vibrational level, immediately comes to the ground state this process is said to be “ fluorescence ”

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INETR SYSTEM CROSING: When the electrons in the excited state, the S 1 vibrational levels are coupled with vibrational levels of T 1 . The electrons in the triplet state take some more time to cross the vibrational level with in the triplet state to reach the ground state and this process takes about 10 -2 to 100sec.This phenomena is said to be ”phosphorescence”

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INSTRUMENTATION:

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1) Light source : Mercury vapor lamp. 2) Aperture: Which allows the light into instrument. 3) Shutter: Based on the usage of light required or not at a particular movement, shutter used. 4) Conducting lens: These lens allow the light through it absolutely. 5) Primary filter: It absorbs visible light and UV-radiation. This UV-light enters the sample by crossing conducting lens. 6) Sample cell: Cells made up of quartz are used as sample cells. 7) Secondary filter: These filter absorbs UV-light which is transmitted through the sample and allows emission radiation of visible light to detector. 8) Detector: Generally photomultiplier detector is used to convert this emission radiation into electrical signal. FLUORIMETRY consist of following component:

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APPLICATIONS : 1) Determination of uranium salt by fluorimetry . 2) It is used to identify cadmium, ruthenium impurities present in pharmaceutical products. 3) Determination of Vitamin B1(Thiamine). - determination of Vitamin B2(riboflavin). 4)It is also used in analysis of Quinine and Streptomycin in quantitative & qualitatively.

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REFERENCES: REFERENCES: Instrumental methods of chemical analysis by Gurudeep.R.Chatwal Principles of instrumental analysis by Skoog . Vogel's Textbook of Quantitative chemical analysis

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