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Add as Friendflame photometry

by: kinjanmehta

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2 : INSTRUMENTATION The basic components for flame photometer are as follows: Burner(source) Mirrors Slits Monochromators Detector Read out device
3 : BURNERS The FLAME used in the flame photometer should possess following functions: The flame should have ability to evaporate the liquid droplets from the sample solution in the formation of solid residue The flame should decompose the compounds in the solid residue resulting in the formation of atoms. The flame must have the capacity to excite the atoms formed and cause them to emit radiant energy. Time for intensity of emission is 1-2 mins.
4 : Factors Controlling Temp. Of Flame. Type of fuel and oxidant and fuel to oxidant ratio. Type of solvent for preparing sample solution. Amount of solvent which is entering into the flame. Type of BURNER USED in flame photometer. The particular region in flame which is to be foused into the spectral isolation unit.
6 : MECKER BURNER This burner employed natural gas and oxygen. Produces relatively low temp. and low excitation energies. This are best used for ALKALI metals only. It has 2 regions in the flame- “oxidation” and “reducing” region. Nowadays it is not used. MEKER BURNER
7 : Total consumption burner. In this burner the FUEL and OXIDANT are HYDROGEN and OXYGEN gas respectively. In this the sample solution is aspirated through a capillary by the high press. Of fuel and fuel and oxidant and burnt at the tip of the burner TOTAL CONSUMPTION BURNER
8 : Contd…… The name “total consumption burner” is used because all the sample that enters the capillary will enter the flame regardless of the droplet size. ADVANTAGE: Design is simple and entire sample is consumed. DEMERITS Uniform and homogeneous flame is not obtd. Since droplet size vary, leading to fluctuations in the flame intensity.
9 : LAMINAR FLOW (PREMIX) 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. IMP. Feature of this is that only a small portion portion (about 5%) of the sample reaches the flame in the form of small droplets and is easily decompose. ADVANTAGES: Premix burner is non-turbulent noiseless and stable. Easy decomposition which leads to high atomozation.
10 : Contd…. Can handle solution up to several % without clogging. DEMERITS: When it contains 2 solvents, the more vol. will evaop. And lesser will remain undiassociated. LAMINAR FLOW BURNER
11 : Lundergraph burner. The sample must be in a liquid form. Large droplets condense in one side and drain away in small droplets and vaporized sample are swept into the flame in the form of the cloud.
12 : SHIELDED BURNERS. Flame was shielded from the ambient atmosphere by the stream of inert gas.
13 : MIRRORS. Concave mirror is used as it covers as wide a solid angle from the flame as possible. A mirror is located behind the burner to reflect the radiation back to the entrance slit of the monochromator. The reflecting part of the mirror is front faced, but they are not physically protected.
14 : SLITS ENTRANCE AND EXIT SLIT are used before and after the dispersion elements. The ENTRANCE slit cuts out most of the radiation from the surrounding and allow only the radiation from the flam and mirrored reflection of the flame to enter the optical system. The EXIT slit is placed after the monochromatic and allows only the selected wavelength to pass through the detectors. For many purposes the wavele. Of the substance should be very narrow.
15 : FUNCTION OF THE SLITS AND MONOCHROMATOR Entrance slit Exit slit Prism
16 : MONOCHROMATORS AND FILTERS In simple flame photometers, the monochromators is the prism. QUARTZ is the material most commomly used for making prisms because quartz is transparent over entire region from FILTERS: the filter is made up of such material which is transparent over a narrow spectral range. When a filter is kept between the flame detector, the radiation of the desired wavelength from the flame will be entering the detector and be measured. The remaining undesired wavelength will be absorbed by the filter and not measured.
17 : DETECTORS The radiation coming from the optical system is allowed to fall on the detector which measures the intensity of radiation falling it. It should be sensitive to radiation of all the wavelengths that has to be examined.
18 : FLAME PHOTOMETER A flame photometer contains , a burner, where the solution to be analysed is sprayed into he droplets after mixing with the fuel and oxidant. A compressor , compresses the air or oxygen and fuel , at a pressure of about 0.5 kg/ The high pressure is required to the sample solution to fine droplets. When the sprayed droplets gets ignited, the solvents is evaporated by the thermal energy of the flame, leaving behind the fine residue. This is converted into neutral atoms and is converted to excited atoms by thermal energy .
20 : Contd… This atoms are unstable and hence loose energy in the form of radiation and atoms to ground state . The wavelength a well as the intensity of the light radiation emitted is detected by using a filter and photometric detector. A concave mirror is used to focus the light onto the filter wheel containing Li. Na, Ca filters. In which the desired position can be selected based upon the element to be measured. The light passes through a slit and falls on the detector, and response is shown in digital display device..
21 : FLAME SPECTROPHOTOMETER A flame spectrophotometer consits of similar component of flame photometer, in which the filter is replaced by a prism or monochromator and photovalic cell is replaced by phototube or photomultiplier.
23 : REFERENCES G.R. Chatwal and S. K. Anand, Instrumental Method Of Chemical Analysis, Himalayan Publishing House, India. Dr. S. Ravi Sankar, Text Book of Pharmaceutical Analysis, Third Edition, Rx Publications, India.,or.r_gc.r_pw.r_qf.&fp=acd297a0b745b272
24 : Thank you.

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