Atomic absorption spectroscopy (aas)

Atomic Absorption Spectroscopy (AAS)

1. Atomic Absorption Spectroscopy ( AAS ) Md. Abdul Karim Mia National Control Laboratory Mohakhali , Dhaka, Bangladesh

2. Determination of even small amounts of mercury , calcium, magnesium, etc ) as follows: Pharmaceutical industry Food industry. Environmental studies: drinking water, ocean water, soil. Environmental studies: drinking water, ocean water, soil . Atomic Absorption Spectroscopy

3. INTRODUCTION: Atomic absorption spectroscopy ( AAS ) is a spectroanalytical procedure for the quantitative determination of chemical elements using the absorption of optical radiation (light) by free atoms in the gaseous state . It is a technique for measuring quantities of chemical elements present samples by measuring the absorbed radiation by the chemical element of interest It can analyze over 62 elements.

4. History The first atomic absorption spectrometer was built by CSIRO scientist Alan Walsh in 1954. In 1955 the modern era of atomic absorption spectroscopy began with the work of Walsh and Alkemade and Milatz . We are now in a period of great change, which started in about 1976, due to the impact of computer technology on individual laboratory instruments.

5. Principle The technique uses basically the principle that free atoms (gas) generated in an atomizer can absorb radiation at specific frequency . Atomic-absorption spectroscopy quantifies the Atomic-absorption of ground state atoms in the gaseous state. The atoms absorb ultraviolet or visible light and make transitions to higher electronic energy levels. The analyte concentration is determined from the amount of absorption. Contents

6. Principle (Continued) Concentration measurements are usually determined from a working curve after calibrating the instrument with standards known concentration.. Atomic absorption is a very common technique for metals and metalloids in environmental samples Contents

7. Atomic Absorption Spectrometer Hollow Cathod Lamp Nebulizer Detector Monochromator Atomizer Theory

8. Principle Concentration measurements are usually determined from a working curve after calibrating the instrument with standards known concentration. of known concentration. Atomic absorption is a very common technique for metals and metalloids in environmental samples Parts with Diagram

9. Light Source Hollow Cathode Lamp are the most common radiation source in AAS. It contains a tungsten anode and a hollow cylindrical cathode made of the element to be determined. These are sealed in a glass tube filled with an inert gas (neon or argon ) . Parts Of AAS

10. Monochromator This is a very important part in an AA spectrometer. It is used to separate out all of the thousands of lines. A monochromator is used to select the specific wavelength of light which is absorbed by the sample, and to exclude other wavelengths The selection of the specific light allows the determination of the selected element in the presence of others Parts Of AAS

11. Detector The light selected by the monochromator is directed onto a detector that is typically a photomultiplier tube, whose function is to convert the light signal into an electrical signal proportional to the light intensity. The processing of electrical signal is fulfilled by a signal amplifier . The signal could be displayed for readout , or further fed into a data station for printout by the further fed into a data station requested format. Parts Of AAS

12. Nebulizer suck up liquid samples at controlled rate. create a fine aerosol spray for introduction into flame. Mix the aerosol and fuel and oxidant thoroughly for introduction into flame. Parts Of AAS

13. Atomizer Elements to be analyzed needs to be in atomic sate Atomization is separation of particles into individual molecules and breaking molecules into atoms. This is done by exposing the analyte to high temperatures in a flame or graphite furnace . Parts Of AAS Atomizer Flame Atomizer Graphite tube Atomizer

14. Determination of even small amounts of mercury , calcium, magnesium, etc ) as follows: Pharmaceutical industry Food industry. Environmental studies: drinking water, ocean water, soil. Application of AAS

15. In Atomic absorption Liquid solvent is evaporated and the dry sample is vaporized to a gas or droplets. Components of the gaseous sample are converted into free atoms, this can be achieved in either a flame or flameless manner using a graphite chamber that can be heated after application of this sample. Mechanism of AAS

16. Gas( Acetyline gas, Nitrous Oxide, Argon gas) Air compressor Standard Solution m u ffle Furnance Matrix Modifier Volumetric Flask Micro pippete Procedure of Cromium Analysis by AAS Required materials

17. 0.1 M HNO3: 34.37ml of 65% Nitric Acid 5.0 L with DI water. Matrix Modifier: Ammonium Chloride Chromium Standard Solutions: 1ml100ml with 0.1 M HNO3 . Dilute 5.0 ml+0.5ml Ammonium Chloride of this to 100ml with 0.1 M HNO3. Sample Preparation: 4.0 gm powder is heated in Crucible at 550-650°c with Muffle Furnance at least 8 hours. Then cool to room temperature. Take 3250 mg powder in 200 ml volumetric flask, add 12 ml Conc. Nitric acid and sonicate for 10-15 min. Then warm to 60-70 °c at water bath for 15 min. Then volume to 200 ml with water and filter. Take 2.0 ml filtrate in a 50 ml volumetric flask add 0.2 ml of Ammonium Chloride and volume to the mark with 0.1 M Nitric Acid. Calculations: Conc. of Sample Soln.X200X50X Average Weight Contents of Chromium/tab(mcg):------------------------------------------------------------ 100X Taken wt of Sample X 2 Procedure of Cromium Analysis by AAS Preparations of Reagents/ Solutions

18. Calibration Curve Abs Conc. Conc (ppm) Abs 1.000 0.4899 2.000 1.0286 3.000 1.4407 4.000 1.7954 Abs=0.43286 conc+0.10650 r= 0.9954

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