Atomic absorption spectrometer

Atomic absorption spectrometer- Instrumentation, principle and uses

1. PUNJAB AGRICULTURAL UNIVERSITY LUDHIANA Production Technology of Summer Season Vegetable Crop s (Veg 502) Atomic Absorption Spectrometer Anusha KR L -2019-H-205-M MSc 1 st yr. Vegetable Science

2. Atomic Absorption Spectroscopy

3. Introduction Atomic Absorption Spectroscopy (AAS) is a very common technique used to detect metals in the samples. It is a spectro -analytical procedure for the quantitative determination of chemical elements using the absorption of optical radiation by free atoms in the gaseous state. It can analyze over 70 elements.

4. Principle AAS utilizes the principle that elements in the gas phase absorb light at very specific wavelengths which gives the technique excellent specificity and detection limits. The sample may be an aqueous or organic solution, indeed it may even be solid provided it can be dissolved successfully. The liquid is drawn in to a flame where it is ionized in the gas phase. Light of a specific wavelength appropriate to the element being analyzed is shone through the flame, the absorption is proportional to the concentration of the element. Quantification is achieved by preparing standards of the element.

5. Schematic diagram of AAS

6. INSTRUMENTATION

7. Light Source The light source is usually a hollow cathode lamp of the element that is being measured 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 ) Each element has its own unique lamp which must be used for that analysis .

8. Atomizer Elements to be analyzed needs to be in atomic state. 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. There are two types of atomization : Flame and Graphite furnace atomization . The solid particles are vaporized into their free gaseous ground state form . In this form atoms will be available to absorb radiation emitted from the light source and thus generate a measurable signal proportional to concentration .

9. Monochromator It plays a crucial part in AAS. It is used to select the specific wavelength of light which is absorbed by the sample, and exclude other wavelengths. This helps in the determination of selected elements in the presence of others.

10. Detector The role of the detector is to convert a light signal into an electrical signal. The type of detector found in AAS is the photomultiplier tube - the principle of operation is the emission of electrons upon exposure to radiation.

11. Applications Clinical analysis : Analyzing metals in biological fluids such as blood and urine. Environmental analysis : Monitoring our environment – e g finding out the levels of various elements in rivers, seawater, drinking water, air, and petrol. Pharmaceuticals . Industry : Many raw materials are examined and AAS is widely used to check that the major elements are present and that toxic impurities are lower than specified.

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