Flame emission spectroscopy

INTRODUCTION
PRINCIPLE
INSTRUMENTATION
LIMITATIONS
APPLICATION

1. FLAME EMISSION SPECTROSCOPY MODERN PHARMACEUTICAL ANALYTICAL TECHNIQUES Submitted by: B.Mamatha M.Pharmacy 1-1 Pharmaceutical Analysis

2. INTRODUCTION: Flame photometry more accurately called Flame Atomic Emission Spectrometry. A flame photometer is an instrument used to determine the concentration of certain metal ions among them sodium, potassium, calcium and lithium. Flame photometry is based on measurement of intensity of the light emitted when a metal is introduced into flame.

3. PRINCIPLE: When a solution of metallic salt is sprayed as fine droplets into a flame. Due to heat of the flame, the droplets dry leaving a fine residue of salt. This fine residue converts into neutral atoms. Due to the thermal energy of the flame, the atoms get excited and there after return to ground state. In this process of return to ground state, exited atoms emit radiation of specific wavelength. This wavelength of radiation emitted is specific for every element. The wavelength of color tells what the element is (qualitative) The color's intensity tells us how much of the element present (quantitative).

4. Under constant and controlled condition ,the light intensity of the characteristic wave length produced by each of the element is directly proportional to the number of atoms that are emitting energy, which in turn is directly proportional to the concentration of substances of interest in the sample. Various metals emits a characteristic color of light when heated.

5. INSTRUMENTATION NEBULIZER: This is the component of sample delivery system. which breaks up the bigger liquid droplet to smaller liquid droplets . The process of conversion of sample to mist of finely divided droplets using a jet of compressed gas is known as Nebulization .

6. Types of Nebulizer: There are two types of Nebulizer: Pneumatic Nebulizer Ultrasonic Nebulizer Pneumatic nebulizer sucks the liquid sample in the flow of high pressure gas and break into small drops when strikes the glass bead.

7. Ultrasonic nebulizer : An ultrasonic nebulizer is a small portable device that uses ultrasonic sound waves to break liquid particles down into a fog on that they can inhaled easily.

8. ZONE OF FLAME

9. REQUIREMENTS OF FLAME : It should have proper temperature. Temperature should remain constant throughout the operation. There should not be any fluctuation during burning. FUNCTION OF FLAME To convert the analyte of the liquid sample into vapor state. To decompose the analyte into atoms and simple molecules. To excite the formed atoms/free atoms/simple molecules to emit radiant energy.

10. 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.

11. TOTAL CONSUMPTION BURNER In this burner fuel and oxidant are hydrogen and oxygen gases. Sample solution is aspirated through a capillary by high pressure of fuel and Oxidant and burnt at the tip of burner. Entire sample is consumed.

12. FUEL OXIDANT TEMPERATURE C Natural gas Air 1 7 00- 1 900 Natural gas Oxygen 2700-2800 Hydrogen Air 2 00 - 2 1 00 Hydrogen Oxygen 2550-2700 Acetylene Air 2 1 - 2 4 00 Acetylene Oxygen 3 5 - 3 1 50 Acetylene Nitrous oxide 2600-2800

13. 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.

14. SLITS The entrance and exit slits are used before and after the dispersion elements. The entrance slit cuts off most if radiation from the surroundings and allows only the radiation from the flame and the mirror reflection of flame to enter the optical system. The exit slit is placed after the monochromator and allows only the selected wavelength range to pass through the detector.

15. DETECTORS PHOTO MULTIPLIER TUBE: The photomultiplier (PM) tube detects and amplifies radiant energy. Incident light strikes the coated cathode, emitting electrons. The electrons are attracted to a series of anodes, known as dynodes, each having a successively higher positive voltage These dynodes are of a material that gives off many secondary electrons when hit by single electrons. Initial electron emission at the cathode triggers a multiple cascade of electrons within the PM tube itself. Because of this amplification, the PM tube is 200 times more sensitive than the phototube.

16. PM tubes are used in instruments designed to be extremely sensitive to very low light levels and light flashes of very short duration.

17. LIMITATIONS Limited number of elements that can be analyzed. The sample requires to be introduced as solution into fine droplets. Many metallic salts, soil, plant and other compounds are insoluble in common solvents. Hence, they can’t be analyzed by this method. Since sample is volatilized, if small amount of sample is present, it is tough to analyze by this method. As some of it gets wasted by vaporization. Further during solubilization with solvents, other impurities might mix up with sample and may lead to errors in the spectra observed.

18. APPLICATIONS To estimate sodium, potassium, calcium, lithium etc., level in sample of serum, urine, CSF and other body fluids. Flame photometry is used for the determination of alkali and alkaline earth metals. Used in determination of lead in petrol. Used in the study of equilibrium constants involving in ion exchange resins. Used in determination of calcium and magnesium in cement.